Rapid organocatalytic aldehyde-aldehyde condensation reactions

We report the results of the systematic optimization of the alpha-methylenation of aldehydes with aqueous formaldehyde, A simple combination of a secondary amine catalyst and a weak acid co-catalyst has been identified, allowing access to alpha-substituted acroleins in a matter of minutes. In the absence of formaldehyde, the catalytic system promoted the self-condensation reaction of alpha,beta-unsaturated aldehydes. Both of these reactions exhibited linear relationships between co-catalyst acidities and reaction rates. A second-order dependence of catalyst concentration was observed, pointing to the involvement of two molecules of the ammonium catalyst in the rate-determining step. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).