Pyrroles arylboronic acid coupling

The Suzuki coupling has been utilized to craft (Toctasubstituted tetramesitylporphyrins using various arylboronic acids [62], and Schluter has adopted this reaction to prepare phenyl-pyrrole mixed polymers 75 [63]. The BOC group is easily removed by heating [64] and polymers with molecular weights of up to 23,000 were synthesized. These polymers are potentiaEy interesting for their electrical and nonlinear optical properties [65]. 

In their studies towards the synthesis of lukianol A, Wong et al. observed the regioselective zp o-iodination of pyrrole 187 followed by Sonogashira coupling to give 189 in quantitative yield overall [109]. lodopyrrole 188 also undergoes Suzuki couplings with arylboronic acids. 

Hu and Yu disclosed an iron-mediated direct Suzuki-Miyaura coupling between IH-pyrrole (1) and arylboronic acids. Macrocyclic polyamines (MCPA) were studied in this process under the reaction conditions, a tertiary pyrrole-MCPA-oxoiron complex 4 is formed which undergoes transmetallation with the arylboronic acid. After elimination of the iron complex, 2-phenyl pyrrole (2) was isolated in 66% yield with only trace amounts of phenol. 

Abstract This review covers the recent recyclable protocols for the C-N bond forming reactions between aromatic, heterocyclic and aliphatic amines such as imidazoles, benzimidazoles, benzylamines, piperidine, pyrrole, imides, anilines, hexyl, cyclohexyl amines, and amides as coupling partners with aryl iodides, bromides, chlorides, and arylboronic acids employing copper-mediated systems. The physical properties and characterization of the catalysts and their use in organic synthesis will be outlined. Most importantly, these recyclable versions developed by many groups in the recent years are potential candidates for commercial exploitation. The effect of additives, solvents, temperature, base, the nature of aryl halides on reactivity, and recycle studies of the heterogeneous catalysts are included in this... 

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