Catalytic Asymmetric Aza-Morita−Baylis−Hillman Reaction of Methyl Acrylate: Role of a Bifunctional La(O-iPr)3/Linked-BINOL Complex

• Published in: Journal of the American Chemical Society Vol. 132; no. 34; pp. 11988 - 11992
• Main Authors: Yukawa, Takafumi, Seelig, Bianca, Xu, Yingjie, Morimoto, Hiroyuki, Matsunaga, Shigeki, Berkessel, Albrecht, Shibasaki, Masakatsu
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.09.2010
• Subjects: Acrylates - chemistry; Catalysis; Coordination Complexes - chemistry; Imines - chemical synthesis; Imines - chemistry; Molecular Structure; Naphthols - chemistry; Organometallic Compounds - chemistry; Stereoisomerism
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja103294a

The catalytic asymmetric aza-Morita−Baylis−Hillman reaction using unactivated methyl acrylate is described. A simple Lewis acidic metal catalyst, such as La(OTf)3, was not suitable for the reaction, but rare earth metal alkoxide/linked-BINOL complexes possessing bifunctional Lewis acid and Brønsted base properties efficiently promoted the reaction in combination with an achiral nucleophilic organocatalyst. The combined use of a La(O-iPr)3/(S,S)-TMS-linked-BINOL complex with a catalytic amount of DABCO promoted the aza-Morita−Baylis−Hillman reaction of a broad range of N-diphenylphosphinoyl imines. Products from aryl, heteroaryl, and alkenyl imines were obtained in 67−99% yield and 81−95% ee. It is noteworthy that isomerizable alkyl imines could be employed as well, giving products in 78−89% yield and 94−98% ee. Initial rate kinetic studies as well as kinetic isotope effect experiments using α-deuterio-methyl acrylate support the importance of both the nucleophilicity of La-enolate and the Brønsted basicity of a La-catalyst for promoting the reaction.