The Synthesis of (±)-α-Vetispirene Via the Dieckmann Condensation of Ethyl 4-(2,6-Dimethyl-1-Carbethoxycyclohex-2-Enyl)-Butyrate

A new process for the synthesis of (±)-α-vetispirene ( 1 ) starting from 2,4-dimethyl-3-carbethaxycyclohexene ( 2 ) is described. The key steps include the stereoselective alkylation of 2 with ethyl 4-bromo-butyrate to yield ethyl 4-(2,6-dimethyl-1-carbethoxycyctohex-2-enyl)-bytyrate ( 3 ) and spiroannulation of 3 by Dieckmann condensation to give 2-carbethoxy-6,10-dimethyl spiro4,5] deca-6-en-1-one ( 4 ).