Table 2. Effect of PTAs on the Aqueous-Phase Reaction of 1a and 2a^a.

entry	PTA	amount of PTA	yield (%)
1	TBAI	20 mol %	67
2	TBAI	1.0 equiv	75
3	TBAI	2.0 equiv	85
4	TBAI	3.0 equiv	88
5	TBAB	2.0 equiv	74
6	TBAC	2.0 equiv	68
7	TBAC/KI	2.0 equiv	83
8	SDS	2.0 equiv	79
9	PEG 2000	10 mol %	82
10	Tween 80	10 mol %	66
11b	TBAI	2.0 equiv	76
12c	TBAI	2.0 equiv	80

^aReaction conditions: 1a (0.3 mmol), 2a (0.6 mmol), H₂O (3 mL) 100 °C (oil bath), 24 h, under air. TBAI: tetrabutylammonium iodide, TBAB: tetrabutylammonium bromide, TBAC: tetrabutylammonium chloride, SDS: sodium dodecane-1-sulfonate.

^b80 °C.

^cUnder Ar.