SELECTIVITE DE LA REDUCTION DE CYCLOHEXEN-2 ONES PAR NBu4BH4 DANS DIVERS SOLVANTS ET PAR NaBH4 DANS DES CONDITIONS DE TRANSFERT DE PHASE

Article abstract of DOI:10.1016/S0040-4020(01)92046-0

The 2-cyclohexenone 1 and isophorone 2 reductions with NBu4BH4 in aprotic solvents lead to a highly preferential 1-4 attack; i.e. 85percent with 1 and 96percent with 2 in THF.These regioselectivities are nearly the same as those observed with LiBH4 in the presence of <2.1.1> cryptand confirming thus the cation influence.This method which is inexpensive and easy to work up, seems to constitute a general way to reduction of α-enones to saturate alcohols while other reagents such as K(sec Bu)3BH are not able to reduce the carbon-carbon double bond of isophoron.Phase transfer catalysis conditions are not useful for selective reduction: large amounts of allylic alcohols are formed in liquid-liquid phase transfer conditions (60percent in toluene-water); a good regioselectivity is only obtained when a cryptand is used as a transfer agent in solid-liquid conditions.