Synthetic Reactions of α-Ketenyl Radicals Based on Radical Carbonylations

以乙烯基自由基与CO的反应为基础，研究了α-烯基自由基的合成化学。以(TMS)_3SiH(TTMS)_3SiH(TTMS)和正硫醇为中间体，将α，β-不饱和的酰基自由基外环化到C-C双键上，得到环戊酮类化合物。炔胺与三丁基锡氢化物的自由基羰基化反应生成α-亚甲基内酰胺和α-亚锡基亚甲基内酰胺的混合物。亲核加成反应是环化反应的关键步骤，在α-烯基自由基的羰基上加成一个内氨基。随后产生的1-羟基烯丙基发生不寻常的1，4-H移动，随后消除了β-三丁基锡自由基，导致α-亚甲基内酰胺的形成。这种自由基/离子结合的概念可以扩展到包括α-烯基自由基和胺的分子间跳跃反应。在过量胺存在的情况下，用加压一氧化碳、三丁基锡氢化物(30%)和异丁基氮化锡处理末端炔烃，可以得到较好的α-亚甲基酰胺。然后，生成的α-酮基自由基经胺亲核捕获羰基，生成1-羟基烯丙基，1，4-H迁移得到α-酮自由基，β-消除得到三丁基锡自由基和α-烷基丙烯酰胺。所有这些成果都代表了通过α-烯基自由基进行炔烃羰基化反应的新方法。

Synthetic chemistry of a-ketenyl radicals was investigated based on the reaction of vinyl radicals and CO. The radical carbonylation of 1,5-enynes was investigated using (TMS)_3SiH (TTMSS) and hexanethiol as radical mediator, which gave cylopentanones via 5-exo cyclization of α,β-unsaturated acyl radicals onto C-C double bond. Radical carbonylation of alkynylamines with tributyltin hydride gives a mixture of α-methylene lactams and α-stannylmethylene lactams. Nucleophilic addition of an internal amino group to the carbonyl group of α-ketenyl radicals is suggested as the key cyclization step. The subsequent unusual 1,4-H shift from the resulting 1-hydroxyallyl radical, followed by elimination of the β-tributyltin radical leads to the formation of α-methylene lactams. This radical/ionic combined concept can be extended to include intermolecular tripping reactions of α-ketenyl radicals by amines. The treatment of terminal alkynes with pressurized carbon monoxide, tributyltin hydride (30 mol%) and AIBN in the presence of excessive amines, led to give good yields of α-methylene amides. The generated α-ketenyl radicals then undergo nucleophilic trapping of a carbonyl group by amines leading to the production of 1-hydroxyallyl radicals, 1,4-H migration to give α-keto radicals, and β-elimination to give the tributyltin radical and α-alkyl acrylic amides. All these achievements represent new methods for alkyne carbonylations via α-ketenyl radicals.