Corey-Bakshi-Shibata reaction

The pioneering work from Itsuno group [11-14] on stoichiometric 1,2-aminoalcohol-borane complex-mediated borane reduction of ketones led to the discovery of well-defined oxazaborolidine catalyzed asymmetric reduction by Corey and coworkers [15-18]. Known as Corey-Bakshi-Shibata reaction, or CBS reduction, this reaction has become a standard method for making chiral secondary alcohols for complex molecule synthesis [19]. The generally accepted mechanism of this reaction is shown in Fig. 2. Coordination of the electrophilic reductant BH3 to the nitrogen atom of... 

The pioneering studies by Itsuno [1] and Corey [2] on the development of the asymmetric hydroboration of ketones using oxazaborolidines have made it possible to easily obtain chiral secondary alcohols with excellent optical purity [3]. Scheme 1 shows examples of Corey s (Corey-Bakshi-Shibata) CBS reduction. When oxazaborolidines 1 were used as catalysts (usually 0.01-0.1 equiv), a wide variety of ketones were reduced by borane reagents with consistently high enan-tioselectivity [2]. The sense of enantioselection was predictable. Many important biologically active compounds and functional materials have been synthesized using this versatile reaction [2-4]. 

Related reactions Corey-Bakshi-Shibata (CBS) reduction, Noyori asymmetric hydrogenation ... 

The Corey-Bakshi-Shibata reduction (CBS reduction) is a highly enantioselective method for arylketones, diaryl ketones, and dialkylketones. In addition, cyclic a,p-unsaturated ketones, acyclic a,p-unsaturated ketones, and a,p-ynones are reduced enantioselectively in a 1,2-fashion. The high enantioselective nature of this reduction relies on the chiral oxazaborolidine catalyst, shown in the reaction scheme, in the presence of borane or a dialkylborane. Reviews (a) Singh, V. K. Synthesis 1992, 605-617. (b) Deloux, L. Srebnik M. Chem. Rev. 1993,93,163-1. (c) Corey, E. J. Helal, C. J. Angew. Chem. Int. Ed. 1998, 37. 1986-2012. 

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