Table 1.

Ni-Catalyzed Cycloaddition of Diynes and Ketenes^a

			1	1a
Entry	Ligand (Ln)	Ni:Ln	% Conv.b	% Yieldb
1	IPrc	1:2	100	12
2	SIPrc	1:2	63	3
3	PPh3	1:2	100	39
4	PCy3	1:2	100	20
5	MePPh2	1:2	100	54
6	CyPPh2	1:2	100	31
7	DPPE	1:1	32	2
8	DCPE	1:1	22	-
9	DPPF	1:1	100	>99 (86)d
10	DPPB	1:1	100	86 (86)d

^aReaction conditions: 5 mol% Ni catalyst, diyne (1 equiv, 0.05), ketene (1.2 equiv), benzene, 60 °C, 12 h.

^bGC yield analyzed using decane as an internal standard.

^cThe catalyst solutions were equilibrated f or at least 6 h before use.

^dIsolated yields.