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Selective Rearrangements of 1λ4,2,4-Benzothiadiazines
Gilchrist, Thomas L.,Rees, Charles W.,Vaughan, David
, p. 55 - 59 (2007/10/02)
1-Aryl-1λ4,2,4-benzothiadiazines (1) rearrange when heated above 180 deg C to give the isomeric 4-aryl-4H-1,2,4-benzothiadiazines (2) by an intramolecular pathway, a -sigmatropic shift.The 1-phenyl-1λ4,2,4-benzoselenadiazine (4) rearranges in a similar way, but 1-alkyl- and 1-morpholino-1λ4,2,4-benzothiadiazines (6) and (8) give 2H-1,2,4-benzothiadiazines (7) with loss of the 1-substituent.On irradiation, the 1-aryl- and 1-alkyl-benzothiadiazines (1), (6), and (13) rearrange to give benzimidazoles by cleavage of the sulphur-nitrogen ylide bond; an intermediate nitrene can be intercepted by dimethyl sulphoxide.
