Table 1. Optimization of the C4-Phosphonation of 3-Cyanopyridine^a.

entry	base	oxidant	solvent	3a, yield [%]b
1	NaHCO3	chloranil	THF
2	NaOH	chloranil	THF
3	tBuOK	chloranil	THF	79
4		chloranil	THF
5	tBuOKc	chloranil	THF
6	tBuOKd	chloranil	THF	52
7	tBuOKe	chloranil	THF	17
8	tBuOK	air	THF
9	tBuOK	S8	THF
10	tBuOK	O2	THF
11	tBuOK	I2	THF
12	tBuOK	DDQ	THF	54
13	tBuOK	chloranil	ACN	64
14	tBuOK	chloranil	Et2O	62
15	tBuOKf	chloranil	THF	71

^aReaction conditions: 3-cyanopyridine 1a (1 mmol, 1 equiv), BF₃·OEt₂ (1.1 mmol, 1.1 equiv), diphenylphosphine oxide 2a (1.2 mmol, 1.2 equiv), tBuOK (1.4 mmol, 1.4 equiv), chloranil (2 mmol), solvent (2 mL) at −78 °C, 10 min.

^bIsolated yield.

^cIn the absence of BF₃·OEt₂.

^dBCl₃ instead of BF₃·OEt₂.

^e0.2 equiv of BF₃·OEt₂.

^fT = −40 °C.