Table 1. Evaluation of Reaction Conditions^a.

entry	THIQ (equiv)	catalyst	time (h)	yield (%)
1	2		48	50
2	2	PhCOOH	7	95
3	2	AcOH	23	92
4	2	2-EHA	21	91
5b	2	PhCOOH	44	56
6	1.5	PhCOOH	12	93
7	1.2	PhCOOH	12	88
8c	1.5	PhCOOH	15	95

^aReactions were performed on a 0.2 mmol scale. All yields correspond to isolated yields. dr >25:1 in all cases.

^bReaction was run at 50 °C and remained incomplete.

^cWithout 4 Å MS.