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Lewis Base Assisted Brønsted Base: Phosphine Oxides and La-Aryloxides
H. Morimoto, T. Yoshino, T. Yukawa, G. Lu, S. Matsunaga*, M. Shibasaki*
The University of Tokyo, Japan
22 January 2009 (online)
Combined acid and base catalysis is a well-established concept which has led to the development of highly reactive systems. However, utilization of a Lewis base to activate a Brønsted base in a catalytic system is genuinely rare. The authors report that addition of a bidentate phosphine oxide Lewis base to a lanthanum aryl oxide produces a highly reactive catalyst for the anti-selective Mannich-type reaction. In control experiments, with the absence of Lewis base, La(OAr)3 gives both poor reactivity and diastereoselectivity.