Synthesis of 2-substituted-4-methyl-5,13-dihydropyrimido[4′,5′:5,6][1,4]thiazepino[2,3-<i>b</i>]quinoxaline as a new heterocyclic system

<p></p> <p>2-Substituted-4-methyl-5,13-dihydropyrimido[4′,5′:5,6][1,4]thiazepino[2,3-<i>b</i>]quinoxalines (<b>7a-g</b>), derivatives of a new heterocyclic system were synthesized through cyclocondensation of 2,4-dichloro-5-(chloromethyl)-6-methylpyrimidine (<b>3</b>) with 3-aminoquinoxaline-2-thiol (<b>4</b>) and subsequent substitution by various secondary amines. Regioselective heterocyclization was confirmed by X-ray crystallographic analysis for 4-methyl-2-(pyrrolidin-1-yl)-5,13-dihydropyrimido[4′,5′:5,6] [1,4]thiazepino[2,3-<i>b</i>]quinoxaline <b>(7a).</b></p