The optimization of the reaction conditions for the synthesis of 1-phenyl-1H-tetrazole.

Entry	Solvent	Catalyst (mol%)	Temp. (°C)	Time (min)	Yielda (%)
1	Water	0.3	Reflux	180	90
2	EtOH	0.3	Reflux	180	82
3	CH3CN	0.3	Reflux	180	50
4	DMF	0.3	100	180	75
5	Neat	0.3	100	20	98
6	Neat	—	100	300	0
7	Neat	0.1	100	45	75
8	Neat	0.5	100	15	95
9	Neat	—b	100	180	Trace
10	Neat	—c	100	180	30
11	Neat	—d	100	180	50
12	Neat	—e	100	60	77
13	Neat	0.3	R.T.	120	40
14	Neat	0.3	50	75	70
15	Neat	0.3	60	45	85
16	Neat	0.3	70	30	92
17	Neat	0.3	80	20	98
18	Neat	0.3	90	20	98

^aReaction conditions: amine (1.0 mmol), triethyl orthoformate (1.2 mmol), and sodium azide (1.2 mmol). 0.3 mol% catalyst was primarily used, as explained in the experimental section.

^bReaction was performed in the presence of Fe₃O₄ as the catalyst.

^cReaction was performed in the presence of Fe₃O₄@NFC as the catalyst.

^dReaction was performed in the presence of Cu(OAc)₂ as the catalyst.

^eReaction was performed in the presence of [(5-Cl-Saloph)Cu(ii)]CO₂H as the catalyst.