Highly Selective Carbon-carbon Bond Cleacage by Super-protic Directory Groups

已知14族有机金属基团稳定位于它们的β&gt；的碳正离子。在这个项目中，研究了这一概念的几个扩展，以开发高选择性的a-键裂解过程，如没有适度考虑的碳-碳键，发现几个-三甲基硅酮肟乙酸酯通过三甲基硅基三氟酸盐的亲电活化，诱导高度区域和结构特异性的Beckmann裂解，产生相应的烷基氰化物。这种方法比更常见的用氟化物激活Si-C键的方法要好得多。这种新的裂解对于烯烃的立体专一性形成特别有用，例如几种昆虫信息素的合成。金属官能团和碳基的选择性引入是通过一锅中烯酮的共轭加成来实现的，或者，有机锡基取代的酮肟通过与四醋酸铅的氧化活化来断裂它们的&lt；β&gt；-碳-碳键。这一新工艺还具有很强的区域性和立体专一性，可以提供烯基氰氧化物中间体，这些中间体在分子内发生偶极环加成反应得到-lt；Delta&gt；-异恶唑啉。14族有机金属基团的超质子性也被应用于~lt；β&gt；-金属羧酸的选择性脱羧基和锡取代肼的吡唑啉的生成。阳离子中心由碳修饰为过渡金属，烯丙基溴(IV)部分，通过新的甲基从硅原子迁移到Ru原子，导致了前所未有的碳-硅键的氟化银活化。

The group 14 organometallic groups have been known to stabilize a carbocations locating at their <beta>. In this project, several extentions of this concept were investigated for seceloping highly selective cleavage processes of a -bond, such as carbon-carbon bonds unser moderate consitions Several<beta>-tri- methylsilylketoxime acetates were found to induce the highly regio-and strtro- specific Beckmann fragmentation to yield the corresponding alkeyl cyanides by an electrophilic activation with trimethylsilyl triflate. This methodology was much superior to the more common activation of a Si-C bond with flurides. This new fragmentation is particularly useful to the stereospecific fromation of olefins as exemplified by synthesis of several insect pheromones. Streroselective introduction of both metallyl function and the carbon moiety was achieved by the conjugate addition of alkenones in one-pot.Alternatively, the organostannyl substituted ketoximes were found to cleave their <beta>-carbon-carbon bonds by oxidative activation with lead tetraacetate. This new process was also highly regio-and stereospecific to furnish alkenyl nitrile oxide intermediates, Which undergo intranolecular dipolar cycloadditions sponta- neously to give <DELTA>-isoxazolines. The super-protic natureof group 14 organo- metallyl groups was also applied to the selective decartboxylation of <beta>-metallyl- carboxylic acids and to the pyrazoline formation of tin-substituted hydrazines.Modification of the cationic center to carbon to a transition-metal, an allylbromoruthenium(IV) moiety, resulted in an unprecedented silver fluoride activation of a carbon-silicon bond by way of a new methyl group migration from silicon to ruthenium atoms.