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Intramolecular 1+2 and 3+2 cycloaddition reactions of cyclopropenone ketals

Academic Article
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Overview

related to degree

  • Patel, Paresma, Ph.D. in Organic Chemistry, Scripps Research 2005 - 2010

authors

  • Patel, Paresma
  • Boger, Dale

publication date

  • June 2010

journal

  • Journal of the American Chemical Society  Journal

abstract

  • The first intramolecular thermal reactions of cyclopropenone ketals are reported and the work examined substrates tethered to an electron-deficient olefin bearing a single electron-withdrawing substituent. Whereas the intermolecular variants of the reactions provide only the products of an endo-selective [1 + 2] cycloaddition or a carbonyl addition reaction of a thermally generated pi-delocalized singlet vinylcarbene, the intramolecular variants provide either [1 + 2] or [3 + 2] cycloadducts in reactions that depend on the reaction conditions, the alkene-activating substituent, and the nature of the tethering. In addition to providing key mechanistic insights into the thermal [3 + 2] cycloaddition reaction for such substrates, they were also found to proceed under conditions that reflect the ease and regioselectivity of the cyclopropenone ketal cleavage for pi-delocalized singlet vinylcarbene generation. The most effective combination of structural features that impact the reactivity was observed with substrates bearing an aldehyde- or ketone-substituted electron-deficient olefin and incorporating an aryl cyclopropenone ketal substituent built into the linking tether. Simply warming a solution of such substrates in toluene at 80-100 degrees C directly provided the [3 + 2] cycloadducts in excellent yields (60-88%) under mild thermal reaction conditions.

subject areas

  • Cyclopropanes
  • Stereoisomerism
  • Temperature
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Identity

PubMed Central ID

  • PMC2892887

International Standard Serial Number (ISSN)

  • 0002-7863

Digital Object Identifier (DOI)

  • 10.1021/ja103933n

PubMed ID

  • 20527885
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Additional Document Info

start page

  • 8527

end page

  • 8529

volume

  • 132

issue

  • 25

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