Synthesis of Quaternary Indoxyl Derivatives by Intramolecular Cyclization of Some Substituted Acetophenones

Abstract

AbstractThe intramolecular cyclization of N,N‐disubstituted 2′‐halogenophenacylamine hydrobromides 1a–h to 1,1‐disubstituted 3‐oxoindolinium bromides 3a–f has been studied. Some 3‐oxoindolinium salts have also been prepared according to a different pattern by intramolecular cyclization of the phenacyl halides resulting from the bromination of 2′‐(dialkylamino)acetophenones 4 or from the treatment of 2′‐(dialkylamino)‐2‐diazoacetophenones 6a, b with hydrogen halides. Removal of hydrogen halide in salts 3a–g gives indolylio oxides 2a–g; these compounds have been shown to be unstable and decompose easily giving in general complex mixtures; only in the case of tetrahydroisoquinoline‐derived ylides 2e, g we have observed clear‐cut reactions leading, via a Stevens rearrangement followed by oxidation, to the 6,7‐dihydro‐13H‐indolo[2,1‐b][3]benzazepin‐13‐ones 8a, b. magnified image