Enantioselective Syntheses of Cyclopentanoid Compounds from Isoprene and trans‐1,3‐Pentadiene

In only two steps, optically active 2 can be prepared from the basic chemicals isoprene, trans-l,3-pentadiene, and acetic anhydride. A chiral diazadiene–iron complex catalyzes the codimerization of isoprene and trans-1,3-pentadiene to 1 with regio- and enantioselectivity (89% yield, 61% ee). In turn, 1 rearranges diastereoselectively to 2 and other bicyclo[3.3.0]octane derivatives under acid catalysis.