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
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.
2] cycloadducts through oxazole ring opening. Zwitterionic mechanisms were proposed on the basis of the solvent effect on the reaction. The molecular structure of 2-isopropyl-substituted product was determined by means of X-ray crystallography. Crystals of the cycloadduct are orthorhombic with space group Pcab having unit-cell dimensions of a = 17.998 (2), b = 27.188 (6), c = 15.833 (3) A, and Z = 16
2-烷基-或2-芳基-取代的5-甲氧基-4-(对硝基苯基)恶唑与四氰基乙烯反应得到5-取代的3,3,4,4-四氰基-2-(对硝基苯基)甲酯)-3,4-二氢-2H-吡咯-2-羧酸作为正式的[3 + 2]环加合物通过恶唑开环。基于溶剂对反应的影响提出了两性离子机理。2-异丙基取代产物的分子结构通过X-射线晶体学确定。环加合物的晶体是正交的,空间群 Pcab 的晶胞尺寸为 a = 17.998 (2)、b = 27.188 (6)、c = 15.833 (3) A 和 Z = 16,其中包含两个晶体学独立的分子。对于 4629 次观察到的反射,最终的 R 值为 0.070。