Knüpfung von CC‐Bindungen durch Addition von Radikalen an Alkene

Giese, Bernd

doi:10.1002/ange.19830951004

Cited by 207 publications

(6 citation statements)

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“…The intramolecular radical addition reactions to the tethered double bond involving both 5-hexenyl and 6-heptenyl radicals 33 have been well studied by Beckwith, , Baldwin, − Giese, Curran, , Stork, and more recently by Rajanbabu. − The efficiency and regiochemistry of such intramolecular cyclization addition reactions have been shown to be controlled by (i) the initial radical structure, (ii) the steric effects resulting from the olefin substitution pattern, and (iii) the geometric constraints on the chain linking the radical center, and the tethered double bond …”

Section: Resultsmentioning

confidence: 99%

Five- and Six-Membered Conformationally Locked 2‘,4‘-Carbocyclicribo-Thymidines: Synthesis, Structure, and Biochemical Studies

et al. 2007

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Two unusual reactions involving the 5-hexenyl or the 6-heptenyl radical cyclization of a distant double bond at C4' and the radical center at C2' of the ribofuranose ring of thymidine have been used as key steps to synthesize North-type conformationally constrained cis-fused bicyclic five-membered and six-membered carbocyclic analogues of LNA (carbocyclic-LNA-T) and ENA (carbocyclic-ENA-T) in high yields. Their structures have been confirmed unambiguously by long range 1H-13C NMR correlation (HMBC), TOCSY, COSY, and NOE experiments. The carbocyclic-LNA-T and carbocyclic-ENA-T were subsequently incorporated into the antisense oligonucleotides (AONs) to show that they enhance the Tm of the modified AON/RNA heteroduplexes by 3.5-5 degrees C and 1.5 degrees C/modification for carbocyclic-LNA-T and carbocyclic-ENA-T, respectively. Whereas the relative RNase H cleavage rates with carbocyclic-LNA-T, carbocyclic-ENA-T, aza-ENA-T, and LNA-T modified AON/RNA duplexes were found to be very similar to that of the native counterpart, irrespective of the type and the site modification in the AON strand, a single incorporation of carbocyclic-LNA and carbocyclic-ENA into AONs leads to very much more enhanced nuclease stability in the blood serum (stable >48 h) as compared to that of the native (fully degraded <3 h) and the LNA-modified AONs (fully degraded <9 h) and aza-ENA ( approximately 85% stable in 48 h). Clearly, remarkably enhanced lifetimes of these carbocyclic-modified AONs in the blood serum may produce the highly desired pharmacokinetic properties because of their unique stability and consequently a net reduction of the required dosage. This unique quality as well as their efficient use as the AON in the RNase H-promoted cleavage of the target RNA makes our carbocyclic-LNA and carbocyclic-ENA modifications excellent candidates as potential antisense therapeutic agents.

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Section: Resultsmentioning

confidence: 99%

Five- and Six-Membered Conformationally Locked 2‘,4‘-Carbocyclicribo-Thymidines: Synthesis, Structure, and Biochemical Studies

et al. 2007

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“…An electron‐poor radical prefers to react with an electron‐rich monomer and vice versa; this leads to an alternating copolymer. This effect is known in physical organic chemistry, but in recent years it has been placed on a quantitative basis by the work of Giese15 and Fischer and Radom 16. A complete discussion of this problem was presented in an earlier highlight 17…”

Section: Alternating Copolymerizationmentioning

confidence: 99%

Organic and polymer chemistry of electrophilic tri‐ and tetrasubstituted ethylenes

Hall

Padías

2004

J. Polym. Sci. A Polym. Chem.

135

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A survey of the spontaneous reactions of electrophilic olefins and nucleophilic olefins is presented as an area in which organic chemistry merges with polymer chemistry. The products include both small molecules and polymers, arising via tetramethylene biradical zwitterions that can cyclize or initiate polymerizations. Electrophilic tri-and tetrasubstituted olefins are particularly useful in delineating the transition from radical chemistry to ionic chemistry. A periodic table embodying these results enables predictions. Charge-transfer complexes, although observed in many of these reactions, play no significant role. Various aspects arising from these investigations include new cationic initiators, Lewis acid catalysis, quinodimethane chemistry, and photochemistry.

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“…Nucleophilic carbon-centred radicals I proceed to add to electron-deficient olefins at rates on the order of 10 6 M −1 s −1 . 3 b ,5 Conveniently, this rate is faster than that of the common counter-productive reactions, including atom-transfer reactions with sensitive functional groups such as alcohols and amines, as well as carbonyl additions, which are on the order of 10 2 M −1 s −1 . 6 This difference in rates underscores the chemoselective advantage of radical conjugate additions, which can proceed in the presence of unprotected functional groups.…”

Section: Introductionmentioning

confidence: 98%