The Pauson–Khand Reaction: the Catalytic Age Is Here!



As a consequence of growing environmental awareness, it is now inappropriate to design a synthetic metal-mediated transformation that involves a noncatalytic use of toxic and expensive transition-metal species. One of the earliest examples of such a metal-mediated transformation is the Pauson–Khand reaction, a [2+2+1] cyclocarbonylation that generates a cyclopentenone. Despite the early descriptions by Pauson and co-workers of catalytic versions of the reaction with octacarbonyldicobalt(0), applications of the Pauson–Khand reaction have to date almost exclusively used approaches that involve stoichiometric quantities of cobalt–carbonyl complexes. In the last decade, and, most markedly, in the last two to three years, however, there have been many exciting and novel developments in the catalytic Pauson–Khand reaction. Furthermore, asymmetric catalysis of the Pauson–Khand reaction has been shown to be a viable process. In view of the impressive developments in Pauson–Khand catalysis in the last two to three years, we present a comprehensive and critical coverage of the catalytic Pauson–Khand reaction that is designed to facilitate its application and to point to exciting future developments.