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DOI: 10.1055/s-0028-1087326
Oxidative Aromatic Umpolung Strategy Applied to Tetrahydrofuran Synthesis
Contributor(s):Mark Lautens, Frédéric MénardUniversité du Québec à Montréal, Canada
Expeditious Total Syntheses of Natural Allenic Products via Aromatic Ring Umpolung
Org. Lett. 2008, 10: 4629-4632
Publication History
Publication Date:
20 November 2008 (online)
Key words
allenes - hypervalent iodines - dihydrobenzofurans - total synthesis
Significance
Two substrates that are typically strong nucleophiles are joined by an oxidative Umpolung reaction. The natural reactivity of phenol is reversed by its oxidation with diacetatoiodobenzene (DIB) and is made into an electrophilic cationic intermediate. The oxidative formal [3+2] cyclization yields a fused bis(dihydrofuran) product regio- and diastereoselectively in one operation. The power of the transformation was demonstrated by impressively short syntheses of panacene and some analogues.
Comment
The method allows rapid and stereocontrolled synthesis of highly functionalized tetrahydrofurans. This is a striking application of a methodology previously reported by the authors (Tetrahedron Lett. 2007, 48, 8238). The yield of the key step calls for improvement, but it is eclipsed by the complexity of the product obtained from readily available starting materials. Noteworthy is an unprecedented stereoselective proto-demetallation of an allenylmercury intermediate with ethanedithiol.