PROCESS FOR THE PREPARATION OF (PYRIDINYLIDENE)-PHTHALIDES

Abstract: A process for the preparation of (pyridinylidene)-phthalides starting from 3-oxo-1,3-dihydro-isobenzofuran-1-carboxylic acids and pyridinecarbaldehydes, is described.

Description: "Process for the preparation of (pyrιdιnyhdene)-phthalιdes " ' ********************************* The present invention relates to a process for the preparation of (pyπdιnylιdene)-phthahdes and, more partιcularly,relates to a process for preparing (pyπdιnylιdene)-phtha des startmg from 3-oxo-l,3-dιh\dro-ιsobenzofuran-l-carboxylιc acids and pyπdinecarbaldehydes The (pyπdιnyhdene)-phthahdes are known compounds,descπbed in the literature In the International patent applications WO 98/35958 in the name of Novartis and WO 00/05218 in the name of the same applicant vaπous (pyπdιny dene)-phthalιdes are used as useful intermediates for preparing phthalazines endowed with inhibitory activπy of angiogenesis and PDE4 enzyme respectively Several methods for synthesizing ary denephthalides are known and some of them particularly, have been employed for preparing (pyπdιnylιdene)-phthalιdes For instance J Ploqum et al In J Het Chem (1980). 17, 961 report the preparation of (pyndιnylιdene)-phthahdes by hot condensation between phthahc anhydride and pyπdines This reaction, however, has a poor applicative interest because, besides presenting poor yields, it is limited to obtain unsubstituted or symmetrically substituted on the phthahc πng derivatives In fact an asymmetrical substitution would inevitably lead to the formation of regioisomers difficult to separate A different process for preparing, inter aha, (pyndιnylιdene)-phthalιdes also asymmetπcalh substituted, reported in the already cited patent application WO 00/05218, is based on the Wittig condensation between a phosphomum salt XI and an aldehyde XII as here depicted XI XII XIII wherein A also represents pyπdine and Z' can be absent Nevertheless this process, although it has a pratically quantitative yield, presents a series of disadvantages that make it of poor industπal interest In fact the preparation of the phosphonium salt XL that occurs according to the following schema XI VIII IX X shows some critical points Particularly the radical IC bromuration reaction of XI is strongh esothermic, the resultant bromurated product X is unstable and therefore it must be quickh used in the reaction with tπphenylphosphme to give the phosphonium salt XI Lastly duπng this last step the molecular weight of the substrate increases considerably involving an undesired increase of the reaction mass Besides, in the subsequent Wittig reaction the formation of equimolar quantities of phosphineoxide occurs that ulteriorly complicates the synthetic feasibility All these problems make the above mentioned process hardly practicable at mdustπal level Among the known alternative methods for preparing aryhdenephthahdes it is of particular interest the one described by R H Pager et al in Tetrahedron, (1984). 40, 1517 that uses differently substituted benzaldehydes (4) and 3-oxo-1.3-dιhydro-l-ιsobenzofurancarboxylιc acid (1) as starting products In all the examined cases the reaction, performed directly by heating the mixture of the reagents, leads to the formation of mixtures of 3-arylιdene-phthalιdes (3) and 3- (arylhydroxymethyl)-phtha des (2) in vaπable ratios, with overall yields from 47 to 90 % 0) (4) (2) (3) The authors study the course of the above reported decarboxylation-condensation reaction by varying some experimental parameters, such as the type and the quantity of de the solvent absence or presence, the reaction time and temperature Regarding the influence exerted by the substituents of the aldehvde (4) upon the course of the reaction the authors declare that "only in the case of electrondonor groups merely the dehydration product (3) is obtained " (see lines 2-4, 1 st column, page 1519) Besides, it seems that the reaction is advantageous only if it is performed w ithout a solvent while it results clearly disadvantageous if it is performed in its presence In particular in apolar solvents a 140°C it doesn't occur, while in the case of polar solvents, such as e g dimethylsulfoxide, it exclusively leads to obtain the alcohol (2) with poor and only with relevant excesses (2-6 equivalents) of aldehyde (see from line 19 forward, 1 st column, pag 1519) Moreover the dehydation of (2) to (3) doesn ' t occur appreciabh in this solvent Therefore from the work presented by Rolf H Prager et al it may be concluded that in order to obtain directly the compounds of formula (3) with significant yields the above mentioned reaction should be performed startmg from electron-rich aldehydes (4) b\ heating in the absence of a solvent On the contrary we have surpnsmgly found that also using electron-poor aldehydes such as the pyndmecarbaldehydes, even in almost stechiometπc ratio it is possible to obtain directly the corresponding aryhdenephthahdes with high vields if the reaction is performed in the presence of anhydndes With reference to this it has been hypothesized that the anhydnde. besides probabh acting as a dehydrator, is directly involved in the initial activation of the carboxyhc function of the 3- oxo-l,3-dihydro-isobenzofuran-l-carboxylic acids. Therefore object of the present invention is a process for preparing pyridinylidene-phthalides of formula wherein Py represents a 2, 3 or 4-pyridinyl group optionally substituted by one or more substituents selected from halogen, nitro, cyano, oxo and carboxy groups; R and Ri, which may be the same or different, represent hydrogen, C C 6 alkyl or a group OR 2 wherein R 2 represents a linear or branched Ci-Ce alkyl, a C 4 -C7 cycloalkyl or a Ci-Cβ polyfluoroalkyl; The bond w * indicates both the isomers E and Z; by reaction of a compound of formula wherein R and Ri have the above reported meanings; with an aldehyde of formula Py-CHO (III) wherein Py has the above reported meaning; by heating the mixture of the compounds having formula II and III in the presence of an anhydride and optionally in admixture with a suitable solvent. The process object of the present invention can be easily performed and it allows to obtain pyndinyhdene-phthahdes of formula I with good yields without usmg the aforesaid phosphonium salt XI The process object of the present invention provides for the reaction between a compound of formula II and a compound of formula III The compounds of formula II are known and easily obtainable for instance according to the synthetic route descnbed in J Chem Soc (1929), 200 In the compounds of formula II the groups R and Ri have the above reported meanings Particularly preferred compounds of formula II are those wherein at least one between R and R t represents OR 2 . even more preferred those wherein one or both between R and Ri are Also the startmg compounds of formula III are generally known, commercially available or obtainable according to processes reported in the literature Particularly preferred compounds of formula III are those wherein Py represents a 4- pyπdinyl group, even more preferred if Py represents a dihalosubstituted 4-pyndmyl residue In the process object of the present invention the compounds of formula III are generally used with respect to the compounds of formula II in a molar ratio from 0,5 to 4 Preferabh they are used in a ratio from 0,8 to 1,5 , even more preferably from 0,9 to 1,1 The present process is performed in the presence of an anhydnde The term "anhydnde" means a reagent selected in the group of the organic or morgamc anhydndes, respectively derived from organic or inorganic acids, or mixed, including in this class also the acyl. alkyl and arylsulfonyl