NiO Nanoparticles: An Efficient Catalyst for the Multicomponent One-Pot Synthesis of Novel Spiro and Condensed Indole Derivatives

Table 3

Comparison of catalytic activity of NiO nanoparticle calcined at 100°C (NiO₁₀₀), 200°C (NiO₂₀₀), 400°C (NiO₄₀₀) in the synthesis of the compound 5a under conventional heating and microwave irradiation methods.

Entry	Type of catalyst	Time (hr/min.)		Yield (%)		Particle size; (nm)
		Δ	MW	Δ	MW
1	NiO100	8 hrs	8 min.	67	90	9.7
2	NiO200	12 hrs	13 min.	60	82	18
3	NiO400	16 hrs	17 min.	53	78	—