Vinyl ether alcohols/esters, asymmetric

Asymmetric hydrogenation of vinyl ether alcohols proceeded in better selectivity than the ester counterparts, but acid sensitivity was observed for 66a-d, and a stoichiometric equivalent of potassium carbonate relative to the substrate was... 

R)-(-)-2,2-Diphenylcyclopentanol (1) is a highly effective chiral auxiliary in asymmetric synthesis. Hydrogenation of chiral 0-acetamidocrotonates derived from this alcohol has afforded the corresponding 0-amido esters with high diastereoselectivity (96% de).6 In addition, (R)-1 has been used as a chiral auxiliary in Mn(lll)-based oxidative free-radical cyclizations to provide diastereomerically enriched cycloalkanones (60% de).7 Our interest in (R)-(-)-2,2-diphenylcyclopentanol is its utility as a chiral auxiliary in Lewis acid-promoted, asymmetric nitroalkene [4+2] cycloadditions. The 2-(acetoxy)vinyl ether derived from alcohol (R)-1 is useful for the asymmetric synthesis of 3-hydroxy-4-substituted pyrrolidines from nitroalkenes (96% ee).8 In a similar fashion, a number of enantiomerically enriched (71-97% ee) N-protected, 3-substituted pyrrolidines have been prepared in two steps from 2-substituted 1-nitroalkenes and (R)-2,2-diphenyl-1-ethenoxycyclopentane (2) (see Table).9... 

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