HIGH RESOLUTION NMR ANALYSIS OF BENZISOXAZOLE, ANTHRANIL AND THEIR 3 METHYL DERIVATIVES

Abstract

The high resolution, 60 MHz NMR spectra of benzisoxazole, 3-methylbenzisoxazole, anthranil and 3-methylanthranil were recorded. The analog spectral data were digitized by means of an analog-to-digital converter and analyzed using an iterative computer program. The 3-methyl-benzisoxazole was not complicated by inter-ring couplings and could therefore be analyzed as an ABCD spin system. However, because of long range coupling over six bonds, the 3-methyl-anthranil had to be treated as a seven spin system. The two unsubstituted molecules were analyzed as ABCDE spectra. LAOCNP (LAOCN3 with plotting) was used in order to facilitate the analyses of the five and seven proton spectra. The spectral parameters are compared with published results of benzoxazole and its 2-methyl derivative, the effect of the relative positions of the heteroatoms on the chemical shifts and coupling constants of the benzenoid protons is discussed.