bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas‐phase thermolysis oftert‐butyl hydroperoxide with benzene and chlorobenzene in the temperature range 200‐300°C
Authors: Mulder Peter , Louw Robert 
Published: September 2010

AbstractThermolysis oftert‐butyl hydroperoxide (1) in nitrogen with an excess of benzene in the temperature range 200‐300°C, leads to biphenyl (2) as the only observable benzene‐derived product. With chlorobenzene, dichlorobiphenyls (4) are formed, together with chlorobiphenyl (5),ca.12% on4, and phenol (20‐25% on4); chlorophenols are not produced. The use ofca.equimolar quantities of iodine based on1results in formation of iodobenzene (3) and chloroiodobenzenes (7), respectively, at the expense of biaryl. In air, chlorobenzene and1produce chlorophenols (8), biaryl then being a minor product.Hydroxyl radicals produced from1abstract hydrogen from benzene to give phenyl radicals (Ph•) which, in nitrogen, arylate benzene. From isomer distributions of7and of4it is inferred that hydrogen abstraction from chlorobenzene leads to chlorophenyl radicals, with a ratioo/m/p∼ 24/52/24. With chlorobenzene,ipsosubstitution, PhCl +•OH→PhOH, also takes place. In the presence of oxygen or iodine, formation of biaryls involves irreversible addition of (chloro)phenyl radical, the intermediate adduct radicals reacting with oxygen or iodine. In nitrogen, however, the first step in arylation is reversible. Apart from undergoing O‐O bond homolysis,1is attacked by•Me (formed from Me3CO•) and, to some extent, by aryl radicals. A large arene/1intake ratio (> 100), or the addition of either iodine or air suppresses ‐ or even prevents ‐ free‐radical‐induced decomposition of1.
Tetraaza‐macrocyclic cobalt(II) and nickel(II) complexes as electron‐transfer agents in the photo(electro)chemical and electrochemical reduction of carbon dioxide
Authors: Tinnemans A. H. A. , Koster T. P. M. , Thewissen D. H. M. W. , Mackor A. 
Published: September 2010

AbstractThe potential of a number of tetraaza‐macrocyclic complexes of cobalt and nickel to mediate the photoreduction of carbon dioxide has been studied. Carbon monoxide and hydrogen are the main products, which result from illumination of an aqueous solution containing Ru(2, 2′‐bipyridine)2+3 as sensitizer, ascorbic acid as sacrificial eletron donor and a tetraaza‐macrocyclic complex as relay. Their ratio strongly depends upon the relay compound used. The complexes can be used as electrocatalysts for CO2 reduction at a mercury electrode since they lower the overpotential for CO2 reduction showing turnover numbers/hour of approximately 3. A minimum potential is required to induce reaction of electrocatalysts and CO2 (and H2O).Finally, the redox properties of the macrocyclic metal complexes at p‐GaP and p‐GaAs photocathodes in acetonitrile are compared with those observed at Pt.
RMN 13C de thiocétones ‐ rǒle du groupement thiocarbonyle
Authors: Mieloszynski J. L. , Schneider M. , Paquet D. , Andrieu C. G. 
Published: September 2010

AbstractThe shielding effects of the sulfur atom on neighbouring carbons in 36 thioketones have been characterized by 13C NMR. The results are compared with those for the carbonyl derivatives. The importance of these data for structural elucidations is discussed.
On the bromination of 1,2,3‐triphenylazulene
Authors: de Wit Peter , Lambrechts Hans J. A. , Cerfontain Hans 
Published: September 2010

AbstractThe bromination of 1,2,3‐triphenylazulene (1) with a tenfold excess of bromine in CHCl3/CCl4 as solvent yields 5,7‐dibromo‐1,3‐bis(p‐bromophenyl)‐2‐phenylazulene and not a dibromo derivative as reported earlier1,2. With 1.0 equivalent of bromine or 2.0 equivalents of NBS, a mixture of the 5‐bromo and 5,7‐dibromo derivatives of 1 is obtained.
Molecular dynamics computer simulation as a tool for the analysis of solvation: A study of dilute aqueous solutions of 1,4‐dioxane and 1,3‐dioxane
Authors: Remerie Klaas , van Gunsteren Wilfred F. , Engberts Jan B. F. N. 
Published: September 2010

