Asymmetric Synthesis. Part 2.† Enantioselective Conjugate Addition of Grignard Reagents to the Cinnamamide and Crotonamide deriving from (R)-(–)-N-(2-Fluorobenzyl)-2-aminobutanol. Determination of Diastereoisomeric Excess by 19F NMR Spectroscopy

Abstract

Conjugate addition of various Grignard reagents to the N-(2-fluorobenzyl)cinnamamide (R)-(+)-5 and crotonamide (R)-(+)-7 afforded the corresponding adducts 8a–e and 9a–f in good yields and in high diastereoisomeric excesses, as evidenced by ¹⁹ F NMR; acidic hydrolysis of these adducts gave the corresponding β-substituted alkanoic acids (R)-10a–e and 11a–f, respectively.