Palladiumkatalysierte Kreuzkupplungen in der Totalsynthese

Abstract

Wenn man die Entwicklung der organischen Chemie betrachtet, kommt man schnell zu dem Schluss, dass kein Reaktionstyp dieses Gebiet in vergleichbarer Weise geprägt hat wie die Kohlenstoff‐Kohlenstoff‐Kupplungen. Grignard‐, Diels‐Alder‐ und Wittig‐Reaktionen sind nur drei herausragende Beispiele für solche Prozesse, die im vergangenen Jahrhundert zweifellos entscheidend am Aufstieg der chemischen Synthese beteiligt waren. Im letzten Viertel des 20. Jahrhunderts bereicherte eine neue Familie von leistungsfähigen Reaktionen zur Knüpfung von Kohlenstoff‐Kohlenstoff‐Bindungen das Repertoire der Synthesechemie: die übergangsmetallkatalysierten Reaktionen, allen voran die palladiumkatalysierten Kreuzkupplungen. In diesem Aufsatz werden Auszüge aus einer Reihe von ausgewählten Synthesen diskutiert. Die Beispiele sollen die enorme Leistungsfähigkeit dieser Prozesse in der Kunst der Totalsynthese aufzeigen und ihr Potenzial für zukünftige chemische Synthesen unterstreichen.

Mizoroki–Heck Reactions with 4‐Phenoldiazonium Salts

“…[5] Apart from photochemical and radical reactions, additions of polar organometallics to carbonyl compounds and transition metal-catalyzed coupling and cross-coupling reactions [6] are commonly used synthetic methods in this field. [7] In this context, the Mizoroki-Heck reaction [8] is one of the most important transformations.…”

Scope and Limitations of Palladium‐Catalyzed Cross‐Coupling Reactions with Organogold Compounds

“…Among the transition metals employed for cross-coupling, palladium is still the most frequently used, [1] which includes the synthesis of natural products and pharmaceuticals. [2] The mechanism of these palladium-catalyzed cross-coupling reactions consists of three different steps, the oxidative addition of aryl or alkenyl halides, triflates etc., the transmetalation step and the reductive elimination which regenerates the active catalyst species and sets free the product of the C À C bond formation (Scheme 1). A number of organometallic compounds derived from electropositive metals has been used for the transmetalation step; the name reactions shown in Scheme 1 go along with the use of B, Sn, Zn and Mg.…”

Transition Metal‐Mediated Direct CH Arylation of Heteroarenes Involving Aryl Radicals

“…A wide variety of halogenated starting materials is commercially available, and many efforts have been made to develop new methodologies to activate the less reactive but less expensive chloride derivatives. The transition metal-catalyzed cross-couplings of electrophilic aryl halides with nucleophilic organometallic reagents, known as the Suzuki-Miyaura, Stille, Hiyama or Kumada-Corriu reactions, [21] are among the most powerful existing methods for the synthesis of (hetero)A C H T U N G T R E N N U N G biaryls. More recently, the direct arylation of aromatic compounds by C À H activation with aryl halides has emerged as a very attractive atom-economical method, especially for the synthesis of heterobiaryls, directly from the heteroarenes, such as furans, thiophenes, pyrroles, oxazoles, thiazoles, etc.…”