Cyclization of 3-dibenzofurylthiourea under the conditions of the Hugershoff reaction gives the linear structure 1. 'H n.m.r. and 13C n.m.r. spectra of the two isomeric aminobenzofurobenzothiazoles (1 and 3), recorded at 220 MHz, 60 MHz and 22,62MHz respectively, were used as aids for the structure determination. The magnetic parameters were obtained partly by first-order analysis and partly by simulation of spectra using LAOCOON 3. The assignments were made by comparing the chemical shifts and coupling constants with those of the parent compounds dibenzofuran (4a) and 2-aminobenzothiazole (5c). In so far as the assignments of 'H n.m.r. and 13C n.m.r. frequencies of the parent compounds themselves were unknown or supported by analogy only, they have been determined using experimental criteria such as deuterium substitution and investigation of changes in chemical shifts caused by derivation.
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