alpha -Alkyl-beta -keto carbonitriles can be reduced stereoselectively to syn- and anti-alpha -alkyl-beta -hydroxy carbonitriles. The stereoselectivity can be explained in terms of properties of the Lewis acid employed. TiCl4 in noncoordinating solvents such as dichloromethane, followed by reduction with the borane/pyridine complex, predominantly led to the syrz-alpha -alkyl-beta -hydroxy carbonitriles, according to a chelate transition state, whereas CeCl3 in coordinating solvents such as THF, followed by reduction with LiBH4, predominantly led to the anti-isomers, in agreement with an open-chain transition state. The reduction to syn-alpha -alkyl-beta -hydroxy carbonitriles is the first general preparation of these compounds

An Efficient Diastereoselective Reduction of alfa-Alkyl-beta-keto Carbonitriles with TiCl4/BH3 or LiBH4/CeCl3 to syn- or anti-alfa-Alkyl-beta-hydroxy Carbonitriles

DE NINO, Antonio;DALPOZZO R;
2001

Abstract

alpha -Alkyl-beta -keto carbonitriles can be reduced stereoselectively to syn- and anti-alpha -alkyl-beta -hydroxy carbonitriles. The stereoselectivity can be explained in terms of properties of the Lewis acid employed. TiCl4 in noncoordinating solvents such as dichloromethane, followed by reduction with the borane/pyridine complex, predominantly led to the syrz-alpha -alkyl-beta -hydroxy carbonitriles, according to a chelate transition state, whereas CeCl3 in coordinating solvents such as THF, followed by reduction with LiBH4, predominantly led to the anti-isomers, in agreement with an open-chain transition state. The reduction to syn-alpha -alkyl-beta -hydroxy carbonitriles is the first general preparation of these compounds
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.11770/137566
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