Development of catalysts for the Baylis–Hillman reaction: the application of tetramethylguanidine and attempts to use a supported analogue
作者:Nicholas E. Leadbeater、Cornelia van der Pol
DOI:10.1039/b106267k
日期:2001.11.1
We show here that tetramethylguanidine (TMG) is a useful catalyst for the BaylisâHillman reaction of aldehydes with methyl acrylate, showing good activity with a range of aldehyde substrates and, unlike many other catalysts or catalyst mixtures, it can be used to good effect with simple aliphatic aldehydes. We show that the activity of the catalyst is decreased when the reaction is run using solvents rather than solvent-free but, in the case where a solvent is necessary, dichloromethane offers the best results. Attempts to use supported or derivatised TMG complexes as catalysts for the reaction have been unsuccessful suggesting that the presence of an amine hydrogen is key to the activity of TMG. Attempts to use stabilised aliphatic phosphines as catalysts for the reaction have proven partly successful, with only modest yields of product being obtained with 2-(dicyclohexylphosphino)biphenyl and 2-(di-tert-butylphosphino)biphenyl. The Verkade superbase, P(MeNCH2CH2)3N,
proved inactive as a catalyst, an adduct with the acrylate being the only product formed.
本文研究表明,四甲基胍(TMG)是巴利斯-希尔曼反应中醛与甲基丙烯酸酯的有效催化剂,对一系列醛底物显示出良好的活性,并且与其他许多催化剂或催化剂混合物不同,它可有效地用于简单脂肪醛。研究表明,当反应在有机溶剂中进行而非无溶剂时,催化剂的活性会降低,但在需要溶剂的情况下,二氯甲烷能提供最佳结果。试图使用负载或衍生化的TMG配合物作为该反应的催化剂均未成功,这表明胺氢的存在对TMG的活性至关重要。尝试使用稳定化的脂肪族膦作为催化剂取得了部分成功,仅在使用2-(二环己基膦基)联苯和2-(二叔丁基膦基)联苯时获得了适度的产物收率。Verkade超碱,即P(MeNCH2CH2)3N,作为催化剂无效,仅形成与丙烯酸酯的加合物。