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SM ISO690:2012 MELNYK, Silvia, PRODIUS, Denis, SHOVA, Sergiu, TURTA, Constantin. Synthesis of new cobalt(III) L-prolinates: potential catalysts for direct aldol reactions. In: Physical Methods in Coordination and Supramolecular Chemistry, 24-26 octombrie 2012, Chişinău. Chisinau, Republic of Moldova: 2012, XVII, p. 109. |
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Physical Methods in Coordination and Supramolecular Chemistry XVII, 2012 |
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Conferința ""Physical Methods in Coordination and Supramolecular Chemistry"" Chişinău, Moldova, 24-26 octombrie 2012 | |||||
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Pag. 109-109 | |||||
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The first enantioselective organocatalytic aldol reactions were described for the proline-catalyzed synthesis of optically active partial structures of steroids by Wiechert and co-workers in 1971 [1]. Excellent results were also achieved by employing different additives such as 2,4-dinitrophenol, (R)- or (S)-binol, d-camphorsulfonic acid, or thiourea in combination with proline. The metal–amino acid or metal–amine chelation also proved to be very useful and such systems have been broadly utilized in various kinds of organic transformations, including aldol reactions [2]. Recently Karmakar and co-workers reported the cobalt(II)-proline catalyzed direct aldol reaction of both cyclic and acyclic ketones with aldehydes in either MeOH or DMSO [3]. Here we present the synthesis, x-ray crystal structure and magnetic properties investigation of novel Co(C4H8NHCOO)3·HX compounds (where X = Cl- (1), NO3 - (2), F- (3) and ClO4 - (4)). The compound 2 crystallizes in the orthorhombic space group P212121 (#19), with unit cell parameters: a = 5.2111(6), b = 13.7293(19), c = 25.394(4) Å, α = β = γ = 90°, Z = 4, Rf = 0.0528. The mononuclear structure in which the Co(III) atom adopts a fac- [CoO3N3] octahedral geometry is shown below.figureFigure 1. Molecular structure of [Co(L-pro)3]·HNO3 (2). H-atoms were omitted for clarity. An interesting feature is the presence of the intramolecular hydrogen bond between HX molecule and one prolinate ligand. |
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