Table 1. Optimization of the reaction conditions ^a .

Entry	Catalyst (mol%)	Additives (equiv.)	Solvent	T (°C)	Yield b (%)
1	TBAI (20)	—	MeCN	70	18
2	TBAI (20)	—	DCM	70	10
3	TBAI (20)	—	1,4-Dioxane	70	Trace
4	TBAI (20)	—	Toluene	70	0
5	TBAI (20)	—	MeCN	100	25
6	I2 (15)	—	MeCN	100	Messy
7	KI (20)	—	MeCN	100	Messy
8	CuI (20)	—	MeCN	100	16
9	TBAI (20)	HOAc (1.0)	MeCN	100	28
10	TBAI (20)	l-Proline (1.0)	MeCN	100	33
11	TBAI (20)	PivOH (1.0)	MeCN	100	35
12	TBAI (20)/CuI (5)	PivOH (1.0)	MeCN	100	49
13	TBAI (30)/Cu(OAc)2 (5)	PivOH (1.0)	MeCN	100	53
14	TBAI (20)/Cu(OAc)2 (5)	PivOH (1.0)	MeCN	100	61
15	TBAI (20)/Cu(OAc)2 (5)	PivOH (2.0)	MeCN	100	71
16	TBAI (20)/Cu(OAc)2 (10)	PivOH (2.0)	MeCN	100	63
17	TBAI (20)/Cu(OAc)2 (5)	—	MeCN	100	33

^aReaction conditions: 1,5-conjugated enyne (1a, 0.25 mmol), tosylhydrazide (2a, 0.50 mmol), BPO (1.0 mmol), solvent (2.5 mL), 12 h.

^bIsolated yields based on 1.