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Steric buttressing changes torquospecificity in thermal cyclo­butenone rearrangements, providing new opportunities for 5H-furanone synthesis

Steric buttressing changes torquospecificity in thermal cyclo­butenone rearrangements, providing new opportunities for 5H-furanone synthesis
Steric buttressing changes torquospecificity in thermal cyclo­butenone rearrangements, providing new opportunities for 5H-furanone synthesis
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.
cyclobutenones, rearrangement, thermolysis, flow chemistry, furanones, steric buttressing, torquoselectivity
0039-7881
3091-3106
Sun, Wei
bca29e03-90fc-4684-875e-61d35f1b5cba
Wilson, Dharyl C.
a64ee73e-0685-4aee-b96d-a43ec736fe33
Harrowven, David C.
bddcfab6-dbde-49df-aec2-42abbcf5d10b
Sun, Wei
bca29e03-90fc-4684-875e-61d35f1b5cba
Wilson, Dharyl C.
a64ee73e-0685-4aee-b96d-a43ec736fe33
Harrowven, David C.
bddcfab6-dbde-49df-aec2-42abbcf5d10b

Sun, Wei, Wilson, Dharyl C. and Harrowven, David C. (2017) Steric buttressing changes torquospecificity in thermal cyclo­butenone rearrangements, providing new opportunities for 5H-furanone synthesis. Synthesis, 49 (14), 3091-3106. (doi:10.1055/s-0036-1588850).

Record type: Article

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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Accepted/In Press date: 3 May 2017
e-pub ahead of print date: 13 June 2017
Published date: July 2017
Keywords: cyclobutenones, rearrangement, thermolysis, flow chemistry, furanones, steric buttressing, torquoselectivity
Organisations: Chemistry, Organic Chemistry: SCF, Southampton Marine & Maritime Institute

Identifiers

Local EPrints ID: 411992
URI: http://eprints.soton.ac.uk/id/eprint/411992
ISSN: 0039-7881
PURE UUID: 4a93bbbf-08bd-4be8-bd55-719425bad6fa
ORCID for David C. Harrowven: ORCID iD orcid.org/0000-0001-6730-3573

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Date deposited: 04 Jul 2017 16:31
Last modified: 18 Feb 2021 16:43

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