CHIRAL CATALYSTS AND EPOXIDATION REACTIONS CATALYZED THEREBY

Abstract: A compound of formula (I), in which M is a transition metal ion; A is a counter-ion if required; r, s and t are independently 0 to 3 such that r+s+t is in the range of 1 to 3; Ra, Rb, Rc are each independently hydrogen or CH2OR' where R' is hydrogen or an organic group; B and E are independently oxygen, CH2, NRd in which Rd is alkyl, hydrogen, alkylcarbonyl, or arylcarbonyl or SOn where n is 0 or an integer 1 or 2, with the proviso that B and E are not simultaneously CH2 and that when B is oxygen, NRd or SOn, then r cannot be 0, and when E is oxygen, NRd or SOn, then t cannot be 0; R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are independently hydrogen, alkyl or alkoxy.

Description: CHIRAL CATALYSTS AND EPOXIDATION REACTIONS CATALYZED THEREBY This invention relates to novel ca ..; and their use in the conversion of certain olefins into chirally enriched epoxides. WO/91/14694 describes certain catalysts of the following formula (A): in which M is a transition metal ion, A is an anion, and n is either 0, 1 or 2. At least one of Xj or X2 is selected from the group consisting of silyls, aryls, secondary alkyls and tertiary alkyls; and at least one of X3 or X4 is selected from the same group. Yj, Y2, Y3, Y4» Y5 and Y are independendy selected from the group consisting of hydrogen, halides, alkyls, aryl groups, silyl groups, and alkyl groups bearing heteroatoms such as alkoxy and halide. Also, at least one of Rj, R2, R3 and R4 is selected from a first group consisting of H, CH3, C2H5 and primary alkyls. Furthermore, if Rj is selected from said first group, then R2 and R3 are selected from a second group consisting of aryl groups, heteroatom-bearing aromatic groups, secondary alkyls and tertiary alkyls. If R2 is selected from said first group, then R^ and R4 are selected from said second group. If R3 is selected from said first group, then Rj and R4 are selected from said second group. If R4 is selected from said first group, then R2 and R3 are selected from said second group. Such catalysts are described as being useful in enantioselectively epoxidising a prochiral olefin. Structurally distinct catalysts have now been prepared which surprisingly possess the ability to catalyse the enantioselective expoxidiation of certain prochiral olefins. Accordingly, the present invention provides a compound of formula (I): in which M is a transition metal ion; A is a counter-ion if required; r, s and t are independendy 0 to 3 such that r+s+t is in the range of 1 to 3; R a , R*\ R c are each independendy hydrogen or CH2OR' where R' is hydrogen or an organic group; B and E are independendy oxygen, CH2, NR^ in which Rd is alkyl, hydrogen, alkylcarbonyl, or arylcarbonyl or SO n where n is 0 or an integer 1 or 2, with the proviso that B and E are not simultaneously CH2 and tiiat when B is oxygen, NR^ or SO n , then r cannot be 0, and when E is oxygen, NR^ or SO n , then t cannot be 0; Rl, R2, R3, R4, R5, R6» R7. Rδ' R 9 ^d R 10 are independendy hydrogen, alkyl or alkoxy. Suitable transition metal ions, M, include Mn, Cr, Fe, Ni, Co, Ti, V, Ru and Os in an appropriate oxidation state. Preferably the transition metal ion, M, is Mn in oxidation state (IT) or (IH). It should be appreciated tiiat in some cases for example when M is Mn (IT), a counter-ion is not required. Suitable counter-ions, A, include tiiose anions mentioned in WO 91/14694. Preferably, A is chloride. Suitable organic groups R' include alkyl, alkylcarbonyl, arylcarbonyl or aryl derivatives. Particular examples of R' include substituted alkyl groups. One example of R' is triphenylmethyl. Preferably s and t are zero, r is 1 and R a is hydrogen, B is oxygen and E is CH2; or r, s and t are 1, R a , R* 5 and R c are hydrogen and B and E are both oxygen; or s is zero, r and t are both 1, R a is hydrogen or triphenylmethyloxymethylene and R c is hydrogen, B is oxygen and E is -CH2 or r and t are both 1, s is zero, R a and R c are hydrogen, B is NR^ where R<* is phenyl carbonyl and E is CH2. Suitably, R2, R4, R5 and R7 each independently represent hydrogen. Suitably Rj, R3, Rg and Rg each independently represent C . alkyl. Favourably Rj and Rg represent branched alkyl groups such as tertiary alkyl groups. R3 and R-6 also advantageously represent branched alkyl groups. One preferred example for each of Rj and Rg is tertiary butyl. Particular examples of R3 and Rg are tertiary butyl and metiiyl. Examples of R2, R4, R5 and R7 are hydrogen. The term 'alkyl' when used alone or when forming part of other groups (for example alkoxy groups or alkycarbonyl groups) includes straight- or branched-chain alkyl groups containing 1 to 12 carbon atoms, suitably 1 to 6 carbon atoms, examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl or tert-butyl group. When used herein the term 'aryl' includes phenyl and naphdiyl optionally substituted witii up to five, preferably up to three, groups selected from halogen, alkyl, phenyl, alkoxy, haloalkyl, alkylcarbonyl and phenylcarbonyl. A preferred aryl group is a substituted or unsubstituted phenyl group. Transition metals M include tiiose having oxidation states of (IT) or more. Suitable substituents for aiyl include alkyl, halogen and alkoxy. Optional substituents for alkyl groups include those mentioned herein for aryl groups, phenyl is a particular example. It should be appreciated th t the carbon atoms marked widi an asterisk are chiral centres and die present invention extends to each individual enantiomer and any mixtures thereof. The present invention also provides a process for d e preparation of compounds of formula (I) which comprises forming a transition metal complex of the following compound of formula (II): where variables Rj to RJQ, B, E, r, s, t R a , R D and R c are as defined in relation to formula (I), and diereafter if necessary separating any enantiomers. Suitably the transition metal ion complex may be formed by the addition of a suitable transition metal salt such as manganese (II) or (III) acetate, preferably manganese (HI) acetate, to a compound of formula (II) in a suitable solvent such as ethanol or methylene dichloride, at elevated temperature. The optional replacement or interconversion of the counter ion may be effected by the addition of an alkali metal salt containing the desired counter-ion such as LiCl. The separation of any enantiomers may be carried out by conventional techniques, such as crystallisation of derivatives or chromatography. However, it should be appreciated that is is preferred that separation of enantiomers is carried out before forming a transition metal complex. The invention further provides a process for the preparation of compounds of formula (II) which comprises condensing sequentially, in any order, a compound of formula (III): where r, s, t, R a , R° and R c E, B are as defined in formula (I) and Rj j and R j 2 independently represent hydrogen or an amine protecting group, providing at least one of R\ \ and Rj2 i* 5 hydrogen, with a compound of formula (IV); and a compound of formula (V), removing any protecting group R j j or R^ as necessary; wherein Rj to RJQ are as defined in relation to formula (I), and thereafter as required isolating the required compound including if necessary separating any enantiomers. It is preferred that the compound of formula (II) is prepared from optically pure compounds of formula (HI) which are preferably prepared tiiemselves from optically pure starting materials. Alternatively, racemates or mixtures of enantiomers of formula (II) or (III) may themselves be resolved using conventional techniques in the art such as crystallisation of derivatives, or chromatography. When compounds of formula (II) are required in which one or more of R j , R2, R3, R4 and R9 are not the same as one or more of Rg, R7, Rg, R5 and RJQ respectively, tiien compounds of formula (III) may be sequentially condensed witii compounds of formula (IV) and formula (V), in any order, by heating a suitably protected compound of formula (III) with a compound of formula (IV) or (V) (in a 1:1 mole ratio) in an inert solvent such as ethanol, if necessary, purifying the resulting intermediate compound of formula (VI) or (VII): wherein variables Rj to Rj2» r» s» t» R a > R**, R c > E and B are as defined in to formula (III), (IV) and (V) using conventional techniques such as chromatography removing any R\ or Rj2 protecting groups and then repeating the reaction using a compound of formula (TV) or (V) as required. Suitable protecting groups Rj \ or R^2 include conventional amine protecting groups such as benzyl groups, silyl groups or acyl groups such as benzoyl groups. The removal of Rj \ or Rj2 when representing protecting groups may be carried out using conventional techniques in the art depending upon die nature of the protecting group. It should be appreciated tiiat when each of Rj, R2, R3, R4 and R9 is the same as each of Rg, R7, Rg, R5 and RJQ respectively die compounds of formula (TV) and (V) are the same, therefore, compounds of formula (III) in which Rj j and R12 is hydrogen are preferably used and two moles of a compound of formula (IV) or (V) are utilised, in an inert solvent, such as ethanol, at elevated temperature, for example at reflux. Compounds of formula (HI) are either known compounds or may be prepared according to known methods or analogously to known methods or analogously to die methods described herein, for example when a compound of formula (HI) is : 3,4- diaminotetrahydrofuran, such a compound may be prepared according to die following scheme, for example, as described in descriptions 1 and 2. H 2 , Pd/C EtOH Alternatively, 3,4-diaminotetrahydrofuran may be prepared according to die following scheme, for example, as described in descriptions 4 to 6. The 5R, 6R-diamino-l,3-dioxepane may be prepared according to die procedures, as described in descriptions 8 to 13. The 3R, 4S-diamino tetrahydropyran may be prepared according to die procedures as described in descriptions 15 to 17. The 3R,4R-diamino-(2R)(triphenyl methoxymethyl)tetrahydrofuran may be prepared according to die procedures as described in descriptions 21 to 24. The (±) trans- l-benzoyl-3,4-diaminopiperidine may be prepared according to the procedures as described in descriptions 25 to 27. Compounds of formula (IV) and (V) are eid er commercially available, are known compounds or may be prepared according to known methods or analogously to known methods for examples such as these described by G.Casiraghi et al J. Chem Soc. Perkin Transactions I. 1980 P1862 - 1865. Novel compounds of formula (II), (III), (IV), (V), (VI) and (VII) form an aspect of the present invention. It should be appreciated that the term chiral catalyst refers to catalysts of formula (I) which have a predominance of one particular enantiomer and tiierefore are useful in forming a predominance of one particular enantiomer of die resulting epoxide produced from a prochiral olefin. It should be appreciated tiiat the catalysts, of formula (I) are preferably prepared in a chiral form by using a resolved compound of formula (III) which may be resolved using conventional techniques. The compound of formula (III) may itself be prepared from suitable precusor compounds such as tiiese outiined in hereinbefore which may be resolved using conventional techniques or may be purchased in a resolved form. Alternatively, die coupled compound of formula (II) may be resolved using conventional techniques. The invention further provides a process for enantioselectively epoxidising a prochiral olefin in the presence of an oxygen source and a chiral catalyst of formula (I). Suitable prochiral olefins include compounds which comprise the following groups as part of their structure, cyclohexene, 5,6-dihydro-2H-pyran, 1,2,5,6- tetrahydropyridine, 1,2,3,4-tetrahydropyridine and 5,6-dihydro-2H-thiopyran. Favoured prochiral olefins include those compounds which comprise the following groups as part of their structure form: 1,2-dihydronaphdιalene, 2H- chromene, 1,2-dihydroquinoline, 1,2-dihydroisoquinoline and 2H-thiochromene. Such compounds are well known in the potassium channel activator field. Preferably, prochiral olefins include diose mentioned in EP-A-0376524, such as die compounds of formula (XIV) therein, and in particular 2,2-dimetiιyl-6- pentafluoroethyl-2H- 1 -benzopyran. It should be appreciated tiiat die present invention particularly extends to the preparation of all epoxide precursors to those compounds of formula (I) in EP-A-0376524 and especially die specific examples thereof using the herein described process. The present invention also particularly extends to die subsequent conversion of all epoxide precursors to all specific examples in EP-A-0376524, to those specific examples in particular to the preparation of (-)trans-3,4-dihydro-2,2-dimetfιyl-4-(2- oxopiperidin- 1 -yl)-6-pentafluoroethyl-2H- 1 -benzopyran-3-ol. Suitable oxygen sources include sodium hypochlorite. It should be appreciated tiiat only one enantiomer of a catalyst of formula (I) is required to produce die 3S,4S enantiomer of the epoxide precursor to compounds described in EP-A- 0376524 which in turn produce the 3S,4R configuration in the compounds of formula (I) as described in EP-A-0376524. Conversely, the 3R, 4R enantiomers of die epoxide precursors produce the 3R, 4S configuration in die compounds of formula (I) as described in EP-A-0376524. The following descriptions and examples illustrate the present invention. Description 1 (±) 2,5-Dihydro-3-nitrofuran (DI) A mixture of (±) trans 3-chloromercurio-4-nitro-2,5-dihydrofuran 1 (38.54g, 109.6 mmol) and Et3N (11.07g, 109.6 mmol) in CH2CI2 (2.2L) at 25°C was stirred for 1.25h. 5% aqueous citric acid (1.1L) was added and stirring was continued for 5 min. The mixture was filtered through celite, separated and d e organic phase washed widi 5% aqueous citric acid (220 ml), dried over Na2SO4 and concentrated in vacua. Chromatography of the residue on silica (Merck 9385, 300g) eluting with CHCI3- Hexane (1:1 -> 1:0) afforded (DI) as a pale yellow oil which crystallised in the freezer, 5.45g (43.2%). δ (CDCI3) 4.95 (4H,S) and 7.10 (1H,S) 1. P. Bitha and Y - 1. Lin, J. Heterocyciic Chem., 1988, 25, 1035-1036. Description 2 (±) 3,4-Diaminotetrahydrofuran (D2) A solution of (±) 4-amino-3-nitrotetrahydrofuran, prepared from (DI) via the method of Bitha and Lin 1 , (4.66g, 35.3 mmol) in EtOH (100 ml) containing 10% palladium on carbon (2.5g) was hydrogenated on a Parr shaker apparatus at 35 psi for 65h at 20°C. The suspension was filtered, d e solids washed widi EtOH (100 ml) and die combined filtrate evaporated in vacua to afford (±) (D2) as a colourless oil, 3.26g (81.5%) δ (CDCI3) 1.40 (4H,bs), 3.20 (2H, m), 3.50 (2H,dd) and 4.08 (2H,dd). Description 3 (±) 3,4-bis (3-terf-ButyI-5-methylsaIicylideamino)tetrahydrofuran (D3) A solution of the racemic diamine (D2) (855 mg, 8.38 mmol) and 3-rerf-butyl- 5-methylsalicaldehyde (3.22g, 16.76 mmol) in EtOH (50 ml) was heated at reflux for 1.5h. The solvent was removed in vacuo and die residue chromatographed on silica (Merck 9385, 300g) using CHCI3 as eluent to afford (±) (D3) as pale yellow needles, 1.35g, (35.8%). δ (CDCI3) 1.42 (18H,s), 2.25 (6H,s), 3.95-4.10 (2H,m), 4.43 (2H,q), 6.90 (2H,d), 7.15 (2H,d), 8.30 (2H,s) and 13.10 (2H,bs). Description 4 (S,S) trans 3,4-bis(methanesuIphonyIoxy)tetrahydrofuran (D4) A solution of 1,4-anhydro-L-threitol (2.45g, 23.5 mmol ex Aldrich Chemical company) in a mixture of THF (75 ml) and Et2θ (75 ml) at 0°C was treated sequentially with triethylamine (7.2 ml, 51.7 mmol, 2.2 eq) and metiianesulphonyl chloride (3.82 ml, 49.35 mmol, 2.1 eq). The mixture was stirred for 4h then stored at 0°C overnight ( 16h). The reaction was filtered and die solids washed widi THF (20 ml). The combined filtrate was evaporated in vacuo and partitioned between 10% aqueous citric acid (60 ml) and EtOAc (150 ml). The organic phase was dried (MgSO4) and evaporated to afford (D4) as a colourless oil, 5.82g (95%). δ (CDCI3) 3.12 (6H,s) 4.00 (2H,dd), 4.18 (2H,dd) and 5.25 (2H,dd). Description 5 (S,S) trans 3,4-Diazidotetrahydrofuran (D5) A mixture of the dimesylate (D4) (5.80g, 22.3 mmol) and litiiium azide (5.46, 111.5 mmol, 2.5 eq) in DMSO (60 ml) was heated at 100-110°C for 40h. After cooling to ambient the reaction was diluted widi water (IL) and extracted widi EtOAc (EL, 2 x 0.75L). The combined organic phase was washed with water (0.5L) and brine (0.5L), dried over MgSO4 and evaporated in vacuo to a pale yellow oil of the title compound, 2.18g (61.5%). δ (CDCI3) 3.75 (2H,dd) and 3.90 - 4.05 (4H,m). Description 6 (S,S) trans 3,4-Diaminotetrahydrofuran To lithium aluminium hydride (2.05g, 54 mmol) in dry THF (150 ml) at 0°C was added the diazide (D5) (2.08g, 13.5 mmol) in THF (50 ml) dropwise over 10 min. After 15 min the solution was allowed to warm to ambient, then stirred for 16h. The reaction mixture was re-cooled to 0°C and quenched sequentially with H2O (2 ml), 15% aqueous NaOH (2 ml) and further H2O (6 ml) and warmed to ambient. After stirring for lh the mixture was filtered through celite, rinsed with THF (2 x 150 ml) and die combined filtrate evaporated in vacuo to afford (D6) as a pale yellow oil, 1.28g (93%). δ (CDCI3) 1.30 (4H,bs), 3.20 (2H,dd), 3.50 (2H,dd) and 4.08 (2H,dd). Description 7 (S,S) trans 3,4-bis(3-/-ert-Butyl-5-methylsalicylideamino)tetrahydrofuran (D7) A solution of the (S,S)-diamine (D6) (1.26g, 12.35 mmol) and 3-tert-butyl-5- methylsalicaldehyde (4.74g, 24.70 mmol) in EtOH (75 ml) was heated at reflux for 3.5h. The solution was cooled and solvent removed in vacuo to afford crude (5) as a yellow oil, 5.50g (99%). A sample of the crude material (4.55g) was chromatographed on silica (Merck 9385, gradient of CHCI3 in hexane) to afford pure (D7) as a yellow foam, 4.39g (95.5% yield). δ (CDCI3) 1.42 (18H,s), 2.25 (6H,s), 3.95 - 4.10 (4H,m) 4.33 (2H,q), 6.90 (2H,d), 7.15 (2H,d), 8.30 (2H,s) and 13.15 (2H,bs). Description 8 (2R- R)-l,4-Dibenzyloxy-2-3-dimethanesuIfonyloxybutane To a solution of (2R,3R)-(+)-l,4-dibenzyloxy-2,3-butanediol (25.3g, 83.7mmol ex Aldrich Chemical Company) in dichloromethane (165ml), cooled in an ice badi, was added metiianesulfbnyl chloride (13.0ml, 167.4 mmol), followed by slow addition of triethylamine (23.3ml, 167.4mmol) such that the temperature did not rise above 5°C. Once the addition was complete the reaction was allowed to stir with ice-badi cooling for 3 hours. Water (600ml) was then added and die organic phase separated. The aqueous phase was re-extracted with dichloromethane (200ml) and die combined organic phases washed with water (400ml) and brine (400ml), dried (MgSO4), and the solvent evaporated to afford a pale yellow solid. Trituration with diediyl etiier afforded die title compound (28.2g, 74%) as colourless crystals m.p. 72- 73°C. l H n.m.r. (CDCl 3 ):δ 3.03 (s,6H,2xCH 3 ), 3.76 (m,4H,2xCH 2 O),4.48 (d,2H,CH 2 Ph), 4.57 (d,2H,CH2Ph), 5.00 (m,2H,2xCH), 7.27-7.39 (m,10H,2xPh) 13 C n.m.r. (CDCl 3 ):δ 38.8 (2xCH 3 ), 68.7 (2xCH 2 ) 73.7 (2xCH 2 ), 78.7 (2xCH), 128.1, 128.2, 128.6, 137.0 (2xPh). EI-MS:m/e 459 (MH+), 367 (M+-CH 2 Ph). 20 H 26°8 S 2 requires: C: 52.39, H:5.72%. found : C: 52.36, H:5.59%. Description 9 (2R,3R)-DimethanesulfonyIoxybutane-l,4-dioI (2R,3R)- 1 ,4-Dibenzyloxy-2,3-dimethanesulfonyloxybutane (27.6g, 60.3mmol) (D8) was dissolved in acetone (500ml), a suspension of 10% Pd/C (29.9g) in acetone (300ml) added, and die mixture hydrogenated at 1 atm. pressure for 2 hours at ambient temperture. The mixture was then filtered ti ree times through a pad of silica and Celite, and the solvent evaporated to give the tide compound as a straw- coloured oil (14.7g, 87%), which solidified on standing. IH n.m.r. (DMSO-d 6 ):δ 3.24 (s,6H,2xCH 3 ), 3.69 (m,4H,2xCH 2 ),4.76 (m,2H,2xCH), 5.33 (t,2H,2xOH). 13c n.m.r. (DMSO-d 6 ):δ 38.1 (2xCH 3 ), 59.7 (2xCH 2 ), 80.3 (2xCH). EI-MS:m/e 279 (MH+), 261 (MH+-H 2 O), 183 (M+-OMs), 165 (M+- OMs,H 2 0). Description 10 (6R,7R)-Dimethanesulfonyloxy-2,4,9,ll-tetraoxadodecane (2R,3R)-Dimethanesulfonyloxybutane-l,4-dιol (14.7g, 52.9 mmol) (D9) was dissolved in dimethoxymethane (89.5ml) and dichlorometiiane (30ml) at 40°C. Lithium bromide (0.91g) and p-toluenesulfonic acid monohydrate (l.Olg, 5.29mmol) were added, and die mixture heated under reflux for 3 hours. The reaction was allowed to cool to ambient temperature, and then poured into saturated sodium bicarbonate solution (200ml), extracted widi ediyl acetate (2x200ml), dried (MgSO4) and evaporated to give a colourless oil. This was purified by column chromatography on silica, during with 0-1% methanol in dichlorometiiane, to afford the title compound as a colourless oil (8.2g, 42%). ■ 1H n.m.r. (CDCl 3 ):δ 3.13 (s,6H,2xCH 3 ), 3.39 (s,6H,2xOCH3), 3-87 (m,4H,2xCH 2 ),4.66 (m,4H,2xOCH 2 O), 5.02 (m,2H,2xCH). 13 C n.m.r. (CDCl 3 ):δ 38.8 (2xSCH 3 ), 55.8 (2xOCH ), 66.1 (2xCH 2 ), 78.4 (2xCH), 96.8 (2xOCH 2 O) CI-MS:m/e 384 (MNH4- 4 -). 