1994 Volume 52 Issue 6 Pages 510-520
Preparation, characterization, and synthetic application of hypercoordinate organosilicon compounds are described. Regiospecific and highly diastereoselective allylation of aldehydes, aldimines, α-hydroxy ketones, α-ketocarboxylicacids, β-hydroxy- and β-amino-α, β-enones, and 1, 2-diketones have been achieved by using pentacoordinate allylsilicates. Typically, reactions of stereohomogeneous (E) - and (Z) -crotyltrifluorosilanes with various aldehydes in the presence of CsF or a wide variety of hydroxy compounds and triethylamine in THE gave the corresponding anti- and syn-β-methylhomoallyl alcohols, respectively, in highly diastereoselective manner. The stereoselectivity and the results of ab initio MO calculations suggest that the present allylation proceeds via six-membered cyclic transition states including the coordination of carbonyl oxygen to the silicon of pregenerated pentacoordinate allylsilicates. Facile reduction of carbonyl compounds by using pentacoordinate hydridosilicates, structural characteristics of pentacoordinate silylsilicates, and oxidative Si-C bond cleavage of, alkyl- and aryltrifluorosilanes by trimethylamine-N-oxide are also described to present the unique feature of the organosilicates.
