Several transition metal complexes derived from Mo, Re, Ru, Co and Fe are known to catalyze the addition of ethyl diazoacetate to carbonyl compounds in the presence of triphenylphosphine leading to the formation of (E)-conjugated esters.

Our research group has developed the first catalytic methylenation of carbonyl compounds using Wilkinson's catalyst in presence of trimethylsilyldiazomethane, i-PrOH and triphenylphosphine. This reaction is very efficient and compatible with a variety of functional groups. However, limited reactivity was observed with heterocyclic compounds and nitro-containing substrates. Here-in, we wish to present the copper-catalyzed methylenation of carbonyl compounds. Not only, copper (I) catalysts are more stable and less expensive than the rhodium catalyst, but also these complexes shows a better catalytic activity with nitro, aromatic and heteroaromatic substrates. Further we have recently found that copper (I) salts efficiently catalyzed the olŽfination of carbonyl compounds with various diazocarbonyl reagents. It is the first transition metal complex which is suitable for the reactions with both types of diazo compounds.

The scope, the selectivity and the mechanism of the copper-catalyzed olefination reaction will be discussed.