AbstractIt is shown how the computer simulation technique of molecular dynamics (MD) can be used to obtain a detailed picture of the static and dynamic properties of a solution at the atomic level. The method is applied to the solvation of a single molecule of 1,4‐dioxane and 1,3‐dioxane dissolved in 122 water molecules. The structure of the solvation shell was found to be clathrate‐like although the dioxane oxygen atoms disturb this arrangement considerably. This is especially apparent for 1,3‐dioxane as a result of its large dipole moment and the favorable position of its oxygen atoms for double hydrogen bonding. Generally, comparison of simulated properties with available experimental data shows good agreement. Consideration of both static and dynamic properties leads to the conclusion that there is a balance between structure‐breaking and structure‐making properties for 1,4‐dioxane. By contrast, 1,3‐dioxane is definitely structure‐breaking. The hydration shell of 1,3‐dioxane is clearly more labile than that of 1,4‐dioxane.
A comparative investigation of 1,4‐pentamethylene and 1,4‐hexamethylene Dewar benzene: Evidence for the intermediate formation of [5]paracyclophane
Authors: van Straten J. W. , Turkenburg L. A. M. , de Wolf W. H. , Bickelhaupt F. 
Published: September 2010

AbstractThe synthesis of the title compounds 1a and 1b is described. Starting from the corresponding 1,2‐dimethylenecycloalkanes 6, the compounds 1 were obtained in four steps, viz. addition of dichlorocarbene, reduction with triphenyltin hydride, treatment with potassium tert‐butoxide and silver‐ion‐catalyzed rearrangement. In the last step, the 1,2‐isomers 11 of 1 were also formed, and their thermal rearrangement to the benzocycloalkenes 4 is briefly described. Compound 1b rearranged to its aromatic isomer [6]paracyclophane (2b) both thermally (60°C in solution, 100‐460°C flow pyrolysis) and under silver‐ion catalysis at room temperature; in this latter reaction, the initially formed 2b was gradually further isomerized to 4b. At higher temperatures, 2b rearranged to the spirotrienes 3b and finally fragmented to give p‐ethylstyrene (17). From 1a, the spirotriene 3a and benzocycloheptene (4a) were obtained by thermolysis and by silver‐ion catalysis, respectively. The mechanism of these reactions is discussed and it is concluded that [5]paracyclophane (2a) is a transient intermediate in the reaction of 1a.
A convenient method for the preparation of terminal methyl phosphates of nucleic acids
Authors: Wreesmann C. T. J. , van den Hoogen Y. Th. , Ledeboer A. H. , van der Marel G. A. , van Boom J. H. 
Published: September 2010

AbstractThe reagent 2‐chlorophenyl bis(1‐benzotriazolyl) phosphate has been used for the preparation of 5′‐O‐(methyl phosphate) esters of the dimers TpT, UpU, Upm26A and m26ApU, as well as 3′,5′‐bis‐O‐(methyl phosphate) esters of uridine (U) and the minor ribonucleosideN6,N6‐dimethyladenosine (m26A). A convenient synthesis of a non‐terminal (9) and a terminal (10) building unit of m26A is also reported.
Degradation of polypyrrole‐modified electrodes in a chloride containing medium
Authors: Vork F. T. A. , Ubbink M. T. , Janssen L. J. J. , Barendrecht E. 
Published: September 2010

AbstractThe behaviour of a polypyrrole‐modified electrode in an aqueous 0.5 M HCl solution at high anodic potentials was studied. Electrochemical experiments and 13C‐NMR analysis showed a decrease in conductivity, due to the formation of CCl bonds in the pyrrole ring structure.
Studies on borate esters III. Borate esters of D‐mannitol, D‐glucitol, D‐fructose and D‐glucose in water
Authors: Makkee M. , Kieboom A. P. G. , van Bekkum H. 
Published: September 2010

