| Abstract
| - A monomeric titanocene(III) derivative, Cp2TiPh, effectively promoted the pinacol coupling of bothan aromatic aldehyde, benzaldehyde, and an aliphatic aldehyde, 3-phenylpropionaldehyde. Thesame reactive complex was successfully generated by a catalytic amount of a precursor, Cp2Ti(Ph)Cl, and its stoichiometric amount of Zn. The Cp2TiPh-catalyzed pinacol coupling of benzaldehydederivatives and aliphatic aldehydes afforded the corresponding 1,2-diols in high yields with moderateto good threo-selectivity. On the other hand, Cp2TiPh-catalyzed pinacol cyclization of dials gavecyclic 1,2-diols with excellent diastereoselectivity. The extension of this protocol to chiral dialsdemonstrated that the phenyltitanium complex catalytically transmitted an axial chirality or acentral chirality of the starting dials to the central chirality of the resultant 1,2-diols.
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