Table 1.

Catalyst screening and optimization of reaction conditions^a.

Entry	Conditions	Solvent	Yieldb (%)
1	no catalyst	DCM	NR
2	[Rh(CH2CH2)2Cl]2	DCM	ND
3	[Rh(Cp*)Cl2]2	DCM	72
4	Rh2(OAc)4	DCM	45
5	Rh2(TFA)4	DCM	52
6	Rh2(esp)2	DCM	68
7	Rh2(cap)4	DCM	40
8	Rh2(5S,R-MenPY)4	DCM	61
9c	Rh2(esp)2	DCM	39
10c	[Rh(Cp*)Cl2]2	DCM	44
11c	Rh2(5S,R-MenPY)4	DCM	58
12c	Rh2(5S,R-MenPY)4	DCE	67
13c	Rh2(5S,R-MenPY)4	hexane	59
14c	Rh2(5S,R-MenPY)4	toluene	59
15c	Rh2(5S,R-MenPY)4	DME	60
16c	Rh2(5S,R-MenPY)4	DMF	33

^aReaction conditions: 1a (0.5 mmol, 0.2 M in degassed solvent), 2a (2.5 mmol), catalyst (1 mol %) under argon at room temperature for 24 h unless otherwise noted. ^bIsolated yield. ^c0.1 mol % of catalyst. esp = α,α,α’,α’-tetramethyl-1,3-benzenedipropionate, cap = caprolactamate, 5S,R-MenPY = (S)-(1R,2S,5R)-2-isopropyl-5-methylcyclohexyl 2-oxopyrrolidine-5-carboxylate, NR = no reaction, ND = not detected.