Neighboring Group Participation of Nitrogen Cation to Form an Unusual Six-Membered Ring Intermediate During Oxime Rearrangement
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Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Tomohiro Fujino1, Tadashi Hyodo2, Yuko Otani1
1Department of Organic and Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Abstract:
Neighboring group participation involving a 6-membered ring structure is rare, despite the privilege of 6-membered ring transition structures in organic chemistry. We examined the putative role of a 6-membered cyclic intermediate with neighboring group participation of nitrogen cation in syn-migration of peri-ester indanone oximes. Direct observation of a peri-methyl ester-iminylium intermediate in solution by means of 1H NMR supported the existence of the 6-membered cation intermediate. Density functional theory (DFT) calculations also supported the intervention of this intermediate in the rearrangement and indicated that it has a planar structure stabilized by electron delocalization.
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