4-Silylated oxazoles have been shown to undergo inter-and intramolecular Diels-Alder/retro-Diels-Alder reactions with electron-poor alkynes to generate polysubstituted furans. The ease of synthesis of the requisite oxazoles by the rhodium-catalysed condensation of nitriles with silylated diazoacetate greatly increases the scope of this reaction. approach to cycloaddition precursors, since the presence of electron-withdrawing groups on the oxazole deactivates the system toward cycloaddition and

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... lso oxazoles bearing carbonyl functions at the 4-position are susceptible to Cornforth rearrangement on thermolysis. 7 Indeed, to our knowledge there are no known successful examples of cycloadditions of oxazoles bearing a carbonyl group at the 4-position with alkynes, and only two reports of reactions with alkenes. 8 We have recently shown that 4-silylated oxazoles can be readily prepared by the condensation of silyl diazoacetates with nitriles under rhodium catalysis. 9 The reluctance of silyl diazoacetates and their derived rhodium carbenoids to undergo dimerisation means that these reactions are operationally simple, requiring no precautions such as high dilution or slow addition of substrate. It therefore became apparent that were these substrates to undergo Diels-Alder reactions with alkynes, followed by subsequent retro-Diels-Alder elimination of silyl cyanide, then this would considerably broaden the scope of the overall furan synthesis. We report herein the successful Diels-Alder/retro-Diels-Alder reactions of silylated oxazoles with electronpoor alkynes in both inter-and intramolecular manifolds.