Reaction Design of Medium-sized Ring Structure Based on the Working Hypothesis of Ethereal Oxonium Ylide Formation

Cerbene类分子的双亲性可以以onylides的形式遗传。虽然乙醚氧叶立德仍然难以进行光谱鉴定，但已通过动力学测量间接证明了它们的形成，例如在(联苯基-4-基)氯卡宾与三氢呋喃的反应中。在此基础上，我们设计了新的通过双环和三环氧叶立德的扩环反应来合成。在Rh催化的重氮酮与五到八元环醚的反应中形成的双环氧叶立德，其中系链链是一个亚甲基单元，经历了一个新的三碳扩环反应，分别有效地生成了相应的八到十一元环醚。与五至八元环缩醛相连的重氮酮也经历了类似的放大反应，其中系链链是一个或两个亚甲基单元。不仅Rg酮卡宾类化合物，而且还有游离卡宾类化合物，如亚烷基碳酸酯…更多的含环醚或缩醛的烯烃的行为类似于生成环二烯醇醚。在所有的反应中，关键中间体是双环氧叶立德，其反应活性受电荷和环张力的稳定性控制。带有重氮功能的双环原酯与一个亚甲基单元连接的反应定量地生成了9元多氧环醚。当系链亚甲基链从一条延长到四条时，放大效率不会减弱。这表明三环氧叶立德的形成及其扩环反应不仅有利于烯醇类化合物的稳定，而且三个醚氧原子的存在使叶立德的正电荷离域，有利于形成扩环的两性离子(1，n-亲环)结构。除了扩环反应外，还揭示了环醚的氧叶立德表现出一种新的有效的开环重排反应，导致了被称为高活性瞬变物种的烷氧基烯烃的形成。较少

The ambiphilicity of cerbene-type molecules can be inherited in the form of onium ylides. While ethereal oxonium ylides still continue to elude spectroscopic identification, their formations have been demonstrated indirectly by kinetic measurements, e.g., in the reaction of (biphenyl-4-yl) chlorocarbene with THF.On this basis, we designed novel ring-expansion reactions via bi-and tricyclic oxonium ylides for synthesis.Bicyclooxonium ylides formed in the Rh-catalyzed reaction of diazoketones tethered to five-to eight-membered cyclic ethers, where the tethering chains are one methylene units, underwent a novel three-carbon ring-enlargement reaction to form effectively the corresponding eight-to eleven-membered cyclic ketoethers, respectively. Diazoketones tethered to five-to eight-membered cyclic acetals, where the tethering chains are one or two methylene units, also underwent the similar enlargement reaction. Not only rhodium ketocarbenoids but also free carbenes such as alkylidenecarb … More enes bearing cyclic ethers or acetals behaved similarly to give cyclic dienol ethers. In all the reactions, key intermediates are bicyclooxonium ylides whose reactivity is controlled by the stability of charges and ring-strain.The reaction of bicyclic orthoester bearing a diazocarbonyl function tethered by one methylene unit produced a 9-membered polyoxygenated cyclic ether quantitatively. The enlargement efficiency is not attenuated when the tethering methylene chain is elongated from one to four. This indicates that the formation of tricyclooxonium ylides and their ring-expansion are highly favored by not only the enolate-stabilization but also the presence of three ethereal oxygen atoms in orthoesters which delocalize the positive charge of the ylides to facilitate the formation of ring-enlarged zwitterion (1, n-ambiphile) structure.In addition to the ring-expansion reaction, it was unveiled that oxonium ylides of cyclic ethers show an effective novel ring-opening rearrangement reaction leading to the formation of alkenyloxyketenes known as highly reactive transient species. Less