Diethylaluminium Chloride‐Mediated Cycloaddition/Conjugate Reduction Sequence towards Imido‐Substituted Norbornenes

Diethylaluminium chloride is a known Lewis acid and can undergo 1,2‐ and 1,4‐additions, whereas conjugate reductions are mostly observed as side reactions. By serendipity we found a Et2AlCl‐promoted sequential cycloaddition / conjugate hydrogenation of cyclopentadiene and 4‐isopropyl‐3‐(3‐phenylpropioloyl)oxazolidin‐2‐one resulting in the clean formation of the corresponding norbornene‐oxazolidin‐2‐one. NMR, kinetic and deuteration experiments provided insight into the mechanism of this reaction sequence.