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

Table 2

Comparison of catalytic activity of NiO₁₀₀ nanoparticle with piperidine in the synthesis of compound 5a and 5g by conventional and microwave irradiation methods.

Entry	Conditions	Type of catalysts	Reaction time (hr/min.)	Yield (%)
5a	MW	No catalyst	30 min.	40
	MW	Piperidine	16 min.	75
	MW	NiO100	8 min.	90
	Δ	No catalyst	30 hrs	35
	Δ	Piperidine	13 hrs	52
	Δ	NiO100	8 hrs	67
5g	MW	No catalyst	30 min.	32
	MW	Piperidine	16 min.	74
	MW	NiO100	8 min.	89
	Δ	No catalyst	30 hrs	25
	Δ	Piperidine	14 hrs	50
	Δ	NiO100	9 hrs	65