Optimization of reaction conditions^a.

Entry	Rh(ii)*	Solvent	Yieldb [%]	erc
1	Rh2(R-DOSP)4	DCE	56	29 : 71
2	Rh2(5S-MEPY)4	DCE	17	50 : 50
3	Rh2(S-BTPCP)4	DCE	61	8 : 92
4	Rh2(S-PTPA)4	DCE	91	91 : 9
5	Rh2(S-PTTL)4	DCE	86	97 : 3
6	Rh2(S-PTAD)4	DCE	93	94 : 6
7	Rh2(S-NTTL)4	DCE	92	96 : 4
8	Rh2(S-TCPTTL)4	DCE	95	98 : 2
9	Rh 2 (S-TFPTTL) 4	DCE	98 d	98 : 2
10	Rh2(S-TFPTTL)4	DCM	88	98 : 2
11	Rh2(S-TFPTTL)4	Toluene	92	98 : 2
12	Rh2(S-TFPTTL)4	MeCN	16	92 : 8
13	Rh2(S-TFPTTL)4	n-Hexane	96	98 : 2
14e	Rh2(S-TFPTTL)4	DCE	65f	96 : 4

^aUnless otherwise noted, reactions were performed at 0.1 M in DCE using 0.20 mmol substrate and catalyst (2 mol%) under a N₂ atmosphere.

^bDetermined by ¹H NMR spectroscopy.

^cThe er value of 2a was determined by HPLC using a chiral stationary phase.

^dIsolated yields.

^e1 mol% catalyst was used.

^f25% starting material was recovered.