Optimization studies for cobalt-catalyzed selective alkyldifluoroalkylation of dienoate with alkylzinc pivalate 3a-I^a.

Entry	Variation	Yieldb (%)	Entry	Variation	Yieldb (%)
1	CoCl2	57	8	CoCl(PPh3)3	Trace
2	CoBr2	58	9	CoI2	78c
3	CoI2	62	10	TMEDA	68c,d
4	Co(acac)2	56	11	1,10-Phen	54c,e
5	Co(acac)3	34	12	Dppbz	31c,e
6	CoBr2·DME	49	13	Dcype	55c,e
7	Co(OAc)2	46	14	Without [Co]	0c

^aReaction conditions: 1a (2.0 equiv.), 2a (0.15 mmol, 1.0 equiv.), 3a-I (2.0 equiv.), [Co] (10 mol%), MeCN (1.5 mL), 25 °C, 16 h.

^bIsolated yields.

^c1a (0.15 mmol, 1.0 equiv.), 2a (1.5 equiv.), 3a-I (2.5 equiv.).

^dTMEDA (30 mol%) as the ligand.

^eLigand (11 mol%).