2-Dihydromethylpiperazinediium-MII(MII= CuII, FeII, CoII, ZnII) double sulfates and their catalytic activity in diastereoselective nitroaldol (Henry) reaction
| Autor: | Fadhel Hajlaoui, Armando J. L. Pombeiro, Tatiana C. O. Mac Leod, Kamran T. Mahmudov, Tahar Mhiri, Maximilian N. Kopylovich, Houcine Naïli |
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| Rok vydání: | 2013 |
| Předmět: | |
| Zdroj: | Dalton Trans.. 42:399-406 |
| ISSN: | 1477-9234 1477-9226 |
| DOI: | 10.1039/c2dt31300f |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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