Synthesis of Pyrimido[4,5-<i>e</i>]tetrazolo[5,1-<i>b</i>][1,3,4]thiadiazepine as a Novel Fused Heterocyclic System

<p>Several derivatives of the novel fused seven-membered heterocyclic system of pyrimido[4,5-<i>e</i>]tetrazolo[5,1-<i>b</i>][1,3,4]thiadiazepine <b>(5a–f)</b> have been synthesized through the heterocyclization reaction of 2,4-dichloro-5-(chloromethyl)-6-methylpyrimidine <b>(1)</b> with sodium 1-amino-1H-tetrazole-5-thiolate <b>(2)</b> under basic conditions. Various derivatives were obtained via treatment with secondary amines.</p

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