2,3,4,5-Tetrahydro-7-nitro-1,4-benzoxapine synthesis

Yield:216008-29-6 96%

Reaction Conditions:

Stage #1: 7-nitro-3,4-dihydro-2H-benzo[f][1,4]oxazepin-5-onewith borane in tetrahydrofuran; for 4 h;Heating / reflux;
Stage #2: with hydrogenchloride in tetrahydrofuran;water at 0; for 1 h;Heating / reflux;

Steps:

9.iv

7-Nitro-3,4-dihydro-l,4-benzoxazepin-5(2H)-one (0.99 g, 4.7 mmol) was suspended in TΗF (7 ml) and BH₃ (1 M in THF, 19 ml, 19 mmol) was added. The mixture was heated at reflux for 4 h. The mixture was cooled to O⁰C and hydrochloric acid (4 M, 7 ml) was added. The mixture was heated at reflux for 1 h and then concentrated by evaporation. The residue was diluted with water (30 ml) and neutralized with solid sodium hydrogen carbonate. The mixture was extracted with EtOAc (3x). The organic phase was dried EPO (MgSO₄) and the solvent was evaporated. The residue was purified by column chromatography on silica eluting with chloroform: methanol 10:1 containg 0.1% triethylamine to give the title compound as an oil (0.88 g, 96%). MS ESI m/z M+H* 195.

References:

WO2007/4959,2007,A1 Location in patent:Page/Page column 35-36