Hydrochloric Acid → 6-amino-3,3-dimethylbenzo[c][1,2]oxaborol-1(3H)-ol

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Reaction Conditions

Reaction Steps

To a solution of 1.20 g of 3,3-dimethyl-6-nitrobenzo[c][1,2]oxaborol-1(3H)-ol (XCVII) (1.20 g, 5.8 mmol) in MeOH (30 mL) was added 3M aqueous HCl (30 mL), and the mixture was cooled to 0° C. To this mixture was added portion-wise zinc dust (3.77 g, 0.058 mol), maintaining the temperature below 5° C. The mixture was stirred for 40 min at room temperature. A gray solid was removed by filtration through a Celite pad. The filtrate was concentrated in vacuo and the residue was dissolved in EtOAc and stirred. 1M aqueous K2CO3 was added to pH=7 and stirring was continued for 10 min. The two phases were separated and the aqueous layer was extracted with EtOAc. The combined organic phases were dried over MgSO4 filtered and concentrated in vacuo. The crude product was purified by silica gel chromatography using DCM then DCM/MeOH 500/1→300/1→200/1→100/1 to give 6-amino-3,3-dimethylbenzo[c][1,2]oxaborol-1(3H)-ol (XCVIII) as an orange solid (0.62 g, 3.5 mmol, yield 60%). 1H NMR (DMSO-d6) δ ppm 1.46 (s, 6H), 7.43 (dd, J=8 Hz, J=2 Hz, 1H), 7.55 (d. J=8 Hz, 1H), 7.67 (d, J=2 Hz, 1H), 9.95-10.72 (brs, 3H) ESIMS found for C9H12BNO2 m/z 178.1 (M+H).

Provenance & Evidence