An attempted Regitz diazo transfer onto homophthalic anhydride led to the discovery of an unexpected ring contraction, which gave N-sulfonyl phthalide-3-carboxamide derivatives. The reaction is thought to proceed via a… Click to show full abstract
An attempted Regitz diazo transfer onto homophthalic anhydride led to the discovery of an unexpected ring contraction, which gave N-sulfonyl phthalide-3-carboxamide derivatives. The reaction is thought to proceed via a [3 + 2] cycloaddition of the substrate's enol form and the azide followed by a two-step fragmentation of the intermediate 1,2,3-triazoline with a loss of the nitrogen molecule.
               
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