Chlorination of N-tritylproline methyl ester

The reaction of N-tritylproline methyl ester with tert-butyl hypochlorite gave 2,4-dichloro-2-methoxycarbonyl-5-pyrroline, which is readily converted to 2-methoxycarbonyl-4-chloropyrrole. The intermediate products were identified by Chromatographic mass spectrometry when the reaction was carried out at low temperatures.