Thioallyl and Related Anions

Yamamoto, H. Yatagai, and K. Maruyama, J- Chem. Soc., Chem. Commun., 1979, 157 Y. Yamamoto, H. Yatagai, and K. Maruyama, Chem. Lett., 1979, 385. 

Methylthioallyl anion undergoes op-1,4-addition to enones in the presence of HMPA, while 1,2-addition occurs in its absence. The anion (53) derived from 2H-thiopyran (52) by abstraction of the 6-proton (this is the anion that is favoured under conditions of thermodynamic control) has been found to undergo alkylation with Bu Br. Rather than involving an unprecedented S 2 attack at Bu Br, the reaction may involve a one-electron-transfer process. Other studies on the reactions of anions related to (53) have been published. Thioallylic anions have been employed in syntheses of 2-vinylthian, l,l-disilylalk-2-enes, and the natural products mokupalide, manicone, ( )-laurencin, and (6Z)-hedycaryol isomers, amongst other compounds.  

Thioallyl and Related Anions. Alkylation of thioallyl anions, often termed Biellmann alkylation, represents a useful method for forming new C—C bonds, as illustrated by the synthesis of dendrolasin (49), which is a furanoterpene 

Duhamel, P. Duhamel, and N. Mancelle, Bull. Soc. chim. France, 1974, 331. 

The regioselectivity of alkylation and carbonyl addition of various thioallyl anions has been examined, particularly with regard to chelation and ion-pairing effects. Thus, Biellmann and co-workers have found that thioallyl-lithium (50), in the presence of [2,2,2]cryptate, adds to acetone exclusively from the 

The regioselectivity of alkylation has also been studied with cyclic thioallyl anions, with thioallyl-copper systems which involve 5n2 reactions, and with the dianion of prop-2-enethiol (5 ). The products of addition of aldehyde at the a-position of (50) have been converted into cyclopropane 

Oshima, H. Yamamoto, and H. Nozaki, Bull. Chem. Soc. Japan, 1975, 48, 1567. 

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