Table 1.

Screening of Conditions for the Oxidative Cycloisomerization of Diyne 6^a

Entry	Conditions	8b / 12bb	Yieldc
1	[Rh(CO)2Cl]2 (5 mol%), P[OCH(CF3)2]3 (20 mol%)	1 : 0	62%
2	[Rh(CO)2Cl]2 (5 mol%)	5 : 1	-
3	[Rh(CO)2Cl]2 (5 mol%), P(OPh)3 (20 mol%)	no reaction
4	[Rh(CO)2Cl]2 (5 mol%), [3,5-(CF3)2C6H3]3P (20 mol%)	5 : 1	-
5	Rh2(OAc)4 (5 mol%)	no reaction
6	Au(PPh3)Cl (10 mol%), AgOTf (10 mol%)	0 : 1	-
7	PtCl2 (5 mol%)	complex mixture
8d	See entry 1 for catalyst	1 : 0	70%
9d,e	See entry 1 for catalyst	1 : 0	78%

^aConditions: pyridine N-oxide (3 equiv), ClCH₂CH₂Cl, 80 °C, 4h, unless noted otherwise.

^bThe ratio was determined by ¹H NMR of crude product.

^cIsolated yield of 8b.

^d3,5-dichloropyridine N-oxide (3 equiv) was used as the oxidant.

^eDioxane was used as the solvent.