Journal of Organic Chemistry p. 855 - 861 (1987)
Update date:2022-07-31
Topics:
Fang, Jim-Min
Hong, Bor-Cherng
Liao, Li-Fan
The crotyllithium compound 1 generated from (E)-2-(1-propen-1-yl)-1,3-dithiane reacted with an aldehyde to give γ-products in favor of the anti isomer.This regio- and diastereoselective reaction is applicable to syntheses of trans β,γ-disubstituted γ-lactones, including natural products of (+/-)-eldanolide and (+/-)-trans quercus lactone.The γ(1,2)-adducts obtained from the reaction of 1 and enals underwent alkoxy-Cope rearrangements on treatment with KH.The consequence is virtually complete α(1,4)-addition of crotyllithium 1 to α,β-unsaturated aldehydes.Crotyllithium 1 reacted with ketones at either the α- or the γ-site, depending on the nature of respective ketone.The regiochemistry is well interpreted by the hard and soft acids and bases principle, when the steric effect is a minor controlling factor.The effects of HMPA and reaction temperature on the regioselectivity were also evaluated.
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