1,6-asymmetric induction during the conjugate addition of arylcopper reagents to a chiral sulfinyl-substituted pyrrolyl α,β-unsaturated amide

The asymmetric conjugate addition of arylcopper reagents derived from aryl Grignard reagents and copper(I) iodide to a chiral 1-[2-(p-tolylsulfinyl)]pyrrolyl cinnamide proceeded smoothly to give (3R)-adducts with high diastereoselectivities (greater than or equal to 92% de) in high yields. Conjugate additions either of the cinnamide with the alkyl Grignard reagent-copper(I) iodide combination or of the crotonamide derivative with aryl Grignard reagent-copper(I) iodide gave moderate to good diastereoselectivities. With these sulfinyl pyrrolyl alpha,beta -unsaturated amides, the chiral auxiliary was efficiently recovered without any loss of optical purity after asymmetric conjugate addition.