Isomerisation of (E)-2-Tetrahydrofurylidenealkanecarboxylic Esters and Amides into Their (Z) Isomers by Chelation Control with Metallated Bases or Lewis Acids

2-(2-Tetrahydrofurylidene)propionates, usually obtained only in the more stable (E) configuration 1, were efficiently isomerised into their (Z) isomers 2 by use of Lewis acids or metallated bases. The (E)/(Z) isomerisation was governed by different factors (type of chelating agent, nature and steric...

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Bibliographic Details
Published in:European journal of organic chemistry 2002, Vol.2002 (13), p.2112-2119
Main Authors: Hanquet, Gilles, Salom-Roig, Xavier J, Lemeitour, Sonia, Solladié, Guy
Format: Article
Language:English
Subjects:
Chemical Sciences
Organic chemistry
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Summary:2-(2-Tetrahydrofurylidene)propionates, usually obtained only in the more stable (E) configuration 1, were efficiently isomerised into their (Z) isomers 2 by use of Lewis acids or metallated bases. The (E)/(Z) isomerisation was governed by different factors (type of chelating agent, nature and steric demand of the α,β-unsaturated group). We demonstrated that judicious selection of the α,β-unsaturated group, in combination with the chelating agent, afforded yields of up to 95% with either LDA [R = N(Me)2, tBu] or MgBr2 and ZnI2 (R = OBn), and that the reaction was also influenced by 1,3-allylic strains.
ISSN:1434-193X
1099-0690
DOI:10.1002/1099-0690(200207)2002:13<2112::AID-EJOC2112>3.0.CO;2-%23