Reaction SMILES: C1([O:6][C:7]2[C:12]3[O:13][C:14]4[CH:19]=[CH:18][C:17]([N+:20]([O-:22])=[O:21])=[CH:16][C:15]=4[C:11]=3[C:10]([CH:23]=[O:24])=[CH:9][CH:8]=2)CCCC1.Br.O.C(=O)([O-])[O-].[K+].[K+]>C(O)(=O)C>[OH:6][C:7]1[C:12]2[O:13][C:14]3[CH:19]=[CH:18][C:17]([N+:20]([O-:22])=[O:21])=[CH:16][C:15]=3[C:11]=2[C:10]([CH:23]=[O:24])=[CH:9][CH:8]=1
Reactant: O=Cc1ccc(OC2CCCC2)c2oc3ccc([N+](=O)[O-])cc3c12
Agent: Br
Agent: O=C([O-])[O-]
Agent: [K+]
Solvent: CC(=O)O
Solvent: O
Product: O=Cc1ccc(O)c2oc3ccc([N+](=O)[O-])cc3c12
Temperature: 85 °C
Yield: 93 %

Procedure:
In a 20 L 4 necked RB flask fitted with a mechanical stirrer, reflux condenser, add 4-cyclopentyloxy-8-nitro-1-formyldibenzofuran (1.2 kg, 3.75 M), 30% Hydrobromic acid in acetic acid (6 L) under stirring. Heat the reaction mixture to 80-90° C. and maintain for 30 min under stirring. Additional quantity of 30% Hydrobromic acid in acetic acid (4.2 L×3 times) was added lot wise in the interval of every 45 minutes at temp. 80-90° C. The progress of the reaction was monitored by HPLC. It was observed that that 2-3% of the starting material was left un reacted, even after prolonging the maintenance for additional 1hr. After this, the reaction mixture was cooled to 10-15° C. and water (24 L) was added at 10-15° C. under stirring. The diluted reaction mixture was brought to 25-35° C. and maintained for 30 min under stirring. The precipitated product was filtered, washed with water (8 L×5) till pH becomes neutral. The wet cake was charged with toluene (12 L) and subjected to azeotropic distillation of water by refluxing to temperature of 110° C. After complete removal of water, the reaction mixture was brought to 25-35° C. filtered and dried in vaccum oven below 60° C. till MC/LOD reaches <1%. The dried product appears as pale yellow solid, weighs about 896-915 g, yield 93-95%, purity 97% by HPLC, m.p>270° C. The product was further purified as follows. In a 10 L four necked RB flask, fitted with a mechanical stirrer, reflux condenser add 4-hydroxy-8-nitro-1-formyldibenzofuran obtained in the above step (1.0 kg, 3.89 M), dimethyl foramide (2 L) at 25-35° C. under stirring. The RM was heated to 80° C. and maintained for 30 min under stirring for complete dissolution. After dissolution, potassium carbonate (850 g, 6.11 M) was added at 80° C. and maintained for 2 h under stirring. The reaction mixture was cooled to 10° C. and filtered. The wet cake was washed with acetone (1 L) and the solid after washing was dissolved in DM water (9 L) and the solution was cooled to 5-10° C. under stirring. The pH of the aqueous solution was adjusted from 10 to 4.5 by neutralizing with conc. HCl (1.5 L). The precipitated product was filtered washed with water (10 L×5) till pH becomes neutral, dried in vacuum. Oven at 60-65° C. till MC<1%. The dried product appears as cream solid, weighs about 800-820 g, yield 83%-85%, m.p.>270; purity>99% by HPLC. The IR (KBr) spectrum shows 3130 (CH str), 1657 (CO str), 1333 (NO2 str) The 1H-NMR (DMSO-d6) shows δ 12.0 (broad, 1H), 10.2 (s, 1H), 9.8 (s, 1H), 8.6 (d, 1H), 8.0 (m, 2H), 7.2 (d, 1H). The CI mass shows m/z 257 (M+). The elemental analysis shows calculated % C, 60.71; % H, 2.74; % N, 5.45; observed % C, 60.59; % H.