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Selectivity in Garratt-Braverman cyclization: an experimental and computational study.

Manasi Maji1, Dibyendu Mallick, Sayantan Mondal

  • 1Department of Chemistry, Indian Institute of Technology, Kharagpur, India.

Organic Letters
|February 10, 2011
PubMed
Summary
This summary is machine-generated.

Synthesized bispropargyl sulfones isomerized to bisallenic sulfones, favoring a diradical mechanism. The electron-rich aromatic ring directed the Garratt-Braverman cyclization pathway, confirmed by DFT calculations.

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Area of Science:

  • Organic Chemistry
  • Reaction Mechanisms

Background:

  • Bispropargyl sulfones are versatile organic compounds.
  • The Garratt-Braverman (GB) reaction is a key transformation in organic synthesis.

Purpose of the Study:

  • To synthesize novel bispropargyl sulfones with dissimilar aromatic rings.
  • To investigate the reaction mechanism of their isomerization and subsequent cyclization under basic conditions.

Main Methods:

  • Synthesis of bispropargyl sulfones.
  • Base-induced isomerization and cyclization experiments.
  • Product distribution analysis.
  • Density Functional Theory (DFT) calculations.

Main Results:

  • Successful synthesis of bispropargyl sulfones with varied aromatic substituents.
  • Isomerization to bisallenic sulfones observed under basic conditions.
  • Product distribution indicates a diradical mechanism, not ionic.
  • Greater involvement of electron-rich aromatic rings in the cyclization was confirmed.
  • DFT calculations corroborated the diradical pathway and selectivity.

Conclusions:

  • The base-catalyzed reaction proceeds via a diradical intermediate.
  • Aromatic ring electronics significantly influence the regioselectivity of the Garratt-Braverman cyclization.
  • DFT calculations provide valuable insights into the reaction mechanism.