An expedient and tandem regioselective one-pot protocol for the sono-synthesis of bis-[1,2,4]-triazol-3-yl amines and bis-2-iminothiazolines from corresponding bis-1,3-disubstituted thioureas has been developed. The products' regioselectivity correlate well with the pK as of the parent amines, in which the amine possessing higher pK a goes to the ring nitrogen, whereas the other nitrogen remains flanked as an exocyclic nitrogen of the bis-triazole or bis-thiazole moieties. Further, the sonochemical preparation of both bis-5-(2-nitrobenzylidene) thiobarbiturates and bis-2-thioxoimidazolidine-4,5-diones from bis-1,3-disubstituted thioureas has also been achieved. The obtained bis-5-(2-nitrobenzylidene)thiobarbiturates easily underwent reductive cyclization to afford the corresponding bis-5-benzo[c]isoxazol-3-ylidenethiobarbiturates. The scope and limitations of these strategies have been studied. Moreover, the suggested methodologies have advantages such as broad functional group tolerance, mild conditions, operational simplicity and applicability on a gram scale. Furthermore, the protocols scored well in a number of green metrics, subsequently showing these approaches to be environmentally benign and sustainable processes.
Keywords: bis-2-iminothiazolines; bis-[1,2,4]-triazol-3-yl amines; green metrics; regioselectivity; ultrasonic irradiation.