Tributylstannane-Mediated Cyclization of Thionocarboxylic Acid Derivatives

Article abstract of DOI:10.1021/jo00051a024

Cyclization reactions of various thionoesters and thioamides involving the addition of tri-n-butylstannyl radical to a thiocarbonyl group and intramolecular addition of the resulting radical to a carbon-carbon multiple bond was studied.Dithiocarbonate and (imidazolyl)thiocarbonyl derivatives of homoallylic alcohols gave α-substituted γ-thionobutyrolactones.The reaction is highly dependent on the substitution pattern on the double bond, a high yield of products being obtained only when the double bond is activated and unhindered. (Z)-4-Phenylbut-3-enyl thionobenzoate afforded 4,5-dihydro-2-phenyl-3-benzylfuran in low yield.In reactions involving a thioamide group, good yields of cyclic products were obtained only from compounds in which the electron density on the nitrogen atom is decreased by an electron attracting group.Cyclization of 1-((E)-4-phenylbut-3-en-1-yl)-5-thioxopyrrolidin-2-one (23) afforded 1-aza-4-benzylbicyclo<3.3.0>oct-4-en-8-one (33).