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Four dinuclear amino acid cadmium(II) complexes [Cd2(tren)2(dl-alaninato)](ClO4)3·H2O(I), [Cd2(tren)2· (l-alaninato)](ClO4)3·H2O(II), [Cd2(tren)2(dl-phenylalaninato)](ClO4)3(III) and [Cd2(tren)2(l-phenylalaninato)]· (ClO4)3(IV), constructed from mixed ligands of tris(2-aminoethyl)amine(tren) and racemic or natural amino ac ids(amino acids=dl or l-alanine, and dl or l-phenylalanine), have been synthesized and characterized by X-ray crys tallography. The structural analysis of complexes I and III reveals that the cadmium centers are coordinated by one tren ligand and one amino acid molecule with the unusual (N,O,O′)-bridged mode, resulting in asymmetric chromo phores of CdN4O and CdN5O in complex I, CdN4O2 and CdN5O in complex III, respectively. The utility of the four complexes as efficient water-compatible Lewis acid catalysts for the direct aldol reaction in water was examined. The reaction proceeded smoothly to afford the corresponding β-hydroxy ketones in up to 99% yield. Moreover, the dias tereoselectivity of the reaction favors the formation of the syn-isomers.
Four dinuclear amino acid cadmium (II) complexes [Cd2 (tren) 2 (dl-alaninato)] (ClO4) 3 · H2O (I), [Cd2 (tren) 2 · (l-alaninato)] (ClO4) (II), constructed from mixed ligands of [Cd2 (tren) 2 (dl-phenylalaninato)] (ClO4) 3 (III) and [Cd2 (tren) 2 (l-phenylalaninato) tris (2-aminoethyl) amine (tren) and racemic or natural amino acids (amino acids = dl or l-alanine, and dl or l-phenylalanine), have been synthesized and characterized by X- ray crys tallography. The structural analysis of complexes I and III reveals that the cadmium centers are coordinated by one tren ligand and one amino acid molecule with the unusual (N, O, O ’) - bridged mode, resulting in asymmetric chromo phores of CdN4O and CdN5O in complex I, CdN4O2 and CdN5O in complex III, respectively. The utility of the four complexes as efficient water-compatible Lewis acid catalysts for the direct aldol reaction in water was examined. The reaction proceeded smoothly to afford the corresponding β-hydroxy ketones in up to 99% yield Mor eover, the dias tereoselectivity of the reaction favors the formation of the syn-isomers.