2749-65-7Relevant academic research and scientific papers
Enantioselective aziridination of cyclic enals facilitated by the fluorine-iminium ion Gauche effect
Molnar, Istvan Gabor,Tanzer, Eva-Maria,Daniliuc, Constantin,Gilmour, Ryan
supporting information, p. 794 - 800 (2014/01/23)
The enantioselective, organocatalytic aziridination of small, medium and macro-cyclic enals is reported using (S)-2-(fluorodiphenyl methyl)-pyrrolidine. Central to the reaction design is the reversible formation of a β-fluoroiminium ion intermediate, which is pre-organised on account of the fluorine-iminium ion gauche effect. This conformational effect positions the fluorine substituent synclinal-endo to the electropositive nitrogen centre thus benefiting from favourable stereoelectronic and electrostatic interactions (σC-H→σC-F*; F δ-···N+). Consequently, one of the shielding groups on the fluorine-bearing carbon atom is positioned above the π-system, forming the basis of an enantioinduction strategy. Treatment of this intermediate with a "nitrene" source furnished a series of novel, optically active aziridines (e.r. up to 99.5:0.5). Further derivatisation of the product aziridines gives facile access to various amino acid derivatives, including β-fluoroamino acids. Crystallographic analyses of both the aziridines and their derivatives are disclosed. Copyright
Catalytic enantioselective allyl- and crotylboration of aldehydes using chiral diol·SnCl4 complexes. Optimization, substrate scope and mechanistic investigations
Rauniyar, Vivek,Zhai, Huimin,Hall, Dennis G.
supporting information; experimental part, p. 8481 - 8490 (2009/02/02)
We report a novel class of C2-symmetric chiral diols derived from the hydrobenzoin skeleton. The combination of these diols with SnCl 4 under Yamamoto's concept of Lewis acid assisted Bronsted acidity (LBA catalysis) leads to high levels of asymmetric induction in the allylboration of aldehydes by commercially available allylboronic acid pinacol ester 1a. The corresponding homoallylic alcohol products of synthetically useful aliphatic aldehydes are obtained in excellent yields with up to 98:2 er. This combined acid manifold is also efficient in catalyzing the diastereo- and enantioselective crotylboration of aldehydes, thus providing the propionate units in >95:5 dr and up to 98:2 er. The X-ray crystal structure of the optimal diol·SnCl4 complex, Vivol (4m)·SnCl 4, unambiguously shows the Bronsted acidic character of this LBA catalyst and its highly dissymmetrical environment. Further controls have ruled out a possible boron transesterification mechanism with the chiral diol and point to LBA catalyst-derived activation of the pinacol allylic boronates 1. Due to slow dissociation of the diol·SnCl4 complex, a small excess of diol is required in order to suppress a competing racemic cycle catalyzed by free SnCl4.
Convenient preparation of cycloalkenyl boronic acid pinacol esters
Rauniyar, Vivek,Zhai, Huimin,Hall, Dennis G.
experimental part, p. 3984 - 3995 (2009/04/11)
A practical method for the preparation of cycloalkenyl boronic acid pinacol esters is described. These important synthetic intermediates are typically made using more expensive methods like transition metal-catalyzed borylation of alkenyl halides or trifl
Structure-activity relationships of xanthene carboxamides, novel CCR1 receptor antagonists
Naya, Akira,Ishikawa, Makoto,Matsuda, Kenji,Ohwaki, Kenji,Saeki, Toshihiko,Noguchi, Kazuhito,Ohtake, Norikazu
, p. 875 - 884 (2007/10/03)
The structure-activity relationships of xanthene carboxamide derivatives on the CCR1 receptor binding affinity and the functional antagonist activity were described. Previously, we reported a quaternarized xanthen-9-carboxamide 1 as a potent human CCR1 receptor antagonist that was derived from a xanthen-9-carboxamide lead 2a. Further derivatization of 2a focusing on installing an additional substituent into the xanthene ring resulted in the identification of 2b-1 with IC50 values of 1.8 nM and 13 nM in the binding assay using human CCR1 receptors transfected CHO cells and in the functional assay using U937 cells expressing human CCR1 receptors, respectively.
