The design and implementation of cascade reactions is a challenging facet of organic chemistry, yet one that can impart striking novelty, elegance, and efficiency to synthetic strategies. The application of cascade reactions to natural products synthesis represents a particularly demanding task, but the results can be both stunning and instructive. This Review highlights selected examples of cascade reactions in total synthesis, with particular emphasis on recent applications therein. The examples discussed herein illustrate the power of these processes in the construction of complex molecules and underscore their future potential in chemical synthesis.

Cascade reactions in total synthesis.

Isolation and synthesis of biologically active carbazole alkaloids

Alan Ford,† Hugues Miel, Aoife Ring,† Catherine N. Slattery,† Anita R. Maguire,*,†,‡ and M. Anthony McKervey* †Department of Chemistry and ‡School of Pharmacy, Analytical and Biological Chemistry Research Facility, Synthesis and Solid State Pharmaceutical Centre, University College Cork, Cork, Ireland Almac Discovery Ltd., David Keir Building, Stranmillis Road, Belfast BT9 5AG, United Kingdom Almac Sciences Ltd., Almac House, 20 Seagoe Industrial Estate, Craigavon BT63 5QD, United Kingdom

Modern Organic Synthesis with α-Diazocarbonyl Compounds

Catalytic cross-coupling reactions in biaryl synthesis

Die Entwicklung und Umsetzung von Kaskadenreaktionen hat zu beachtlichen neuartigen, eleganten und effizienten Synthesestrategien gefuhrt. Als besonders anspruchsvoll erwies sich die Anwendung von Kaskadenreaktionen in der Naturstoffsynthese, doch gerade hier winken verbluffende und zugleich aufschlussreiche Ergebnisse als Belohnung. In diesem Aufsatz werden ausgewahlte Kaskadenreaktionen in der Totalsynthese erlautert, wobei neuere Anwendungen besonders hervorgehoben werden. Die erorterten Beispiele sollen die Leistungsfahigkeit dieser Prozesse beim Aufbau von komplexen Molekulstrukturen veranschaulichen und ihr Potenzial fur zukunftige chemische Synthesen verdeutlichen.

Kaskadenreaktionen in der Totalsynthese

An improved method for the synthesis of .alpha.-diazo ketones

A general strategy for the synthesis of highly substituted polycyclic aromatic and heteroaromatic compounds has been developed. The new aromatic annulation is achieved simply by the irradiation of a dichloroethane solution of an acetylene derivative and a vinyl or aryl α-diazo ketone. Mechanistically, the reaction proceeds via the photochemical Wolff rearrangement of the diazo ketone to generate an aryl- or vinylketene, followed by a cascade of three pericyclic reactions. A variety of substituted phenols, naphthalenes, benzofurans, benzothiophenes, indoles, and carbazoles can be prepared by using the method

An annulation method for the synthesis of highly substituted polycyclic aromatic and heteroaromatic compounds

A Convenient Synthesis of Dimethyl (Diazomethyl)phosphonate (Seyferth/Gilbert Reagent)

A method is described for a mild and efficient synthesis of azulenone skeletons via the addition reactions of 2-phenyl-2-acylketenes with 1-alkynyl ethers. A mechanism is presented to account for both azulenone formation as well as the solvent and substrate dependency of a competitive pyrone formation. The azulenone rings have been subsequently transformed into both substituted azulenes or hydroazulenes by derivatization and/or decarboxylation of an angular carboxyl substituent or by hydrogenation.

Synthesis of Azulenone Skeletons by Reaction of 2-Phenyl-2-acylketenes [RCO(Ph)CCO] with Alkynyl Ethers: Mechanistic Aspects and Further Transformations

Ronald G. Brisbois

Papers

An improved method for the synthesis of .alpha.-diazo ketones

An annulation method for the synthesis of highly substituted polycyclic aromatic and heteroaromatic compounds

A Convenient Synthesis of Dimethyl (Diazomethyl)phosphonate (Seyferth/Gilbert Reagent)

Synthesis of Azulenone Skeletons by Reaction of 2-Phenyl-2-acylketenes [RCO(Ph)CCO] with Alkynyl Ethers: Mechanistic Aspects and Further Transformations

Regiocontrolled Synthesis of CpCo-Cyclobutadienyl-Bridged p-Cyclophanes via Annulation of Acyclic Diynes