Analogs of cannabinoids: synthesis of some 7H-indolo-, 5H-imidazolo, 7H-benzimidazolo[1,2-c] [1,3]benzoxazines – novel ring systems

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Abstract
Tetrahydrocannabinol 1, the active constituent of CannabissativaLinn, is a well-known CNS-active compound and introduction of a nitrogen atom at the ring junction of the pyran and alicyclic ring is of considerable interest. This prompted the synthesis of 7H-indolo[1,2-c] [1,3]-, 5H-imidazolo[1,2-C] [1,3],- and 7H-benzimidazolo[1,2-c] [1,3]-benzoxazine, a novel heterocyclic system. 2-(2′-Hydroxyphenyl) indoles, 2-(2′-hydroxyphenyl) imidazoles, and 2-(2′-hydroxyphenyl) benzimidazoles are suitable intermediates for the preparation of this type of benzoxazines, as the second heterocycle (ring B) can then be constructed by introduction of a methylene bridge between the hydroxyl of the 2′-hydroxy phenyl substituent and the imino group of the heterocyclic system.