Diastereoselectivity in the triethylamine-catalyzed sulfa-Michael addition of thiols to nitroalkenes: kinetic and thermodynamic control

Stereoselective Synthesis of Z-Styryl Sulfides from Nucleophilic Addition of Arylacetylenes and Benzyl Thiols

The stereoselective synthesis of Z-anti-Markovnikov styryl sulfides via an anionic thiolate-alkyne addition reaction was achieved when the terminal alkynes and benzyl mercaptans were reacted using tBuOLi (0.5 equiv) in EtOH under ambient conditions. Exclusive stereoselectivity (ca. 100%) was achieved by stereoelectronic control via anti-periplanar and anti-Markovnikov addition of benzylthiolates to phenylacetylenes. Solvolysis of lithium thiolate ion pairs in ethanol significantly suppresses the competing formation of the E-isomer. A remarkable enhancement of the Z-selectivity under a longer reaction time was observed.

Sequential Addition Reaction of Sulfanylmethyllithiums and Grignard Reagents to Thioformamides Leading to the Formation of 2-Phenyl-2-sulfanylethyl Tertiary Amines

The reaction of sulfanylmethyllithiums generated from benzylsulfanes and n-BuLi with N,N-dimethylthioformamide followed by the addition of Grignard reagents gave 2-phenyl-2-sulfanyl tertiary amines in moderate to good yields. A range of Grignard reagents involving primary alkyl, aryl, vinyl, and alkynyl Grignard reagents were used. Two carbon-carbon bond-forming reactions were achieved through a one-pot reaction. The reaction showed good to high diastereoselectivity, particularly with alkynyl Grignard reagents.