Table 1.

Optimization of Anhydride CO₂ Extrusion–Recombination^a

entry	conditions	base	ligand	byproduct 10b	ketone
1	as shown	Cs2CO3	11	20%	40%
2	as shown	DBU	11	14%	70%
3	as shown	DBU	12	3%	84%
4	no photocatalyst	DBU	12	0%	0%
5	no Ni catalyst	DBU	–	0%	0%
6	no base	–	12	0%	0%
7	no light	DBU	12	0%	0%
8c	as shown	DBU	12	5%	73%

^aReactions performed using photocatalyst 7 (1 mol%), NiCl₂·glyme (5 mol%), bipyridine ligand (5 mol%), hydrocinnamoyl chloride (0.10 mmol), N-Boc-l-proline (0.13 mmol), and base (0.13 mmol). Yields determined by GC analysis using an internal standard.

^bMajor byproduct.

^cAnhydride was synthesized and isolated prior to reaction.