trans-3,4-Disubstituted pyrrolidines by 1,3-dipolar cycloaddition: enantioselective approaches and their limitations
作者:Staffan Karlsson、Fusen Han、Hans-Erik Högberg、Patrizia Caldirola
DOI:10.1016/s0957-4166(99)00244-x
日期:1999.7
presence of a chiral Lewis acid as co-catalyst, the acid-catalysed 1,3-dipolar cycloaddition reaction yielding trans-3,4-disubstituted pyrrolidines from an azomethine ylide and achiral α,β-unsaturated dipolarophiles proceeded with low enantioselectivity. Therefore a number of α,β-unsaturated dipolarophiles linked to chiral auxiliaries were examined as substrates. Camphorsultam was the best auxiliary and gave
在手性路易斯酸作为助催化剂的存在下,该酸催化的1,3-偶极环加成反应从偶氮甲碱中得到反式-3,4-二取代的吡咯烷,而非手性的α,β-不饱和偶极亲和剂则以低对映选择性进行。因此,研究了许多与手性助剂连接的α,β-不饱和双极性亲和体作为底物。樟脑是最好的助剂,并具有良好的非对映选择性(dr = 74:26)。当将手性路易斯酸与连接到手性助剂的偶极亲子结合时,对映选择性可能会略有提高。通过13 C NMR判断,手性路易斯酸对选择性的影响很小,这可能是由于最初形成的与偶极亲子的偶极亲和体形成的配合物分解所致。