Sulfoxides, vinyl Michael-type addition

Allyl vinyl ethers have also been obtained by elimination reactions, e.g., intramolecular bromo-etherification/base-catalyzed hydrogen bromide elimination164 166( 0r the phenylseleno etherifi-cation/selenoxide elimination reaction158 167. Tertiary allylic alcohols have been vinylated by a Michael-type addition to a vinyl sulfoxide followed by elimination of benzenesulfenic acid168. 

Tertiary allylic alcohols can be vinylated by a Michael-type addition to a vinyl sulfoxide 4, followed by eUmination of PhSOH (Eq. 3.1.6) [11]. A solution of the sulfoxide 5 was heated in the presence of both sodium bicarbonate and a-pinene, which is utihzed to scavenge released sulfinic acid and minimizing unwanted side reactions, to give the bicycUc alcohol 6 in 45% yield. 

There are numerous reports of the P-addition of organometallic reagents to racemic a,p-unsaturated sulfoxides [62,63]. For example, the Michael-type reaction of dialkylcuprates with p-chlorophenyl vinyl sulfoxide (65), followed by reaction of the initially formed a-sulfinyl carbanion (66) with electrophiles such as benzophenone, gave the products (67) (Scheme 5.21) [66]. 

An intramolecular version of enolate Michael addition to enantiomerically pure vinylic sulfoxides is represented by reaction of a cyclopentenone sulfoxide with dichloroketene (Scheme 5)90 this type of additive Pummerer rearrangement has been developed by Marino and coworkers91 into a highly effective way of constructing variously substituted lactones in very high enantiomeric purity (equation 43). 

Michael-Additions The most important application of this type of reaction is the carbon-carbon bond formation p to a carbonyl function by the addition of carbanion. The asymmetric version of the Michael-addition has been known since 1973. An optically active vinyl sulfoxide served as chiral auxiliary198). 

---