Synthesis of silylzinc reagents^a.

Entry	Activator	Additive, solvent, temperature	2a (M)
1	—	THF, 60 °C	ND
2	TMSCl	THF, 60 °C/toluene, 70 °C	ND
3	Iodine	DMA, 80 °C/toluene, 70 °C	ND
4	—	LiCl, toluene, 70 °C	ND
5	DBE	LiCl, toluene, 70 °C/THF, 60 °C	NDb
6	Iodine	TMEDA, toluene, 66 °C, 63 h	0.21
7	Iodine	TMEDA, toluene, 70–90 °C, 63 h	0.68c
8	Iodine	NMP/DMA, toluene, 85 °C	ND

^aReaction conditions: additive/activator: Me₃SiCl (0.12 eq.), iodine (0.03/0.05 eq.), DBE (0.03 eq.), LiCl (1.0 eq.), TMEDA (1.1 eq.), NMP/DMA (1.5 eq.).

^bMe₃SiCl (1.5 mol%) was used.

^cAn average of 5 isolated runs. M: molarity, DBE: 1,2-dibromoethane, NMP: N-methyl-2-pyrrolidone, DMA: dimethylacetamide, ND: not detected.