The Intermolecular Pauson–Khand Reaction of meso‐Substituted Porphyrins

The intermolecular Pauson–Khand reaction is often limited by the poor reactivity and selectivity of simple alkenes. Here we expanded the range of reagents to simple alkenyl‐ and alkynyl‐substituted porphyrins. The two expected regioisomers could be obtained in a combined yield of up to 72 %. In addition, use of the Pauson–Khand reaction provides a simple and novel pathway for the preparation of porphyrin dimers in a nearly quantitative yield. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)