Selective Production of Acetone in the Electrochemical Reduction of CO2 Catalyzed by a Ru–Naphthyridine Complex

The controlled potential electrolysis of [Ru(bpy)(napy)₂(CO)₂](BF₄)₂ ( 1 ; bpy=2,2′‐bipyridine, napy=1,8‐naphthyridine) in the presence of LiBF₄ in CO₂‐saturated DMSO at −1.65 V (vs. Ag/Ag⁺) produced CO and Li₂CO₃ [Eq. (a)], while similar electrolysis in the presence of (CH₃)₄NBF₄ resulted in formation of acetone together with (CH₃)₃N and {(CH₃)₄N}₂CO₃ [Eq. (b)]. This represents the first almost selective generation of acetone upon electrochemical reduction of CO₂. The selectivity is ascribed to depression of reductive cleavage of the Ru−CO bond of 1 due to an attack of the nonbonded nitrogen atom of napy at the carbonyl carbon atom.     

New and direct route to 5-trifluoromethyl-5,6-dihydrouracils by means of palladium complex catalyzed “ureidocarbonylation” of 2-bromo-3,3,3-trifluoropropene

Palladium complex catalyzed carbonylation of 2-bromo-3,3,3-trifluoropropene (2-Br-TFP) with ureas afforded 5-trifluoromethyl-5,6-dihydrouracils in moderate to good yields, which were converted into 5-trifluoromethyluracils in nearly quantitative yields.     

The asymmetric hydrogenation of α-keto esters catalyzed by rhodium(I) complexes with chiral diphosphine ligands. On the catalytic cycles and the mechanism of asymmetric induction

Asymmetric hydrogenations of n-propyl pyruvate and ketopantoyl lactone catalyzed by rhodium complexes with (—) DIOP and BPPM were carried out under a variety of conditions. It was found that i) the Schrock-Osborn mechanism was not operative in these reactions at all since no acceleration of the reaction rate by the addition of water (1%) was observed, ii) there was a clear difference between cationic and neutral (in situ) rhodium catalysts in their enantioselectivity, and iii) there was a remarkable solvent effect on the extent and direction of asymmetric induction. Possible mechanisms are discussed on the basis of these results.     

Pico-second transient luminescence of resonantly excited excitonic molecules in CuCl

Time-resolved luminescence spectra of excitonic molecules in CuCl created by the two-photon resonance excitation are studied at 4.2 K with a time resolution of ～ 60 psec. Two sharp emission lines observed are ascribed to the radiative decay of “cold” excitonic molecules with k ～ 2K₀. Stimulated emission process gives a considerable influence on luminescence properties.     

Pico-second time-resolved luminescence spectra of excitonic molecules in CuCl

Transient luminescence behavior of excitonic molecules in CuCl is studied at 4.2 K with a time resolution of ～ 10 ps. The lifetime of the excitonic molecule state is determined to be several hundred pico-seconds. The spectral shape and the time characteristics of the luminescence intensity depend on excitation wavelength and also on the direction of observation. This is explained by the effect of the stimulated emission process.