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Regioselective inverse electron demand Diels-Alder reactions of N-acyl 6-amino-3-(methylthio)-1,2,4,5-tetrazines

Academic Article
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Overview

related to degree

  • Garbaccio, Robert, Ph.D. in Chemistry, Scripps Research 1994 - 1999

authors

  • Boger, Dale
  • Schaum, R. P.
  • Garbaccio, Robert

publication date

  • September 1998

journal

  • Journal of Organic Chemistry  Journal

abstract

  • The regioselective inverse electron demand Diels-Alder reactions of 6-[(tert-butyloxycarbonyl)amino]-3-(methylthio)-1,2,4,5-tetrazine (2), 6-(acetylamino)-3-(methylthio)-1,2,4,5-tetrazine (3), and 6-(benzyloxycarbonyl)amino-3-(methylthio)-1,2,4,5-tetrazine (4) are disclosed. All three underwent regioselective [4 + 2] cycloaddition with electron-rich dienophiles to form the corresponding functionalized 1,2-diazines in excellent yields. An order of reactivity with electron-rich dienophiles was observed with both 2 and 3 being more reactive than 3,6-bis(methylthio)-1,2,4,5-tetrazine (1, i.e. 3 > 2 > 1), and both 3 and 4 were shown to be more robust than 2 at the higher temperatures necessary for [4 + 2] cycloaddition with less reactive dienophiles. The cycloaddition regioselectivity is consistent with the polarization of the diene and the ability of the methylthio group to stabilize a partial negative charge at C-3, and the N-acylamino group to stabilize a partial positive charge at C-6. While intermolecular reactions of unactivated alkynes either did not proceed or required high temperatures and long reaction times, intramolecular Diels-Alder reactions utilizing tethered unactivated acetylenes led to five- and six-membered bicyclic 1,2-diazines under mild conditions.
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Identity

International Standard Serial Number (ISSN)

  • 0022-3263

Digital Object Identifier (DOI)

  • 10.1021/jo980795g

PubMed ID

  • 11672266
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Additional Document Info

start page

  • 6329

end page

  • 6337

volume

  • 63

issue

  • 18

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