Ruthenium Complex-Catalyzed Highly Selective Organic Syntheses

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We have been studying on ruthenium complex-catalyzed novel selective organic syntheses, especially from the view point of novel and selective carbon-carbon bond forming reactions. In the present work, ruthenium complex catalyzed novel methods for construction of carbon skeleton via pi-allylruthenium complexes as key intermediates or formyl C-H bond activation, together with the selective organic syntheses using related transition metal complex catalysts, have been developed. This year, 1. we have found that several eta^3-allylruthenium (II) complexes, such as (eta^3-allyl) Ru (OAc) (CO)_3 or cationic (eta^3-allyl) Ru (CO)_3] ^+ (OTf)^-, can function as both a nucleophile and an electrophile, i.e., as an ambiphile. 2. The following ruthenium complex-catalyzed novel transformations of alkyl formates were developed : selective decarbonylation of alkyl formates to alcohols, alkylation of arenes and alkenes using alkyl formates in neutral media, and addition of alcohols to alkenes. 3. Photo-, electro-, and thermal carbonylation of alkyl iodides in the presence of group 7 and 8-10 metal carbonyl catalysts, including ruthenium complexes. 4. In the course of the study on ruthenium complex-catalyzed reactions, we have found that Co_2 (CO)_8-catalyzed ring-opening carbonylation of oxiranes and oxetane smoothly proceeds with high regioselectivity under 1 atm of carbon monoxide at room temperature to give the corresponding beta- and gamma-siloxyamides in high yields, respectively. In addition, the PdCl_2 (PPh_3)_2-SnCl_2 system was found to show high catalytic activity for the reductive N-heterocyclization of nitrobenzenes to indole and 2H-indazole derivatives. The intermolecular reductive N-heterocyclization of 2-nitrobenzaldehyde or 2-nitrophenyl ketones with formamide using PdCl_2 (PPh_3)_2 with MoCl_5 was found to give the corresponding quinazoline derivatives in moderate yields.