Catalytic asymmetric reactions of alpha-beta-unsaturated 2-acyl imidazoles

I. Catalytic asymmetric reactions of bidentate alpha,beta-unsaturated 2-acyl aza-heteroaromatics. The lower LUMO energy and facile cleavage chemistry makes alpha,beta-unsaturated 2-acyl aza-heteroaromatics attractive substrates for reaction development. This review presents an up-to-date account on the chemistry of bidentate alpha,beta-unsaturated 2-acyl aza-heteroaromatics such as N-acyl pyrazoles, 2-acyl pyridine, 2-acyl pyridine- N-oxides and 2-acyl imidazoles in various catalytic asymmetric reactions.*II. Sc(III)-catalyzed enantioselective indole Friedel-Crafts reactions of alpha,beta-unsaturated 2-acyl imidazoles. Highly enantioselective indole Friedel-Crafts reactions have been developed with a variety of beta-substituted alpha,beta-unsaturated 2-acyl imidazoles catalyzed by Sc(III)---Inda-PyBox triflate complex (A). The 2-acyl imidazole products were efficiently transformed into various carbonyl functional groups: esters, amides, ketones, aldehydes, and carboxylic acids. In order to account for catalyst loading profile and absolute stereochemistry of reaction products, a 1:1:1 product:substrate:catalyst complex was hypothesized.*III. Ce(IV)-catalyzed enantioselective nitrone dipolar cycloadditions of alpha,beta-unsaturated 2-acyl imidazoles. Ce(IV)- cis-bis-Ph-PyBox triflate complex (B) catalyzed highly enantioselective nitrone dipolar cycloaddition reactions with a wide substrate scope for both beta-substituted alpha,beta-unsaturated 2-acyl imidazoles and nitrones. The 2-acyl imidazole products were efficiently transformed into densely functionalized beta'-hydroxyl-beta-amino acid derivatives.*IV. Ni(II)-catalyzed enantioselective diazoalkane dipolar cycloadditions of alpha,beta-unsaturated 2-acyl imidazoles. Highly enantioselective diazoalkane dipolar cycloaddition reactions have been investigated with a variety of beta-substituted alpha,beta-unsaturated 2-acyl imidazoles. The reaction with trimethylsilyldiazomethane (E) was efficiently catalyzed by Ni(II)-i-Pr-PyBox triflate complex (C) and Ni(II)- trans-bis-Ph-PyBox triflate complex (D) catalyzed the corresponding reaction with dimethylphenylsilyldiazomethane (F). The cycloaddition product (J) was subjected to Fleming-Tamao oxidation to afford hydroxylated conjugated pyrazolines (L) with retention in stereochemistry. Such selective formation of products (G) or (J) has been unprecedented in enantioselective diazoalkane dipolar cycloaddition reactions.**Please refer to dissertation for diagrams.