Screening of reaction conditions in the double hydroboration of 4-methylpyridine 1a^a.

Entry	Deviation from standard conditions	Yield [%]
		3a	2a
1	None	56	12
2	Toluene-d8 as solvent	44	34
3	THF-d8 as solvent	16	60
4	3.3 equiv. HBpin	56	13
5	5 mol% Co2	48	19
6b	0.6 M	63c	8
7	0.6 M, toluene-d 8 , 100 °C	86	4
8b	No catalyst, toluene-d8, 100 °C	0	0
9b	3 mol% L1H, toluene-d8, 100 °C	0	0
10b	3 mol% (L1H + KOtBu), toluene-d8, 100 °C	0	1
11b	3 mol% [Cp*CoCl]2 (Co4), toluene-d8, 100 °C	0	5
12	3 mol% Cp*2Co (Co5), toluene-d8, 100 °C	0	10

^aStandard conditions: 1a (0.20 mmol), HBpin (2.2 equiv.), Co2 (3 mol%), 0.3 m in C₆D₆, 50 °C, 20 h, in a headspace vial (5 mL) with magnetic stirring unless otherwise specified. Yields from ¹H-NMR vs. internal hexamethylbenzene (in C₆D₆) or 1,3,5-trimethoxybenzene (in toluene-d₈).

^b0.40 mmol reaction.

^cIsolated after N-acetylation in 54% yield.