Efficient formal syntheses of (±)-Asterisca-3 (15), 6-diene, a natural product with a bicyclo [6.3. 0] undecane skeleton, and (±)-Pentalenene, a natural product with a tricyclo [6.3. 0.04, 8] undecane skeleton, have been achieved by using Rh (I)-catalyzed [(5+ 2)+ 1] cycloaddition. The [(5+ 2)+ 1] reaction provides an expeditious approach to reach the bicyclic cyclooctenone 4, which was quickly transformed (via hydroboration then oxidation ...
