Table 4.

Synthesis of pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidines in the presence of various catalysts.

Entry	Catalyst	(mol%)	Time (min.)	Yield (%)
1	FeCl3	10	90	20
2	H2SO4	10	120	25
3	Fe3O4	10 mg	120	Trace
4	NH4NO3	10	100	20
5	CF3SO3H	10	80	25
6	GTBSA29	10	120	20
7	MIL-100(Cr)/NHEtN(CH2PO3H2)249	10	90	45
8	H3[p(W3O10)4].XH2O	10	120	Trace
9	SBA-15/(CH2)3 N(CH2PO3H2)(CH2)2-N(CH2PO3H2)218	10	60	52
10	[PVI-SO3H]FeCl450	10	120	30
11	p-TSA	10	120	20
12	SSA51	10 mg	100	30
13	Et3N	10	120	–
14	MHMHPA27,28	10	100	30
15	[Py-SO3H]Cl52	10	120	20
16	APVPB53	10 mg	70	40
17	Fe3O4@Co(BDC)-NH254	10 mg	85	45
18	H3PO3	10	70	55
19	CQDs55	10 mg	40	60
20	CQDs-N(CH2PO3H2)219	10 mg	30	75
21	CQDs-N(CH2PO3H2)2/SBA-15	10 mg	15	91