A new cyclization reaction of an aryl or vinyl halide bearing a carbonyl group such as ketone or ester has been developed by use of a stannyl anion generated in DMF from Bu(3)SnSiMe(3) and Bu(4)NCl.
Metal free stannyl anion generated from Bu3SnSiMe3 and R4NX in DMF reacted with an aryl or vinyl halide to produce the aryl or vinyl anion via so-called halogen-metal exchange process, which reacted with internal carbonyl group to afford cyclized product in good yield.