Facile Preparation of 2-Substituted Benzoxazoles and Benzothiazoles via Aerobic Oxidation of Phenolic and Thiophenolic Imines Catalyzed by Polymer-Incarcerated Platinum Nanoclusters
Platinum nanoclusters supported on a polymer/carbon black composite material was found to be an excellent catalyst for the oxidative cyclization of phenolic and thiophenolic Schiff bases to 2-substituted benzoxazoles and benzothiazoles under ambient conditions.
Cyanide as a powerful catalyst for facile synthesis of benzofused heteroaromatic compounds via aerobic oxidation
作者:Yeon-Ho Cho、Chun-Young Lee、Cheol-Hong Cheon
DOI:10.1016/j.tet.2013.05.138
日期:2013.8
Highly efficientsynthesis of benzofused heteroaromatic compounds via aerobicoxidationcatalyzed by cyanide anion has been developed. The Schiff bases derived from 2-aminophenol and aldehydes provided the corresponding benzoxazoles in high yields in the presence of a catalytic amount of cyanide in an open flask under ambient conditions without the use of any external metal co-oxidants and bases. Furthermore
Neighboring phenolic group-activated <i>gem</i>-difluoroallylboration of imines for the catalyst-free synthesis of <i>gem</i>-difluorohomoallylamines
作者:Xing Yang、Feng Zhang、Yang Zhou、Yi-Yong Huang
DOI:10.1039/c8ob00541a
日期:——
We herein report an unprecedented addition reaction of pinacol gem-difluoroallylborates and imines enabled by a neighboring phenolic group in an N-protecting group under catalyst-free conditions, thus facilitating the construction of a wide range of racemic gem-difluorohomoallylamine derivatives. Based on the control experiments, a plausible transition state via the Zimmerman–Traxler model was proposed
The asymmetric Povarov reaction with α‐alkyl styrenes as dienophiles was catalyzed by an N,N′‐dioxide L4–Sc(OTf)3 complex. Enantiopure tetrahydroquinoline derivatives with a quaternary stereocenter at the C4 position were synthesized for the first time. A wide variety of α‐alkyl styrenes and N‐aryl aldimines were tolerated in the reaction, to give excellent diastereo‐ (up to 99:1 d.r.) and enantioselectivities
2-Trimethylsiloxyfuran underwent a vinylogous Mannich-typereaction with aldimines under the action of a new chiral phosphoric acid, bearing iodine on the 6,6′-positions of the binaphthyl group, as a chiral Brønsted acid to give γ-butenolide derivatives bearing an amino functionality with high diastereo- and enantioselectivity.