One-pot three-component condensation reaction in water: An efficient and improved procedure for the synthesis of pyrimido[2,1-b]benzothiazoles

Industries are constantly in search of efficient and green chemistry protocols for the synthesis of pyrimido [2,1-b]benzothiazoles. One-pot reaction of 2-aminobenzothiazole, active methylene derivatives, and carbonyl compounds expeditiously annulate a pyrimidine ring on the benzothiazole nucleus to yield pyrimido [2,1-b]benzothiazole under microwaves or ultrasonic waves using water as energy transfer medium. The title compounds are easily accessible by various approaches; even waste-free procedures have been developed. The operational simplicity, environmentally friendly conditions, and high yield achieved in a very short reaction time are major benefits that meet the requirements of green production, including saving energy and high efficiency. The results are compared with conventional heating. Structural assignments are based on spectroscopic data.