Oxidative Ring Closure and Metal Triggered Ring Opening: Syntheses of Macrocyclic and Linear Hexapyrroles

Abstract

A C6F5-substituted hexapyrrane (1) was synthesized in one step. Oxidative cyclization of 1 with DDQ afforded a phlorin-dipyrrin conjugate (2), and subsequent FeCl3-assisted oxidative cleavage of 2 afforded a terminally di-α-methoxy substituted hexapyrrin (3). On the other hand, oxidation of 1 with FeCl3 afforded 3, a hexapyrrinone Fe(3+) complex (4), and a hexaphyrin (1,1,1,1,1,0) (5). These results indicate that the oxidation of hexapyrranes may be developed as an effective approach for the syntheses of novel linear and macrocyclic hexapyrroles.