10 H 22°10 S 2 requires: C: 32.78, H:6.05%. found : C: 32.22, H:5.62%. Description 11 (5R,6R)-Dimethanesulfonyloxy-l,3-dioxepane A solution of (6R,7R)-dimetiιanesulfonyloxy-2,4,9,ll-tetraoxadodecane (8.2g, 22.4mmol) (D10) and p-toluenesulfonic acid monohydrate (0.26g, 1.34mmol) in toluene (165ml) was heated under reflux overnight. The solvent was evaporated and the brown residue triturated with diediyl ether to afford die title compound as an off-white solid (5.9g, 91%) m.p. 133-134°C. l H n.m.r. (CDCl3):δ 3.13 (s,6H,2xCH3), 3.84 (m,2H,CH 2 ),4.06 (m,2H,CH2), 4.77 (s,2H,OCH 2 O), 4.81 (m,2H,2xCH). 13c n.m.r. (CDCl ):δ 38.8 (2xCH ), 64.1 (2xCH 2 ) 78.3 (2xCH), 94.6 (OCH 2 O) EI-MS:m/e 291 (MNH + ).195 (M+-OMs). C 7 H 14°8 S 2 requires: C: 28.96, H:4.86%. found : C: 29.22, H:4.61%. Description 12 (5R,6R)-Diazido- 1,3-dioxepane A mixture of (5R,6R)-dimetiιanesulfonyloxy-l,3-dioxepane (5.0g, 17.2mmol) Dll and lithium azide (4.2g, 86mmol) in dimethylsulphoxide (60ml) was stirred and heated to 110-120°C overnight. The reaction mixture was then cooled, poured into water (200ml), and extracted with etiryl acetate (2x150ml). The combined organic phases were washed with water (2x150ml) and brine (150ml), dried (MgSO4) and evaporated to give the title compound as a brown oil (2.7g, 85%). H n.m.r. (CDCl3):δ 3.49 (m,2H,2xCH), 3.74 (m,2H,2xCH 2 ), 3.93 (m,2H,CH2), 4.73 (s,2H,OCH 2 O). 13C n.m.r. (CDCl3):δ 64.3 (2xCH), 64.6 (2xCH 2 ) 94.3 (OCH 2 O). EI-MS:m/e 185 (MH+), 157 (MH+-N2), 142 (M+-N 3 ). C 5 HgN 6 O2 requires: C: 32.61, H:4.38, N:45.63%. found : C: 32.33, H.4.67, N:45.38%. Description 13 (5R,6R)-Diamino-13-dioxepane To a slurry of lithium aluminium hydride (2.1g, 55.3mmol) in dry tetrahydrofuran (70ml) at 0°C under an argon atmosphere was added dropwise a solution of (5R, 6R)-Diazido-l,3-dioxepane (2.6g, 14.1mmol) (D12) in dry tetrahydrofuran (50ml). During the addition the reaction temperature was maintained below 10°C with an ice-salt bath. One completion, die reaction mixture was allowed to warm to ambient temperature, and stirred for a further 1.5 hours. It was then re- cooled and die reaction quenched by addition of water (2ml), 2M NaOH (2ml), and water (4rnl), the temperature again being maintained below 10°C by means of an ice- salt bath. The quenched reaction mixture was allowed to warm to ambient temperature, stirred for a further 2 hours, then filtered through Celite, and die filter pad washed well widi tetrahydrofuran. The combined filtrates were evaporated to afford the title compound as a pale yellow oil (1.3g, 70%). !H n.m.r. (CDCl3):δ 1.56 (brs,4H,2xNH3), 2.62 (m,2H,2xCH),3.58 (m^H,CH 2 ), 3.77 (m,2H,2xCH 2 ), 4.72 (s,2H,OCH 2 O) 13c n.m.r. (CDCl3):δ 57.9 (2xCH), 67.5 (2xCH 2 ) 93.8 (OCH 2 O). C5H12N2O2 requires: C: 45.44, H:9.15, N:21.20%. found : C: 45.13, H:8.76, N: 19.58%. EI-MS:m/e 133 (MH+), 116 (M+-NH 2 ) + , 90 (M-2NH 2 ) + . Description 14 Preparation of (5R,6R)-Di-(3,5-di-tert-butyI) salicyIidenamino-l-3-dioxepane (5R,6R)-Diamino-l,3-dioxepane (l.Og, 7.6mmol) (D13) and 3,5-di-tert- butylsalicaldehyde (3.6g, 15.4mmol, 2eq.) were dissolved in ed anol (100ml), and die solution stirred under reflux for 3 hours. The reaction mixture was then allowed to cool, the solvent was evaporated, and die residue purified by column chromatography on silica, eluting with 4% diethyl ether in hexane. This afforded die title compound as a bright yellow foam (3.5g, 82%). IH n.m.r. (CDCl 3 ):δ 1.23 (s,18H,6xCH ), 1.41 (s,18H,6xCH 3 ),3.85 (m,2H,CH2), 4.07 (m,2H,CH 2 ), 4.87 (s,2H,OCH 2 O), 6.99 (d,2H,Ar), 7.33 (d,2H,Ar), 8.33 (s,2H,2xCH=N), 13.20 (brs, 2H,2xOH). 13c n.m.r. (CDCl3):δ 29.4 (6xCH 3 ), 31.4 (6xCH 3 ) 34.1 (2x£CH 3 ), 35.0 (2x£CH 3 ),.67.7 (2xCH), 73.8 (2xCH 2 ), 94.2 (OCH 2 O), 117.6, 126.4, 127.4, 136.6, 140.3, 157.9 (Ar), 168.4 (2xC=N) C35H52N2O4 requires: C: 74.43, H:9.28, N:4.96%. found : C: 74.56, H:9.15, N: 4.92%. CI-MS:m/e 565 (MH+). Description 15 (3R, 4R)-Diacetoxytetrahydropyran (D15) A solution of 3,4-di-O-acetyl-D-Xylal (11.16g) in 50% aqueous ethanol (400ml) containing Ptθ2 (400mg) was hydrogenated at atmospheric pressure for 3.5 hours at 25°C. The suspension was filtered through celite, washed with 50% aqueous ethanol (50ml) and water (50ml), and the combined filtrate evaporated in vacuo to afford the title compound as a colourless oil, 9.6g (85%). δ (CDCI3): 1.30-1.50 (lH,m), 2.10 (6H,S), 2.10-2.20 (lH,m), 3.35-3.60 (2H,m). 3.80-4.00 (2H,m) and 4.80-5.00 (2H,m). 2. Dictionary of Organic Compounds, 5th Edition, 1982, Chapman & Hall, London, 579 and references therein. Description 16 (3R,4R)-Dimethanesulfonyloxytetrahydropyran(D16) Sodium (~50mg) was dissolved in methanol (100ml) at ambient. To the resulting solution was added a solution of the diester (D15) (9.56g, 47.3mmol) in methanol (100ml) and the mixture stirred for 72 hours. Amberlite IR 120H + resin (20g) was added and the mixture filtered. Concentration of the filtrate in vacuo afforded the diol as a colourless oil. This was dissolved in a mixture of tetrahydrofuran (220ml) and diethyl ether (220ml). Triethylamine (10.86g, 107.5mmol,) was added and the solution cooled to 0°C. Methanesulphonyl chloride (11.76g, 102.7mmol) was added dropwise at 0°C, die solution was stirred for a further hour then stored at 4°C for 16 hours. The resulting suspension was filtered and die solids washed widi tetrahydrofuran (2x95ml) and diediyl ether (2x180ml). The combined filtrate was evaporated in vacuo and die residue partitioned between ethyl acetate (200ml) and 10% aqueous citric acid (200ml). The organic phase was dried (MgSO4), filtered and concentrated in vacuo to a colourless foam to afford the title compound, 12.07g (93%). δ (CDCI3): 3.10 (6H,s), 2.00-2.40 (2H,m), 3.40-4.20 (4H,m), 4.55-4.65 (lH,m) and 4.70-4.85 (lH,m). Description 17 (3R,4S)-Diaminotetrahydropyran (D17) The dimesylate (D16) (12.07g, 44 mmol) was dissolved in dimediylsulphoxide (88ml) and treated wid lidiium azide (10.8g, 220mmol). The mixture was heated at 100°C for 40 hours, then cooled to ambient and poured into water (1.03L) and extracted widi etiiyl acetate (1.03L, 2 x 0.59L). The combined organic phase was washed widi water (300ml) and brine (300ml), dried over MgSO4 and concentrated in vacuo to give die crude diazide as a brown oil, 3.7g. This was dissolved in tetrahydrofuran (45ml), and added dropwise to a cold (0°C) suspension of lidiium aluminium hydride (3.34g, 88mmol) in tetrahydrofuran (220ml), maintaining the temperature below +10°C. After completion of addition the suspension was stirred at 0°C for 0.5 hours then warmed to ambient and stirred for 16 hours. The mixture was recooled to 0°C and quenched sequentially widi water (3.34ml) in tetrahydrofuran (5ml), 15% aqueous sodium hydroxide (3.34ml) and further water (10ml). The mixture was allowed to warm to ambient, stirred for one hour then filtered through celite, rinsing with tetrahydrofuran (2x400ml). The combined filtrate was concentrated in vacuo to give the title diamine (3) as a colourless oil, 2.62g (51%). δ (CDCI3): 