Table 1.

Optimization of the reaction conditions

Entry	Catalyst (x mol%)	Solvent	Yield (%)a
			2a	3a
1b	ZnCl2 (20.0)	DCM	<5	6
2c	AgSbF6 (5.0)	DCM	–	–
3c	JohnPhos(MeCN)AuSbF6 (5.0)	DCM	–	–
4	Cu(MeCN)4PF6 (5.0)	DCM	15	30
5	[PdCl(η3-C3H5)]2 (5.0)	DCM	21	<5
6	Rh2(OAc)4 (2.0)	DCM	44	20
7	Rh2(Oct)4 (2.0)	DCM	45	19
8	Rh2(TPA)4 (2.0)	DCM	41	15
9	Rh2(OPiv)4 (2.0)	DCM	54	10
10	Rh2(esp)2 (2.0)	DCM	43	9
11	Rh2(pfb)4 (2.0)	DCM	20	17
12	Rh2(TFA)4 (2.0)	DCM	16	14
13	Rh2(tfacam)4 (2.0)	DCM	20	65
14	Rh2(cap)4 (2.0)	DCM	NR	NR
15	Rh2(OPiv)4 (2.0)	DCE	74	13
16	Rh2(OPiv)4 (2.0)	toluene	47	12
17	Rh2(OPiv)4 (2.0)	CH3CN	71	10
18	Rh2(OPiv)4 (2.0)	EtOAc	81	<5
19	Rh2(OAc)4 (2.0)	EtOAc	80	<5
20	Rh2(OPiv)4 (1.0)	EtOAc	83	<5
21d	Rh2(OPiv)4 (1.0)	EtOAc	88 (84)e	<5

Reaction conditions: to a solution of metal catalyst (x mol%) in 1.0 mL solvent, was added 1a (0.1 mmol, 34.4 mg) in the same solvent (1.0 mL) slowly over 10 min via a syringe at 40 °C under an argon atmosphere, and the reaction mixture was stirred for additional 1.0 h under these conditions.

DCM dichloromethane, DCE dichloroethane, EtOAc ethyl acetate.

^aYields were detected by proton NMR of the crude reaction mixture using 4-nitrobenzaldehyde as the internal standard.

^bLow conversions (<20%) were observed, and most of the material was recovered.

^cThe material 1a was decomposed into a complex mixture.

^d100 mg 4 Å MS was added.

^eIsolated yield.