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- Title
A zwitterion produced by a strong intramolecular N→B interaction in 1-hydroxy-2-(pyridin-2-ylcarbonyl)benzo[ d][1,2,3]diazaborinine.
- Authors
Sarina, Evan A.; Olmstead, Marilyn M.; Kanichar, Divya; Groziak, Michael P.
- Abstract
2-Acylated 2,3,1-benzodiazaborines can display unusual structures and reactivities. The crystal structure analysis of the boron heterocycle obtained by condensing 2-formylphenylboronic acid and picolinohydrazide reveals it to be an N→B-chelated zwitterionic tetracycle (systematic name: 1-hydroxy-11-oxo-9,10,17λ5-triaza-1λ4-boratetracyclo[8.7.0.02,7.012,17]heptadeca-3,5,7,12,14,16-hexaen-17-ylium-1-uide), C13H10BN3O2, produced by the intramolecular addition of the Lewis basic picolinoyl N atom of 1-hydroxy-2-(pyridin-2-ylcarbonyl)benzo[ d][1,2,3]diazaborinine to the boron heterocycle B atom acting as a Lewis acid. Neither of the other two pyridinylcarbonyl isomers ( viz. nicotinoyl and isonicotinoyl) are able to adopt such a structure for geometric reasons. A favored yet reversible chelation equilibrium provides an explanation for the slow D2O exchange observed for the OH resonance in the 1H NMR spectrum, as well as for its unusual upfield chemical shift. Deuterium exchange may take place solely in the minor open (unchelated) species present in solution.
- Subjects
ZWITTERIONS; LEWIS bases; INTRAMOLECULAR forces
- Publication
Acta Crystallographica Section C: Structural Chemistry, 2015, Vol 71, Issue 12, p1085
- ISSN
2053-2296
- Publication type
Article
- DOI
10.1107/S2053229615021841