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Highly Stereoselective and Efficient Addition of Organocerium Reagents to syn-β-Alkyl-β-hydroxy-α-methyl Ketones by Way of Their Titanium Alkoxides − Synthesis of Complex 1,3-Diol Units with Three Stereodefined Centres

2001; Wiley; Volume: 2001; Issue: 15 Linguagem: Inglês

10.1002/1099-0690(200108)2001

1434-193X

Giuseppe Bartoli, Marcella Bosco, Emanuela Di Martino, Enrico Marcantoni, Letizia Sambri,

Oxidative Organic Chemistry Reactions

A highly efficient and stereoselective technique for additions to syn-β-alkyl-β-hydroxy-α-methyl ketones is now available. The methodology is based on the conversion of the starting material into a trichlorotitanium alkoxide derivative, which is able to assume a stable cyclic arrangement exhibiting high stereofacial discrimination towards nucleophilic alkyl transfer by an appropriate organometallic species. The use of Grignard reagents has serious limitations; in fact, highly hindered and basic reagents do not work well with enolizable substrates. Organocerium compounds can obviate these drawbacks, since side processes such as enolization or interaction with titanium(IV) are almost completely suppressed. The method permits the introduction of a large variety of carbon systems, including primary, secondary and tertiary alkyl chains, as well as aromatic, alkynyl and benzylic moieties, in high yields and with good stereoselectivities.