Heterocyclization of N-[2-(cyclopent-1-enyl)phenyl]acetamides and ethyl N-[2-(cyclopent-1-enyl)phenyl]carbamates under the action of hydrogen peroxide

The oxidation of N-[2-(cyclopent-1-enyl)phenyl]acetamides and ethyl N-[6-methyl-2-(cyclopent-1-enyl)phenyl]carbamate with hydrogen peroxide in methanolic NaOH gave spiro[4H-3,1-benzoxazine-4,1′-cyclopentanes]. On the other hand, ethyl [2-(cyclopent- 1-enyl)phenyl]carbamate reacted with hydrogen peroxide in the presence of acetonitrile and NaOH to give ethyl 3a-hydroxy-2,3,3a,8b-tetrahydrocyclopenta[b]indole-4(1H)-carboxylate, which was dehydrated with polyphosphoric acid to ethyl 2,3-dihydrocyclopenta[b]indole-4(1H)-carboxylate.