Diazocinones: Synthesis and conformational analysis

Lori I. Robins, Richard D. Carpenter, James C. Fettinger, Makhluf J. Haddadin, Dino S. Tinti, Mark J. Kurth

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

1,2,4,5-Tetrazines (prepared from aryl nitriles) condense with isoxazolylcyclobutanones (prepared from 3-benzenesulfonyl-3-vinylcyclobutanol) in methanolic KOH to give conformationally restricted 6-isoxazol-5-yl-6,7- dihydro-5H-[1,2]diazocin-4-ones. The solution 1H NMR spectra of dihydrodiazocinone 1a with phenyl moieties at C3 and C8 reveal two conformations of the eight-membered heterocycle that are non-interconverting on the NMR time scale at ambient temperature. The kinetics of the conversion process, followed by 1H NMR between 21 and 70 °C in DMSO solution, yield an activation energy of ∼21 kcal/mol relative to the kinetic conformer and show an equilibrated ratio of ∼5:1 of the thermodynamic to the kinetic conformers. The electronic structure calculations on a model dihydrodiazocinone predict geometries for the two conformations. One of these geometries agrees with the X-ray crystallographic analysis of the thermodynamic conformation of 1a.

Original languageEnglish (US)
Pages (from-to)2480-2485
Number of pages6
JournalJournal of Organic Chemistry
Volume71
Issue number6
DOIs
StatePublished - Mar 17 2006

ASJC Scopus subject areas

  • Organic Chemistry

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    Robins, L. I., Carpenter, R. D., Fettinger, J. C., Haddadin, M. J., Tinti, D. S., & Kurth, M. J. (2006). Diazocinones: Synthesis and conformational analysis. Journal of Organic Chemistry, 71(6), 2480-2485. https://doi.org/10.1021/jo052577a