Shimoi Masaki, Maeda Katsuhiro, Geib Steven J, Curran Dennis P, Taniguchi Tsuyoshi
Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
Angew Chem Int Ed Engl. 2019 May 6;58(19):6357-6361. doi: 10.1002/anie.201902001. Epub 2019 Apr 4.
Substituted propargyl acetates are converted into 4-boryl-2(5H)-furanones upon thermolysis in the presence of an N-heterocyclic carbene borane (NHC-borane) and di-tert-butyl peroxide. The acetyl methyl group is lost during the reaction as methane. Evidence suggests that the reaction proceeds by a sequence of radical events including: 1) addition of an NHC-boryl radical to the triple bond; 2) cyclization of the resultant β-borylalkenyl radical to the ester carbonyl group; 3) β-scission of the so-formed alkoxy radical to provide the 4-boryl-2(5H)-furanone and a methyl radical; and 4) hydrogen abstraction from the NHC-borane to return the initial NHC-boryl radical and methane.
在氮杂环卡宾硼烷（NHC - 硼烷）和二叔丁基过氧化物存在下进行热解时，取代的炔丙基乙酸酯会转化为4 - 硼基 - 2(5H)-呋喃酮。反应过程中乙酰甲基以甲烷形式脱去。有证据表明该反应通过一系列自由基反应进行，包括：1）NHC - 硼基自由基加成到三键上；2）所得β - 硼基烯基自由基环化到酯羰基上；3）如此形成的烷氧基自由基进行β - 断裂，生成4 - 硼基 - 2(5H)-呋喃酮和一个甲基自由基；4）从NHC - 硼烷中夺取氢，使初始的NHC - 硼基自由基再生并生成甲烷。
