Rearrangement of radicals derived from bicyclo[5.1.0]octa-2,4-diene, tricyclo[6.1.0.02,4]nona-6-ene and tetracyclo[7.1.0.02,4.05,7]decane

Culshaw, Peter N.; Dalton, Michael K.; MacCorquodale, Finlay; Walton, John C.

doi:10.1039/p29900000531

Cited by 9 publications

(2 citation statements)

References 15 publications

(12 reference statements)

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“…Delicate balances of rearrangement possibilities can easily be redirected by structural changes. This was illustrated by the fact that the vinylogous bicyclo[5.1.0]octa‐2,4‐dienyl radical did not undergo an analogous walk 163, 164…”

Section: Repeating and Infinite Free‐radical Cascadesmentioning

confidence: 99%

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

McCarroll

Walton

2001

Angew. Chem. Int. Ed.

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233

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Cascade, domino, or tandem processes, that link together two or more transformations in one pot, are increasing in popularity because they lead to improvements in synthetic efficiency and decreases in environmental impact. Not only do these cascades contain choice mechanistic gems but they also deliver compact and elegant syntheses of complex natural products. Longer cascades require more functional groups precisely configured within carefully designed initial molecular architectures. Such “purposeful” molecules can be thought of as chemical algorithms.This article surveys the phenomenal range of unimolecular free‐radical cascades. A convenient system for classifying free‐radical cascades is described that is useful for evaluating and comparing cascades and aids the design of synthetic routes to polycyclic structures.Double cyclization cascades lead to cyclopentylcyclopentane or bicyclo[3.3.0]octane derivatives. Precursors that contain a ring as a template have been used to control stereochemistry in syntheses of triquinanes and many related compounds. Of the cascades containing ring‐cleavage steps, the most useful are the ring expansions which have opened up new synthetic routes to medium ring polycycles.The key design features of three‐stage unimolecular free‐radical cascades that yielded steroid structures, are linear arrays of radical acceptor units associated with methyl groups distributed every fifth C‐atom in the precursor polyenes. Ring cleavage is the reverse of cyclization. In special, symmetrical structures, therefore, this led to sequences that were reversible, thus launching endlessly repeating cascades supported by delightfully fluxional structures. The science of “programming” organic molecules to achieve particular target structures is maturing rapidly. Coordination and classification of the welter of information in this area is intended to facilitate design and hence to extend the range and complexity of attainable structures.

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Section: Repeating and Infinite Free‐radical Cascadesmentioning

confidence: 99%

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

McCarroll

Walton

2001

Angew. Chem. Int. Ed.

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233

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“…In einem empfindlichen Gleichgewicht stehende Umlagerungsmöglichkeiten kann man leicht durch strukturelle Veränderungen in eine andere Richtung leiten. Dies wird dadurch belegt, dass das vinyloge Bicyclo[5.1.0]octa‐2,4‐dienylradikal keinen analogen Rundgang beschreitet 163, 164…”

Section: Sich Wiederholende Und Endlose Radikalische Kaskadenunclassified

Programmierung organischer Moleküle: Design und Management organischer Synthesen über radikalische Kaskaden

McCarroll

Walton

2001

Angew. Chem.

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1. Einleitung 1.1. Beschreibung, Anwendungsbereich und Nutzen von Kaskadenreaktionen Chemische Prozesse, bei denen zwei oder mehr molekulare Veränderungen räumlich und zeitlich eng verknüpft sind (¹Eintopfreaktionenª), wurden als Kaskaden-, Domino-oder Tandemreaktionen oder auch Reaktionsfolgen bezeichnet. Die Wahrnehmung und das chemische Verständnis solcher Prozesse lassen noch zu wünschen übrig, doch das Tempo der Entwicklung ist in letzter Zeit deutlich schneller geworden, da man ihre tatsächlichen und potentiellen Vorteile mehr und mehr erkennt. Mit ihrer Hilfe kann man die Zahl der für den Aufbau eines komplexen Moleküls nötigen Arbeitsschritte im Labor verringern und damit Arbeits-und Gerätezeit sparen und muss weniger Laborplatz beanspruchen. Damit einher geht ein geringerer Verbrauch von Lösungsmitteln und Chemikalien, und es fallen weniger unerwünschte Begleitprodukte an. All diese Faktoren können die Effizienz einer Synthese beträchtlich verbessern und die Umweltbelastung reduzieren. Dieses Potential im Hinblick auf rationelle Synthesen im Labor und im industriellen Maûstab garantiert den Kaskadenprozessen eine glänzende Zukunft.Je gröûer die Zahl der Kaskadenstufen ist, um so mehr Funktionalitäten müssen sich im sorgfältig entworfenen Startmolekül genau an der richtigen Position befinden. Diese Bedingung kann sehr wohl einige der möglichen Vorteile der Kaskadenmethode aufwiegen. Die Struktur der Vorstufe(n) muss sorgfältig ¹programmiertª werden, wenn eine komple-

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Simmons‐Smith Cyclopropanation Reaction

2001

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Almost 30 years after Emschwiller prepared IZnCH 2 I, Simmons and Smith discovered that the reagent formed by mixing a zinc‐copper couple with CH 2 I 2 in ether could be used for the stereospecific conversion of alkenes to cyclopropanes. Nowadays, the Simmons‐Smith cyclopropanation reaction is one of the most widely used reactions in the organic chemist's arsenal for the conversion of olefins into cyclopropanes. This popularity is mainly due to the stereospecificity of the reaction with respect to the double bond geometry and its compatibility with a wide range of functional groups. The chemoselectivity of the reaction toward some olefins is excellent and very few side reactions are observed with functionalized substrates. The metal carbenoid is electrophilic in nature and electron‐rich alkenes usually react much faster than electron‐poor alkenes. Furthermore, the ability to use proximal hydroxy or ether groups to dictate the stereochemical outcome of the CC bond forming process was recognized early on, and this unique property has been successfully exploited on numerous occasions. It has been recognized that halomethylmetal reagents are powerful synthetic tools for the stereoselective addition of a methylene unit to chiral acyclic allylic alcohols and allylic ethers. In addition, the use of halomethylzinc reagents in the presence of chiral additives is one of the few ways to cyclopropanate allylic alcohols efficiently and with good enantiocontrol. Carbenoids can be divided into the following two classes: (1) those of general structure MCH 2 X and (2) those corresponding to M = CH 2 . This chapter is focussed exclusively on the first class in which M = Zn, Sm, or Al. Although other metal carbenoids of type MCH 2 X, such as those derived from Cu, Cd, Hg, and In, have been reported to be effective reagents for the cyclopropanation of some olefins, they have been used only sporadically, and this review does not highlight these reactions. This chapter covers cyclopropanation reactions involving haloalkylzinc, aluminum, and samarium reagents published since the comprehensive chapter in Organic Reactions by Simmons that surveyed the literature up to 1973.

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Rearrangement of radicals derived from bicyclo[5.1.0]octa-2,4-diene, tricyclo[6.1.0.02,4]nona-6-ene and tetracyclo[7.1.0.02,4.05,7]decane

Cited by 9 publications

References 15 publications

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

Programming Organic Molecules: Design and Management of Organic Syntheses through Free-Radical Cascade Processes

Programmierung organischer Moleküle: Design und Management organischer Synthesen über radikalische Kaskaden

Simmons‐Smith Cyclopropanation Reaction

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