174758-61-3Relevant academic research and scientific papers
The formation of hemiacetal complexes of rhenium(V) by degradation of a Schiff base
Barandov, Ali,Abram, Ulrich
, p. 2542 - 2547 (2013/11/19)
Mono- and dinuclear oxidorhenium(V) complexes with hemiacetal ligands were isolated from a reaction of (NBu4)[ReOCl4] with a potentially tetradentate Schiff base prepared from (1R,2R)-cyclohexane-1, 2-diamine and (2-formylphenyl)diphenylphosphine in methanol. The hemiacetal is formed by solvolysis of first one imine functionality of the Schiff base, whereas the second remains intact. The resulting amine/iminophosphine coordinates as a tridentate N,N, P ligand in a dinuclear compound. Ongoing degradation of the Schiff base gives more hemiacetal (HL1a) and the final product, the monomeric complex [ReOCl(L1a)2] is formed. Cleavage of the organic framework is not observed during the reaction of (NBu4)[ReOCl4] with a related Schiff base derived from ethylene-1, 2-diamine and (2-formylphenyl)diphenylphosphine. The Schiff base reacts as a bis-bidentate N, P ligand and a dinuclear oxorhenium(V) compound with a central ethylene bridge is formed. Copyright
Continuous Application of Chemzymes in a Membrane Reactor: Asymmetric Transfer Hydrogenation of Acetophenone
Laue, Stephan,Greiner, Lasse,W?ltinger, Jens,Liese, Andreas
, p. 711 - 720 (2007/10/03)
The application of homogeneously soluble catalysts is limited by the recovery in cases where the price of the catalyst is high. Biological catalysts, enzymes, can be efficiently recycled by means of an ultrafiltration membrane due to their high molecular weight, for example, in the continuously operated membrane reactor. In order to transfer this principle to chemical catalysis, we have attached a transfer hydrogenation catalyst, first invented by Gao and Noyori, to a polymer. The resulting homogeneously soluble, polymer-bound catalyst (chemzyme) can now be retained by ultrafiltration membranes like enzymes. On applying this catalyst in continuously operated membrane reactors, a continuous isopropoxide dosage is necessary in order to compensate deactivation caused by water residues in the feed stream. Thus, high space-time yields up to 578 g L-1 d-1 and enantioselectivities up to 94% can he achieved. These results were compared to an enzyme catalyzed system consisting of a carbonyl reductase that also utilizes 2-propanol as a hydrogen source for the cofactor regeneration of NADH.
