Mechanisms for formation of diazocinones, pyridazines, and pyrazolines from tetrazines - Oxyanion-accelerated pericyclic cascades?

Michael W. Lodewyk, Mark J. Kurth, Dean J. Tantillo

Research output: Contribution to journalArticle

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Abstract

(Chemical Equation Presented) A computational approach is utilized to study the diazocinone- and pyridazine-forming cascade reactions resulting from the reaction of 1,2,4,5-tetrazines with cyclic enolates. Many of the proposed reaction steps can be formulated as oxyanion-accelerated pericyclic processes. In examining these, a unique stepwise version of a formal (4 + 2) cycloaddition/(4 + 2) cycloreversion was discovered. For the key ring-opening step in these cascades, theoretical evidence for two distinct processes is reported. Of these two possibilities, an allowed six-electron electrocyclic ring-opening is predicted to be highly favored both kinetically and thermodynamically. Evidence for an unexpected oxyanion-accelerated 1,2-sigmatropic shift was also found for certain systems, leading to the theoretical prediction that seven- and eight-membered ring-fused pyrazoline systems could be formed experimentally under conditions similar to those for diazocinone and pyridazine formation.

Original languageEnglish (US)
Pages (from-to)4804-4811
Number of pages8
JournalJournal of Organic Chemistry
Volume74
Issue number13
DOIs
StatePublished - Jul 3 2009

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Pyridazines
Cycloaddition
Electrons
pyridazine

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  • Organic Chemistry

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Mechanisms for formation of diazocinones, pyridazines, and pyrazolines from tetrazines - Oxyanion-accelerated pericyclic cascades? / Lodewyk, Michael W.; Kurth, Mark J.; Tantillo, Dean J.

In: Journal of Organic Chemistry, Vol. 74, No. 13, 03.07.2009, p. 4804-4811.

Research output: Contribution to journalArticle

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abstract = "(Chemical Equation Presented) A computational approach is utilized to study the diazocinone- and pyridazine-forming cascade reactions resulting from the reaction of 1,2,4,5-tetrazines with cyclic enolates. Many of the proposed reaction steps can be formulated as oxyanion-accelerated pericyclic processes. In examining these, a unique stepwise version of a formal (4 + 2) cycloaddition/(4 + 2) cycloreversion was discovered. For the key ring-opening step in these cascades, theoretical evidence for two distinct processes is reported. Of these two possibilities, an allowed six-electron electrocyclic ring-opening is predicted to be highly favored both kinetically and thermodynamically. Evidence for an unexpected oxyanion-accelerated 1,2-sigmatropic shift was also found for certain systems, leading to the theoretical prediction that seven- and eight-membered ring-fused pyrazoline systems could be formed experimentally under conditions similar to those for diazocinone and pyridazine formation.",
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AB - (Chemical Equation Presented) A computational approach is utilized to study the diazocinone- and pyridazine-forming cascade reactions resulting from the reaction of 1,2,4,5-tetrazines with cyclic enolates. Many of the proposed reaction steps can be formulated as oxyanion-accelerated pericyclic processes. In examining these, a unique stepwise version of a formal (4 + 2) cycloaddition/(4 + 2) cycloreversion was discovered. For the key ring-opening step in these cascades, theoretical evidence for two distinct processes is reported. Of these two possibilities, an allowed six-electron electrocyclic ring-opening is predicted to be highly favored both kinetically and thermodynamically. Evidence for an unexpected oxyanion-accelerated 1,2-sigmatropic shift was also found for certain systems, leading to the theoretical prediction that seven- and eight-membered ring-fused pyrazoline systems could be formed experimentally under conditions similar to those for diazocinone and pyridazine formation.

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