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Regioselective Ring Expansion of 2,4-Diiminoazetidines via Cleavage of C–N and C(sp3)–H Bonds: Efficient Construction of 2,3-Dihydropyrimidinesulfonamides

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posted on 15.02.2012, 00:00 by Yang Wang, Yue Chi, Wen-Xiong Zhang, Zhenfeng Xi
A highly regioselective base-mediated ring expansion of 2,4-diiminoazetidines via cleavage of C–N and C­(sp3)–H bonds is achieved for the first time to afford efficiently 2,3-dihydropyrimidinesulfonamides. The mechanism of the ring expansion via tandem 4π electrocyclic ring-opening/1,5-H shift/6π electrocyclic ring-closing is well confirmed by the trapping experiments of two key intermediates and deuterium labeling studies.