Enantioselective Olefin Hydrocyanation without Cyanide
作者:Alexander W. Schuppe、Gustavo M. Borrajo-Calleja、Stephen L. Buchwald
DOI:10.1021/jacs.9b10875
日期:2019.11.27
The enantioselective hydrocyanation of olefins represents a conceptually straightforward approach to prepare enantiomerically enriched nitriles. These, in turn, comprise or are intermediates in the synthesis of many pharmaceuticals and their synthetic derivatives. Herein, we report a cyanide-free dual Pd/CuH-catalyzed protocol for the asymmetric Markovnikov hydrocyanation of vinyl arenes and the anti-Markovnikov
Chemistry of 5-oxodihydroisoxazoles. Part 18.1 Synthesis of oxazoles by the photolysis and pyrolysis of 2-acyl-5-oxo-2,5-dihydroisoxazoles
作者:Rolf H. Prager、Jason A. Smith、Ben Weber、Craig M. Williams
DOI:10.1039/a700134g
日期:——
N-Acylisoxazol-5-ones lose carbon dioxide under
photochemical and thermal conditions affording iminocarbenes which
undergo intramolecular cyclisation through the oxygen of the acyl group
to give oxazoles. Under photochemical conditions those acylisoxazolones
with electron withdrawing groups at C-4 usually give high yields of
oxazoles, while those with electron donating groups at C-4 give only
poor yields: the reverse is observed under thermal conditions.
Five 4,4'-bithiazole-based tetraarylenes were prepared and their photochromic behavior investigated. With their 1,3,5,7-octatetraene photoreactive backbone, they offer not only more available sites for further functionalizations, but also a novel design principle for the development of a new class of biphotochromes.
Synthesis and Reaction of the First Oxazol-4-ylboronates: Useful Reagents for the Preparation of the Oxazole-Containing Biaryl Compounds
作者:Munenori Inoue、Hiroshi Araki、Tadashi Katoh
DOI:10.1055/s-2006-932471
日期:——
The first oxazol-4-ylboronates were prepared from the corresponding 4-bromo- and 4-trifluoromethanesulfonyloxy-oxazoles. The Suzuki coupling using the resulting boron reagents with various aryl halides, including benzene, pyridine, oxazole and thiazole rings, in the presence of palladium catalyst proceeded to produce the oxazole-containing biaryl compounds in moderate to good yields.
diarylbenzenes bearing thiazole and oxazole rings as the aryl groups to improve the coloring under ultraviolet (UV) irradiation. The substitution of the aryl groups with thiazole and oxazole rings having lower aromaticity than thiophene brought about the deceleration of the thermal bleaching reaction, the blue-shift of the absorptionspectra of the closed-ring isomers, and the increase of the photocyclization