Diastereoselective 1,3-dipolar cycloadditions of both electronically modified phenyl-nitrile oxides and stilbenes
作者:Jan Romanski、Piotr Nowak、Anna Maksymiuk、Christian Chapuis、Janusz Jurczak
DOI:10.1039/c3ra41718b
日期:——
stable syn-s-cis conformer in the reaction pathway, given its smaller difference of calculated energies in the corresponding transition states. Such an explanation is further supported by the negative influence of either a polar solvent, stabilizing these more polar transition states (phenyl nitrile oxide in hexane, 76% d.e.; CH2Cl2, 71% d.e.; MeCN, 67% d.e.), or a chelating Lewis acid (MgCl2, 66% d.e.)
(E)-1,2-二苯乙烯(12%de)的添加选择性比其对应的(1 R)-8-苯基-薄荷基(38%de)或(2 R)-降冰片烷的薄荷基羧酰腈的选择性低[10,2] sultam(48%de)类似物。当将手性助剂置于亲二氟体上时,也观察到这种较低的选择性,如对-NO 2-苯基腈腈与(1 R)-薄荷醇(4%de)的丙烯酰基衍生物的[3 + 2]环加成反应和(2 R)-硼烷[10,2]杜鹃(60%de)。我们设法通过利用两个假体的Tolbert和Ali合作影响来提高这些非对映选择性,如在(1 R)-薄荷醇(30%de)和( 2 R)-冰片烷[10,2] sultam(98%de)。在该具体情况下Ñ -丙烯酰基莰烷[10,2]磺内酰胺中,我们发现用于电子缺陷的一小预测的负面影响的证据对-取代的苯基腈氧化物上非对映选择性(p -Me 2 N,72%去; p - F,65%de;p- NO 2,60%d