A Novel Use of the Anions of Fischer-type Carbene Complexes as Alkenyl Metallic Species

The anions generated by deprotonation of Fischer-type carbene complexes or by 1,4-addition of lithium enolates to α,β-unsaturated complexes are found to act as alkenyl metallic species on iodine oxidation. Various α-methoxy-α,β-unsaturated esters are formed by the treatment of such anions with iodine in the presence of methanol and silver trifluoromethanesulfonate. In addition, alkylcerium reagents are found to undergo 1,4-addition to α,β-unsaturated carbene complexes with high efficiency.