halides Examples of anhydndes uti zable in the present process are, m the case of the orgamc anhydndes, acetic, tnfluoroacetic, or tnfluoromethansulfonic anhydnde, in the case of inorganic anhydndes, phosphonc or sulphunc anhydride or thionylchlonde, while among the mixed anhydndes. acetyl, tosyl or mesyl chloride, these acyl chlondes being consider herewith as anhydndes of an orgamc acid and hydrogen chlonde This, for example, acetyl chlonde is the mixed anhydnde of acetic acid and drogen chlonde The organic anhydndes are particularly preferred For practical reasons acetic anhydnde is preferably used In the process object of the present invention the above cited anhydnde can be employed in a large excess as regards the startmg compound of formula II acting also as solvent, for example in a molar ratio of 10 1 as regards the compound of formula II Alternatively the anhydnde can be used as regards the compound III in a narro er molar ratio, for example from 1 to 3 In that case the reaction may request the presence of an appropnate co-solvent In this connection examples of usable solvents are high boiling apolar solvents, such as for example the aromatic hydrocarbons, optionally chlorosubstituted Preferred aromatic solvents are toluene, xylene and chlorobenzene, particularly preferred is toluene For practical reasons the process object of the present invention is preferably performed in an excess of acetic anhydnde Also the usage of other activatmg systems, such as for example the Lewis acids, or dehλdrators, such as the distillation of appropriate azeotropic mixtures, falls, moreover, within the scope of the present invention as an alternative to the anhydnde The present process is performed by heating the mixture of the compounds of formula II and III. in the presence of the anhydride and optionally of the appropnate solvent Preferably the reaction mixture is heated at the reflux temperature The process object of the present invention allows to obtain a final raw product. essentialK constituted by the mixture E/Z of the compounds of fomula I, usable directly without further treatment of purification The compounds of formula I, prepared according to the process object of the present invention, can for example be directly used in the synthesis of PDE4 inhibitors having a phthalazinic structure, as descnbed in the already cited International application WO 00/05218 Said compounds have the formula wherein R, Ri and Py have the above reported meanings, is a single or double bond, Y represents two hydrogen atoms or a group =0 when is a single bond, or when is a double bond Y is hydrogen, cyano, (C|-C 4 )- alkoxycarbonyl, amido, optionally sustituted aryl or heterocyclyl, (Cι-C 8 )-alkyl. (C C 8 )- cyclylamino, W is absent when IS a double bond or, when is a smgle bond, it represents a) hydrogen, b) (Cι-C 6 )-alkyl optionally substituted by aryl. heterocyclyl or by a group CORs wherein Rs is hydroxy, (C]-C 4 )-alkoxy or hydroxyamino, c) -CORs wherein Re is hvdrogen, aryl, aryl-(Cι-C 6 )-alkyl, optionalh alkvlated or monohydroxylated ammo, In droxy, carboxy, (Cι-C 4 )-alkoxycarbonyl, 2 , or (C t -C 4 )-alkyl optionally substituted by a heterocycle, d) (Cι-C 4 )-alkylsulfonyl The present process is preferabh applied to the synthesis of 4-pyπdιnyl derivatives, even more preferably to the synthesis of dihalo-substituted 4-pyndιnyl derivatives The application of the present process to the synthesis of 3-[(3,5-dιchloro-4- -l-(3H)-ιsobenzofuranone is particularly preferred In a preferred embodiment of the process object of the present invention, the mixture of the compound II. the compound III and the anhydride is refluxed until the reaction is complete The mixture is evaporated and the residue, recovered with the appropnate solvent and nevaporated up to dryness, can be directly used in the following step The process