The reaction products of the title substances in hot acetic acid were separated by preparative TLC into compounds A–L according to the Rf-values, and the structural assignments for these products were now made as follows: A, 14H-[1,4]benzoxazino[3′,2′ : 3,4]cyclohepta[1,2-b][1,4]benzoxazine; B, 1-formylphenoxazine; F, cyclohepta[2,1-b : 2,3-b′]di[1,4]benzoxazine; G, cyclohepta[b][1,4]benzoxazin-10(11H)-one or its enolic form; J, cyclohepta[b][1,4]benzoxazin-6(11H)-one; L, 6-(o-hydroxyanilino)cyclohepta[b][1,4]benzoxazine hydrobromide. A small amount of 2-methylamino-3H-phenoxazin-3-one was also produced. Possible reaction pathways for the formation of these products are also discussed.
Cyclohepta[b][1,4]benzoxazine and 2-(o-hydroxyanilino)tropone were obtained by the reactions of 2-chloro- and 2-methoxytropone with o-aminophenol. A similar reaction with o-methoxylaniline gave 2-(o-methoxyanilino) tropone and 1-(o-methoxyanilino)-7-(o-methoxyphenylimino)-1,3,5-cycloheptatriene. The chemical and physical properties of cyclohepta[b][1,4]benzoxazine were discussed.
The reaction of 6-bromocyclohepta[b][1,4]benzoxazine (19) and o-aminophenol (3) was studied and compared with that of 3-bromo-2-methoxytropone (2) with 3. 14H-[1,4]Benzoxazino[3′,2′:3,4]cyclohepta[1,2-b][1,4]benzoxazine, 10-(o-hydroxyanilino)cyclohepta[b][1,4]benzoxazine (D), 1- and 4-formylphenoxazines and their Schiff bases (C and X) were obtained in very good yields by modifying the conditions of the reaction of 19 with 3. Structures of D, C, and their isomers were determined and the possible reaction pathways for the formation of various products are discussed.
The title compounds, namely, the chiral acetals and their positional isomers were efficiently prepared by heating 6-bromocyclohepta[b][1,4]benzoxazines and the substituted o-aminophenols at 120 °C in acetic acid.
The benzoxazine moiety of 7-, 8-, and 9-isopropyl-as well as 6-bromocyclohepta[b][1,4]benzoxazines was easily exchanged with o-aminophenol and its methyl derivatives in methanol or acetic acid. A possible pathway of this novel intermolecular heterocycle exchange reaction is discussed.
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