Selective reductions. 52. Efficient asymmetric reduction of α-acetylenic α′-fluoroalkyl ketones with either B-chlorodiisopinocampheylborane or B-isopinocampheyl-9-borabicyclo[3.3.1]nonane in high enantiomeric purity. The influence of fluoro groups in such reductions
作者:P.Veeraraghavan Ramachandran、Baoqing Gong、Aleksandar V. Teodorovic'、Herbert C. Brown
DOI:10.1016/0957-4166(94)80056-1
日期:1994.6
whereas 1 is ineffective for these types of ketones. In all of the above reductions, the fluoroalkyl group acts as the enantiocontrolling group with one exception. A remarkable inversion in selectivity in the reduction of monofluoromethyl acetylenic ketones with 1 is observed as compared to the reduction with 2, indicating that in the transition state the acetylenic moiety acts as the enantiocontrolling
( - ) -与所述不对称还原前手性α-炔α'氟烷基酮的的系统研究乙-chlorodiisopinocampheylborane [( - ) - DIP-氯化物,1 ]和( - ) -乙-isopinocampheyl -9-硼杂双环[3.3.1 .1]壬烷(R -Alpine-Borane,2)显示,使用这两种试剂,都可以在很高的ee(92->-99%)中还原全氟烷基炔酮。例如,1,1,1-三氟-4-苯基-3-丁炔-2-酮,1,1,1,2,2-五氟-5-苯基-4-戊炔-3-酮和4, 4,5,5,6,6,6-七氟-1-苯基-1-己炔-3-酮在-25°C下EE中在0.25-2 h内以98%,96%和98%的比例被还原为1 ee分别为94%。相同的酮减少2在纯净条件下,在室温下1-4小时内,ee分别为98%,97%和96%。相似地,1,1,1-三氟-3-辛炔-2-酮,1,1,1,2,2-五氟-4-壬炔-3-酮和1