Table 1. Optimisation of the Cu-catalysed cross-coupling of aryl boronic acid 6a with ethyl bromofluoroacetate towards ester 7a and the corresponding carboxylic acid 8a ^a .

Entry	Solvent	Cu-source	Ligand	Product	Yield b
1 c	Dioxane (0.2 M)	CuI	L1	7a	7%
2 c	Dioxane (0.2 M)	CuI	L2	7a	58%
3	Toluene (0.2 M)	CuI	L3	7a	63%
4 d	Toluene (0.4 M)	CuI	L3	7a	82% e
5 d	Toluene (0.4 M)	CuI	L3	8a	75% e , f
6 d	Toluene (0.4 M)	CuI	—	7a	0%
7 d	Toluene (0.4 M)	—	—	7a	0%
8 d	Toluene (0.4 M)	CuCl2	L2	7a	0%
9 d	DMF or DMSO (0.2 M)	CuI	L3	7a	0%

^aScreening reactions performed on 0.1 mmol scale.

^bYield determined by ¹⁹F-NMR using α,α,α-trifluorotoluene as internal standard.

^c2 equiv. of 6a and 1 equiv. of ethyl bromofluoroacetate.

^d1 equiv. of 6a, and 2 equiv. of ethyl bromofluoroacetate.

^eYield of isolated product.

^fOne-pot procedure towards 8a.