Quinoxalines display a broad spectrum of biological and pharmacological activities such as insecticides, fungicides, herbicides, antibacterial, antimycobacterial, antiprotozoal and anticancer properties [1]. Furthermore, quinoxaline units are present in the structure of various antibiotics such as echinomycin, levomycin and actinoleutin, which are known to inhibit the growth of gram positive bacteria and are active against various transplantable tumours [2]. In addition, quinoxaline derivatives have found applications in dyes, electron luminescent materials and chemically controllable switches, as building blocks for the synthesis of anion receptors, cavitands, dehydroannulenes, organic semiconductors and as electron transport materials in multilayer OLEDs [3]. Although great attempts have been performed for the synthesis of quioxaline-fused heterocyclic derivatives, the development of new strategies for the preparation of structurally diverse five-cyclic pyrazolo-pyrimido-thiazino-quinoxaline still remains as an important and challenging goal for the organic chemists, due to its synthesis involving several reaction steps. We now wish to report a straightforward approach to the synthesis of various derivatives of pyrazolo[5\'\',1\'\':2\',3\']pyrimido[4\',5\':5,6][1,4]thiazino[2,3-b]quinoxaline as a novel 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.

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