The synthesis of oxazoles by thermolysis or photolysis of 2-acylisoxazol-5-ones
作者:Kiah H. Ang、Rolf H. Prager、Jason A. Smith、Ben Weber、Craig M. Williams
DOI:10.1016/0040-4039(95)02240-6
日期:1996.1
N-acylisoxazol-5-ones are converted into the corresponding 2-substituted oxazoles by photolysis at 300 or 254nm, or by flash vacuum pyrolysis. The former procedure is favoured for isoxazolones with electron withdrawing groups at C-4, and pyrolysis for all others.
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.
Synthesis of 2,4-Disubstituted Oxazoles by a Copper-Catalyzed [3+2] Annulation/Olefination Cascade between Amides and IIII/PV Hybrid Ylides
作者:Zhaofeng Wang、Xingchen Ye
DOI:10.1055/a-2185-0673
日期:——
We report a novel and efficient method for oxazole synthesis through a copper-catalyzed [3+2] annulation/olefination cascade between readily available iodonium–phosphonium hybrid ylides and amides. An unprecedented α-phosphonium Cu carbenoid acts as the key intermediate. This method features excellent regioselectivity with mild reaction conditions and a broad substrate scope. Its synthetic utility