A Simple, One-Step Synthesis of 3,4-Dihydro-4-phenacyl-2<i>H</i>-1,3-benzoxazin-2-ones
作者:Nazih Latif、Fahmy M. Asaad、Nabil Grant
DOI:10.1055/s-1988-27532
日期:——
2-Hydroxychalcones 1a, b react readily with alkyl and aryl isocyanates in the presence of potassium hydroxide to give directly the corresponding 3-alkyl- and 3-aryl-3,4-dihydro-4-phenacyl-2H-1,3-benzoxazin-2-ones 3. The 2-thione analogues 5a, b are similarly obtained by reacting 1a, b with methyl isothiocyanate. Thiones 5 are readily oxidized by yellow mercuric oxide to the corresponding oxo compounds 3. The direct formation of benzoxazinones from chalcones apparently proceeds through the intermediate formation of open chain carbamates.The latter are cleaved readily by p-toluenesulfonyl chloride under base catalysis to give the corresponding sulfonates.