Tandem organic reactions Involving Michael addition

Over the last twenty years, the tandem process involving transition metal-promoted cyclization reactions initiated or determined by a Michael addition has attracted an increasing interest in organic chemistry. The diversity of examples discussed in this work demonstrates the high potential of these tandem reactions for the efficient one-pot synthesis of complex structures with limiting catalysts and remarkable atom economy. It is expected that the development of further useful new sequences founded on this concept will be developed in the near future. 

Synthetic Routes to Chromanes Chromanes are important structural motifs in organic synthesis and have been found as core structural elements commonly present in many bioactive compounds. J0rgensen et al. [32] have developed a tandem reaction that involves a Lewis acid-catalyzed oxa-Michael addition of phenols 208 to p,y-unsaturated a-ketoesters 209, followed by an intramolecular FC alkylation to form chromanes 211 (Scheme 2.29). The reaction proceeds under the influence of a Mg-BOX (210) catalyst to give diastereomerically pure chromanes with enanti-oselectivities up to 81% and excellent yields. The best results were obtained with m-methoxyphenol, while m-A(Al-dimethylaminophenol afforded the corresponding chromane as single diastereomer in excellent yield but with low enantioselectivity (<20% ee). 

---