Asymmetric epoxidation of substituted chalcones and chalcone analogues catalyzed by α-d-glucose- and α-d-mannose-based crown ethers
作者:Attila Makó、Zsolt Rapi、György Keglevich、Áron Szöllősy、László Drahos、László Hegedűs、Péter Bakó
DOI:10.1016/j.tetasy.2010.05.009
日期:2010.4
The chiral monoaza-15-crown-5 lariat ethers annellated to methyl-4,6-O-benzylidene-α-d-glucopyranoside-1 or mannopyranoside 2 have been applied as phase-transfer catalysts in the epoxidation of substituted chalcones and chalcone analogues with tert-butylhydroperoxide resulting in significant asymmetric induction. It was found that the position of the substituents in the aromatic ring of the chalcone
与甲基-4,6- O-亚苄基-α-d-吡喃吡喃糖苷-1或甘露吡喃糖苷2甲基化的手性单氮杂-15冠-5套索状醚已被用作相取代的催化剂,用于取代的查耳酮和查尔酮类似物的环氧化与叔-butylhydroperoxide导致显著不对称诱导。发现查尔酮的芳环中取代基的位置对化学收率和对映体过量都有影响。在邻位取代的模型化合物中,对映选择性最低(62-83%ee)。在的情况下获得的最高EE值(83-97%ee)的对位替换模型。在查耳酮类似物中,对于具有α-叔丁基和β-芳基基团的模型化合物,可检测到最大ee(90-92%)。使用基于葡萄糖的冠醚1,优选形成(-)-对映体,而将基于甘露糖的2用作催化剂,则(+)-对映体过量。