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Pure Appl. Chem., 2006, Vol. 78, No. 2, pp. 511-518

Dabbling with air-stable organoaluminum species

Kallolmay Biswas, Alex Chapron, Thea Cooper, Paul K. Fraser, Andrew Novak, Oscar Prieto and Simon Woodward

School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, UK

Abstract: Highly stereoselective 1,2-additions of AlMe3 or its air-stable analog DABCO(AlMe3)2 to aldehydes are realized in the presence of a Ni(acac)2-derived catalyst using phosphoramidite ligands giving sec-alcohols in up to 95 % ee. Very high turnover number (TON) (>1500) and turnover frequency (TOF) (>350 h-1) values can be realized in these reactions. The substrate range, trials of various (DABCO)a(AlR3)b reagents (a = 0.1; b = 1.2; R = Me, Et, Bui), ligands, and molecular modeling studies are used to propose a working model for the catalytic cycle and the origin of the stereoselectivity. The phosphoramidite ligand is proposed to bind the nickel in an η2 manner via the P-donor and one of the C=C aryl bonds of the CHAr amine group. Preliminary studies indicate that DABCO(AlMe3)2 can also be used as a methyl source in Pd-catalyzed cross-coupling reactions of ArX (X = Br, I) species.