1.20-1.90 (6H,m), 2.40-2.50 (2H,m), 2.90-3.40 (2H,m) and 3.80-4.00 (2H,m). Description 18 (3R,4S)-bis-(3^-Di-tert-Butylsalicylideamino)tetrahydropyran, (D18) To the diamine (D17) (2.55g, 22mmol) in ethanol (220ml) was added 3,5-di- tertbutylsalicaldehyde (10.3g, 44mmol). The mixture was heated at reflux for 2 hours, cooled to ambient filtered, and die crystalline product dried in vacuo to afford the title compound as yellow crystals, 4.8 lg, (40%). δ (CDCI3): 1.20 (18H,s), 1.40 (18H,s), 1.50-2.20 (2H,m), 3.50-3.70 (4H,m), 4.00-4.15 (2H,m), 7.00 (2H,bs), 7.35 (2H,bs), 8.33 (lH,s), 8.37 (lH,s) and 13.20 (2H,bs). Description 19 (3R,4S)-bis (3- rt-Butyl-5-methyIsalicylideamino) tetrahydropyran (D19) A solution of the diamine (D17) (0.62g, 5.35mmol) and 3-tertbutyl-5- mediylsalicaldehyde (2.05g, 10.7mmmol) in ethanol (40ml) was heated at reflux for 2 hours. The solution was cooled tiien stored at 4°C for 70 hours to afford a yellow precipitate. This was filtered, washed wid cold 95% aqueous ethanol (5ml) and dried in vacuo to afford d e title compound, 1.22g (49%). δ (CDCI3): 1.40 (18H,s), 1.80-2.20 (2H,m), 2.20 (6H,s), 3.40-3.70 (4H,m), 4.00-4.20 (2H,m), 6.80 (2H,bs), 7.05 (2H,bs), 8.27 (lH,s), 8.30 (lH,s) and 13.30 (2H,bs). Description 20 (3S,4S)-bis (3,5-di-tert-ButylsaIicyIideamino) tetrahydrofuran (D20) A solution of (S,S)-diamine (D6) (0.96g, 9.4mmol) and 3,5-di- tertbutylsalicaldehyde (4.4g, 18.8mmol) in ethanol (90ml) was heated at reflux for 2 hours. The mixture was cooled to 0°C, filtered and die solids washed widi cold ethanol and dried to afford die title compound as yellow crystals, 3.07g (61%). δ (CDCI3): 1.27 (18H,s), 1.45 (18H,s), 3.95-4.10 (4H,m), 4.30-4.40 (2H,m), 7.05 (2H,d), 7.40 (2H,d), 8.35 (2H,s) and 13.20 (2H,s). Description 21 (3S,4R)-Dihydroxy-(2R)-(hydroxymethyl)tetrahydropyran (D21) A solution of D-Glucal (16.0g, 0.11 mole) in 50% aqueous ethanol (500ml) was treated with platinum oxide (0.75g) and hydrogenated at ambient at atmospheric pressure for 5 hours. The suspension was treated with charcoal (50g) filtered tiirough celite (200g) and the solids washed with 50% aqueous ethanol (300ml). The combined filtered was evaporated in vacuo and dried over P2O5 to afford the title compound as a colourless oil, 16.0g (99%). δ (CD3OD): 1.50-1.70 (lH,m), 1.80-2.20 (lH,m), 3.00-3.20 (2H,m), 3.30- 3.70 (3H,m), 3.80-4.00 (2H,m) and 4.90 (3H,bs) 3. Dictionary of Organic Compounds, 5dι Edition, 1982, Chapman and Hall, London, 2754, and references therein. Description 22 (3S,4R)-Dihydroxy-(2R)-(triphenylmethoxvmethyI) tetrahydropyran (D22) A solution of die triol (D21) (1.76g, 11.9mmol) in pyridine (20ml) was treated widi trityl chloride (3.3 lg, 11.9mmol) and 4-(dimedιylamino)pyridine (50mg). Diisopropylediylamine (1.92g, 14.8mmol, 1.25eq) was added and the solution stirred for 4 hour at ambient temperature. The mixture was poured into water (200ml) and extracted wid dietiiyl ether (2x200ml). The combined organic phase was washed with 10% aqueous citric acid (100ml) and brine (100ml), dried over MgSO4 and cencentrated in vacuo to an oil. The residue was chromatographed on silica (eluent: gradient of methanol in chloroform) to afford die title compound as a colourless foam, 3.70g (79.7%). δ (CDCI3): 1.60-1.80 (lH,m), 1.90-2.00 (lH,m), 2.70 (2H,bs,D 2 O exch), 3.25-3.50 (5H,m), 3.60-3.70 (lH,m), 3.90-4.00 (lH,m) and 7.20-7.50 (15H,m). Description 23 (3R,4R)-DimethanesulphonyIoxy-(2R)- (triphenylmethoxymethyl)tetrahydropyran (D23) To the diol (D22) (3.10g, 7.95mmol) in a mixture of dietiiyl etiier and tetrahydrofuran (2:1, 150ml) was added triethylamine (1.76g, 17.5mmol). The mixture was cooled to 0°C and medianesulphonyl chloride (1.91g, 16.7mmol) added. After 2 hours the suspension was filtered and die filtrate concentrated in vacuo, tiien redissolved in ethyl acetate (200ml). The solution was washed with 10% aqueous citric acid (100ml) and brine (50ml), then dried over MgSO4. Solvent was removed in vacuo and the residue dried to afford (12) as a colourless solid, 4.26g (95%). δ (CDCI3): 2.20-2.50 (2H,m), 2.50 (3H,s), 3.10 (3H,s), 3.20-3.30 (lH,m), 3.40-3.60 (3H,m), 3.95-4.10 (lH,m), 4.70-4.80 (2H,m) and 7.20-7.50 (15H,m). Description 24 (3S,4S)-bis(3,5-Di-tert-butylsalicylideamino)-(2R)-(triphenyl methoxymethyl)tetrahydropyran (D24) A mixture of the dimesylate (D23) (2.85g, 5.22mmol) and lithium azide (1.28g, 26.1mmol) in dimethyl sulphoxide (20ml) was heated at 100-110°C for 24 hour. The solution was cooled, poured into water (200ml) and extracted with ethyl acetate (2x300ml). The combined organic phase was washed with water (2x300ml) and brine (300ml), and dried over MgSO4- Removal of the solvent afforded die intermediate diazide as a yellow foam (1.52g). A 1.40g portion of the diazide in tetrahydrofuran (10ml) was added to a suspension of lithium aluminium hydride (470mg, 12.4mmol) in tetrahydrofuran (30ml) at 0°C. After stirring at 0°C for 1 hour the mixture was allowed to warm to ambient and stirred for 16 hours. The suspension was recooled to 0°C and quenched sequentially widi water (0.5ml), 15% aqueous sodium hydroxide (0.5ml) and further water (1.5ml). After warming the ambient and stirring for 1 hour the mixture was filtered, die solids washed widi tetrahydrofuran (2x20ml) and die combined filtrate evaporated to afford die crude diamine as a foam (1.28g). A portion of the diamine (1.18g) and 3,5-di-tert butylsalicaldehyde (1.42g, 6.08mmol) in ethanol (30ml) was heated at reflux for 4 hour then cooled to ambient. Solvent was removed in vacuo and die residue chromatographed on silica (eluent: gradient of chloroform in hexane) to afford die title compound as a yellow powder, 210mg, in 8.4% overall yield from (D23). δ (CDC1 3 ): 1.25 (9H,m), 1.30-1.60 (2H,m), 1.32 (9H,s) 1.40 (9H,s), 1.50 (9H,s), 2:40-2.55 (lH,s), 2.70-2.80 (lH,s), 3.30-3.60 (2H,m), 3.90-4.30 (3H,m), 6.85 (lH,bs), 7.00-7.35 (16H,m), 7.38 (lH,bs), 7.45 (lH,bs), 8.30 (lH,s), 8.50 (lH,s), 13.25 (lH,s) and 13.50 (lH,s). Description 25 (±)trans-l-BenzoyI-3,4-bis(methanesulphonyloxy)piperidine (D25) (±)trans-l-Benzoylpiperidine-3,4-diol (3g, 13.6mmol) was suspended in dichlorometiiane (70ml) and triethylamine (5.74ml, 43mmol) was added. The mixture was cooled to -10°C and methanesulphonyl chloride (2.6ml, 34mmol) added over 5 min. After a further 15 min the mixture was poured into ice-water (50ml) and the organic layer washed with 5% aqueous citric acid (30ml). The solution was dried over MgSO4 and concentrated in vacuo to a foam, 5.3g (100%). δ H (CDC1 3 ):1.95 (2H,m), 2.30 (2H,m),3.15 (6H,s), 4.70 (2H,m), 4.85 (2H,m) and 7.45 (5H,m). 