A catalyst system consisting of RuCl2[(S)-tolbinap][(R)-dmapen] and t-C4H9OK in 2-propanol effects asymmetric hydrogenation of arylglyoxal dialkylacetals to give the alpha-hydroxy acetals in up to 98% ee. Hydrogenation of racemic alpha-amidopropiophenones under dynamic kinetic resolution predominantly gives the syn alcohols in up to 99% ee and > 98% de, while the reaction of racemic bezoin methyl ether gives the anti alcohols in excellent stereoselectivity.
Asymmetric reduction of α-keto acetals with potassium 9-O-(1,2-isopropylidene-5-deoxy-D-xylofuranosyl)-9-boratabicyclo[3.3.1]nonane. Enantioselective synthesis of α-hydroxy acetals with high optical purities
作者:Byung Tae Cho、Yu Sung Chun
DOI:10.1016/0957-4166(94)80142-8
日期:1994.7
Asymmetric reduction of alpha-keto acetals with a chiral borohydride, potassiun 9-O-(1,2-isopropylidene-5-deoxy-alpha-D-xylofuranosyl)-9-boratabicyclo[3.3.1]nonane in THF at -78 degrees C provided the corresponding alpha-hydroxy acetals with 87-99% ee.