Vinyl sulphoxides reactions

The reaction of the phenylsulphinyl allylic lithium a-carbanion 342 with oxiranes was found by Guittet and Julia to give, after rearrangement and desulphurization, dihydroxy-dienes 343427 (equation 197). Demoute and coworkers have described the alkylation reaction of a very sophisticated 2-alkenyl sulphoxide 344 as a part of the total synthesis of a juvenile hormone 345428 (equation 198). Since the allylic sulphoxide carbanion has an ambident character, the alkylation may occur sometimes also at the y-position. This direction of alkylation is observed in the case of acyclic allylic sulphoxide anions 346, and results in the formation of the corresponding allylic sulphoxide 347 and vinylic sulphoxide 348423 (equation 199). 

Mercaptanes add easily to divinyl sulphoxide in the presence of catalytic amounts of bases, giving / -alkylthioethyl vinyl sulphoxides 545 and / , / -di(alkylthioethyl)sulphoxides 546 (equation 344). When an excess of divinyl sulphoxide is applied the reaction can be stopped at the stage of monoaddition63 5-636. 

Halogenovinyl sulphoxides 551 react with nucleophiles to give -substituted vinyl sulphoxides 552. The first step in the reaction is a Michael addition, followed by an elimination of a halide anion605,627 (equation 351). 

For a recent discussion on the stereochemical aspects of the Diels-Alder reaction with vinyl sulphoxides see References 662, 663. It should be pointed out that vinyl sulphoxides can be considered in [2 + 4]-cycloadditions as acetylene synthons since the sulphinyl moiety may be removed from the product by sulphenic acid elimination. Paquette and coworkers took advantage of this fact in the synthesis of properly substituted anthracenes 562664, (equation 360). 

On the other hand, a very high asymmetric induction was observed in the 1,3-dipolar cycloaddition of (/ )-( + )-p-tolyI vinyl sulphoxide 578 with acyclic nitrones. The reaction... 

Aryl vinyl sulphones, reactions of 646 Aryl vinyl sulphoxides 620 optical resolution of 287 reactions of 354, 355, 360, 361, 621 Asscher-Vofsi reaction 189 Asymmetric induction 625 Asymmetric oxidation 72-78 Asymmetric reduction 78, 79 Asymmetric synthesis 824-846 Atomic orbitals 2, 3 Azetidinones 790, 791 ot-Azidoaldehydes, synthesis of 811 Azidosulphones, photolysis of 883, 884 Azosulphones, photolysis of 879 Azoxysulphones, photolysis of 879 1-Azulyl sulphoxides, synthesis of 265... 

Allyl p-tolyl sulphoxide 535 reacts with sodium methoxide in methanol by initial prototropic isomerization and subsequent addition of methanol to give 536 (equation 333). Protic solvents are photochemically incorporated by the open chain olefinic bond of trans methyl )S-styryl sulphoxide 537 in a Markovnikov regiospecificity (equation 334). Mercaptanes and thiophenols add to vinyl sulphoxides in a similar manner (compare also Reference 604 and Section IV.B.3) to give fi-alkylthio(arylthio)ethyl sulphoxides 538 (equation 335). Addition of deuteriated thio-phenol (PhSD) to optically active p-tolyl vinyl sulphoxide is accompanied by a low asymmetric a-induction not exceeding 10% (equation 336) . Addition of amines to vinyl sulphoxides proceeds in the same way giving )S-aminoethyl sulphoxides in good to quantitative yields depending on the substituents at the vinyl moiety When optically active p-tolyl vinyl sulphoxides are used in this reaction, diastereoisomeric mixtures are always formed and asymmetric induction at the p- and a-carbon atoms is 80 20 (R = H, R = Me) and 1.8 1 (R = Me, R = H), respectively (equation 337) ... 

