28534-37-4Relevant articles and documents
Asymmetric Hydrogenation of Cationic Intermediates for the Synthesis of Chiral N,O-Acetals
Sun, Yongjie,Zhao, Qingyang,Wang, Heng,Yang, Tilong,Wen, Jialin,Zhang, Xumu
supporting information, p. 11470 - 11477 (2020/08/10)
For over half a century, transition-metal-catalyzed homogeneous hydrogenation has been mainly focused on neutral and readily prepared unsaturated substrates. Although the addition of molecular hydrogen to C=C, C=N, and C=O bonds represents a well-studied paradigm, the asymmetric hydrogenation of cationic species remains an underdeveloped area. In this study, we were seeking a breakthrough in asymmetric hydrogenation, with cationic intermediates as targets, and thereby anticipating applying this powerful tool to the construction of challenging chiral molecules. Under acidic conditions, both N- or O-acetylsalicylamides underwent cyclization to generate cationic intermediates, which were subsequently reduced by an iridium or rhodium hydride complex. The resulting N,O-acetals were synthesized with remarkably high enantioselectivity. This catalytic strategy exhibited high efficiency (turnover number of up to 4400) and high chemoselectivity. Mechanistic studies supported the hypothesis that a cationic intermediate was formed in situ and hydrogenated afterwards. A catalytic cycle has been proposed with hydride transfer from the iridium complex to the cationic sp2 carbon atom being the rate-determining step. A steric map of the catalyst has been created to illustrate the chiral environment, and a quantitative structure–selectivity relationship analysis showed how enantiomeric induction was achieved in this chemical transformation.
TEMPLATE HOUBEN-HOESCH REACTION ON METAL PHENOLATES. SYNTHESIS OF AROMATIC KETONES, NITRILES AND AMIDES. CRYSTAL STRUCTURE OF DICHLORO-BORON
Bigi, Franca,Maggi, Raimondo,Sartori, Giovanni,Casnati, Giuseppe,Bocelli, Gabriele
, p. 283 - 289 (2007/10/02)
The crystal structure of dichloro-boron (6dx) establishes for the first time the coordination mechanism of the ortho-selective reaction of metal phenolates and nitriles.Crystal data: chemical formula C9H7BCl5NO2; a = 11.743(2), b = 13.390(2), c = 8.765(3) Angstroem, β = 99.71(2) deg; space group P21/n.Variously substituted aromatic ketones, nitriles and amides have been obtained in a "one-pot" reaction.
