An Exploratory Study of Type II [3 + 4] Cycloadditions between Vinylcarbenoids and Dienes

The intramolecular type II [3 + 4] cycloaddition between vinylcarbenoids and furans is a practical method for the construction of 5-oxo-10-oxatricyclo[6.2.1.04,9]undeca-3,8(11)-dienes, containing two anti-Bredt double bonds. These tricyclic systems are well functionalized for eventual elaboration to the natural product CP-263,114. The rhodium-stabilized vinylcarbenoids are generated by dirhodium tetracarboxylate catalyzed decomposition of vinyldiazoacetates. The [3 + 4] cycloaddition is generally considered to occur by a tandem cyclopropanation/Cope rearrangement, although evidence is presented that with these substrates the [3 + 4] cycloaddition may occur in a concerted manner.