Formation, dealkylation, and nucleophilic substitution of some mono- and di-alkoxypyridoazepines
The photo-induced ring-expansions of 5-azido-, 8-azido-, 6-azido-8-methoxy, and 8-azido-6-methoxy-quinolines to alkoxypyridoazepines in alcohol–alkoxide–dioxane solution containing 18-crown-6 are reported, although in some instances azepinone and/or azepine ring-contraction products are noted. In addition, ring-expansions in the presence of phenoxide ion have been achieved for the first time. 1H N.m.r. spectra indicate that some of the pyrido-azepines and -azepinones are formed as mixtures of the 5H- and 7H-isomers.
Dealkylations and nucleophilic substitutions of the alkoxypyridoazepines are discussed, the latter in some instances being accompanied by ring-contraction to diaminoquinolines.