AbstractA combination of 11B and 13C NMR spectroscopy with several model compounds has been used to elucidate the nature of the ester formation between borate and D‐mannitol, D‐glucitol, D‐fructose and D‐glucose in aqueous solution at pH 6‐12 and at 25 °C. At high carbohydrate/borate ratios, D‐mannitol shows the selective formation of bis(D‐mannitol) 3,4:3′4′ ‐borate, whereas D‐glucitol forms a mixture of six different bis(D‐glucitol) borate esters involving both 2,3‐ and 3,4‐dihydroxyl moieties. Bis(D‐fructose) and bis(D‐glucose) borate esters consist of pairs of diastereomers of the 2,3‐β‐and 1,2‐α‐furanose moieties, respectively. At low carbohydrate/borate ratios, mono‐, di‐ and, sometimes, tri‐borate esters are formed, e.g. mixture of α‐D‐glucofuranose 1,2:3,5‐diborate and α‐D‐glucofuranose 1,2:5,6‐diborate for D‐glucose and a mixture of β‐D‐fructopyranose 1,2:4,5‐diborate and β‐D‐fructopyranose 2,3:4,5‐diborate for D‐fructose. The overall stability constant for the borate di‐esters of D‐mannitol, D‐glucitol and D‐fructose is about two orders of magnitude higher than that of D‐glucose.
C‐Nitroso compounds. Part XXXVII. The reactivity of α‐chloronitroso compounds towards organoaluminium reagents
Authors: Lub J. , Beekes M. L. , de Boer Th. J. 
Published: September 2010

AbstractWith sterically unhindered and certain moderately hindered α‐chloronitroso compounds 1 trimethylaluminium at low temperature gives, via complexes 2 and 3, the methyl nitrones 4 (Scheme 1). Several intermediate complexes 3 lose methane upon heating and rearrange to α‐chloroimines 5 (Scheme 2), the structure of which is determined by that of the precursors (E‐ or Z‐geometry; cf. Scheme 6).More sterically hindered α‐chloronitroso compounds containing quaternary carbon undergo C‐C rupture when treated with trimethylaluminium, thus forming hydroxamic acid chlorides, formally HCI adducts of nitrile oxides (cf. 8j in Scheme 3; 8k in Scheme 4). In the latter case, subsequent reactions lead to overall ring enlargement, i.e. formation of the seven‐membered cyclic oxime 12. With triethyl‐aluminium and triisobutylaluminium, α‐chloronitroso compounds are mainly reduced to oximes and the isomeric amides (Scheme 7).
Scission of the epoxy ring in 4,5α‐epoxymorphinans: A convenient synthesis of β‐dihydrothebaine, 6‐demethoxy‐β‐dihydrothebaine and desoxycodeine‐A (Chemistry of opium alkaloids, Part XXI)
Authors: Linders J. T. M. , Adriaansens R. J. O. , Lie T. S. , Maat L. 
Published: September 2010

AbstractThe use of zinc and aqueous potassium hydroxide for the reductive epoxy ring opening of thebaine (1) and 6‐demethoxythebaine (2) is described. The reaction affords exclusively β‐dihydrothebaine (3) and 6‐demethoxy‐β‐dihydrothebaine (4), respectively. The synthesis of desoxycodeine‐A (9) has been improved and evidence for its configuration is discussed.
Polymer‐supported synthesis of deoxyoligonucleotides using in‐situ prepared deoxynucleoside 2‐cyanoethyl phosphoramidites
Authors: Nielsen J. , Taagaard M. , Dahl O. , Marugg J. E. , van Boom J. H. 
Published: September 2010

AbstractThe easily accessible reagent 2‐cyanoethyl‐bis (diisopropylamino) phosphoramidite is shown to be suitable for the in‐situ, 1H‐tetrazole catalysed, preparation of d‐nucleoside‐3′‐phosphoramidites. The latter compounds could be applied successfully as building blocks in a solid‐phase DNA synthesis using an automated DNA synthesizer.
Synthesis of spin‐labelled di‐ and tri‐2‐deoxyadenylates
Authors: Claesen C. A. A. , Daemen C. J. M. , Tesser G. I. 
Published: September 2010

