Crossed aldol-type reactions catalyzed by rhodium complexes

Article abstract of DOI:10.1016/0022-328X(88)83037-7

Crossed aldol-type reactions of enol trimethylsilyl ethers with aldehydes and ketones are smooth when carried out with a catalytic amount of a rhodium complex, Rh4(CO)12 or X (X=PF6 and ClO4; COD=cycloocta-1,5-diene, DPPB=1,4-bis(diphenylphosphino)butane), under neutral conditions.A suitable catalyst enables the isolation of three different types of aldol reaction product, β-trimethylsiloxy ketones, β-hydroxy ketones, and α,β-unsaturated ketones.Rh4(CO)12 and ClO4 also catalyze the reaction of enol trimethylsilyl ethers with acetals or ketals, whereas PF6 does not.When ClO4 is used as the catalyst, this type of aldol reaction is extended to the one-pot synthesis of trisubstituted furans from enol trimethylsilyl ether and α-trimethylsiloxy acetal.