Die Diarylprolinolsilylether: zehn Jahre später

Abstract

Die asymmetrische Organokatalyse hat seit Beginn dieses Jahrhunderts eine unglaubliche Entwicklung erlebt, die zu einer Vielzahl leistungsfähiger Katalysatortypen führte. Darunter sind die 2005 eingeführten Diarylprolinolsilylether eine der in der Aminokatalyse am häufigsten verwendeten Gruppen. In diesem Kurzaufsatz – zehn Jahre nach Einführung der Diarylprolinolsilylether – wollen wir einen Rückblick wagen. Dabei liegt der Schwerpunkt auf den Möglichkeiten der verschiedenen Aktivierungsmodi, die dieses katalytische System zugänglich macht. Nach einer kurzen Einführung in die Aminokatalyse gehen wir auf die Eigenschaften ein, die Diarylprolinolsilylether zu häufig gewählten Katalysatoren gemacht haben. Des Weiteren werden die Hauptrichtungen der Aktivierung sowie die im Hinblick auf Reaktionsmuster entwickelten Reaktionskonzepte und Kombinationen mit anderen Aktivierungskonzepten beschrieben.

Catalytic Asymmetric Oxidative γ‐Coupling of α,β‐Unsaturated Aldehydes with Air as the Terminal Oxidant

“…[1] Readily available chiral amines have been extensively used as catalysts in the field of polar reactivity for the activation of carbonyl compounds,which by reaction with electrophiles and nucleophiles provide products in ah ighly stereoselective manner. [2] In contrast, the involvement of short-lived open-shell species in asymmetric catalysis has remained relatively unexplored until recently,o wing to the inherent challenge of efficiently controlling the stereoselectivity of product formation from high-energy intermediates. [3] Among the most fundamental reactions in organic synthesis are carbon-carbon bond-forming reactions.…”

“…Ther esults with Cu(OAc) 2 encouraged us to investigate whether the copper source could be integrated in ac atalytic fashion with O 2 from the air as the terminal oxidant. Satisfyingly,w hen the coupling reaction was performed with only 2mol %C u(OAc) 2 in an open-air system, smooth conversion into the g-coupling product 3a in moderate yield with excellent diastereo-and enantioselectivity was observed ( To obtain ab etter understanding of the enantioselective oxidative catalytic coupling system, we performed several control experiments (Scheme 2a). No coupling reactivity was observed in the absence of the Cu II salt or without the aminocatalyst 2,t hus confirming the necessity for both systems to be present.…”

Regioselective Asymmetric Formal (3+2) Cycloadditions of Nitrone Ylides from Isatins and Enals

“…Consequently, we initially investigated the reaction between nitrone 1a and cinnamaldehyde 2a in toluene, by employing chiral amine C1 and benzoic acid. However, no reaction occurred after 24 h at 40 °C (Table , entry 1).…”

Asymmetric Catalysis within the Chiral Confined Space of Metal–Organic Architectures

“…In some cases, the pyrrolidine catalysts provided high catalytic turnover but modest selectivities, and the lack of stereocontrol in the reaction was hypothesized to arise from insufficient steric shielding around the active site. Therefore, subtly tuning the stereochemical environment of the active sites of a catalyst to give highly functionalized, optically active molecules with excellent diastereo‐ and enantioselectivity is a major challenge . New strategies for introducing specific chiral organocatalysts into the pore environments of MOFs have been developed in recent years, and the confined microenvironment around the introduced active pyrrolidines may provide additional spatial constraints and shielding effects to facilitate the synthesis of products with high enantioselectivity.…”