Table 1.

Various conditions for the in situ preparation of boronic acid precursor 4

Entry	Conditions	Concentration, mg 3 in HCl: MeOH	Time, min	LCMS Conversion, %
1	HCl in dioxane	2 mg in 0.25:2 mL	40	0
2	HCl in MeOH	3 mg in 0.5:3 mL	40	24
3	HCl in H2O	1.9 mg in 0.5:2 mL	190	39a
4	HCl in H 2 O	1.8 mg in 22:54 μL	32	0
5	HCl in H2O	1.8 mg in 0.2:0.5 mL	37	38b

^aAq. HCl added in 2×0.25 mL portions.

^bReaction performed with the crude material.