Transition Metal-Catalyzed Asymmetric Synthesis Based on Allene and Cyclopropane Chemistry

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We have developed novel asymmetric synthetic methodologies with transition metal catalysts using allene and cyclopropane functionalities. Unsaturated compounds such as dienes and enynes are activated with metal catalysts to form new carbon-carbon bonds easily, providing carbocycles or heterocycles. Introduction of allene and cyclopropane functions in such systems provides much interest for us in term of their chemical characteristics for elaboration of complex organic molecules. Our recent results of the asymmetric reactions of allenes and cyclopropanes using metal catalysts are as follows.1. Asymmetric synthesis by asymmetric carbopalladation of allenes The palladium-catalyzed reaction of allenes with iodobenzene and nucleophiles using chiral phosphine ligands provided high enantioselectivity of α, β -functionalized compounds.2. Palladium-catalyzed reactions of allenes bearing iodophenyl groups with nucleophiles The palladium-catalyzed reactions of allenes bearing iodophenyl groups wi … More th nucleophiles provided directly tricyclic compounds by intramolecular carbopalladation followed by intramolecular nucleophilic substitution.3. Asymmetric synthesis of heterocycles by palladium-catalyzed reactions of allenes The palladium-catalyzed reactions of allenes bearing iodophenyl groups with nucleophiles were carried out in the presence of chiral phosphine ligands to give optically active tricyclic compounds with high enantioselectivity. On the use of amino components as nucleophiles, asymmetric synthesis of cyclic indole compounds was achieved with high enantioefficiency.4. Intramolecular metal-catalyzed reactions of allene-ene compounds Titanium-catalyzed reactions of allene-ene systems provided intramolecular cycloaddition products, [2+2] cycloaddition and ene reaction products. The stereospecificity of the reactions was obtained by appling the reactions to chiral allene systems.5. Palladium-catalyzed reactions of cyclopropylidenemethylcyclopropane systemsThe palladium-catalyzed reactions of cyclopropylidenemethylcyclopropane systems with electrophilic olefin provided [3+2] cycloaddition reaction products in high yields. This result indicates the existence of rather reactive 1, 3-dipolarophiles generated by the palladium-catalyzed reactions. Less