Synthesis of sterically encumbered porphyrins as catalysts for shape-selective oxidations

摘要

A general method is described for the synthesis of sterically encumbered porphyrins whose shielding superstructure can take on the enzymatic role of substrate discrimination. This method is based on an improved synthesis of pyrroles substituted with a 2,6-dibromophenyl group, followed by a Suzuki cross-coupling to replace the Br with aryl groups. Porphyrins assembled from such pyrrole units have a barrel shape with the metal center completely fenced by four beta-substituted terphenyl shielding wings. The Fe and Mn porphyrins prove to be excellent catalysts for regioselective epoxidation of alkenes. [References: 20]