Proton donors isopropyl alcohol

Reduction of a series of cyclohexanones (2- and 4-methyl, 4-isopropyl, 4-r-butyl and 3,3,5-trimethyl), both in the presence and absence of proton donors gave a 99 1 ratio of equatorial to axial alcohol. For 3-methylcyclohexanone the ratio was 94 6. Also, reduction of menthone (4) affords a 97 3 ratio of equa-... 

A series of dialkylcyclopentenones (67) has been reduced with Li-NHs in the presence of various proton donors (phenol and methyl, ethyl, isopropyl and r-butyl alcohols). These reductions gave complex mixtures of products, most of which were cyclopentanols (68), arising from sequential conjugate reduction to the cyclopentanone followed by reduction to the saturated secondary alcohol. In all cases, and regardless of the relative stereochemistry of R, R and X, the major product was a secondary alcohol in which the hydroxy group was rrans to the adjacent alkyl group (68). ... 

While the reactions ofketenes with enantiopure alcohols usually give modest selectivities [769], the use of (ethyl lactate (isopropyl lactate (/ )-2.1 (R = Me, R = i-Pr) or (R)-pantolactone 1.16 as proton donors has allowed the highly enantioselective formation of 2-arylpropionic esters. A mild hydrolysis (AcOH/HCl or LiOH) leads to the corresponding adds, which are anti-inflammatory drugs [554,923] (Figure 4.8). This method has been extended by Durst and Koh [861, 999] to the synthesis of enantioenriched a-halogenated esters, which are precursors of aminoacids (Figure 4.8). 

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