A zwitterion produced by a strong intramolecular N→B interaction in 1‐hydroxy‐2‐(pyridin‐2‐ylcarbonyl)benzo[d][1, 2, 3]diazaborinine. Issue 12 (1st December 2015)

• Record Type: Journal Article
• Authors: Sarina, Evan A.; Olmstead, Marilyn M.; Kanichar, Divya; Groziak, Michael P.
• Is Part Of: Acta crystallographica. Volume 71:Issue 12(2015:Dec.)
• Page Start: 1085
• Page End: 1088
• Publication Date: 2015-12-01
• Subjects: Lewis base -- Lewis acid -- zwitterion -- boron–nitrogen -- crystal structure -- 2, 3, 1‐benzodiazaborine -- benzo[d][1, 2, 3]diazaborinine -- boron heterocycle -- condensation reaction -- NMR analysis; Crystallography -- Periodicals; Crystals -- Periodicals; 548.3
• DOI: 10.1107/S2053229615021841
• Languages: English
• ISSNs: 2053-2296

Abstract

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, 17λ 5 ‐triaza‐1λ 4 ‐boratetracyclo[8.7.0.0 2, 7 .0 12, 17 ]heptadeca‐3, 5, 7, 12, 14, 16‐hexaen‐17‐ylium‐1‐uide), C13 H10 BN3 O2, 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 D2 O exchange observed for the OH resonance in the 1 H 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.