Table 1.

Reaction approach and optimization

Entrya	Solvent	% cat.	Equiv MsOH	Temp. (°C)	2 (%)b	3 (%)b	4 (%)b
1	THF	20	-	rt	78	-	-
2	Dioxane	20	-	rt	96	-	-
3	Diethyl ether	20	-	rt	59	-	-
4	MTBE	20	-	rt	64	-	-
5	2-methyl THF	20	-	rt	66	-	-
6c	Dioxane	10	-	rt	68	-	-
7d	Dioxane	5	-	rt	trace	-	-
8c	Dioxane	5	-	45	trace	-	-
9	THF	20	6.5	rt	70	0	0
10	Dioxane	20	6.5	rt	30	36	38
11e	Dioxane	20	7.5	rt, then 40	0	0	90

^aoptimization reactions conducted on a 0.04 mmol scale (0.1 M) using 20% catalyst, 1.2 equivalents of aldehyde, and 1.2 equivalents of Cs₂CO₃ unless otherwise noted.

^byield of isolated material

^cconducted at 0.2 M concentration

^dconducted at 0.4 M concentration

^econducted on a 0.4 mmol scale; cyclization reaction went to completion overnight.