Department of Chemistry , Emory University , 1515 Dickey Dr , Atlanta Georgia 30329 , United States.
J Org Chem. 2018 Aug 3;83(15):7939-7949. doi: 10.1021/acs.joc.8b00812. Epub 2018 Jun 25.
Donor/acceptor carbenes provide a powerful platform for building molecular complexity, but the majority of their reactions have been limited to aryl and vinyl donor groups. We found that a N-containing donor/acceptor carbene precursor, 4-phthalimido- N-methanesulfonyl-1,2,3-triazole, reacts with unactivated arenes resulting in a mixture of [3+2]-cycloadducts, [3a,7a]-dihydroindoles, and formal C-H functionalization products in up to 82% yield upon heating. We also demonstrate that the formal C-H functionalization products arise from ring-opening of the [3+2]-cycloadducts. Computational studies suggest that the formal cycloaddition process takes places through a tandem arene cyclopropanation/6π electrocyclization/6π electrocyclic ring-opening/3,5-sigmatropic rearrangement reaction, which also accounts for the distinctive regioselectivity of the formal cycloaddition reaction.
供体/受体卡宾为构建分子复杂性提供了一个强大的平台，但它们的大多数反应仅限于芳基和乙烯基供体基团。我们发现，一种含氮供体/受体卡宾前体，4-邻苯二甲酰亚氨基-N-甲磺酰基-1,2,3-三唑，与未活化的芳环反应，在加热时以高达 82%的收率得到[3+2]-环加成物、[3a,7a]-二氢吲哚和形式的 C-H 官能化产物的混合物。我们还证明，形式的 C-H 官能化产物是由[3+2]-环加成物的开环产生的。计算研究表明，形式的环加成过程通过串联芳环环丙烷化/6π电环化/6π电环开环/3,5-σ迁移重排反应进行，这也解释了形式环加成反应的独特区域选择性。