Reduction of nitroalkanes RNO2 with samarium(II) iodide, obtained from samarium and 1,2-diiodoethane, yields either alkylhydroxylamines RNHOH or alkylamines RNH2, depending on the amount of the reagent434. The base-catalysed reaction of nitroalkanes with phenyl(vinyl) sulphoxide (399) yields the conjugate adducts 400, which fragment to allylic nitro compounds 401 on thermolysis435. 

A substituted o-hydroxyacetophenone (97.4) may be converted in high yield into a 2//-chromene by reaction at — 78°C with phenyl vinyl sulphoxide. Recent developments in the chemistry of fused pyrans (and thiopyrans) have been reviewed [3986]. 

Nitrogen Systems.—Monoaza-compounds. Treatment of the azapentalene anion (745) with dichloromethane and butyl-lithium yields a mixture of indolizine (746 R = H) and compound (747) it has been established that the latter is not a precursor of indolizine.3-Diethylaminoindolizine (746 R = NEt2) is formed by the reaction of 2-bromopyridine with propargyl alcohol and diethylamine in the presence of bis(triphenylphosphine)palladium(ll) dichloride and copper(i) iodide. The pyridinium ylide (748) undergoes 1,5-dipolar cyclization to the tran -dihydroindolizine (749). As in previous years, there have been several reports on the synthesis of the indolizine ring system from pyridinium ylides the methide (750 R = H, R = Ph) adds benzylideneacetophenone to form the tetrahydroindolizine (751), the action of phenyl vinyl sulphoxide. 

The formation of a- and 9-allylated sulphides by the Pummerer-type reaction of vinylic sulphoxides with allylmagnesium bromide has been reported by Iwata et al. Monoallylation and diallylation can take place, depending on the bulkiness of the yS-substituent, and both acyclic and cyclic vinyl sulphoxides undergo the reaction. This method offers applicability to asymmetric synthesis using sulfinyl chirality. 

The use of phenyl vinyl sulphoxide, PhSOCH=CH2, as an acetylene equivalent in Diels-Alder cycloadditions has been developed/ an example being the synthesis of 3,6-diphenylpyridazine (191 Ar = Ph R = H) in 97% yield (Scheme 44 path a). 4-Amino-pyridazines are available also by cycloaddition reactions, in this case between lV-acetyl-4-oxazolin-2-ones, or (better) the unsubstituted oxazolinone, and 1,2,5,6-tetrazines, as illustrated in Scheme 44 (path... 

Apart from one citation, all the papers collected here to illustrate the reactions of vinyl sulphoxides deal with addition reactions. " As would be expected from the nature of the sulphoxide functional group, there are several novel features in these addition reactions compared with those of other vinyl compounds. Pyrolysis of alkyl styryl sulphoxides gives benzothiophens. The proposed mechanism, which involves formation and homolysis of a sulphenic acid followed by cyclization, (54) (55), is supported by the formation of benzo-... 

Asymmetric induction is a factor in nucleophilic and electrophilic additions to a chiral vinyl sulphoxide. " A full account is available of asymmetric syntheses involving the addition of piperidine and of bromine to chiral propenyl and vinyl p-tolyl sulphoxides, respectively (see Vol. 2, p. 50). An observation enhancing the value of a vinyl sulphoxide enantiomer in organic synthesis concerns the control exerted by the metal counterion in Michael addition of the diethyl malonate carbanion to (/ )-(+)-/ra/w-)S-styryl p-tolyl sulphoxide (58). The K-i- and Na salts in EtOH lead to a diastereoisomer mixture in which (59) predominates, while the Li+ salt in THF as the reaction medium leads to a preponderance of the epimeric adduct. ... 

The thiourea derived from the chiral vinyl sulphoxide sulphoraphene (60), a constituent of radish seeds, undergoes cyclization to give unequal amounts of diastereoisomer (61) and its epimer, a consequence of asymmetric induction in the intramolecular addition reaction. ... 

An additive Pummerer rearrangement is an apt description of the course of the reaction between AcCl and the vinyl sulphoxide (62). Hot AcgO converts (62) into products (63) and (64) of a vinylogous Pummerer rearrangement. ... 

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