Peterson alkenation phosphorus substituted alkenes

In the original study by Peterson, the alkenation procedure was found to be compatible with sulfur and phosphorus substitution. The alkenation reaction has been tqrplied successfully to a variety of substituted alkenes. Because of the aiuon-stabilizing nature of the thiophenyl, the p-hydroxysiliuie is not isolated and the elimination to the alkene takes place directly to form a 1 1 mixture of ( )- and (Z)-isomers. Ager studied the reaction of the lithio anions of phenyl (trimethylsilyl)methyl sulfides (318) with a variety of carbonyl compounds (equation 72). Yields of this process were good, and addition occurred even with enolizable substrates. This reaction was extended to vinyl sulfones. In contrast to the sulfide case, the substituted sulfone silyl anion behaves as a base, leading to undesired enolization. The best yields were observed for the case where R is a hydrogen or phenyl. 

In the Peterson reaction of an a-silyl carbanion bearing a phosphorus substituent on the anionic carbon atom, there are two possibilities for alkene formation, that is, the Peterson reaction to form phosphorus-substituted alkenes and the Wittig-Horner reaction and the Wadsworth-Emmons reaction to form silicon-substituted alkenes. Most of the reports on these competing reactions have been focused on the reactions of a-silyl phosphonates with carbonyl compounds. It is noteworthy that the alkenylphosphonates have been exclusively obtained in almost every case. That is, the Peterson reactions override the Wittig and Wadsworth-Emmons reactions. 

---