Development of catalysts for the Baylis-Hillman reaction: the application of tetramethylguanidine and attempts to use a supported analogue

We show here that tetramethylguanidine (TMG) is a useful catalyst for the B aylis-Hillman reaction of aldehydes with methyl acrylate, showing good acti vity with a range of aldehyde substrates and, unlike many other catalysts o r catalyst Mixtures, it can be used to good effect with simple aliphatic al dehydes. We show that the activity of the catalyst is decreased when the re action is run using solvents rather than solvent-free but, in the case wher e a solvent is necessary, dichloromethane offers the best results. Attempts to use supported or derivatised TMG complexes as catalysts for the reactio n have been unsuccessful suggesting that the presence of an amine hydrogen is key to the activity of TMG. Attempts to use stabilised aliphatic phosphi nes as catalysts for the reaction have proven partly successful, with only modest yields of product being obtained with 2-(dicycloliexylphosphino)biph enyl and 2-(di-tert-butylphosphino)biphenyl. The Verkade superbase, P(MeNCH 2CH2)(3)N, proved inactive as a catalyst, an adduct with the acrylate being the only product formed.