Reductive opening of phenyl substituted thiacycloalkanes: New way for sulphur-containing organolithium compounds

The reaction of 2-phenyl substituted four, five and six membered thiacycloalkanes (1, 4 and 7) with lithium and a catalytic amount of DTBB (5 mol %) in THF at -78 degrees C leads to the corresponding sulphur-containing benzylic organolithium compounds (2, 5 and 8), which by reaction with different electrophiles [D2O, Me(3)SiCl, Bu(t)CHO, Me(2)CO, Et(2)CO, (CH2)(4)CO, CO2] followed by hydrolysis with water afford the expected functionalised mercaptans (3, 6 and 9) in a regioselective manner. Some reaction products (3, 6) are cyclised under acidic conditions (85% phosphoric acid) to yield the corresponding homologous substituted sulphur-containing saturated heterocycles (10, 11). (C) 1997 Elsevier Science Ltd.