2-Dihydromethylpiperazinediium-M^II(M^II= Cu^II, Fe^II, Co^II, Zn^II) double sulfates and their catalytic activity in diastereoselective nitroaldol (Henry) reaction

Abstract

A series of double dihydromethylpiperazinediium metallic sulfates 1-7 [H(2)mpz]M(II)(SO(4))(2)·nH(2)O (mpz = 2-methylpiperazine, C(5)H(12)N(2)) are prepared by slow evaporation using a racemic (R/S)-mpz (for 1, 2) or enantiopure R-mpz (for 3), S-mpz (for 4-7) and sulfates of Cu(II) (for 5), Fe(II) (for 1, 4), Co(II) (for 7) and Zn(II) (for 2, 3, 6), and characterized by infrared spectroscopy, elemental analysis and single crystal X-ray diffraction. The [M(II)(H(2)O)(6)](2+), [(R/S)-H(2)mpz](2+), [(R)-H(2)mpz](2+) or [(S)-H(2)mpz](2+) cations and 2SO(4)(2-) anions are linked together via two types of hydrogen bonds, Ow-Hw···O and N-H···O, leading to supramolecular arrangements. The use of the racemic 2-mpz provides alternatives in crystallization: a centrosymmetric structure where the enantiomers are related by an appropriate crystallographic symmetry operation or one where the enantiomers occupy the same crystallographic position, generating disorder. Compounds 1-7 act as diastereoselective catalysts for the nitroaldol (Henry) reaction. The diastereoselectivity can be regulated from exclusive threo to exclusive erythro isomer preparation with typical yields of 50-99%, depending on the catalyst and the substrate used.

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

“…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].…”

Cu6S6 Clusters as a Building Block for the Stabilization of Coordination Polymers with NiAs, NaCl, and Related Structures: Synthesis, Structure, and Catalytic Studies

“…The nitroaldol or Henry reaction is an important C–C bond‐coupling reaction involving a nitroalkane and aldehyde . We desired to explore this reaction by employing the present compounds I–IV as heterogeneous catalysts.…”

Ni(II)-Aroylhydrazone Complexes as Catalyst Precursors Towards Efficient Solvent-Free Nitroaldol Condensation Reaction

“…The reaction takes place via construction of asymmetric centers (one or two) through the new C-C junction leading to optically active products. Inorganic metal complexes or inorganic/organic bases can catalyze this reaction [1][2][3][4][5][6][7][8][9][10]. The prepared functionalized β-nitroalcohols are known as important synthetic precursors, can be converted by nucleophilic displacement into other functionalities like α-hydroxy ketones, aldehydes, carboxylic acids, azides, sulphides, etc., of pharmaceutical significance [5][6][7][8], polyfunctionalized materials [11], and are used to generate compounds of biological importance such as 1,2-diaminoalcohol, [12] aminosugars, [13] nitroketones, [14] α,β-unsaturated nitro compounds [15], and many other important bifunctional compounds.…”