Asymmetric Synthesis Using Chiral Acetals : Highly Diastereoselective Nucleophilic Addition of Grignard Reagents to Chiral 1-Oxo-β-tetralone 1-Acetals

Abstract

Nucleophilic addition of organometallic reagents (Grignard reagents and organolithium reagents) to two chiral 1-oxo-β-tetralone 1-acetals (1a, b) was studied. Extremely high stereoselectivity was achieved in the reactions of 1a and 1b with Grignard reagents leading to the α-hydroxy acetals (6) bearing a chiral tertiary alcohol moiety at the homobenzylic position. The stereochemistry of the products derived from 1a was determined by correlation with compound 9 and that of the products derived from 1b was determined by consideration of the citcular dichroism spectrum of the benzoate (11) prepared from 6bC.