Synthesis of hexahydro‐5 H ‐benz[ g ]imidazo[2,1‐ a ]‐ isoindole 2 via an intramolecular diels‐alder reaction and a novel lawesson's reagent mediated cyclization

The 2‐(5,6‐dihydroxy‐1,2,3,4‐tetrahydro‐1‐naphthyl)imidazoline 1 is a recently reported potent alpha ‐adrenergic agent [1]. In continuation of our work on the synthesis of potential adrenergic agents we required imidazoisoindole 2 in order to investigate the biological effects of incorporation of additional rigidity into the parent system. This paper describes the synthesis of 2 via an intramolecular Diels‐Alder reaction and a novel Lawesson's reagent mediated cyclization.