Table 1.

Evaluation of Pauson–Khand reaction conditions.

entry	conditions*	dr†	yield (%)‡
1	Co2(CO)8 (1.2 equiv), THF, 12 h; then DMSO, 65 °C	2.2 : 1	46
2	Co2(CO)8 (1.2 equiv), CH2Cl2, 9 h; then NMO, 23 °C	4.5 : 1	78
3	Mo(CO)6 (1.2 equiv), DMSO, PhMe, 110 °C	--	trace
4	Mo(CO)3(DMF)3 (1.1 equiv), CH2Cl2, 23 °C	> 20 : 1	67
5	[RhCl(CO)2]2 (1 mol %), CO (1 atm), m-xylene, 110 °C	>20 : 1	85

^*Reactions conducted on 0.2 mmol scale.

^†Determined by ¹H NMR spectroscopy.

^‡Isolated yield after purification by silica gel chromatography.