object of the present invention is advantageous chiefly for the sιmphcιt\ of realization and therefore it is particularly suitable for the industrial application It allows to prepare the compounds of formula I with high yields and in a short time without usmg the above mentioned phosphonium salt XI, avoiding therefore the relative problems, such as for example the formation of unstable bromurated intermediates through exothermic reactions, the considerable increase of molecular weight and the formation of phosphineoxides A further reason of interest is the obtainment of a raw product usable directly in the subsequent reaction without requesting further purifications Besides, as regards the already cited synthetic process reported in the International application WO 00/05218, the present process allows to reduce the total number of steps startmg from the same benzoic acid derivative precursor With the aim to better illustrate the present invention the following examples are now given Example 1 Preparation of 3- (3.5-dιchloro-4-pyrιdιnyl)methylenel-6-methoxy-l-(3H)-ιsobenzo-fura- none The mixture prepared at room temperature of 5-methoxy-3-oxo-1.3-dιhydro-l- lsobenzofurancarboxylic acid (12,4 g, 0,06 moles), prepared as descnbed in J Chem Soc (1929), 200, and 3,5-dιchloro-4-pyπdιnecarbaldehyde (10,8 g, 0.061 moles), prepared accordmg to Heterocycles (1995), 41 . , 675, in acetic anhydnde (60 ml) was refluxed, under stirring, for 30 minutes The reaction was evaporated under vacuum, collected with toluene (50 ml) and evaporated agam This treatment was repeated for other two times obtaining the desired compound (19,3 g, quantitative yield) as a yellow solid Η-NMR (200 MHz, CDC1 3 ) δ (ppm) 8,60 and 8.50 (s, 2H, Py), 7,77-6,20 (m. 4H. Ar and CH), 3,90 and 3,80 (s, 3H, OMe), lsomeπc ratio 9 1 Example 2 Preparation of 4-f(3,5-dιchloro-4-pyndιnyl)methyll-1.2-dιhvdro-7-metho\\-l-phthala- zinone In a 4 liter reactor at room temperature 3-[(3.5-dιchloro-4-pyπdmyl)methylene]-6-metho\ - l-(3H)-ιsobenzofuranone (335 g, 1,04 moles), prepared as descnbed in the example 1 and methanol (1785 ml) were charged Then acetic acid (178 ml) and, maintaimng the temperature under 40°C by external cooling, hydrazine monohydrate (171,7 ml) were added by dnpping The reaction mixture became a solution, then a new precipitate began to form The mixture was refluxed for 2 hours The end of the reaction was checked by TLC ( a sample was drawn and diluted with CH 2 C1 , elutant hexane ethylacetate=7 3) When the reaction ended the mixture was cooled at 0°C and filtered The filtrate was washed with methanol (215 ml) The solid was dπed under vacuum at 40°C obtaining the desired compound (328,5 g, yield 99%) as a light yellow solid Example 3 Preparation of 3- (3,5-dιchloro-4-pyndιnyl)methylenl-6-methoxy-l-(3H)-ιsobenzofuranone A mixture of 5-methoxy-3-oxo-l,3-dιhydro-l-ιsobenzofurancarboxylιc acid (5 g. 24 mmoles) and 3,5-dιchloro-4-pyπdιnecarboxaldehyde (4 3 g, 24 mmoles) in toluene (32 5 ml) and acetic anhydnde (7 5 ml) was refluxed, under stimng, for 8 hours The mixture was cooled at 0°C and filtered The filtrate was washed with hexane The desired compound was obtained (5 6 g) as yellow solid Yield 73% 'H-NMR m conformity with that reported in Example 1 The same reaction was performed with 4 5 ml, 5 ml and 10 ml of acetic anhydirde In all cases the yields were comparable The reaction time was inversely proportioned to the acetic anhydnde concentration Example 4 Preparation of 3-f(3-chloro-4-pyndιnyl)methylenl-6-methoxy-l-(3H)-ιsobenzofuranone A mixture of 5-methoxy-3-oxo-l,3-dιhydro-l-ιsobenzofurancarboxylιc acid (0 7 g. 3 4 mmoles) and 3-chloro-4-pyndιnecarboxaldehyde (0 52 g, 3 7 mmoles), prepared as descnbed in J Organometallic Chem (1981). 