Highly efficient stereoconservative syntheses of new, bifunctional atropisomeric organocatalysts

Abstract

The first synthesis of new organocatalysts with 1-phenylpyrrole atropisomeric skeleton containing a thiourea group is reported. A possible structural reason for the stereochemical lability of an atropisomeric intermediate is described together with a way to preserve the isomeric purity during the synthesis. The catalytic activities of the new atropisomeric organocatalysts have been tested in Michael addition reactions.

Organocatalytic Cascade β-Functionalization/Aromatization of Pyrrolidines via Double Hydride Transfer

“…Among these prominent chemical scaffolds, arylpyrroles play an increasingly important role, serving as chiral resolving agents, ligands, and catalysts (Figure ). Therefore, great attention has been focused on the construction of these skeletons. However, the majority of methods for synthesis of pyrrole derivatives are limited to the construction of α-functionalized pyrroles and multisubstituted pyrroles .…”

Atroposelective Synthesis of Axially Chiral N‐Arylpyrroles by Chiral‐at‐Rhodium Catalysis

“…Among them, axially chiral N‐arylpyrroles are increasingly popular building blocks due to their specific structural and electronic properties among biaryls, in addition to a straightforward functionalization of the electron‐rich aromatic pyrrole moiety. For example, axially chiral N‐arylpyrroles have been used as reagents for resolving racemates, as chiral coordinating ligands, and as chiral organocatalysts . Interestingly, Beller and co‐workers introduced 2‐phosphino‐1‐arylpyrroles as highly effective phosphine ligands, some of which are commercially available (e.g.…”

“…Despite their undeniable importance in organic synthesis, methods for accessing axially chiral N‐arylpyrroles are surprisingly scarce, and most methods developed to date rely on optical resolution of racemic starting materials . Only two catalytic asymmetric strategies have been reported, both by Tan and co‐workers.…”

“…For example, axially chiral N-arylpyrroles have been used as reagents for resolving racemates, [7] as chiral coordinating ligands, [8] and as chiral organocatalysts. [9] Interestingly, Beller and co-workers introduced 2-phosphino-1-arylpyrroles as highly effective phosphine ligands, some of which are commercially available (e.g. cataCXium P).…”

“…Despite their undeniable importance in organic synthesis, methods for accessing axially chiral N-arylpyrroles are surprisingly scarce, and most methods developed to date rely on optical resolution of racemic starting materials. [7][8][9] Only two catalytic asymmetric strategies have been reported, both by Tan and co-workers. One of them is a combined Lewis acid and chiral phosphoric acid (CPA) catalyzed asymmetric Paal-Knorr reaction for constructing the pyrrole ring from anilines and 1,4-diketones (Figure 1 a).…”