ADDITION OF ORGANOCOPPER REAGENTS TO ALLYLIC ACRYLATES - THE PREPARATION OF GAMMA,DELTA-UNSATURATED ACIDS AND SUBSEQUENT FUNCTIONALIZATION TO GAMMA-LACTONES

Conjugate addition of monoorganocopper compounds with iodotrimethylsilane (TMSI) or lithium diorganocuprates, with or without halosilanes, to allylic acrylates give allylic silyl ketene acetals/ester enolates. These can undergo Claisen rearrangement to give diastereomeric mixtures of gamma,delta-unsaturated acids after aqueous work-up. For organocuprates, the diastereomeric ratio is strongly affected by the halosilane. Either diastereomer can be obtained as major product by proper choice of copper reagent. Cyclization of the acids followed by reduction gives gamma-lactones in good yields. A copper iodide/dimethyl sulfide complex is introduced as an excellent precursor to organocopper reagents.