Studies on diastereoselective reduction of cyclic β-ketoesters with boron hydrides. Part 4: The reductive profile of functionalized cyclohexanone derivatives

Abstract

Reduction of 2-allyl-2-carboalkoxycyclohexanones ( 3d- f ), 2-propyl-2-carboethoxycyclohexanone ( 3g ) and 2-benzyl-2-carboethoxycyclohexanone ( 3h ) with boron hydrides in the presence and absence of several chelating agents were studied. Molecular modeling studies using semiempirical PM3 method were performed in order to find a suitable explanation of the diastereoselection of ketone carbonyl faces during the reductive process, which yielded trans-2-allyl-2-carboethoxycyclohexanol ( 6e ) and cis-2-allyl-2-carboethoxycyclohexanol ( 7e ) in good diastereomeric excess by using inexpensive sodium and tetrabutylammonium borohydrides.