Medium- and large-ring heterocyclic systems by intramolecular nitrile imine cycloadditions

A series of hydrazonyl chlorides bearing an alkenyl chain have been synthesised and treated with silver carbonate. The propensity of the so-formed nitrile imine intermediates to undergo intramolecular cycloaddition is markedly dependent on the length and the flexibility of the chain. The latter also affected the regio- and the stereo-chemistry of the intramolecular process. In certain circumstances, tandem intermolecular-intramolecular cycloadditions took place, to produce large-ring heterophanes.