Graduate Thesis Or Dissertation


New Methods for the Synthesis of All-Carbon Quaternary Centers via the Reactions of N-Vinyl Nitrones and Phenyl Hydrazines with Ketenes Public Deposited

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  • This dissertation describes the development of new cascade reactions for the synthesis of quaternary carbons bearing additional proximal hindrance. The general reaction design principles are described which include the in-situ generation of a vicinal di-π system capable of undergoing a charge-accelerated [3,3]-sigmatropic rearrangement facilitated by the cleavage of a weak heteroatom-heteroatom bond. Also described is a practical route for the synthesis of N-vinyl nitrones that utilizes a 1,4-conjugate elimination as the key step. The reaction of an N-vinyl nitrone and a disubstituted ketene to form all-carbon quaternary centers is also detailed. Mechanistic studies provide evidence that the reaction proceeds by a pericyclic cascade reaction involving an initial [3 + 2] dipolar cycloaddition followed by two consecutive [3,3]-sigmatropic rearrangements. An asymmetric version of this reaction based on a chiral auxiliary approach is also described. Finally, a new method for the synthesis of oxindoles containing a quaternary carbon at the 3-position is described. This novel method proceeds via the copper triflate-mediated reaction of a phenyl-hydrazine and a ketene.
Date Issued
  • 2013-01-01
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  • 2019-11-13
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