Table 1 Optimized conditions to prepare triazolo[1,2-a]indazole-trione and spiro triazolo[1,2-a]indazole-tetraones.

1

P-TSOH

Solvent-free/90 °C

20

270

57

2

CH₃COOH

Solvent-free/90 °C

20

290

51

3

SiO₂

Solvent-free/90 °C

20

260

56

4

GO/f–SiO₂

Ethanol/90 °C

20

150

61

5

GO/f–SiO₂/Co

Solvent-free /50 °C

20

90

69

6

GO/f–SiO₂/Co

Solvent-free /70 °C

20

60

77

7

GO/f–SiO₂/Co

Ethanol/90 °C

20

100

76

8

GO/f–SiO₂/Co

Solvent-free /90 °C

20

19

93

9

GO/f–SiO₂/Co

H₂O/90 °C

20

90

79

10

GO/f–SiO₂

Solvent-free /90 °C

20

45

81

11

GO/f–SiO₂/Co

MeCN/90 °C

20

160

61