One-pot synthesis of γ-butyrolactones and 4,5-dihydrofurans from α-chloro-α-ketosulfides and olefins

Lewis acid (SnCl4) catalyzed reaction of ethyl α-chloro-α-( p -chlorophenylthio)acetate ( 1b ) with several olefins afforded the corresponding γ-butyrolactones ( 9 ) in good yields (51 – 92%). Under almost the same conditions, α-( t -butylthio)-α-chloroacetone ( 1c ) reacted with olefins to give the expected 4,5-dihydrofurans ( 10 ) in moderate yields (41 – 55%).