Yamada Takayuki, Shibata Yu, Tanaka Ken
Department of Chemical Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo, 152-8550, Japan.
Chemistry. 2019 Dec 13;25(70):16022-16031. doi: 10.1002/chem.201904156. Epub 2019 Nov 18.
It has been established that a cyclopentadienyl (Cp) Rh complex with two aryl groups and a pendant amide moiety catalyzes the formal Lossen rearrangement/alkenylation cascade of N-pivaloyl heterole carboxamides with internal alkynes, leading to alkenylheteroles. Interestingly, the use of sterically demanding internal alkynes afforded not the alkenylation but the [3+2] annulation products ([5,5]-fused heteroles). In these reactions, the pendant amide moiety of the CpRh complex may accelerate the formal Lossen rearrangement. The use of five-membered heteroles may deter reductive elimination to form strained [5,5]-fused heteroles; instead, protonation proceeds to give the alkenylation products. Bulky alkyne substituents accelerate the reductive elimination to allow the formation of the [5,5]-fused heteroles.
已经确定，具有两个芳基和一个侧链酰胺部分的环戊二烯基（Cp）铑配合物催化N-新戊酰基杂环羧酰胺与内炔的形式上的洛森重排/烯基化级联反应，生成烯基杂环化合物。有趣的是，使用空间位阻较大的内炔得到的不是烯基化产物，而是[3+2]环化产物（[5,5]稠合杂环化合物）。在这些反应中，CpRh配合物的侧链酰胺部分可能会加速形式上的洛森重排。使用五元杂环可能会阻止还原消除以形成张力较大的[5,5]稠合杂环化合物；相反，质子化会发生，生成烯基化产物。庞大的炔基取代基会加速还原消除，从而形成[5,5]稠合杂环化合物。