4. V. Petrow and O. Stepehnson, J Pharm. Pharmacol, 1962, J_4, 306-314. Description 26 (±)trans-l-Benzoyl-3,4-diazidopiperidine (D26) A mixture of the dimesylate (D25) (5.3g, 14mmol) and lithium azide (3.4g, 69mmol) in dimethylsulphoxide (36ml) was heated at 100°C for 18 hours. After cooling the reaction mixture was partitioned between dichloromethane (200ml) and water (50ml). The aqueous phase was separated and further extracted with dichloromethane (100ml, 50ml) and the combined organic extracts washed with water (3x50ml), dried (Na2SO4) and concentrated in vacuo. The residue was chromatographed on silica (eluent: gradient of metiianol in dichlorometiiane) to afford the title compound as a colourless solid, 900mg (24%). δ H (CDC1 ):1.60 (2H,m), 2.10 (2H,m),3.05 (2H,m), 3.20 (2H,m) and 7.40 (5H, m). Description 27 (±)trans-l-Benzoyl-3,4-diaminopiperidine (D27) A solution of the diazide (D26) (450mg, 1.7mmol) in ethanol (30ml) was treated widi Lindlar catalyst (5%Pd/ CaCO3, 250mg) and stirred under hydrogen ( 1 atm) for 24 hour. The mixture was filtered and solvent removed in vacuo to afford die title compound as oil, 350mg (94%). δ H (DMSO):1.20 (lH,m), 1.65-1.80 (2H,m),2.20 (2H,m), 2.70 (lH,m), 3.00 (lH,m), 3.30 (lH,m), 4.40 (lH,m) and 7.40 (5H,m). Description 28 (•)trans-l-Benzoyl-3,4-bis(3^-di-tert-butylsaIicyIideamino)piperidine (D28) A solution of the amine (D27) (350mg, 1.6mmol) and 3,5-di- tertbutylsalicaldehyde (960mg, 4.1 mmol) in ethanol (40ml) was heated at reflux for 3 hours. The mixture was cooled and filtered to afford d e racemic bis-imine, 652mg (63%). A lOOmg sample was separated by chiral hplc (CHIRALPAK AD, eluent 2% ethanol in hexane) to afford die title compound as a single enantiomer, rαi 2 D 5 - 228° (c=0.13, CHCl 3 ). δ H (CDC1 3 ):1.20 (18H,s), 1.45 (18H,s), 2.00 (2H,m), 3.25 (2H,m), 3.45 (lH,m), 3.55 (lH,m), 4.35 (2H,m), 6.95 (2H,s), 7.40 (7H,m), 8.30 (2H,s) and 13.15 (2H,bs). Example 1 (±) 3,4-bis (3-tert ButyI-5-methylsalicyIideamino) tetrahydrofuran manganese (IH) chloride (El) A suspension of the racemic ligand (D3) (690 mg, 1.53 mmol) in EtOH (25 ml) was heated with Mn(OAc)2- H2θ (750 mg, 3.06 mmol) at reflux for 18h. LiCl (195 mg, 4.49 mmol) was added and reflux continued for a further 0.5h. Solvent was removed in vacua and die residue chromatographed on silica (Merck 9385, lOOg) eluting widi a gradient of MeOH in CHCI3, to afford the title compound as a brown powder (90 mg, 11%) together widi unreacted (D3), 420 mg (61% recovery). Example 2 The epoxidation of 2,2-dimethyl-6-pentafluoroethyI-2H-l-benzop ran using (El) to give (±) 2,2-dimethyI-3,4-epoxy-6-pentafluoroethyl-2H-l-benzopyran (E2) Aqueous sodium hypochloride solution (16.75% w/v, 4.44 ml, 2 eq) was diluted to 12.5 ml with H2O. 0.05M Na2HPO4 (aq) (5 ml) was added and th pH adjusted to 11.3. The resulting solution was cooled to 0°C and added to a solution of 2,2-dimetiιyl-6-pentafluoroethyl-2H-l-benzopyran (1.39g, 5 mmol) and the catalyst (El) (45 mg, 0.1 mmol, 2 mol%) in CH2CI2 (5 ml). The mixture was stirred at 0°C for lh then allowed to warm to room temperature and stirred for a further 16h. Hexane (50 ml) and H2O (25 ml) were added and the organic layer separated. The aqueous phase was washed wid hexane (50 ml) and die combined organic phase dried over MgSO4 anα ' concentrated in vacua to give a pale yellow oil, 1.42g. Quantitive hplc analysis showed this to contain 1.08g (74%) of the desired epoxide (E2) together with a trace (<5% recovery) of starting material both compounds identical (IH nmr) with authentic samples. Example 3 (S,S) trans 3,4-bis (3-tert Butyl-5-methylsalicyIideamino)tetrahydrofuran manganese (III) chloride (E3) Method A (using manganese (II) acetate) A solution of (D7) (0.95g, 2.11 mmol) and Mn(OAc)2-4H2θ (1.03g, 4.22 mmol) in EtOH (40 ml) was heated at reflux for 17h. Lithium chloride (268 mg, 6.33 mmol) was added and reflux continued for a further 0.5h. After cooling to ambient the solvent was removed in vacuo and die residue chromatographed on silica (Merck 9385, gradient of MeOH in CHCI3) to afford (E3) as a brown powder, 26 mg (2.3%), together widi unreacted (D7), 683 mg (72%). Method B (using manganese (III) acetate)5. A solution of (D7) (1.53g, 3.4 mmol) in a mixture of CH2CI2 (17 ml) and MeOH (17 ml) was treated with Mn(OAc)3-2H2θ (O.Olg, 3.4 mmol). The mixture was heated at reflux for 3h, cooled to ambient and treated widi lithium chloride (0.2 lg, 5.1 mmol). After stirring for 16h the solvent was reduced in vacuo to ca. 8 ml, Et2θ (70 ml) was added and die suspension stirred for lh. The mixture was filtered and die solids washed widi Et2θ (3 x 20 ml) and dried in vacua to afford (E3) as a brown powder, 1.57g (86%). 5 T. Matsushita and T. Shono, Bull. Chem. Soc. Japan, 1981, 54, 3743-3748. Example 4 The chiral epoxidation of 2,2-dimethyl-6-pentafluoroethyI-2H-l-benzopyran using (E3) to give (3R,4R)-2,2-dimethyl-3,4-epoxy-6-pentafluoroethyl-2H-l- benzopyran (E4) Aqueous sodium hypochlorite solution (16.75% w/v, 8.9 ml 20.0 mmol) was diluted to 25 ml with H 2 O. 0.05M NaH 2 PO4 (aq) (10 ml) was added and the pH adjusted to 11.3. The resulting solution was cooled to 0°C and added to a solution of 2,2-dimetiιyl-6-pentafluoroethyl-2H-l-benzopyran (2.78g, 10.0 mmol) and die catalyst (E3) (0.108g, 0.2 mmol, 2 mol%) in methylene chloride (10 ml). The mixture was stiπed at 0°C for lh then allowed to warm to room temperature and stirred for a further 20h. Hexane (100 ml) and H2O (50 ml) were added and the organic layer separated. The aqueous phase was washed with hexane (100 ml) and die combined organic phase dried over MgSO4 and concentrated in vacuo to give a pale yellow oil, 2.86g. Quantitative hplc analysis showed this to contain 2.09g, (71%) of the desired epoxide (E4) and a small quantity (about 10%) of starting material, both compounds identical ( H NMR, TLC, HPLC) with authentic samples, e.e. = 66% by chiral HPLC. Example 5 Preparation of (R,R)-5,6-bis-(3,5-di-tert-butylsaIicylidenamino)-l,3-dioxepane]- mangenese (III) chloride (5R,6R)-Di-(3,5-di-tert-butyl)salicylidenamino-l,3-dioxepane (l.Og, 1.77mmol) (D14) and manganese (II) acetate tetrahydrate (2.17g, 8.87mmol) were suspended in 95% ethanol (50ml), and the mixture stirred under reflux overnight. Lithium chloride (0.38g, 8.96mmol) was dien added and heating continued for a further 30 minutes. The reaction mixture was then cooled, water (60ml) added, and filtered through Celite. The dark precipitate was washed well with water, then dissolved in dichloromethane (80ml), dried (MgSO4), and d e solvent evaporated to give the tide compound as a dark brown solid (0.9g, 78%). C35H5θN 2 O 4 MnCl requires: C:64.36, H:7.72, N:4.29%. found: C: 64.57, H: 7.57, N: 4.09% CI-MS: m/e 565 (MH-Mn,Cl) + , 235 (3,5-di-tert-butylsalicaldehydeH)+. Example 6 Preparation of (3S,4S)-2-2-dimethyI-3,4-epoxy-6-pentafluoroethyl-2H-l- benzopyran by oxidation of 2,2-dimethyl-6-pentafluoroethyI-2H-l-benzopyran using sodium hypochlorite catalysed by (R,R)-5,6-bis-(3,5-di-tert- butylsalicyIideamino)-l,3-dioxepane]-manganese (III) chloride Sodium hypochlorite solution (11.4% w/v, 13.1ml, 2eq.) was diluted to 25ml with water, followed by die addition of 0.05 molar sodium dihydrogen phosphate (10ml). The pH of this solution was adjusted to 11.3 with 2 molar aqueous sodium hydroxide, and it was then added to a solution of 2,2-dimetiιyl-6-pentafluoroethyl- 2H-l-benzopyran (2.78g, lOmmol), and (R,R)-[l,2-bis-(3,5-di-tert- butylsalicylidenamino)- 1 ,3-dioxepane]-manganese (IH) chloride (0.131 g, 2mol%) in dichlorometiiane (10ml), which had been cooled in an ice bath. The reaction mixture was allowed to warm to ambient temperature and stirred for 22 hours, by which time die reaction was essentially complete. The reaction mixture was diluted with water (50ml) and hexane (100ml), filtered tiirough Celite, the organic phase separated and the aqueous extracted with a further portion of hexane (100ml). The combined organic phases were dried (MgSO4) and evaporated to give the title compound as a yellowish solid (2.6g, 88%). Hplc determination of the chiral purity of the crude product gave an e.e. of 86.0%. The crude product was recrystallised from hexane to afford colourless crystals, m.p. 72-73°C. l H n.m.r.