Table 1.

Optimization of the transition metal-catalyzed C(CO)−C bonds insertion reaction (reaction conditions: 1a (0.2 mmol), 2a (0.1 mmol), catalyst, and additive (50 mg) in DMF (0.5 mL) at room temperature under air atmosphere for 12 h).

Entry	Catalyst (x mol %)	Additive	Yield (%)a
1	[RuCl2(p-cymene)]2 (5)	—	51
2	Rh2(OAc)4 (2)	—	65
3	AgOAc (10)	—	60
4	Pd(OAc)2 (10)	—	0
5	Cu(OAc)2 (10)	—	0
6	[RhCp*Cl2]2 (2)	—	24
7	[Rh(cod)Cl]2 (2)	—	Trace
8	Rh2(esp)2 (2)	—	62
9	—	—	0
10	Rh2(OAc)4 (2)	4 Å MS	85
11b	Rh2(OAc)4 (2)	4 Å MS	70
12c	Rh2(OAc)4 (2)	4 Å MS	81
13	Rh2(OAc)4 (1)	4 Å MS	67
14	Rh2(OAc)4 (5)	4 Å MS	84
15d	Rh2(OAc)4 (2)	4 Å MS	80
16e	Rh2(OAc)4 (2)	4 Å MS	84

^aIsolated yields based on 2a.

^b4 Å MS (25 mg) was used.

^c4 Å MS (75 mg) was used.

^d1 mL of DMF was used.

^eReaction was carried out under nitrogen atmosphere. esp: α,α,α′,α′-Tetramethyl-1,3-benzenedipropionic acid.