The chiral monoaza-15-crown-5 lariat ethers annellated to methyl-4,6-O-benzylidene-α-D-glucopyranoside- (1) or – mannopyranoside (2) used as phase transfer catalysts in the Michael addition of 2-nitropropane to substituted chalcones and chalcone analogues resulted in a significant asymmetric induction. The type of substituent on the chalcone molecule was found to have a significant influence on both the chemical yield and the enantioselectivity of the reaction: 24 novel chiral Michael adducts were prepared in 14-68% ee. These ee values were somewhat lower than that experienced in the case of the unsubstituted chalcone (85% ee). In the series of chalcone analogues, the 1-naphthyl Michael adduct was formed in 87% ee. Using glucose-based crown ether 1, formation of the (+)-enantiomers was preferred, while applying mannose-based 2 as the catalyst, the (-)-enantiomers were in excess.
                                    在含取代基
查尔酮和查尔
酮类似物的迈克尔加成反应中,使用手性单氮-
15-冠-5套索醚作为相转移催化剂,该套索醚与甲基-4,6-O-苄叉-α-
D-吡喃葡萄糖苷(1)或-
吡喃
甘露糖苷(2)并环,产生了显著的不对称诱导效应。研究发现,
查尔酮分子上的取代基类型对反应的
化学产率和立体选择性均有显著影响:合成了24种新型手性迈克尔加成产物,其对映体过量值为14-68%。这些对映体过量值略低于无取代基
查尔酮的情况(85% ee)。在查尔
酮类似物系列中,1-
萘基迈克尔加成产物形成于87% ee。使用基于
葡萄糖的
冠醚1时,优先形成(+)-对映体,而使用基于
甘露糖的2作为催化剂时,(-)-对映体过量。