The carbonyl ene reaction

This report has aimed to give the synthetic chemist an appreciation of the relative reactivity of enophiles and alkenes such that an informed decision regarding the viability of their use in a synthesis can be made. The examples chosen do not represent comprehensive coverage of the area, but, hopefully, do serve to cover most types of carbonyl ene reactions that might be used in synthesis. Some fascinating and elegant syntheses have already been accomplished using ene methodology, and it is envisaged that the coming years will see further interesting applications and, hopefully, progress on some of the more challenging reactions. The main problem with ene reactions is the high activation barrier of many of the reactions, which often limits the scope to specific enes and enophiles. In addition to guiding chemists towards reactions that proceed effectively, we hope this review has also highlighted some of the challenges that lie ahead. © 2008 Elsevier Ltd.