The BF3-catalyzed decomposition of m- and p-substituted α-diazoacetophenones in excess of methyl thiocyanate and ethyl thiocyanate gave the corresponding 2-methylthio-, and 2-ethylthio-5-aryloxazoles, respectively in good yields along with s-alkyl-n-aroylmethylthiocarbamates and α-ethoxyacetophenones. However, yields of 2-dimethylamino-5-aryloxazoles by the reaction of dimethylcyanamide with α-diazoacetophenones
A modified Kondrat’eva cycloaddition involving an unprecedented thermally controlled metal-free decarboxylative aromatization affords an expedient access to natural 3-hydroxypyridine/piperidine systems.
Metal-Free Decarboxylative Hetero-Diels–Alder Synthesis of 3-Hydroxypyridines: A Rapid Access to <i>N</i>-Fused Bicyclic Hydroxypiperidine Scaffolds
作者:Laurie-Anne Jouanno、Vincent Di Mascio、Vincent Tognetti、Laurent Joubert、Cyrille Sabot、Pierre-Yves Renard
DOI:10.1021/jo402729a
日期:2014.2.7
A complete experimental and theoreticalstudy of the thermally controlled metal-free decarboxylative hetero-Diels–Alder (HDA) reaction of 5-alkoxyoxazoles with acrylic acid is reported. This strategy offers a new entry to valuable 2,6-difunctionalized 3-hydroxypyridines from readily available 2- and 4-disubstituted 5-alkoxyoxazoles. The reaction conditions proved compatible with, among others, ketone
A rapid and general access to diversely substituted 5-alkoxyoxazoles 2 (i.e., R1, R2 = alkyl, phenyl) from easily accessible α-triflyloxy/hydroxy esters 1 and nitriles with good yields (41–76%) is reported. The versatility of the cyclization is shown for a range of substrates with high selectivity toward triflates over mesylates and proved to be compatible with sensitive functional groups. As an illustration
Herein, a visible light-induced synthesis of polysubstituted oxazoles from diazo compounds is reported. This developed synthetic method differs from traditional routes that rely on transition metals and external chemical oxidants. Our method uses readily available and inexpensive diazonium compounds as well as nitrile substrates with a catalytic amount of (i-Pr)3SiCl species, delivering the corresponding