AbstractTwo spin‐labelled dinucleotide derivatives and two spin‐labelled trinucleotide derivatives have been prepared and their constitution established using HPLC and enzymatical degradation. 1H NMR spectroscopy was performed prior to and after reduction of the spin label with ascorbic acid. 2‐(tert‐Butylsulphonyl)ethyl N6‐(diphenylacetyl)‐5′‐O‐(4,4′‐dimethoxytrityl)‐2′‐deoxyadenosyl phosphoromorpholidite (4) was prepared and used for the phosphitylation of N6‐(diphenylacetyl)‐3′‐O‐levulinoyl‐2′‐deoxyadenosine (7) to give the dinucleotide derivative 8 and the trinucleotide derivative 10. The spin label was introduced in the 5′‐position of these compounds, using (5), to give compounds 9 and 11 in the fully protected form.Unexpectedly, the stability of the spin label was found to be so high that the function could be used as the definite blocking for the 3′‐hydroxyl group in the 2′‐deoxyadenosine moiety. Thus, starting from 3 and using compound 5, 2‐(tert‐butylsulphonyl)ethyl N6‐(diphenylacetyl)‐2′‐deoxy‐3′‐adenosyl 1‐oxyl‐2,2;6,6‐tetramethyl‐4‐piperidinyl phosphate (6) was obtained. This compound afforded the protected di‐ and tri‐nucleotide derivatives 12 and 13, following one or two phosphitylations with 4 and subsequent oxidation.Deprotection of the derivatives 9,11,12 and 13 to the spin labelled end‐products was achieved in one step using concentrated aqueous ammonia.
C‐Nitroso compounds. Part XXXVIII: Radical reactions of α‐chloro‐nitroso compounds with trialkylaluminium‐ether complexes
Authors: Lub J. , Beekes M. L. , de Boer Th. J. 
Published: September 2010

AbstractEther complexes of trialkylaluminium compounds react with α‐chloro‐nitroso compounds via radicals which can abstract hydrogen from various solvents. In the presence of olefinic solvents, radical addition to the double bond also takes place.When the trialkylaluminium compounds are not complexed by ethers, they react with α‐chloro‐nitroso compounds predominantly via heterolytic processes1,2.
A novel synthetic route to 6‐azabicyclo[3.2.1]oct‐3‐enes via silicon directed N‐Acyliminium chemistry: Synthesis of (±)‐gabaculine
Authors: Hiemstra Henk , Klaver Wim J. , Nico Speckamp W. 
Published: September 2010

AbstractAlkylation of the lithium enolate, derived from 5‐ethoxy‐2‐pyrrolidone 1 (Scheme 1), using alkyl halides containing either the vinylsilane or 2‐propynylsilane moiety, provides substrates 3 for cyclization studies passing through N‐acyliminium intermediates 4 toward the 6‐azabicyclo[3.2.1]‐octanes 5 and 7. These ring‐closure experiments are unsuccessful in the case of vinylsilanes, and an explanation for this failure is presented. Ring closures of 2‐propynylsilanes lead, in high yield, to bicyclic allenes 5, which, in a few steps (ozonolysis, Shapiro reaction), are transformed into 7. This methodology constitutes the basis of a total synthesis of (±)‐gabaculine (10). The synthesis is completed from 52 by lactam hydrolysis and sulfoxide elimination.
A 15N study of the ammonia‐induced deamination of 1‐aminopurinium salts
Authors: Jongejan H. , Kos N. J. , van der Plas H. C. 
Published: September 2010

AbstractReaction of 1‐aminoadeninium mesitylenesulfonate (1) and 1,2‐diaminopurinium mesitylenesulfonate (8) with methanolic ammonia for 17 h at 100°C leads to deamination at N(l), yielding adenine and 2‐aminopurine, respectively, as well as dideamination, yielding purine. It is very likely that 6‐hydrazinopurine is formed in the dideamination of 1 and that 2‐hydrazinopurine is an intermediate in the dideamination of 8. From both hydrazinopurines, purine is formed.Labelling studies, using 15N‐labelled methanolic ammonia, show that, in the deamination reactions, a ring‐opening reaction (ANRORC mechanism) is involved.
Analysis of the potentiometric titration curves of poly(acrylic acid), poly(methacrylic acid) and poly(ethacrylic acid) in terms of species population distributions
Authors: Jager Jan , Engberts Jan B. F. N. 
Published: September 2010

AbstractFor atactic poly(methacrylic acid) (PMAA) and poly(ethacrylic acid) (PEA) the conformational transition from a compact coil to a random coil upon ionization in aqueous solution is revealed by an analysis of the potentiometric titration curves. The treatment, proposed by Strauss, is couched in terms of successive ionization constants of a suitably sized subunit of the polymer chain. Consideration of the bimodal population distribution indicates that the conformational transition in PEA is more pronounced than in PMAA. This is most likely the result of the more hydrophobic side‐chain in PEA. In agreement with previous work, no “two‐state” conformational transition is observed upon ionization of poly(acrylic acid) (PAA).
X‐Ray structure of tetrameric 1‐lithio‐3‐methoxypropane
Authors: Klumpp G. W. , Geurink P. J. A. , van Eikema Hommes N. J. R. , de Kanter F. J. J. , Vos M. , Spek A. L. 
Published: September 2010

