[NH:1]1[CH:5]=[CH:4][C:3]([C:6]([O:8][CH3:9])=[O:7])=[CH:2]1.C(O[Cl:15])(C)(C)C>C(Cl)Cl>[Cl:15][C:5]1[NH:1][CH:2]=[C:3]([C:6]([O:8][CH3:9])=[O:7])[CH:4]=1Methyl pyrrole-3-carboxylate (2.5 g., 20 mmoles) was dissolved in 50 ml. of methylene chloride. The solution, stirred under nitrogen, was cooled in an ice-water bath while t-butylhypochlorite (1.95 g., 18 mmoles) in 25 ml. of methylene chloride was added dropwise. The reaction was stirred for 1 hour at room temperature, filtered and evaporated to an oil. The oil was chromatographed (100 g. silica gel with ethyl acetate-1/hexane-7 as eluant). The column elution was monitored by thin layer chromatography (silica gel plates with chloroform-8/ethyl acetate-2 as eluant). Cuts containing pure product (Rf 0.4) were combined and evaporated to yield crystalline methyl 5-chloropyrrole-3-carboxylate (900 mg., m.p. 92°.95° C., m/e 159/161).
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