Table 1.

Reaction optimization.

entry	Lewis acid	ligand	% yielda
1	none	none	0
2	20 mol% Sc(OTf)3	none	34
3	20 mol% Mg(OTf)2	none	14
4	20 mol% Cu(OTf)2	none	8
5	20 mol% Zn(OTf)2	none	19
6	20 mol% Fe(OTf)3	none	7
7	20 mol% La(OTf)3	none	4
8	20 mol% Yb(OTf)3	none	7
9	20 mol% Sc(OTf)3	30 mol% bipy	14
10	20 mol% Sc(OTf)3	30 mol% terpy	50
11	20 mol% Sc(OTf)3	30 mol% dMepybox	47
12 b	10 mol% Sc(OTf) 3	15 mol% terpy	72
13c	20 mol% Sc(OTf)3	30 mol% terpy	0
14d	20 mol% Sc(OTf)3	30 mol% terpy	0
15e	20 mol% Sc(OTf)3	30 mol% terpy	24

Unless otherwise noted, reactions were conducted using 0.1 mmol 12a, 0.5 mmol 2a, 2 mol% 14, and 2 mL solvent.

^aYields were determined by ¹H NMR analysis of the crude reaction mixture using CH₂Br₂ as an internal standard.

^b0.3 mmol scale, 3 mL CH₂Cl₂, 25 mol% imidazole, isolated yield.

^cNo photocatalyst.

^dRun in the dark.

^eNo imidazole.