title: Urea/thiourea: efficient, inexpensive and reusable catalysts for the synthesis of pyrazole derivatives with 2-iminothiazolidin-4-one and 2,4-thiazolidinediones under solvent-free conditions.
abstract: An efficient and green synthesis of pyrazolyl-2,4-thiazolidinediones/pyrazolyl-2-iminothiazolidine-4-ones 7(a-j) has been developed using urea/thiourea as catalyst. Two methods (A and B) have been introduced for the synthesis of these compounds. Method A performed well for the condensation of pyrazole-4-carboxaldehydes 4(a-e) with 2-iminothiazolidin-4-one 5a and with 2,4-thiazolidinedione 5b at 110 [Formula: see text] for 16-20 min to furnish (Z)-5-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)thiazolidine-2,4-diones 7(a-j) in excellent yields. In method B, the pyrazole-4-carboxaldehydes 4(a-e) were condensed with urea/thiourea at 110 [Formula: see text] for 10 min to give key intermediates 6(a-j) which were later condensed with 5a and 5b to afford 7(a-j) via the elimination of urea/thiourea rather than the formation of a Biginelli product. These two protocols are inexpensive, eco-friendly and high yielding to provide the final products. The synthesis of compound 7f.
authors.affiliation: Department of Chemistry, Jawaharlal Nehru Technological University Hyderabad, College of Engineering, Kukatpally, Hyderabad, T.S., 500 085, India. veeruchem06@gmail.com.
authors.forename: Veera Swamy
authors.initials: VS
authors.lastname: Konkala
authors.affiliation: Department of Chemistry, Jawaharlal Nehru Technological University Hyderabad, College of Engineering, Kukatpally, Hyderabad, T.S., 500 085, India.
authors.forename: Pramod Kumar
authors.initials: PK
authors.lastname: Dubey
mesh_terms: D002384:Catalysis; D060326:Chemistry Techniques, Synthetic; D003365:Costs and Cost Analysis; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry*; D013844:Thiazoles / Q000737:chemistry*; D045162:Thiazolidinediones / Q000737:chemistry*; D013890:Thiourea / Q000737:chemistry*
chemical_list: C000625699:2-iminothiazolidin-4-one; D011720:Pyrazoles; D013844:Thiazoles; D045162:Thiazolidinediones; C089946:2,4-thiazolidinedione; D013890:Thiourea
keywords: Addition–elimination; Green chemistry; Knoevenagel condensation; MCRs; Multi-component reactions; Solvent-free; Urea/thiourea