Diazepines. Part 23. The formation and structure of 1,5-diaza- and 5-aza-1-oxa-pentadienium salts and their use in the preparation of 2,3-dihydro-1,4-diazepinium salts

Abstract

1,5-Diaza- and 5-aza-1-oxa-pentadienium salts serve as excellent precursors for the preparation of 2,3-dihydro-1,4-diazepinium salts, including some that are not readily obtained by other methods. Sometimes imidazolinium rings are formed instead of or in addition to the desired product. The preparation of these precursors is discussed. The shape of diazapentadienium salts is considered, based on spectroscopic evidence. The formation of fourteen-membered rings from azaoxapentadienium salts is also mentioned.