Table 1.

Optimization study

Entry	Precursor	Ligand	Yield (%)a	Z/E ratiob
1	CoCl2	CNC-H	0	–
2	CoCl2	CNC-Me	71%	3:97
3	CoCl2	CNC-Et	78%	36:64
4	CoCl2	CNC-iPr	99%	2:98
5	CoCl2	CNC-tBu	7%	<1:99
6	CoCl2	CNC-Mes	0	–
7c	CoCl2	CNC-iPr	99%	96:4
8d	CoCl2	CNC-iPr	70%	>99:1
9e	CoCl2	CNC-iPr	45%	97:3
10e	Co(acac)2	CNC-iPr	98%	51:49
11f	Co(acac)2	CNC-iPr	99% (90%)g	98:2
12f,h	Co(acac)2	CNC-iPr	98% (90%)g	>99:1

Reaction conditions: CoCl₂ (5.0 mol%), 1a (0.4 mmol, 1.0 equiv), ligand (5.0 mol%),

^tBuOK (20.0 mol%), HBpin (3.0 equiv), DMF (2 ml), room temperature (r.t.), N₂ atmosphere, 12 h.

^aNMR yield determined using methylene bromide as the internal standard.

^bZ/E ratio based on ¹H NMR analysis.

^cReacted for 10 min.

^dHBpin used in 1.5 equiv., 24 h.

^eCo precursor (0.2 mol%), ligand (0.22 mol%),

^tBuOK(0.8 mol%), DMF (1 ml).

^fCo(acac)₂ (0.1 mol%), ligand (0.14 mol%),

^tBuOK(0.56 mol%), DMF (0.5 ml).

^gIsolated yield.

^hHBpin (1.3 equiv.).