二酸化炭素の資源化を指向する 触媒的精密有機合成反応の開発

A silver/DBU catalyst system was developed for the effective synthesis of cyclic carbonates from the reaction of CO₂ with propargylic alcohols in high yields under mild conditions. In DMF solvent, it was found that the [3,3]-sigmatropic Meyer-Schuster-type rearrangement of the propargylic alcohol was mediated by CO₂ to afford the corresponding α,β-unsaturated carbonyl compounds. The silver salt combined with the chiral Schiff base ligand was applied to enantioselective chemical CO₂ incorporation into various bispropargylic alcohols to produce the corresponding cyclic carbonate with high enantioselectivity. Next, we successfully developed a catalytic C-C bond-forming reaction with CO₂; this reaction employed catalytic silver benzoate in the presence of MTBD to afford lactone derivatives under mild reaction conditions. The geometry of the C-C double bond of the products was confirmed to be Z based on X-ray analysis and NOE experiments. The silver catalyst system catalyzed the C-C bond forming reaction of o-alkynylacetophenone derivatives and CO₂ to afford the corresponding dihydroisobenzofuran derivatives. Benzoxazine-2-one derivatives are important heterocycle structures, though their synthetic methods had been limited. It was found that a silver catalyst successfully promoted the incorporation of CO₂ into o-alkynylanilines to afford the corresponding benzoxazine-2-ones bearing Z exo-olefin via 6-exo-dig cyclization at the activated C-C triple bond. For the o-alkynylanilines with primary amine, 4-hydroxyquinolin-2(1 H)-one derivatives were obtained via intramolecular isocyanate rearrangement in high yields. From easily available propargylic amines, a conceptually new synthetic strategy including intramolecular isocyanate rearrangement was proposed to afford tetramic acid derivatives. Through the reaction of conjugated ynones with CO₂, facile and versatile access to highly functionalized tetronic acids has been achieved. This reaction was successfully applied to synthesis of Aspulvinone E. The silver-catalyzed three-component reaction of propargylic amines, CO₂, and electrophiles was studied. By using NIS and NBS, the corresponding (E)iodo- and (E)-bromo-vinyloxazolidinones were obtained, respectively. By using DBAD or DEAD as electrophiles, the corresponding amino-vinyloxazolidinones were obtained, although the geometry of the aminated product was opposite to that of the previous study, due to a radical mechanism. Kolbe-Schmitt type reaction under ambient conditions was achieved with the combined use of an organic base for resorcinols. Decarboxylation of the cyclic carbonates obtained in silver catalyst system was also studied. Using Lewis acid catalysts, highly substituted 2-cyclo-pentenones were stereospecifically and regioselectively constructed with high catalytic efficiency.