Zinc(ii) ortho-hydroxyphenylhydrazo-β-diketonate complexes and their catalytic ability towards diastereoselective nitroaldol (Henry) reaction

Abstract

The zinc(II) complexes with ortho-hydroxy substituted arylhydrazo-β-diketonates [Zn(2)(CH(3)OH)(2)(μ-L(1))(2)] (5), [Zn{(CH(3))(2)SO}(H(2)O)(L(2))] (6), [Zn(2)(H(2)O)(2)(μ-L(3))(2)] (7) and [Zn(H(2)O)(2)(L(4))]·H(2)O (8) were synthesized by reaction of a zinc(II) salt with the appropriate hydrazo-β-diketone, HO-2-C(6)H(4)-NHN=C{C(=O)CH(3)}(2) (H(2)L(1), 1), HO-2-O(2)N-4-C(6)H(3)-NHN=C{C(=O)CH(3)}(2) (H(2)L(2), 2), HO-2-C(6)H(4)-NHN=CC(=O)CH(2)C(CH(3))(2)CH(2)C(=O) (H(2)L(3), 3) or HO-2-O(2)N-4-C(6)H(3)-NHN=[CC(=O)CH(2)C(CH(3))(2)CH(2)C(=O) (H(2)L(4), 4). They were fully characterized, namely by X-ray diffraction analysis that disclosed the formation of extensive H-bonds leading to 1D chains (5 and 6), 2D layers (7) or 3D networks (8). The thermodynamic parameters of the Zn(II) reaction with H(2)L(2) in solution, as well as of the thermal decomposition of 1-8 were determined. Complexes 5-8 act as diastereoselective catalysts for the nitroaldol (Henry) reaction. The threo/erythro diastereoselectivity of the β-nitroalkanol products ranges from 8:1 to 1:10 with typical yields of 80-99%, depending on the catalyst and substrate used.

A new cyclic binuclear Ni(II) complex as a catalyst towards nitroaldol (Henry) reaction

“…The stereoselectivity of the reaction was first time reported by Shibasaki in 1992 [11] and a number of works have appeared in recent years [3][4][5][6], showing the current interest of the Henry reaction and its application. The reaction has been studied in homogeneous [3][4][5][6], heterogeneous [12][13][14], ionic liquids or supercritical fluids [15], mesoporous nanocomposite conditions [16], etc. However, the achievement of a good selectivity is still a challenge, and it is also important the search for new catalysts which can be prepared easily and are commercially cheap.…”

“…Depending on the nature of the reactants, the reaction involves the formation of one or two asymmetric centres at the new carbon-carbon junction, where the optically active forms are useful intermediates in the synthesis of biologically active compounds [4] or polyfunctionalized materials [10]. The stereoselectivity of the reaction was first time reported by Shibasaki in 1992 [11] and a number of works have appeared in recent years [3][4][5][6], showing the current interest of the Henry reaction and its application. The reaction has been studied in homogeneous [3][4][5][6], heterogeneous [12][13][14], ionic liquids or supercritical fluids [15], mesoporous nanocomposite conditions [16], etc.…”

“…The reaction can be catalyzed by inorganic/organic bases or metal complexes [2][3][4][5][6][7][8][9] and can be used as a tool for the syntheses of a variety of valuable building blocks of pharmaceutical significance [3][4][5][6]. Depending on the nature of the reactants, the reaction involves the formation of one or two asymmetric centres at the new carbon-carbon junction, where the optically active forms are useful intermediates in the synthesis of biologically active compounds [4] or polyfunctionalized materials [10].…”

Aquasoluble iron(III)-arylhydrazone-β-diketone complexes: Structure and catalytic activity for the peroxidative oxidation of C5–C8 cycloalkanes

“…The utilization of an aromatic amine with a sulfo-substituent allows the easy introduction of the water-solubilizing functionality. Further, AHBD compounds contain a O,N,O donor site of high flexibility, which can chelate a number of metal-ions, thus leading to Cu II [18][19][20][21][22][23][24], Zn II [25][26][27][28], Ni II [19,29], Na I [30], K I [24,29], Pb II [25], Cd II [26] complexes. The preparative procedures for these complexes are usually rather straightforward giving high yields of the final products.…”

Water-soluble heterometallic copper(II)-sodium complex comprising arylhydrazone of barbituric acid as a ligand

“…For example, arylhydrazones of β-diketones contain a flexible O,N,O donor site which can chelate a number of metal ions, thus leading to Cu II [1][2][3][4][5][6][7], Zn II [8][9][10][11], Ni II [2,12], Na I [13], K I [7,12], Pb II [8], Cd II [9], Co II [14] complexes of different nuclearities and topologies. Moreover, the first example of an heterometallic Cu II -K AHAMC complex has been recently reported by some of us [7].…”