Cyclic 3-alkoxy-3-aryloxyvinylcarbenes can be generated by a highly exo-selective intramolecular cyclization of a dioxycarbene onto a tethered triple bond. Like their dialkoxy counterparts, the 3-alkoxy-3-aryloxyvinylcarbene intermediates are capable of interesting reactions. In contrast to 3,3-dialkoxyvinylcarbenes, which undergo a formal [3 + 2] cycloaddition with highly electron-deficient olefins such as benzylidenemalononitrile, 3-alkoxy-3-aryloxyvinylcarbenes undergo a highly diastereoselective [1 + 2] cycloaddition with benzylidenemalononitrile to give cyclopropylketene acetals. At high temperatures, those cyclopropylketene acetals undergo a clean vinylcyclopropane rearrangement in which the stereochemical integrity of the cyclopropane is retained. Keywords: carbene, alkoxyaryloxy, [1 + 2] cycloaddition, ketene acetal, vinylcyclopropane rearrangement, oxadiazoline.
环状的3-烷氧基-3-芳氧基乙烯基卡宾可以通过二氧化碳卡宾高度外部选择性的分子内环化反应生成,反应中三键上存在一个连接链。与它们的双烷氧基对应物一样,3-烷氧基-3-芳氧基乙烯基卡宾中间体也能够进行有趣的反应。与3,3-双烷氧基乙烯基卡宾相比,后者与高度电子亏损的烯烃(如苯基亚甲基丙二腈)发生形式为[3+2]的环加成反应,而3-烷氧基-3-芳氧基乙烯基卡宾则与苯基亚甲基丙二腈发生高度对映选择性的[1+2]环加成反应,生成环丙酮醇酯。在高温下,这些环丙酮醇酯会发生干净的乙烯基环丙烷重排反应,环丙烷的立体化学完整性得到保留。关键词:卡宾,烷氧基芳氧基,[1+2]环加成,酮醇酯,乙烯基环丙烷重排,噁二唑啉。