Thioamides and Thioformamides for Sequential Reactions with Organolithium and Grignard Reagents

Sequential reactions of thioamides and thioformamides with organolithium and Grignard reagents are described. Thioiminium salts derived from these sulfur isologues of amides readily react with lithium acetylides to lead to several types of products, including α,β-unsaturated ketones, whereas sequential additions of lithium acetylides and Grignard reagents afford propargylamines. The direct addition of organolithium and Grignard reagents to thioformamides proceeds with high efficiency to give a range of tertiary amines.