Kaskadenreaktionen in der Totalsynthese

Abstract

Die Entwicklung und Umsetzung von Kaskadenreaktionen hat zu beachtlichen neuartigen, eleganten und effizienten Synthesestrategien geführt. Als besonders anspruchsvoll erwies sich die Anwendung von Kaskadenreaktionen in der Naturstoffsynthese, doch gerade hier winken verblüffende und zugleich aufschlussreiche Ergebnisse als Belohnung. In diesem Aufsatz werden ausgewählte Kaskadenreaktionen in der Totalsynthese erläutert, wobei neuere Anwendungen besonders hervorgehoben werden. Die erörterten Beispiele sollen die Leistungsfähigkeit dieser Prozesse beim Aufbau von komplexen Molekülstrukturen veranschaulichen und ihr Potenzial für zukünftige chemische Synthesen verdeutlichen.

Asymmetric One‐Pot Sequential Organo‐ and Gold Catalysis for the Enantioselective Synthesis of Dihydropyrrole Derivatives

“…[6] Consequently, the combination of efficient catalytic methods in a tandem [7] or one-pot process [8] could provide a powerful tool for preserving both energy and resources. [9] To this end a multicatalytic asymmetric cascade reaction to cyclopentene carbaldehydes from a,b-unsaturated aldehydes and alkyne-tethered nucleophiles employing a combination of iminium-enamine and Lewis acid catalysis was recently reported.…”

Gold‐Catalyzed Cascade Friedel–Crafts/Furan‐Yne Cyclization/Heteroenyne Metathesis for the Highly Efficient Construction of Phenanthrene Derivatives

“…37, 126.03, 126.98, 127.10, 127.44, 127.51, 128.33, 128.36, 128.57, 128.66, 128.71, 128.84, 130.06, 130.24, 132.15, 132.44, 133.49, 137.07, 138.21, 138.62, 140.51, 200.36 Method A and column chromatography on silica gel (petroleum ether:dichloromethane = 2:1) afforded the title product as a sticky yellow oil; yield: 72%. 1 95, 20.73, 125.96, 126.21, 126.63, 126.68, 127.34, 128.08, 128.32, 128.38, 128.61, 128.84, 128.86, 129.50, 130.06, 130.30, 132.37, 132.92, 133.62, 135.82, 136.82, 137.80, 138.36, 140.96, 203 …”

“…1 126.15, 126.77, 126.81, 127.43, 127.92, 128.13, 128.16, 128.30, 128.33, 128.66, 128.76, 128.99, 130.06, 130.27, 132.63, 134.23, 134.77, 135.14, 136.25, 138.55, 140.68, 145.31, 194.49 24, 21.23, 125.90, 126.61, 126.90, 127.85, 127.92, 128.38, 128.55, 128.77, 128.82, 128.99, 129.01, 129.43, 129.91, 130.44, 132.73, 133.61, 133.70, 136.63, 137.08, 137.42, 137.75, 138.64, 202.35 …”

“…[1] These processes enable multiple bond-forming and bond-cleaving events to occur in one sequence which greatly enhances the synthetic efficiency, while producing less waste and minimizing handling. Although much progress has been achieved in this field, metal-catalyzed cascades involving three or more than three reactions are still a major challenge in synthetic organic chemistry.…”

Asymmetric Synthesis of Polyfunctionalized Mono‐, Bi‐, and Tricyclic Carbon Frameworks via Organocatalytic Domino Reactions

“…[1] In particular, biomimetic approaches by which complex organic molecules bearing several stereocenters are stereoselectively assembled from simple precursors constitute a very promising concept. [2] In this respect, organocatalytic domino reactions seem to be the perfect way to achieve this goal because the advantages of both fields, organocatalysis [3] and domino reactions, [4] are merged.…”