Cross-Coupling Reactions of Organosilanols

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The basic objectives of this application are the development and application of a newly invented silicon- based carbon-carbon bond forming reaction that proceeds via a silyloxmetallic intermediate. This programis divided into three sections: the first and major effort will be methodological exploration of the new process, the second will be the investigation of the mechanism, and the third will be the application of the reaction to the synthesis of selected targets that illustrate the power of the technology. The methodological program is the most extensive and is subdivided into many projects. The first involves the development of new and general methods for the introduction of the silanol (or its surrogate) into organic structures using direct installation, cross- and ring closing metathesis and other ring forming processes. The second and most ambitious part of the methodological study is the exploration and development of the various structural scenarios in which the silicon cross coupling process can function, for example: cyclopropyl-, oxiranyl-, aliyl-, alkenyi- aryl-, heteroaryl-, and bifunctional bissiyl dienes. Included in this section will be the examination of the scope of organic electro-philic components that will serve as partners in the cross-coupling reaction such as chlorides and triflates. The extension of the silyloxmetallic intermediate to transmetalation to other metals such as mercury copper and gold will be investigated. The opportunities for catalysis of the transmetalation from silicon to palladium will be studies. The parallels between mercury and gold offer excellent opportunity to use silanols to generate rare organogold(lll) compounds which can be intercepted by conjugate acceptors. The section on mechanistic studies will focus on structurally and kinetically characterizing the silyloxy- metaltic intermediates. A key focus will be to identify the elementary steps in the transmetalation. A major effort will be the development of functionalized ligands to effect nucleopnilic catalysis of transmetalation. The synthesis targets to be tackled belong to a wide range of natural product families. The selection of synthetic challenges is mostly driven by the successes achieved in the methodological section. Synthetic approaches to isodomoic acid H, hepatitis C viral inihibiting indole alkaloids, the salicylihalimide macrolactone oximidine II, and polyene antiviral antibiotic viridenomycin are detailed.