Mechanistic studies of direct and sensitized photolysis of methyl (4-nitrophenyl)diazoacetate in the presence of an electron-donating amine: photochemical generation of the diazoalkane radical anion
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
Abnormal Diels–Alder Reaction of Oxazoles with 4-Phenyl-3<i>H</i>-1,2,4-triazole-3,5(4<i>H</i>)-dione and Diethyl Azodicarboxylate, and X-Ray Crystal Structure of an Adduct
作者:Toshikazu Ibata、Hiroyuki Suga、Yasushi Isogami、Hatsue Tamura、Xiaolan Shi
DOI:10.1246/bcsj.65.2998
日期:1992.11
The reaction of substituted oxazoles with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione (PTAD) or diethyl azodicarboxylate gave the corresponding 1,2,4-triazoline derivatives through formal [3+2] cycloaddition accompanying ring opening of oxazoles. The molecular structure of an adduct of 5-methoxy-4-methyl-2-(p-tolyl)oxazole with PTAD was determined by means of X-ray crystallography.
Photoreaction of Methyl (<i>p</i>-Nitrophenyl)diazoacetate in the Presence of an Electron-Donating Amine: Evidence for Intermediacy of the Carbene Radical Anion
by the addition of an electron-donating amine, where the formation of the products derived from the carbene was quenched completely. On the basis of the direct observation of transient species and the dependence of the products on amine concentration, the reaction scheme involving a single electron transfer to afford the carbeneradicalanion is proposed.
The high pressure Diels–Alderreactions of 5-methoxy-2-methyl-4-(p-nitrophenyl)oxazole with ethylenic dienophiles such as N-methylmaleimide, N-phenylmaleimide, dimethyl maleate and dimethyl fumarate gave the corresponding adducts in good to excellent yields. The effects of pressure, temperature, solvents on the yields were investigated. The high pressure also increased the formation of 3-hydroxypyridine
Synthesis of 2,5-Dihydro-1,2,4-oxadiazoles through Formal [3 + 2] Cycloaddition of Oxazoles with Nitrosobenzene Derivatives
作者:Hiroyuki Suga、Xiaolan Shi、Toshikazu Ibata
DOI:10.1246/bcsj.71.1231
日期:1998.5
The reactions of substituted oxazoles with nitrosobenzene gave 2-phenyl-2,5-dihydro-1,2,4-oxadiazoles regioselectively through formal [3 + 2] cycloadditions proceeding via a ringopening of oxazoles by an attack of nitrosobenzene. The reactions with 1-chloro- and 1-methyl-4-nitrosobenzenes also produced the corresponding 2,5-dihydro-1,2,4-oxadiazoles regioselectivity.