A series of 4-pyrazolylmethylene-3-phenylisoxazol-5(4H)-ones have been prepared from Knoevenagel condensation of pyrazole-4-carbaxaldehyde with isoxazolone precursors or via one-pot three-component cyclocondensation of pyrazole-4-carbaxaldehyde with β-ketoesters and hydroxylamine hydrochloride in the presence of sodium benzoate in water under the influence of ultrasonic waves. The merits of this method are efficient, clean, green, easy work-up, high yields, and shorter reaction time, and the catalyst could be recycled easily without affecting the catalytic activity.

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.

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Condensation of 2‐((1H‐benzo[d]imidazol‐2‐yl)thio)acetic acid (1) with anthranilamide (2) in PEG‐600 (polyethylene glycol), at 100 oC for 3hr. gave 2‐(((1H‐benzo[d]imidazol‐2‐yl)thio)methyl)quinazolin‐4(3H)‐one (3). Treatment of 3 with DMS, DES and Ph‐CH2‐Cl, individually in PEG‐600, at RT for 1 hr. without using any base, followed by easy process resulted in 4 (a‐c). The later on reaction with H2O2 in PEG‐600, for 3 hr, without using any base, followed by simple processing resulted in 5 (a‐c). Alternatively, 5 (a‐c) the sequence of reactions could be prepared by tandem procedure with good yields. Thus novel quinazolinone products have been prepared with new synthetic routes and strategies by using PEG‐600 as solvent, in polyethylene glycol (PEG‐600) in four routes. i.e. (tandem‐1, tandem‐2, stepwise‐1 and stepwise‐2) Probably, this is the first case of four variable but identical end‐products‐ giving tandem syntheses, under green conditions, of 5 (a‐c). Obviously, as figures pointed out, tandem‐1 route gave good yields compared to the stepwise routes. In this process PEG‐600 recycled and reused.