AbstractThe crystal structure of (LiCH2CH2CH2OMe)4 [(3)4] consists of a distorted (CH2)4Li4 cube, four parallel edges of which are spanned by CH2CH2OMe chains. The interatomic distances provide insights into the nature of alkyllithium‐Lewis base (ethers, tertiary amines) interactions and into the structural basis of the differential reactivity and stability of primary and secondary alkyllithium tetramers.NMR of hydrocarbon solutions indicates that under these conditions the solid state tetramer is in equilibrium with a stereoisomer.
Synthesis with sulfones, Part XLIII. Preparation ofγ‐functionalized vinyl sulfones by nucleophilic substitution of allylidene disulfones; stereospecific reduction of 3‐hydroxy‐(E)‐1‐propenyl sulfones to (Z)‐allylic alcohols
Authors: Cuvigny T. , du Penhoat C. Herve , Julia M. 
Published: September 2010

AbstractThe substitution of a sulfonyl moiety of allylidene disulfones by various nucleophiles (PhSNa, PhSO2Na, H2O and R2NH) leads toγ‐functionalized (E)‐vinyl sulfones. The stereospecific reduction of 3‐hydroxy‐(E)‐1‐propenyl sulfones affords (Z)‐allylic alcohols in greater than 98% purity.
Structure‐odour relationships of some new synthetic sandalwood aroma chemicals: Synthesis and olfactive properties in a series of bicyclo[4.4.0]decan‐3‐ols
Authors: Witteveen Jan G. , van der Weerdt Anton J. A. 
Published: September 2010

AbstractThe relationship between chemical structure and sandalwood fragrance in a series of four isomers of 8‐tert‐butylbicyclo[4.4.0]decan‐3‐ol (4a‐d), the unsaturated analogue 5 and the methyl‐substituted derivative 17 has been examined. The sandalwood fragrance of decalol 4c suggests a potentially new class of compounds having a sandalwood odour.
The synthesis, properties and reactivity of model systems for protonated chromophores in biliproteins
Authors: Hoef K. v. D. , Hempenius M. A. , Koek J. H. , Lugtenburg J. , Fokkens R. 
Published: September 2010

AbstractThree 2,3,22,23,24‐pentahydro‐21H‐biline‐1,19‐dion‐10‐enium salts have been prepared: 17,18,22,23‐tetramethyl‐2,3,22,23,24‐pentahydro‐21H‐biline‐1,19‐dion‐10‐enium methanesulphonate (1) with a central flexible structure, its 10‐syn‐locked 22,23‐methylene homologue (2) with a central Z‐syn structure and its 8,12‐isopropylidene homologue (3), the first bile pigment with a central E‐anti structure. For comparison, the corresponding E‐anti 22,23,24‐trihydrobilinedionium salt 3a was also prepared. The 2,3 single bond induces a more delocalized charged system, having higher fluorescence quantum yields than observed for the fully conjugated systems. The flexible systems 1, 1a, which adopt an E‐anti conformation, do not show fluorescence. The E‐anti systems have a larger Stokes shift than do the Z‐syn systems. In the pentahydrobilinedionium salts, the highest positive charge resides on the central C10 atom as apparent from 1H NMR spectroscopy and as was corroborated by the finding that the site of nucleophilic attack is invariably at C10. The pentahydro salts also undergo electrophilic H‐D exchange at positions 5, 7 and 12. From the spectral data presented it would appear that the chromophore in (allo)phycocyanine will occur as a protonated system in a rigid protein environment in the E‐anti conformation.
Bacteriorhodopsin: The influence of the cyclohexene‐ring methyls
Authors: Courtin J. M. L. , Verhagen L. , Biesheuvel P. L. , Lugtenburg J. , van der Bend R. L. , van Dam K. 
Published: September 2010

