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An Efficient Diastereoselective Reduction of α‐Alkyl‐β‐keto Carbonitriles with TiCl 4 /BH 3 or LiBH 4 /CeCl 3 to syn ‐ or anti ‐α‐Alkyl‐β‐hydroxy Carbonitriles
Author(s) -
Dalpozzo Renato,
Bartoli Giuseppe,
Bosco Marcella,
De Nino Antonio,
Procopio Antonio,
Sambri Letizia,
Tagarelli Antonio
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200108)2001:15<2971::aid-ejoc2971>3.0.co;2-k
Subject(s) - chemistry , alkyl , pyridine , stereoselectivity , dichloromethane , medicinal chemistry , reduction (mathematics) , lewis acids and bases , chelation , organic chemistry , catalysis , solvent , geometry , mathematics
Abstract α‐Alkyl‐β‐keto carbonitriles can be reduced stereoselectively to syn ‐ and anti ‐α‐alkyl‐β‐hydroxy carbonitriles. The stereoselectivity can be explained in terms of properties of the Lewis acid employed. TiCl 4 in noncoordinating solvents such as dichloromethane, followed by reduction with the borane/pyridine complex, predominantly led to the syn ‐α‐alkyl‐β‐hydroxy carbonitriles, according to a chelate transition state, whereas CeCl 3 in coordinating solvents such as THF, followed by reduction with LiBH 4 , predominantly led to the anti ‐isomers, in agreement with an open‐chain transition state. The reduction to syn ‐α‐alkyl‐β‐hydroxy carbonitriles is the first general preparation of these compounds.