Table 2.

Optimisation of BF₃·Et₂O/3HF·Et₃N mediated hydrofluorination.

Entry	BF3·Et2O (equiv)	3HF·Et3N (equiv)	Time	Temp.	Solvent	Conversion	Yield
1	1.5	3.0	16 h	0 °C to rt	DCM	>90%	35%
2	1.5	3.0	5 h	0 °C to rt	DCM	39%	28%
3	1.0	2.0	16 h	0 °C to rt	DCM	>80%	30%
4	0.5	3.0	16 h	0 °C to rt	DCM	–	–
5	1.5	3.0	5 days	0 °C	DCM	20%	–
6	1.5 × 2	3.0	7 h	0 °C	DCM	20%	–
7	1.5	3.0	5 h	40 °C	DCM	>95%	30%
8a	1.5	3.0	16 h	0 °C to rt	DCM	70%	28%
9	1.5 × 2	3.0 × 2	21 h	b	THF	25%	–
10	1.5	3.0	16 h	0 °C to rt	DCE	<5%	–
11	1.5	3.0	21 h	c	DCE	10%	–
12	1.5 x 2	3.0 x 2	21 h	d	DCE	n.a.e	–

^aBF₃·Et₂O and 3HF·Et₃N were pre-mixed at 0 °C prior to adding starting material 1a. ^bMixture stirred for 16 hours at room temperature, then heated to 50 °C for 5 hours. ^cMixture stirred for 16 hours at room temperature, then stirred under reflux for 5 hours. ^dMixture stirred for 5 hours at room temperature, then stirred under reflux for 16 hours. ^eSubstrate decomposed.