Polycyclic nitrogen compounds. Part II. Tricyclic quinoxalinones and their 4‐ or 6‐aza analogues
1,2,3,3a‐Tetrahydro‐9‐nitropyrrolo[1,2‐α]quinoxalin‐4‐one and 7,8,9,10‐tetrahydro‐3‐nitropyrido[1,2‐α]quin‐oxalin‐6‐one (V‐VI) were reduced and deaminated to give new parent tricyclic quinoxalinone skeletons I‐II. The latter compounds were identical with the tricycles obtained by an unambiguous independent synthesis. New 6‐aza‐1,2,3,3a‐tetrahydropyrrolo[1,2‐α]quinoxalin‐4‐one (III) and 4‐aza‐7,8,9,10‐tetrahydropyrido[1,2‐α]‐quinoxalin‐6‐one (IV) were prepared by selective hydrogen transfer reductive cyclisation of esters of N‐(2‐nitro‐3‐pyridyl)pyrrolidine‐2‐carboxylic acid and N‐(2‐nitro‐3‐pyridyl)piperidine‐2‐carboxylic acid (Xb and XIb) respectively.