88915-94-0Relevant articles and documents
Regiochemical Convergence in the Reaction of Heterosubstituted Allylic Carbanions via Allylic Aluminum and Boron "Ate" Complexes
Yamamoto, Yoshinori,Yatagai, Hidetaka,Saito, Yoshikazu,Maruyama, Kazuhiro
, p. 1096 - 1104 (1984)
The regiochemistry in reactions of heterosubstituted allylic carbanions (1) is highly controlled via allylic aluminum or boron "ate" complexes which direct both carbonyl compounds and reactive halides to the α-position with high regioselectivity.For example, carbonyl compounds react with the oxygen- (3), sulfur- (12), selenium- (20), and silicon- (25) substituted allylic carbanions at the α-position via the ate complexes.Although the reactions of the ate complexes (2) with aldehydes generally produce a mixture of erythro and threo isomers, the aluminum ate comlex of 3b gives the erythro isomer (5) with very high stereoselectivity.This procedure is applied to the stereoselective synthesis of exo-brevicomin (9).With allylic halides, the oxygen- (3a) and sulfur- (12) substituted allylic carbanions again react at the α-position via the ate complexes.However, the coupling mode is entirely different; the α-α' coupling product (10) is obtained from 3a, while the α-γ' coupling product (15) is produced from 12.
