From lithium ketazides to isomeric silylketazine-rings - imine-enamine tautomerism

Depending on the reaction conditions, lithium salts of di(tert-butylmethyl)ketazine react with F2SitBu2 to give structural isomeric four-, five-, and seven-membered rings containing imine and enamine units, e.g. the seven-membered ring with intramolecular imine- and enamine units. According to quantum chemical calculation the seven-membered ring is the most stable followed by the five- and four-membered ring system.