Heterocyclic Ions From N-Oxides of N-(4-Nitrobenzylidene)-2-cyclopropylaniline and N-(4-Nitrobenzylidene)-2-cyclopropylmethylniline: Formation, Isomerization, and Conversions

Abstract

The N-oxide of N-(4-nitrobenzylidene)-2-cyclopropylaniline is converted by the action of strong acids into the corresponding 2,1-benzoxazinium derivative. Under identical conditions the N-oxide of N-(4-nitrobenzylidene)-2-cyclopropylmethylaniline forms the corresponding 2,1-benzoxazinium and 2,1-benzoxazepinium salts in a ratio of 1 : 2. The 2,1-benzoxazepinium ions are thermodynamically less stable and are isomerized with time into 2,1-benzoxazinium ions. Treatment of 2,1-benzoxazinium salts with hydrobromic acid solution and subsequent neutralization leads to o-(2-hydroxyalkyl)anilines and p-nitrobenzaldehyde. The effect of the nature of the ortho substituent on the direction of the conversions of the corresponding arylcyclopropanes is discussed.