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.

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

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

Intramolecular 1,3-dipolar cycloaddition reactions in targeted syntheses

In this tutorial review, the rhodium(II)-catalyzed domino reactions of α-diazo carbonyl compounds are summarized. The article will emphasize some of the more recent synthetic applications of the rhodium carbenoid cyclization/cycloaddition domino cascade for alkaloid synthesis. The many structurally diverse and highly successful examples of both oxa and azapolycyclic ring formation cited in this tutorial review clearly demonstrate that the domino cyclization/cycloaddition cascade of metallo carbenoids has evolved as an important strategy for the synthesis of nitrogen containing natural products.

Domino reactions of rhodium(II) carbenoids for alkaloid synthesis

Total synthesis of (-)-colchicine via a Rh-triggered cycloaddition cascade.

[reaction: see text] A synthesis of the antimitotic alkaloids (-)-colchicine and (-)-isocolchicine is reported. Important steps are (a) enantioselective transfer-hydrogenation of an alkynone, (b) iodine/magnesium exchange with subsequent aromatic acylation, (c) Rh-catalyzed transformation of an alpha-diazoketone into an oxatetracyclic key intermediate through intramolecular [3 + 2]-cycloaddition of an in situ generated carbonyl ylide, and (d) regioselective conversion of the cycloadduct into a tropolone derivative. The new synthetic strategy opens an efficient enantioselective access to colchicine and structural analogues.

/pdf/total-synthesis-of-colchicine-via-a-rh-triggered-268c1nbt0n.pdf

Virginie Bette

Papers

Total synthesis of (-)-colchicine via a Rh-triggered cycloaddition cascade.

Total Synthesis of (-)-Colchicine via a Rh-Triggered Cycloaddition Cascade