Benzyloxy(4-substituted benzyloxy)carbenes. Generation from oxadiazolines and fragmentation to radical pairs in solution
作者:Nadine Merkley、John Warkentin
DOI:10.1139/v00-078
日期:2000.7.1
Thermolysis of 2,2-dibenzyloxy-5,5-dimethyl-Δ3-1,3,4-oxadiazoline in benzene at 110°C leads to dibenzyloxycarbene. The carbene was trapped with tert-butyl alcohol to afford dibenzyl-tert-butyl orthoformate. In the absence of a trapping agent for the carbene, it fragmented to benzyloxycarbonyl and benzyl radicals, as shown by trapping the latter with TEMPO. In the absence of both TEMPO and tert-butyl
2,2-二苄氧基-5,5-二甲基-Δ3-1,3,4-恶二唑啉在苯中在 110°C 下的热解产生二苄氧基卡宾。用叔丁醇捕获卡宾,得到原甲酸二苄基叔丁酯。在没有卡宾捕获剂的情况下,它会分裂为苄氧羰基和苄基自由基,如用 TEMPO 捕获后者所示。在不存在 TEMPO 和叔丁醇的情况下,自由基在与苯乙酸苄酯偶联和脱羧之间分配,随后形成联苄。通过比较两种可能的酯 ArCH2O(CO)CH2Ph 和 PhCH2O(CO)CH2Ar 的产率,确定了类似的卡宾从苄氧基-(p-取代的-苄氧基)卡宾的优选断裂意义。发现对位的吸电子基团有利于裂解为含有该基团的苄基。数据的哈米特图与 σ- 取代基常数 (r = 0.994, ρ(PhH, 110°C) = 0.7) 给出了最佳拟合,表明 ...