Sustainable approach to tandem catalysis: Expedient access to quinoxalines and pyrido[2,3-b]pyrazines from α-hydroxyketones via microwave-induced [(NH4)6Mo7O24·4H2O – PEG 300] polar paste catalyst system

[(NH4)6Mo7O24·4H2O–PEG 300] is introduced as a polar paste catalyst system for tandem synthesis of quinoxalines and pyrido[2,3-b]pyrazines under open-vessel focused microwave irradiation. Low conversions were obtained when catalyst or PEG was used individually. Accordingly, a convenient combination of catalyst and PEG mostly led to quantitative yield of products within 15 min microwave irradiation with good turnover frequency values (11–20 h−1) taking a tandem process into consideration. The salient features of this environmentally benign method are fast conversions, high product selectivity and the use of a low-cost, readily available, nontoxic, catalyst and medium.