Pyridine → 1,1-di(methoxycarbonyl)-5-nitro-1,2-dihydro-3H-benz[e]indole-2one

Participants

Reaction Conditions

Reaction Steps

A stirred suspension of 6 (7.00 g, 20.16 mmol) and powdered NaN3 (3.28 g, 50.44 mmol) in CH2'Cl2 (100 mL) was treated with pyridine (3.99 g, 50.44 mmol), then cooled to -5° C. and treated in one portion with N,N-dimethyl(chlorosulfonyl)methaniminium chloride [SOCl2 /DMF adduct] (4.26 g, 22.18 mmol). After stirring at 20° C. for 2 h, the mixture was washed twice with water, dried (Na2SO4) and filtered through a short column of silica gel, eluting with further CH2Cl2 (400 mL). Removal of the solvent under reduced pressure below 30° C. gave the crude carbonyl azide (7), which was immediately heated with stirring in dry toluene (65 mL) under reflux for 8 min. The mixture was cooled to 0° C. to complete precipitation of the product, which was collected and washed with toluene. This was stirred as a suspension in CH2Cl2 (25 mL) for 10 min at 20° C., diluted with iPr2O, and the resulting solid collected to give 1,1-di(methoxycarbonyl)-5-nitro-1,2-dihydro-3H-benz[e]indole-2one (8) (5.60 g, 81%). A sample crystallised from CH2Cl2 had mp 218-222° C. (dec.). 1H NMR [CD3)2SO] δ 11.59 (s, 1H, NH), 8.21 (d, J=8.7 Hz, 1H, H-7), 7.95 (s, 1H, H-9), 7.87 (d, J=8.5 Hz, 1H, H-4), 7.74 (t, J=7.6 Hz, 1H, H-6), 7.65 (t, J=7.7 Hz, 1H, H-5), 3.72 (s, 6H, 2×CO2CH3). Anal. Calculated for C16H12N2O7.1.5 H2O: C, 51.8; H, 4.1; N, 7.5. Found: C, 52.1; H, 3.1; N, 7.8%.

Provenance & Evidence