| Research Abstract |
The following stereoselective pinacol-type reactions are developed. (1) A cross-pinacol-type coupling reaction of α,β-unsaturated ketones and aldehydes is accomplished with CrCl_2 and Me_3SiCl in DMF. The diastereoselectivity of the reaction is proved to depend on the reaction temperature. (2) A cross-coupling reaction of oxygen-substituted dienes and aldehydes leading to 1,2-diol derivatives is performed with CrCl_2 in the presence of a catalytic amount of B_<12> and water. (3) A dl-selective pinacol-coupling reaction of aliphatic aldehydes is achieved with CrCl_2, manganese, and Me_3SiCl.
In addition, we collected information on the pinacol coupling reactions with low-valent metals. (1) A titanium(III) complex TiCl_3(tmeda)(thf) which is effective for a dl-selective pinacol-coupling of aromatic aldehydes, is isolated, and the molecular structure of the complex are examined by X-ray crystallographic analysis. (2) Titanium(III) and vanadium(III) complexes having a Tp ligand are isolated, and the structure of an aldehyde-coordinated vanadium(III) complex is determined by X-ray crystallographic analysis.
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