Water → 7-Methyl-2,3-dihydro-1H-pyrrolo[1,2-a] benzimidazole-5,8-dione

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Reaction Steps

To a suspension of 218 mg (0.83 mmol) of 25 in 10 mL of water, containing 200 mg of monobasic potassium phosphate, was added a solution of 1.34 g of Fremy's salt in 50 mL of water containing 500 mg of monobasic potassium phosphate. The reaction mixture was stirred at room temperature for 2 hours and extracted with 3×50 mL portions of chloroform. The dried extracts (sodium sulfate) were concentrated and then chromatographed over silica gel, employing chloroform as the eluant, to afford yellow-colored 26, 105 mg (61%) yield. Recrystallization from chloroform/hexane afforded analytically pure 26: mp 162°-164° C.; TLC (methanol chloroform[10:90]), Rf =0.62; IR(KBr pellet) 1675, 1659, 1647, 1515, 1154 cm-1 ; 1H NMR (dimethyl sulfoxide-d6) δ6.54 (1 H, quartet, J=1.6 Hz, C(6) proton coupled to 7-methyl), 4.16 (2 H, t, J~7 Hz, C(1) methylene), 2.86 (2 H, t, J~7 Hz, C(3) methylene), 2.62 (2 H, quintet, J~7 Hz, C(2) methylene), 2.00 (3 H, d, J=1.6 Hz, 7-methyl coupled to C(6) proton); mass spectrum (EI mode) m/z 202 (P+), 174 (P+ -CO), 146 (P+ -2CO), Anal. Calcd for C11H10N2O2 : C, 65.33; H, 4.98; N, 13.85. Found: C, 65.15; H, 4.70; N, 13.61.

Provenance & Evidence