Improved Synthesis of Functionalized 2,2‘-Bipyrroles

Abstract

A series of 2,2'-bipyrroles has been efficiently synthesized using an improved synthetic approach based on Pd(0)-catalyzed homocoupling of various 2-iodopyrroles. This new synthetic approach takes place at room temperature and in the presence of water. Functional groups such as formyl, ester, and nitrile are able to survive these reaction conditions. Solvents are found to play an important role in this reaction.

Phosphoric acid-catalyzed atroposelective construction of axially chiral arylpyrroles

“…Furthermore, the treatment of 3a with 4-methyl-benzenesulfonylisocyanate provided compound 14 without loss of stereochemical integrity. Noteworthy, arylpyrrole ( R )- 3a could be readily oxidized to dialdehyde 15 with cerium(IV) ammonium nitrate as the oxidative reagent 49 . Moreover, the obtained product 3 h possessing an iodo substituent was an applicable reactant for classic transition metal-mediated coupling reactions (Fig.…”

Palladium(0) catalyzed 2,2′-bipyrrole syntheses

“…Palladium, 10% on activated carbon was purchased from Strem Chemicals. Zinc dust, <10 micro, 98+%, was purchased from Sigma-Aldrich and actived according to the literature [12]. Monopyrroles used to make 2-iodopyrroles were synthesized according to the literature [13].…”

“…Although Pd-C has been previously used as a catalyst in the Ullmann coupling, phase-transfer reagents and 100 °C reflux conditions are required [10]. Inspired by recent improved syntheses of biaryls through Pd(0) catalyzed couplings at ambient temperature [11], our improved syntheses reduced the synthetic steps for most of the 5,5′-diformyl-2,2′-bipyrroles studied [12] by using Pd-C and zinc as co-catalyst with the presence of water. Considering the substituent array, and especially those at the 2- or 5-position of pyrroles, generally affect both the Ullmann and oxidative coupling reactions, the versatility of this reaction and the photo-physical properties of the resulting 2,2′-bipyrroles are now discussed in the present paper.…”

Five‐Membered Heterocycles: Pyrrole and Related Systems

“…Moreover, a protocol for assembly of various 2,2 0 -bipyrrole-5,5 0 -dicarboxaldehydes by homocoupling of 5-iodopyrrole-2-carboxaldehyde precursors employed palladium on carbon and activated zinc dust as the catalyst [733]. Classical cross-coupling techniques have also found new applications, further demonstrating their extraordinary synthetic potential in pyrrole chemistry.…”