Lewis-Acid-Assisted Methyl Exchange Reactions In Silylated Aminodichloroarsanes

Lewis-acid-assisted methyl/chlorine, methyl/azide, and methyl/triflate exchange reactions between silicon and arsenic centers have been studied and applied to different silylated aminoarsane species leading to a number of new methylarsane compounds: bis(trimethylsilyl)amino(dichloro)arsane (3) was reacted with GaCl3 yielding a bis(chlorodimethylsilyl)-tetramethyl-cyclo-disilazane (4) accompanied by the release of Me2AsCl, while trimethylsilyl(m-terphenyl)amino(dichloro)arsane (5) (m-terphenyl = 2,6-Mes2-C6H3, Mes = 2,4,6-Me3C6H2) reacted with GaCl3 to give dichloromethylsilyl(m-terphenyl)aminodimethylarsane (6). In the presence of trimethylsilylazide, trimethylsilyl(m-terphenyl)amino(dichloro)arsane displays a methyl/azide exchange triggered by the action of GaCl3 yielding azidodimethylsilyl(m-terphenyl)amino(chloro)methylarsane (7). Moreover, methyl/triflate exchange reactions have been observed in the reaction of trimethylsilyl(m-terphenyl)amino(dichloro)arsane (i) with 1 equiv of AgOTf (OTf = triflate) yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)amino(methyl)chloroarsane (8) and (ii) with 2 equiv of AgOTf yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)trifluoromethylsulfonatomethylarsane (9). All new compounds (3−9) have been fully characterized by means of vibrational spectroscopy, X-ray, CHN analysis, MS, and NMR studies. A possible reaction mechanism is discussed starting from an initial chloride abstraction and the intermediate formation of a cationic iminoarsane species. In a second step, a methyl shift from the silicon to the arsenic center occurs.

通过研究并应用硅和砷中心之间的路易斯酸辅助甲基/氯、甲基/叠氮和甲基/三氟甲磺酸交换反应，已对不同硅基化氨基砷烷物种进行处理，从而得到了一系列新型的甲基砷烷化合物：双(三甲基基硅基)氨基(二氯)砷烷(3)与GaCl3反应，生成双(氯二甲基基硅基)-四甲基环二硅氮烷(4)，同时释放出Me2AsCl，而三甲基基硅基(m-terphenyl)氨基(二氯)砷烷(5)（m-terphenyl代表2,6-Mes2-C6H3，Mes代表2,4,6-Me3C6H2）与GaCl3反应则得到二氯甲基基硅基(m-terphenyl)氨基二甲基砷烷(6)。在存在三甲基基硅基叠氮的存在下，三甲基基硅基(m-terphenyl)氨基(二氯)砷烷在GaCl3的作用下表现出甲基/叠氮交换，生成叠氮二甲基基硅基(m-terphenyl)氨基(氯)甲基砷烷(7)。此外，在trimethylsilyl(m-terphenyl)氨基(二氯)砷烷(i)与1摩尔当量AgOTf（OTf代表三氟甲磺酸）反应中，观察到甲基/三氟甲磺酸交换反应，生成N-(三氟甲基磺酰二甲基基硅基)-N-(m-terphenyl)氨基(甲基)氯砷烷(8)，以及在(ii)与2摩尔当量AgOTf反应中生成N-(三氟甲基磺酰二甲基基硅基)-N-(m-terphenyl)三氟甲基磺酰甲基砷烷(9)。所有新化合物(3-9)均通过振动光谱学、X射线、CHN分析、质谱和核磁共振等手段进行了全面表征。可能的反应机制从初始的氯离子抽象和阳离子亚胺砷烷物种的中间体形成开始进行讨论。在第二步中，甲基从硅中心转移到砷中心发生甲基迁移。