Carbon-Carbon Bond Formation by Radical Cyclisation: Regioselective Synthesis of Coumarin-Annulated Sulfur Heterocycles
作者:K. C. Majumdar、A. Biswas、P. P. Mukhopadhyay
DOI:10.1055/s-2003-41068
日期:——
A simple convergent synthesis of cis-benzothiopyrano[3,2-c]benzopyran-7(2H)-ones 4a-f (70-75%) through implementation of a regioselective ‘6-endo-trig’ aryl radicalcyclisation of the respective 4-[(2-bromobenzyl)sulfanyl]-2H-chromen-2-ones 3a-f (80-85%) with tributyltin hydride in the presence of a radical initiator (AIBN) is described. The starting materials 3a-f are synthesised by phase-transfer-catalysed