Purpose of this research are (1) development of photocatalysts which selectively drive hydride transfer and (2) their application to the enantioselective redn. of an unsatd. substrate. Photocatalysis of [Ru(bpy)2(py)2]2+ (I) and [Ru(tpy)(bpy)(py)]2+ (II) (bpy = 2,2'-bipyridine, tpy = 2,2':6',2''-terpyridine, py = pyridine) for redn. of unsatd. compds. was investigated using triethylamine as a reductant. Formation of the hydrogenated compds. was obsd. but the corresponding one electron reduced compds. were not detected at all. The complex (I) photocatalyzed the redn. of trifluoroacetophenone and gave the alc. in a 67% yield but (II) gave only a 27% yield. The reaction proceeds via the photosubstitution of a py ligand of the ruthenium complex, followed by photochem. formation of the hydride complex. The ruthenium hydride complex reacts with trifluoroacetophenone to give [Ru(tpy)(bpy)(OCHPhCF3)]+ (III). Dissocn. of (III) to the alc. was not efficient and the yield was 10%. [on SciFinder(R)]
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