Abstract
Methylmagnesium bromide adds to trimethylsilyloctyne (1) in the presence of 10 mol% 1:0.67 nickel acetylacetonate-trimethylaluminum to give a 9:1 mixture of alkenyl Grignard reagents 2a and 3a. This mixture reacts with water, deuterium oxide, formaldehyde, acetaldehyde, carbon dioxide, iodine, vinyl bromide or allyl bromide to give the expected products 2, 3b to 2, 3j. Nickel catalyzed carbometallation of 4 with MeMgBr followed by quenching with formaldehyde and desilylation gives trans, trans-farnesol (5c). Nickel catalyzed addition of MeMgBr to 6a and 6b proceeds analogously, except that initially formed alkenyl Grignard reagents 7a and 7b isomerize completely to 8a and 8b which are stabilized by chelation. This carbometallation reaction allows the synthesis of both isomers of an allylic alcohol, such as 12 and 13, from a common intermediate 2a.