Protic Functionality-Tolerant Decarboxylative Thioester syn-Aldol Reactions
D. Magdziak, G. Lalic, H. M. Lee, K. C. Fortner, A. D. Aloise, M. D. Shair*
Harvard University, Cambridge, USA
21 September 2005 (online)
Traditional aldol reactions use quite basic conditions; often requiring protecting groups on protic functionalities. Aldol reactions under neutral conditions avoid this requirement, and an efficient precursor for such reactions is methyl malonic acid half thioester (MeMAHT). In the presence of Cu(OTf)2, (R,R)-Phbox, and an enolizable aldehyde (which can contain unprotected protic functional groups), MeMAHT undergoes syn-aldol reaction in good yield, with excellent enantioselectivity and moderate to excellent diastereoselectivity. The reaction is insensitive to other reactive functionalities including methyl ketones, acetals, ketals, and acid-sensitive indole-containing aldehydes.