Pyrrole and Oligopyrrole Synthesis by 1,3‐Dipolar Cycloaddition of Azomethine Ylides with Sulfonyl Dipolarophiles

Abstract

A procedure for the synthesis of functionalized, substituted pyrroles by 1,3-dipolar cycloaddition of azomethine ylides has been developed. This protocol is based on the metal-catalyzed cycloaddition of alpha-iminoesters with sulfonyl dipolarophiles, followed by the base-promoted elimination of the sulfonyl groups. A wide variety of 2,5-disubstituted and 2,3,5- and 2,4,5-trisubstituted pyrroles have been prepared in satisfactory yields from 1,2-bis(sulfonyl ethylene), beta-sulfonylenones, and beta-sulfonylacrylates. This method can be applied in an iterative and straightforward manner to the construction of oligopyrroles, from bipyrroles to pentapyrroles. Iterative [n+1] and [n+2] approaches have been devised, the latter involves double 1,3-dipolar cycloaddition from pyrrolyl-based bis(iminoesters).

4.22 Intermolecular 1,3-Dipolar Cycloadditions of Alkenes, Alkynes, and Allenes

“…They have also reported a catalytic asymmetric 1,3-dipolar cycloaddition using (Ε)-β-phenylsulfonyl enones 115 as dipolarophiles to provide highly functionalized pyrrolidine derivatives 116 (Scheme 56). 68 In the presence of chiral CuI-SEGPHOS catalysts, the adducts were obtained with high regio-, diastereo-, and enantioselectivities. Interestingly, the endo/exo-selectivity of this procedure is controlled by the aryl groups on the P atom of chiral ligands, as those from endo-to exo-selectivity were observed when SEGPHOS 117 or DTBM-SEGPHOS 113 ligand was used.…”

Synthesis of Pyrrole via a Silver-Catalyzed 1,3-Dipolar Cycloaddition/Oxidative Dehydrogenative Aromatization Tandem Reaction

“…However, despite considerable progress toward the synthesis of indolizines, there have been very few reports pertaining to the synthesis of pyrroles using a one-pot 1,3-cycloaddition reaction. The few methods that have been reported in this area are generally limited by their requirement for electron-deficient alkyne substrates and their analogues, such as ( E )-1,2-bis­(phenyl­sulfonyl)­ethane, ((1-bromo­vinyl)­sulfonyl)­benzene, and ( E )-4-ethoxy-1,1,1-trifluoro­but-3-en-2-one, which are expensive and difficult to access, as well as lacking in sufficient structural diversity. These limitations could be attributed in part to a lack of suitable methods for the oxidative dehydrogenative aromatization of pyrrolidines.…”

Stereochemical diversity in pyrrolidine synthesis by catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides

“…In 2010 our research group described the catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides with sulfonylenones. 47 The regioselectivity of the reaction catalyzed by Cu I /Segphos-type ligands was mainly controlled by the carbonyl group, leading to 4-acetyl pyrrolidines as major products. Interestingly, the endo/exo selectivity could be controlled by the substitution on the phosphorous atoms of the segphos-type ligands.…”