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Rearrangements of Aromatic Nitrile Oxides and Nitrile Ylides: Potential Ring Expansion to Cycloheptatetraene Derivatives Mimicking Arylcarbenes
Author(s) -
Marchais Jérémy,
Bégué Didier,
Dargelos Alain,
Wentrup Curt
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003782
Subject(s) - nitrile , chemistry , benzonitrile , ring (chemistry) , singlet state , photochemistry , cycloaddition , excited state , medicinal chemistry , organic chemistry , physics , catalysis , nuclear physics
Nitrile imines, nitrile oxides and nitrile ylides are widely used in 1,3‐dipolar cycloaddition reactions. They also undergo thermal and photochemical rearrangements to carbodiimides, isocyanates, and ketenimines, respectively. Calculations at DFT and CASPT2 levels of theory reveal novel, potential rearrangements, in which the aromatic 1,3‐dipoles mimic phenylcarbene and undergo ring expansion to cycloheptatetraene derivatives. These rearrangements can potentially take place in both the singlet ground states and the triplet excited states, and they are accelerated by m,m’ ‐bis(dimethylamino) substitution on the phenyl moieties. The new rearrangement becomes the energetically preferred path for m,m’ ‐bis(dimethylamino)benzonitrile oxide in the triplet state. In the m,m’ ‐bis(dimethylamino)benzo nitrile ylide, the cyclization to the 2‐phenyl‐1‐azirine is favored over the ring expansion to a cycloheptatetraene by ca. 5 kcal mol −1 in the singlet state. In the bent triplet states, 1,3‐hydrogen shifts interconverting nitrile ylides are potentially possible.