Synthesis 2017; 49(14): 3091-3106
DOI: 10.1055/s-0036-1588850
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© Georg Thieme Verlag Stuttgart · New York

Steric Buttressing Changes Torquospecificity in Thermal Cyclo­butenone Rearrangements, Providing New Opportunities for 5H-Furanone Synthesis

Wei Sun, Dharyl C. Wilson, David C. Harrowven*
  • Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK   Email: dch2@soton.ac.uk
The authors thank the European Regional Development Fund for their partial support of this work via AI-Chem (InterReg IVa programme 4494/4196) and EPSRC for the equipment grant, reference EP/K039466/1.
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Publication History

Received: 07 April 2017

Accepted after revision: 03 May 2017

Publication Date:
13 June 2017 (eFirst)

Abstract

Thermally induced rearrangements of 4-hydroxycyclo­butenones are known to provide clean and reliable access to an array of useful carbocyclic and fused heterocyclic ring systems. Rarely, such reactions have been diverted to an alternative pathway leading to furanone formation. Herein, we show that these switches in the course of the rearrangement occur when a substrate bears a bulky substituent and are due to adverse steric buttressing as the transition state for electrocyclisation is approached. We also show how the reaction provides new opportunities for furanone synthesis and how bulky proton and halogen surrogates can be used to divert classical rearrangement pathways toward furanone formation. Additionally, we show that classical rearrangement pathways can be promoted by the simple expedient of alcohol protection.

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