- Asymmetric Hydrogenation of Cationic Intermediates for the Synthesis of Chiral N,O-Acetals
-
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.
- Sun, Yongjie,Zhao, Qingyang,Wang, Heng,Yang, Tilong,Wen, Jialin,Zhang, Xumu
-
supporting information
p. 11470 - 11477
(2020/08/10)
-
- 5-SULFAMOYL-2-HYDROXYBENZAMIDE DERIVATIVES
-
The invention is directed to substituted salicylamide derivatives. Specifically, the invention is directed to compounds according to Formula (I): wherein R, R1 and R2 are as defined herein, or a pharmaceutically acceptable salt thereof. The compounds of the invention are inhibitors of CD73 and can be useful in the treatment of cancer, pre-cancerous syndromes and diseases associated with CD73 inhibition, such as AIDS, the treatment of HIV, autoimmune diseases, infections, atherosclerosis, and ischemia–reperfusion injury. Accordingly, the invention is further directed to pharmaceutical compositions comprising a compound of the invention. The invention is still further directed to methods of inhibiting CD73 activity and treatment of disorders associated therewith using a compound of the invention or a pharmaceutical composition comprising a compound of the invention.
- -
-
-
- TEMPLATE HOUBEN-HOESCH REACTION ON METAL PHENOLATES. SYNTHESIS OF AROMATIC KETONES, NITRILES AND AMIDES. CRYSTAL STRUCTURE OF DICHLORO-BORON
-
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.
- Bigi, Franca,Maggi, Raimondo,Sartori, Giovanni,Casnati, Giuseppe,Bocelli, Gabriele
-
p. 283 - 289
(2007/10/02)
-
- Antiproliferative cyclic compounds
-
A compound of formula (I) capable of inhibiting thymidylate synthase, a method for making such and a therapeutic process utilizing the compound of formula (I).
- -
-
-