ZnO Nanoparticles as an Efficient, Heterogeneous, Reusable, and Ecofriendly Catalyst for Four-Component One-Pot Green Synthesis of Pyranopyrazole Derivatives in Water

Table 1

Nano-ZnO catalyzed synthesis of pyrano[2,3-c]pyrazole derivatives in water at room temperature (5a–j).

Entry	Ar	Time (min.)	Yield (%)	M.P. (°C)
Ethyl-6-amino-1,4-dihydro-4-(3,4-dimethoxyphenyl)-3-methylpyrano[2,3-c]pyrazole-5-carboxylate; (5a)	3,4-Dimethoxy; phenyl	60	90	135
Ethyl-6-amino-1,4-dihydro-4-(3-methoxyphenyl)-3-methylpyrano[2,3-c]pyrazole-5-carboxylate; (5b)	3-Methoxyphenyl	55	85	120
Ethyl-6-amino-1,4-dihydro-4-(3,4,5-trimethoxyphenyl)-3-methylpyrano[2,3-c]pyrazole-5-carboxylate; (5c)	3,4,5-Trimethoxy; phenyl	55	86	160
Ethyl-6-amino-4-(4-chlorophenyl)-1,4-dihydro-3-methylpyrano[2,3-c]pyrazole-5-carboxylate; (5d)	4-Chlorophenyl	60	87	140
Ethyl-6-amino-1,4-dihydro-4-(4-methoxyphenyl)-3-methylpyrano[2,3-c]pyrazole-5-carboxylate; (5e)	4-methoxyphenyl	55	89	130
Ethyl-6-amino-1,4-dihydro-3-methyl-4-(5-methylfuran-2-yl)pyrano[2,3-c]pyrazole-5-carboxylate; (5f)	3-methyl-2-furyl	60	86	142
Ethyl-6-amino-1,4-dihydro-3-methyl-4-(thiophen-2-yl)pyrano[2,3-c]pyrazole-5-carboxylate; (5g)	2-thienyl	55	87	115
Ethyl-6-amino-1,4-dihydro-3-methyl-4-(pyridin-3-yl)pyrano[2,3-c]pyrazole-5-carboxylate; (5h)	3-pyridyl	60	85	125
Ethyl-6-amino-1,4-dihydro-4-(2-hydroxyphenyl)-3-methylpyrano[2,3-c]pyrazole-5-carboxylate; (5i)	2-Hydroxyphenyl	60	87	143
Ethyl-6-amino-1,4-dihydro-4-(3-hydroxy-4-methoxy phenyl)-3-methylpyrano[2,3-c]pyrazole-5-carboxylate; (5j)	3-hydroxy, 4-methoxyphenyl	60	85	145

Reaction conditions: hydrazine hydrate (1) (1 mmol), methyl acetoacetate (2) (1 mmol), substituted aromatic aldehyde (3) (1 mmol), ethylcyano acetate (4) (1 mmol), and ZnO nanoparticle (9 mol%) in water (2 mL).