A One-Pot Procedure for the Synthesis of Highly Functionalized Derivatives of a Novel Five-Cyclic Scaffold: Pyrazolo[ 5 ,1 :2 ,3 ]pyrimido[4 ,5 :5,6][1,4]thiazino[2,3-b]quinoxaline

Quinoxalines display a broad spectrum of biological and pharmacological activities such asinsecticides, fungicides, herbicides, antibacterial, antimycobacterial, antiprotozoal and anticancerproperties [1]. Furthermore, quinoxaline units are present in the structure of variousantibiotics such as echinomycin, levomycin and actinoleutin, which are known to inhibit thegrowth of gram positive bacteria and are active against various transplantable tumours [2]. Inaddition, quinoxaline derivatives have found applications in dyes, electron luminescent materialsand chemically controllable switches, as building blocks for the synthesis of anion receptors,cavitands, dehydroannulenes, organic semiconductors and as electron transport materialsin multilayer OLEDs [3]. Although great attempts have been performed for the synthesis ofquioxaline-fused heterocyclic derivatives, the development of new strategies for the preparationof structurally diverse five-cyclic pyrazolo-pyrimido-thiazino-quinoxaline still remains asan important and challenging goal for the organic chemists, due to its synthesis involving severalreaction steps. We now wish to report a straightforward approach to the synthesis of variousderivatives of pyrazolo[5 ,1 :2 ,3 ]pyrimido[4 ,5 :5,6][1,4]thiazino[2,3-b]quinoxaline as anovel heterocyclic system. These potential pharmacologically active and fluorescent derivatives(3a-e) were synthesized via domino reaction of 3-aminoquinoxaline-2-thiol (1) with pyrazolo[1,5-a]pyrimidine (2) and N-alkylation with some alkyl halides in K2CO3/N,Ndimethylformamide.