Our previous studies have shown vinyl sulfoxonium salts (α,β-unsaturated sulfoxonium salts) to be excellent Michael acceptors for the synthesis of 3,4-trans-γ-lactones. Investigation of recoverable tetramine reagents (Koga amines) as chiral ligands for the reaction of lithium enediolates (derived from 2-arylacetic acids) with vinyl sulfoxonium salts resulted in γ-lactones being formed in moderate to good yields (generally 60-70%), with good diastereoselectivity (up to 91:9 dr), and with moderate to high enantioselectivity (up to 90% ee). We also observed a curious change in the sense of diastereoselectivity from favoring the trans-isomer (in the absence of Koga amine) to favoring the cis-isomer when a Koga tetramine was employed, thus allowing for great synthetic versatility with variations on the protocol. Details of reaction optimization, substrate scope, and possible models for diastereoselectivity and enantioselectivity will be presented.

Asymmetric synthesis of γ-lactones from vinyl sulfoxonium salts

251st National Meeting (2016)

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