2-oxo-2,3-dihydrobenzooxazole-5-boronic acid synthesis

Yield:710348-42-8 92%

Reaction Conditions:

Stage #1: 5-bromo-1,3-benzoxazol-2(3H)-onewith n-butyllithium in tetrahydrofuran at -78 - -40; for 1 h;
Stage #2: Trimethyl borate in tetrahydrofuran at -40 - 20;

Steps:

26

Add n-BuLi (1.6M in hexanes, 8.76mL, 14. 02MMOL) portionwise (exotherm) to a solution OF 5-BROMO-3H-BENZOOXAZOL-2-ONE (L. OOG, 4. 67MMOL) in dry THF (28mL) at-78°C under N2. Stir AT 40°C for lh and add trimethylborate (1.94g, 18. 68MMOL) at once. Warm up to room temperature overnight. Add 1N aqueous HC1 (50ML) and stir for 3h at room temperature. Extract into ethyl acetate, dry (MGS04) and concentrate organics to a brown solid. Triturate with hexanes/toluene and collect 766mg (92%) of the title compound as a brown powder. MS (ES) 179 (M+H), 177 (M-H) ; HPLC shows 80% purity.

References:

WO2004/52847,2004,A2 Location in patent:Page 255