A new tautomeric zwitterion form of 2‐acylamino‐4<i>H</i>‐1,3,4‐oxadiazino[5,6‐<i>b</i>]quinoxalines in solution

Abstract

Abstract The reaction of 2‐acyiamino‐8‐chloro‐4‐methyl‐4 H ‐1,3,4‐oxadiazino[5,6‐ b ]quinoxalines 2a‐d with methyl iodide/base gave the 8‐chloro‐4,10‐dimethyl‐4 H ‐1,3,4‐oxadiazino[5,6‐ b ]quinoxalin‐10‐ium‐2‐acylamidates 4a‐d , respectively. Comparison of the nmr spectral data between compounds 2a‐d and 4a‐d in deuteriodimethyl sulfoxide or in deuteriotrifluoroacetic acid established that compounds 2a‐d existed as the zwitterionic tautomers 2′a‐d in solution.