(CDCl 3 ):δl.29 (s,3H,CH 3 ), 1.59 (s,3H,CH 3 ), 3.53 (d,lH,H-3), 3.94 (d,lH,H-4), 6.90 (dd,lH,H-8), 7.46 (dd,lH,H-7), 7.57 (dd,lH,H-5). 13c n.m.r. (CDCI3): δ 22.9 (CH3), 25.5 (CH3), 50.4 (C-3), 62.5 (C-4), 74.1 (C-2), 113.4 (tq,CF 3 ), 118.4 (C-8), 119.1 (qt, CF 2 ), 120.4 (C-4'), 121.1 (t,C-6), 128.1, 128.6 (2xt,C-5,7), 155.7(C-8'). EI-MS:m/e 294 M+, 279 (M-CH3)+. C13H11F5O2 requires: C53.07, H: 3.77%. found: C:52.69, H: 3.82%. Example 7 (3R,4S)-bis-(3-5-di-tert-butylsaIicylideamino)tetrahydropyran-manganese (III) chloride (E7) A solution of the ligand (D 18) (4.81 g, 8.8mmol) in dichloromethane-methanol (1:1, 88ml) was treated widi maganese triactate dihydrate (2.35g, 8.8mmol) and die mixture heated at reflux for 4 hours. Lidiium chloride (0.56g, 13.2mmol) was added and heating at reflux continued for a further 1 hour. The mixture was cooled, concentrated in vacuo and die residue triturated widi diethyl etiier (220ml). The solid product was filtered, washed widi dietiiyl etiier (2 x 65ml) and dried to afford (5) as a brown powder, 5.3g (94%). Example 8 The chiral epoxidation of 2,2-dimethyI-6-pentafluoroethyl-2H-l-benzopyran using (E7) to give (3S,4S)-2,2-dimethyl-3,4-epoxy-6-pentafluoroethyl-2H-l- benzopyran (E8) Aqueous sodium hypochlorite (15.24% w/v, 9.8ml, 20mmol) was diluted to 25ml with H20. 0.05M NaH2PO4(aq) (10ml) was added and the pH adjusted to 11.3. The resulting solution was cooled to 0°C and added to a solution of 2,2-dimetiιyl-6- pentafluoroedιyl-2H-l-benzopyran (2.78g, lOmmol), and die catalyst (E7) (127mg, 0.2mol%) in dichloromethane (10ml). The mixture was stirred at 0°C for 1 hour then allowed to warm to ambient and stirred for a further 18 hours. Hexane (100ml) and water (50ml) were added and the organic layer separated. The aqueous phase was washed widi hexane (100ml) and die combined organic phase dried over MgSO4 and concentrated in vacuo to afford a yellow solid (2.60g). Quantitative hplc analysis showed diis to contain 2.47g (84%) of the desired epoxide (E8), identical ( H nmr, tic, hplc) with an authentic sample, ee=88.4% by chiral hplc. Example 9 (3R,4S)-bis-(3-tert-butyl-5-methylsalicyIidenamino)tetrahydropyran-manganese (IH) chloride (E9) A solution of the ligand (D19) (928mg, 2mmol) in dichloromediane-methanol (1:1, 20ml) was treated with manganese triacetate dihydrate (536mg, 2mmol) and heated at reflux for 3 hours. The mixture was cooled to ambient, lithium chloride (128mg, 3mmol) was added and the solution stirred for 1 hour. The reaction mixture was concentrated in vacuo and die residue triturated with diethyl ether (40ml). The solid product was filtered, washed with diethyl ether (2 15ml) and dried in vacuo to afford the title compound as a brown powder, 1.09g (98%). Example 10 The chiral epoxidation of 2,2-dimethyl-6-pentafluoroethyl-2H-l-benzopyran using (E9) to give (3S,4S)-2,2-dimethyl-3,4-epoxy-6-pentafluoroethyl-2H-l- benzopyran (E8) Aqueous sodium hypochlorite (15.24% w/v, 9.8ml, 20mmol) was diluted to 25ml with H20. 0.05M NaH2PO4(aq) (10ml) was added and the pH adjusted to 11.3. The resulting solution was cooled to 0°C and added to a solution of 2,2-dimethyl-6- pentafluoroethyl-2H-l -benzopyran (2.78g, lOmmol) and die catalyst (E9) (lllmg, 0.2mmol, 2mol%) in dichloromethane (10ml). The mixture was stirred at 0°C for 1 hour then allowed to warm to ambient and stirred for a further 18 hour. Hexane (100ml) and water (50ml) were added and die organic layer separated. The aqueous phase was washed with hexane (100ml) and the combined organic phase dried over MgSO4 and concentrated in vacuo to give (E8) as a yellow oil (2.72g, 93%), identical (1H nmr, tic, hplc) widi an authentic sample, ee=73% by chiral hplc. Example 11 (3S,4S)-bis-(3,5-di-tert-Butylsalicylideamino)tetrahydrofuran-manganese (III) chloride (Ell) A solution of the ligand (D20) (1.07g, 2mmol) and manganese triacetate dihydrate (536mg, 2mmol) in a mixture of dichlorometiiane and methanol (1:1, 20ml) was heated at reflux for 6.5 hour. The solution was cooled to ambient, lithium chloride (128mg, 3mmol) was added and die mixture stirred for 16 hours. The reaction mixture was concentrated in vacuo and the residue triturated widi diethyl etiier (50ml). The solid product was filtered, washed widi dietiiyl ether (2x15ml) and dried in vacuo to afford the title compound as a brown powder, 1.12g (89%). Example 12 The chiral epoxidation of 2,2-dimethyI-6-pentafluoroethyl-2H-l-benzopyran using (Ell) to give (3R,4R)-2,2-dimethyl-3,4-epoxy-6-pentafluoroethyI-2H-l- benzopyran (E4) Aqueous sodium hypochlorite (15.24% w/v, 9.8ml, 20mmol) was diluted to 25ml with H 2 0.0.05M NaH 2 PO4(aq) (10ml) was added and the pH adjusted to 11.3. The resulting solution was cooled to 0°C and added to a solution of 2,2-dimethyl-6- pentafluoroethyl-2H-l -benzopyran (2.78g, lOmmol) and the catalyst (El l) (124.5mg, 0.2mmol, 2mol%) in dichloromethane (10ml). The mixture was stirred at 0°C for 1 hour then allowed to warm to ambient and stirred overnight. Hexane (100ml) and water (50ml) were added and die organic layer separated. The aqueous phase was washed with hexane (100ml) and die combined organic phase dried over MgSO4 and concentrated in vacuo to a yellow oil, 2.73g. Quantitative hplc analysis showed this to contain 2.47g (84%) of die desired expoxide (E4), identical ( H nmr, tic, hplc) with an authentic sample, ee=85.6% by chiral hplc. Example 13 (3R,4S)-bis-(3,5-Di-tert-ButylsaIicylidenaminoM2R)- (triphenylmethoxymethyl)tetrahydropyran-manganese (III) chloride (E13) To the ligand (D24) (160mg, 195μmol) in dichloromethane-medianol (3:2, 5ml) was added NaOH (0.93ml of 0.417 molar in metiianol, 390 μmol) and manganese triacetate dihydrate (52.5mg, 195 μmol). The solution was heated at reflux for 3 hours, lithium chloride (12.5mg, 300 μmol) added and the mixture stirred for 15 hours. Solvent was removed in vacuo and the residue triturated wid dietiiyl etiier (10ml). The solid product was filtered, washed with dietiiyl etiier (2x2ml) and dried widi afford die title compound as a brown powder, 136mg (77%). Example 14 The chiral epoxidation of 2,2-dimethyl-6-pentafluoroethyl-2H-l-benzopyran using (E13) to give (3S,4S)-2,2-dimethyl-3,4-epoxy-6-pentafluoroethyI-2H-l- benzopyran (E8) Aqueous sodium hypochlorite (11.4% w/v, 2.6ml, 4mmol) was diluted to 5ml with water. 