Development of Efficient Vinylation and Ethynylation Reactions

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Vinylation and ethynylation are fundamental transformations in organic synthesis, which provide synthetically important intermediates for functionalized polymers and biologically interesting heterocyclic compounds. Conventional methods employed stepwise transformation, and were not efficient in terms of economical and environmental demands. This project is aimed to develop novel and efficient methods to vinylate and ethynylate C-H bonds of organic molecules.Previously, we developed phenol o-vinylation reaction with ethyne in the presence of Sn Cl_4 and Bu_3N. The method required use of excess tin reagent, and a catalytic method was developed. In the presence of SnCl_4 and BuLi, o-substituted phenols can he vinylated with silylacetylene with the turnover number close to 10. Enolate vinylation reaction using GaCl_3 was also examined, and the method was found to be applicable not only to ketones but also to thioesters and malonates. It is notable that thermodynamically unstable vinylmalonates can be prepared. As for the stereochemistry, the reactions exhibit an equatorial selectivity in the vinylation of cyclohexanone derivatives.Ethynylation reactions were developed using addition/elimination reaction of organogallium compounds to chloroacetylene. Silyl enolates can be ethynylated at the α-position in the presence of GaCl_3, and phenols at the 0-position. Catalytic processes using GaCl_3 was developed.A novel catalyst system was developed employing a transition metal and sulfonic acid, which allows addition of trianylphosphines to allenes and 1,3-dienes.The present project provided a series of vinylation and ethynylation reactions of organic compounds, which may find a broad application in the synthesis of functionally interesting compounds.