Alkoxy‐substituted N‐acyliminium salts — synthesis, structure, reactivity

Alkylation of aliphatic imides 5 by use of oxonium salts takes place at one of the carbonyl oxygen atoms, leading to alkoxy‐substituted N‐acyliminium salts 1. These new reactive intermediates are fully characterized by IR, 1H‐ and 13C‐NMR spectroscopy and X‐ray analysis. The stereochemical and dynamical properties of the model compounds 6, 7 are investigated by ab initio model calculations (MP2/6–31G*//6–31G*). The barrier of rotation around the central C—N bond in 6 is calculated to 10.2 kcal/mol. The reaction with CH acids 8 yields new types of enamides (9); primary amines 10 are converted to N‐acylamidines 11. Primary amidines 12 react with 1 to form new 1,3‐diazabutadiene derivatives 13. The reaction with primary amides 14 gives N,N‐bisacylamidines 15. With primary N‐acylamidines 16 new doubly azavinylogous imides 17 (1‐oxa‐3,5‐diazahexatriene derivatives) are formed.