Investigation of the optimal conditions for the synthesis of diphenyl ether in the presence of Cu–ninhydrin@GO–Ni MNPs.

Entry	Amount of catalyst (mg)	Solvent	Base	Temperature (°C)	Time (min)	Yield (%)
1	—	DMSO	KOH	130	300	N.R.
2	30	DMSO	KOH	130	120	98
3	20	DMSO	KOH	130	160	90
4	35	DMSO	KOH	130	105	93
5	30	PEG	KOH	130	120	48
6	30	DMF	KOH	130	120	72
7	30	H2O	KOH	Reflux	120	35
8	30	DMSO	Na2CO3	130	120	20
9	30	DMSO	NaHCO3	130	120	27
10	30	DMSO	Et3N	130	120	55
11	30	DMSO	NaOCH3	130	120	31
12	30	DMSO	NaOH	130	120	74
13	30	DMSO	KOH	100	120	67