Intramolecular capture of pummerer rearrangement intermediates. I. Synthesis of pyrrolo[2,1‐c][1,4]benzothiazines

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Abstract
Treatment of 1‐(2‐alkylsulfinylphenyl)pyrroles with trifluoroacetic acid in refluxing toluene gives 4‐substituted pyrrolo[2,1‐c][1,4]benzothiazines in good yield when the alkyl group bears an electron withdrawing substituent on the α‐carbon. In the absence of such a group, starting material is recovered. The sulfoxides are prepared by oxidation (mCBPA) of the corresponding sulfide. The sulfides are prepared from 2‐aminobenzenethiol either by S‐alkylation followed by conversion to the pyrrole using 1,4‐dimethoxytetrahydrofuran in glacial acetic acid or by S‐alkylation of 1‐(2‐phenylmercapto)pyrrole followed by oxidation to the sulfoxide.