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Construction of 2,3‐Dihydrofuran Cores through the [3+2] Cycloaddition of Gold α‐Carbonylcarbenoids with Alkenes
Author(s) -
Li ChiaWen,
Lin GuanYou,
Liu RaiShung
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201000009
Subject(s) - cycloaddition , alkene , oxonium ion , chemistry , catalysis , medicinal chemistry , stereoselectivity , enol , redox , photochemistry , organic chemistry , ion
Abstract Treatment of 2‐epoxy‐1‐alkynylbenzenes with electron‐rich alkenes and a [AuCl(PR 3 )]/AgX catalyst in CH 2 Cl 2 led to the formation of 2‐alkenyl‐1‐(2,3‐dihydrofuran‐4‐yl)benzenes. This transformation comprises of a gold‐catalyzed redox reaction to form a gold α‐carbonylcarbenoid initially, which then reacts in situ with an alkene in a [3+2] cycloaddition. A range of alkenes are amenable to this tandem reaction, amongst them α‐substituted styrenes, enol ethers, and 2,3‐dimethylbutadienes. Deuterium‐labeling experiments suggest a stepwise mechanism for the α‐carbonylcarbenoid/alkene [3+2] cycloaddition. The resulting 2,3‐dihydrofuran products allow access to diverse oxacyclic compounds through a stereoselective ene–oxonium reaction initiated by treatment with HOTf (1 mol %; Tf=trifluoromethanesulfonyl). A stepwise pathway is proposed for this reaction. The feasibility for direct transformation of 2‐alkenyl‐1‐alkynylbenzenes into the desired 2,3‐dihydrofuran products through initial m ‐chloroperbenzoic acid oxidation, followed by the addition of gold catalyst and alkene, has also been demonstrated.