AbstractFour ring‐demethylated retinals, viz. 1,1,5′‐tridemethylretinal, 1,1′‐didemethylretinal, 1,5‐didemethylretinal and 1‐didemethylretinal, have been synthesized via new and simple schemes. The properties of these modified retinals, their protonated Schiff bases and the corresponding bacteriorhodopsins have been studied and compared with the native system. These bacteriorhodopsin analogues have also been tested for their proton‐pump efficiencies. A large decrease in proton‐pump activity was found for the analogues lacking the 5‐methyl group. On the whole, the opsin shifts of the modified bacteriorhodopsins were much lower than those of the native system. UV‐Vis and 1H NMR data support a planar 6‐s‐trans conformation for the demethylated retinals in solution rather than a twisted 6‐s‐cis conformation (torsion angle 40‐60°) as found in retinal. This explains the lower opsin shift and the better fit of these demethylated retinals in bacteriorhodopsin's binding site, which, in its native form, contains a 6‐s‐trans chromophore.
The unexpected formation of trans‐β‐lactams in the reaction of α‐iminoesters (RNC(H)C(O)OR′) with diethylzinc. Crystal structure of trans‐1‐(N‐t‐butyl)‐3‐(N‐t‐butyl‐N‐ethylamino)‐4‐ methoxycarbonylazetidin‐2‐one
Authors: van Vliet M. Robert P. , Klaver Wim J. , Jastrzebski Johann T. B. H. , van Koten Gerard , Goubitz Kees 
Published: September 2010

AbstractReaction of iminoesters, RNC(H)COOR′, (R  tBu, i‐Pr; R′  Me, Et) with diethylzinc affords in a selective quantitative reaction trans‐β‐lactams. An X‐ray crystal structure determination of the obtained trans‐1‐(N‐t‐butyl‐3‐(N‐t‐butyl‐N‐ethylamino)‐4‐methoxy‐ carbonylazetidin‐2‐one has been carried out. The formation of the trans‐β‐lactams is believed to proceed via zinc enolates.
Conformational transmission in silatranes. Confirmation of the pentacoordinated structure in solution
Authors: van Genderen Marcel H. P. , Buck Henk M. 
Published: September 2010

AbstractA 300‐MHz 1H‐NMR conformational analysis study of a set of pentacoordinated silicon compounds (silatranes) and their tetracoordinated counterparts is presented. The solution conformation of the silatranes shows a close resemblance to known X‐ray structures, although the silatrane conformation was found to depend upon the solvent polarity. Comparison of the conformation of a 2‐methoxyethoxy fragment in the tetra‐ and pentacoordinated systems showed the existence of conformational transmission, similar to that known for phosphorus compounds. Enhanced electrostatic repulsion between the vicinal oxygens in the 2‐methyoxyethoxy fragment produces a trans conformation around the CC bond in the pentacoordinated silatranes. The conformational transmission effect is smaller in silatranes than in phosphorus compounds, due to a relatively weak fifth bond.
Solvent dependence of the rotamer population around the interglycosidic C(5)C(6) bond of (1→6)‐β‐linked digalactopyranosides
Authors: de Vries Nanne K. , Buck Hendrik M. 
Published: September 2010

AbstractA 300‐MHz 1H NMR study of the rotamer population around the interglycosidic C(5)C(6) bond of methyl 2,3,4‐tri‐O‐methyl‐6‐O‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐galactopyranosyl)‐β‐ (1) and ‐α‐D‐galactopyranoside (2) is reported. The existence of the (1→6)‐β‐linkage in these compounds is established by homo‐ and heteronuclear 2‐D NMR techniques. It is shown that the dependence on solvent polarity of the population around the C(5)C(6) bond for the dissaccharides is almost identical to that for monosaccharides. The influences of stereoelectronic effects and solute–solvent interactions on the conformational properties of the interglycosidic linkage are discussed briefly.
A new approach to 1, 2‐dilithioethane; easy preparation of dilithiomethane
Authors: van Eikema Hommes N. J. R. , Bickelhaupt F. , Klumpp G. W. 
Published: September 2010

Abstract1,2‐Dilithioethane (I) is postulated to be formed together with dilithiomethane (VIII, main product) from methylene iodide and lithium 4, 4′‐di‐tert‐butylbiphenyl in THF at T < ‐70°C. With Me3SnCl the tin derivatives of I, VIII and their C3 and C4 homologues are obtained.