Synthesis of 2,2-Dimethyl-2H-thiochromenes, the Sulfur Analogs of Precocenes

Article abstract of DOI:10.1055/s-1987-27866

A new general synthesis of 2,2-dimethyl-2H-thiochromenes in good yield consists of the Michael addition of thiophenols to 3-methyl-2-butenoic acid, intramolecular cyclocondensation of the resultant 3-methyl-3-phenylthiobutanoic acids, reduction of the 2,2-dimethyl-4-oxothiochromenes thus obtained with sodium borohydride, and acid-catalyzed dehydration of the resultant 4-hydroxy-2,2-dimethylthiochromans.