Table 1. Selected Optimization Studies for the Reaction of Oxetane Acid 1 with Ethyl Acrylate.

		yield (%)a
entry	change from standard conditions	2a	2a′	3	4
1b	none	61 (58)	8 (8)	1	1
2	cat. = Ru(bpy)3(PF6)2	<5	0	2	0
3	cat. = Mes-Acr+	0	0	0	0
4	0.5 mol % Ir cat.	46	11	2	0
5	28 °C (fan cooling)	54	11	3	0
6	solvent = MeCN	41	7	2	1
7	solvent = 1,4-dioxane	28	3	3	1
8	[0.1 M]	59	15	2	3
9	2.0 equiv of acrylate	59	7	1	1
10	0.7 equiv of acrylate	59c	8c	2	3
11	DBU as base	39	4c	2	1
12	no photocatalyst	0	0	0	0
13	no light	0	0	0	0
14	no base	0	0	0	0

^aReactions run on a 0.2 mmol scale under argon. Yield calculated by analysis of the ¹H NMR spectrum of the crude mixture of the reaction using 1,3,5-trimethoxybenzene as internal standard and a 30 s relaxation delay (d1).

^bReported yields are the mean average of 6 experiments, isolated yields of a single run are in parentheses.

^cYields vs ethyl acrylate.