216, 139, m toluene (5 ml) and acetic anhydnde (1 ml) was refluxed, under stirring, for 10 hours The mixture was cooled at 0°C and filtered The filtrate was washed with hexane The compound 3-[(3-chloro-4-pyπdιnyl)methylen]-6-methoxy-l-(3H)-ιsobenzofuranone was obtained (680 mg) as yellow solid Yield 70% 'H-NMR (200 MHz, CDC1 3 ) δ (ppm) 8 58 (s. IH, C1C=CH-N), 8 47 (d, IH. JHH=5 3 Hz, N-*CH=CH), 8 11 (d, IH, N-CH=*CH), 7 74 (d. IH, JHH=8 5 Hz, *CH=CH-0Me), 7 35- 7 28 (m. 2H, Ar). 6 61 (s, IH, *CH-Py), 3 90 (s. 3H. CH 3 -0) Example 5 Preparation of 3-[(3.5-dιchloro-4-pyπdιnyl)methylenl-6-methoxy-l-(3H)-ιsobenzofuranone By following the same procedure as in Example 4 but by using tnfluoroacetic anhydnde instead of acetic anhydnde, startmg from 5-methoxy-3-oxo-1.3-dιhydro-l- lsobenzofurancarboxyhc acid (100 mg) the desidered compound (109 mg) was obtained Yield 70% H-NMR in conformity with that reported in Example 1

Claims: Claims 1) A process for the preparation of pyndinylidene-phthahdes of formula wherein Py represents a 2, 3 or 4-pyndmyl group optionally substituted by one or more substituents selected from halogen nitro, cyano, oxo and carboxy. R and R ]; which can be the same or different between them, represent hydrogen. C C 6 alkyl or a group OR 2 wherein R 2 represents a linear or branched Ci-Cβ alkyl, a C 4 -C7 cvcloalkyl or a Cι-C 6 polyfluoroalkyl, The bond w„ indicates both the isomers E and Z, which compnses the reaction of a compound of formula wherein R and Rj have the meanmgs above reported, with an aldehyde of formula Py-CHO (III) wherein Py has the above reported meaning, by heating of the mixture of the compounds of formula II and III in the presence of an anhydnde and optionally in admixture with a suitable solvent 2) A process according to claim 1 wherein Py represents a dihalosubstituted 4-pyndιnyl group 3) A process according to claim 2 wherein Py represents a 3,5-dιchloro-4-pyndιnyl group 4) A process according to claim 1 wherein one or both between R and Ri represent OCH 3 5) A process according to claim 1 wherein the compounds of formula III are employed with respect to the compounds of formula II in a molar ratio from 0,5 to 4 6) A process according to claim 5 wherein the compounds of formula III are employed with respect to the compounds of formula II in a molar ratio from 0,8 to 1,5 7) A process according to claim 6 wherein the compounds of formula III are employed with respect to the compounds of formula II in a molar ratio from 0,9 to 1,1 8) A process according to claim 1 wherein the anhydride is an organic anhydride 9) A process according to claim 8 wherein the anhydride is acetic anhydnde 10) A process according to claim 1 wherein the dπde is used in an excess 11) A process for preparing phthalazines of formula wherein R, Ri and Py have the above reported meanings. is a single or double bond, Y represents two hydrogen atoms or a group =0 when is a single bond, or when is a double bond Y is hydrogen, cyano, (C C 4 )- alkoxycarbon\ 1, amido, optionally sustituted aryl or heterocyclyl, (Cι-C 8 )-alkyl, (Cι-C 3 )- cyclylamino, W is absent when is a double bond or, when is a smgle bond, it represents a) hydrogen, b) (Cι-C 6 )-alkyl optionally substituted by aryl, heterocyclyl or by a group CORs wherein R 5 is hydroxy, (Cι-C 4 )-alkoxy or hydroxyamino, c) -CORg wherein Rg is hydrogen, aryl, aryl-(Cι-C 6 )-alkyl, optionally alkylated or monohydroxylated amino, hydroxy, (Cι-C 4 )-alkoxy. carboxy, (Cι-C 4 )-alkoxycarbonyl, , or (Cι-C 4 )-alkyl optionally substituted by a heterocycle; d) (Cι-C 4 )-alkylsulfonyl; which comprises the preparation of the intermediate of formula I wherein R, Ri and Py have the above reported meanings; according to the process of claim 1.

Inventors: NAPOLETANO MAURO, NAPOLETANO, MAURO
Applicants: NAPOLETANO MAURO, ZAMBON SPA, NAPOLETANO, MAURO, ZAMBON GROUP S.P.A.
Application year: 2001
Main classification: C07D405
IPC codes: C07B61, C07D401, C07D405