0.05M NaH2PO4(aq) was added and the pH adjusted to 11.3. The resulting solution was cooled to 0°C and added to a solution of 2,2-dimethyl-6- pentafluoroethyl-2H-l -benzopyran (560mg, 2mmol) and die catalyst (El 3) (36mg, 0.04mmol) in dichlorometiiane (2ml) at 0°C. The reaction was stirred for 1 hour at 0 °C then at room temperature overnight. Hexane (20ml) and water (10ml) were added and the organic layer separated. The aqueous phase was extracted with further hexane (20ml) and the combined organic phase dried (MgSO4) and die solvent removed in vacuo to afford (E8) as a yellow oil (0.55g). Quantitative hplc analysis showed this to contain 0.496g (84%) of the desired epoxide (E8), identical ( H nmr, tic, hplc) with an authentic sample, ee=84% by chiral hplc. Example 15 (-)trans-l-BenzoyI-3,4-bis(3,5-di-tertbutylsalicyIideamino) piperidine-manganese (III) chloride (E15) A mixture of the (-) ligand (D28) (20mg, 0.013mmol) and manganese triacetate dihydrate (lOmg, 0.037mmol) in dichloromediane-methanol (3:2, 5ml) was heated at reflux for 4 hour. Lidiium chloride (1.6mg, 0.038mmol) was added and reflux continued for a further 1 hour. Solvent was removed in vacuo and the residue chromatographed on silica (eluent: 10% methanol in dichlorometiiane) to afford the title compound as a brown powder, 22mg (97%). Example 16 The chiral epoxidation of 2,2-dimethyI-6-pentafluoroethyI-2H-l-benzopyran using (E15) to give (3R,4R)-2,2-dimethyl-3,4-epoxy-6-pentafluoroethyl-2H-l- benzopyran (E4) A solution of 2,2-dimetiιyl-6-pentafluoroethyl-2H- 1 -benzopyran (560mg, 2mmol) and the catalyst (El 5) (22mg, 0.03mmol) in dichlorometiiane (2ml) was cooled to 0°C. A mixture of aqueous sodium hypochlorite solution (2.6ml of 11.4% w/v, 4mmol) and 0.05M NaH2PO4(aq) (2ml, adjusted to pH 11.3) was added, the mixture stirred at 0°C for 1 hour, then allowed to warm to ambient and stirred overnight. The mixture was diluted with water (10ml) and extracted with hexane (4x20ml). The combined organic phase was washed with water (10ml), dried over Na2SO4 and evaporated to afford the desired epoxide, 492mg (83%). Analysis by chiral hplc showed an ee of 77%.

Claims: CLAIMS 1. A compound of formula (I) : n which M is a transition metal ion; A is a counter-ion if required; r, s and t are independently 0 to 3 such tiiat r+s+t is in the range of 1 to 3; R a , R D , R c are each independendy hydrogen or CH2OR' where R' is hydrogen or an organic group; B and E are independently oxygen, CH2, NR^ in which R^ is alkyl, hydrogen, alkylcarbonyl, or arylcarbonyl or SO n where n is 0 or an integer 1 or 2, with the proviso that B and E are not simultaneously CH2 and tiiat when B is oxygen, NRd or SO n , then r cannot be 0, and when E is oxygen, NR^ or SO n , then t cannot be 0; R\, -2, R3, R4, R5, Rg, R7, Rg, R9 and RJQ are independently hydrogen, alkyl or alkoxy. 2. A compound according in claim 1 in which M is Mn. 3. A compound according to claim 2 in which Mn is in an oxidation state (II) or (HI). 4. A compound according to claim 1 in which A is chlorine. 5. A compound according to any one of claims 1 to 4 in which s and t are zero, r is 1 and R a is hydrogen, B is oxygen and E is CH2; or r, s and t are 1, R a , Rb and R c are hydrogen and B and E are both oxygen; or s is zero, r and t are both 1, R a is hydrogen or triphenylmethyloxymethylene and R c is hydrogen, B is oxygen and E is - CH2-; or r and t are both 1, s is zero, R a and R c are hydrogen, B is NR^ where R^ is phenyl carbonyl and E is CH2. 6. A compound according to any one of claims 1 to 5 in which Rj and Rg are tertiary butyl, R3 and Rg are tertiary butyl or methyl and R2, R4, R5 and R7 are hydrogen. 7. A compound selected from (±) 3,4-bis (3-tert Butyl-5-methylsalicylideamino) tetrahydrofuran manganese (IH) chloride; (S,S) trans 3,4-bis (3-tert Butyl-5-methylsalicylideamino)tetrahydrofuran manganese (HI) chloride; Preparation of (R,R)-5,6-bis-(3,5-di-tert-butylsalicylidenamino)- 1 ,3-dioxepane]- mangenese (Til) chloride; (3R,4S)-bis-(3,5-di-tert-butylsalicylideamino)tetrahydropyran-manganese (πi) chloride; (3R,4S)-bis-(3-tert-butyl-5-memylsalicylidenamino)tetrahydropyran-manganese (πi) chloride; (3S,4S)-bis-(3,5-di-tert-Butylsalicylideamino)tetrahydrofuran-manganese (III) chloride; (3R,4S)-bis-(3,5-Di-tert-Butylsalicylidenamino)-(2R)- (triphenylmethoxymethyl)tetrahydropyran-manganese (III) chloride and (-)trans- 1 -Benzoyl-3,4-bis(3,5-di-tertbutylsalicylideamino) piperidine-manganese (HI) chloride. 8. A process for the preparation of compounds of formula (I), as defined in claim 1 which comprises forming a transition metal complex of the following compound of formula (II): where variables Rj to RJO, B, E, r, s, t R a , R D and R c are as defined in relation to formula (I), in claim 1 and thereafter if necessary separating any enantiomers. 9. A process for the preparation of compounds of formula (II), in claim 1 which comprises condensing d of formula (IH): where r, s, t, R a , R^ and R c E, B are as defined in formula (I) and R \ and R j 2 independently represent hydrogen or an amine protecting group, providing at least one of Rj 1 and Rj2 is hydrogen, wiώ a compound of formula (IV); and a compound of formula (V), removing any protecting group Rn or R^ as necessary ; wherein Rj to RJQ are as defined in relation to formula (I), and thereafter as required isolating the required compound including if necessary separating any enantiomers. 10. A process for enantioselectively epoxidising a prochiral olefin in the presence of an oxygen source and a chiral catalyst of formula (I) as defined in claim 1. 11. A process according to claim 10 in which the prochiral olefin comprises one of the following list of groups as part of its structure: cyclohexene, 5,6-dihydro-2H- pyran, 1,2,5,6-tetrahydropyridine, l,2,3,4-tetrahydropyridine and 5,6-dihydro-2H- thiopyran. 3 12. A process according to claim 10 or 11 in which the prochiral olefin comprises one of the following list of groups as part of its structure: 1,2-dihydronaphdιalene, 2H-chromene, 1,2-dihydroquinoline, 1,2-dihydroisoquinoline and 2H-dιiochromene. 13. A process according to any one of claims 10 to 12 in which the prochiral olefin is 2,2-dimethyl-6-pentafluoroethyl-2H-l -benzopyran. 14. A process according to claim 13 in which die 2,2-dimetiιyl-6- pentafluoroethyl-chromene (3S,4S)-epoxide product is subsequently converted to trans -6-pentafluoroethyl-3,4-dihydro-2,2-dimethyl-4R-(piperidin-2-on- 1 -yl)-2H-l- benzopyran-3S-ol.

Inventors: ATTRILL ROBIN PATRICK, BELL DAVID, MILLER DAVID, ATTRILL, ROBIN, PATRICK, BELL, DAVID, MILLER, DAVID
Applicants: ATTRILL ROBIN PATRICK, BELL DAVID, MILLER DAVID, SMITHKLINE BEECHAM PLC
Application year: 1993
Main classification: B01J31
IPC codes: B01J31, C07B53, C07B61, C07D211, C07D301, C07D307, C07D309, C07D321, C07D493, C07F9, C07F11, C07F13, C07F15