One or More CH and/or CC Bond(s) Formed by Rearrangement

Ducrot, Paul‐Henri

doi:10.1016/b0-08-044655-8/00009-x

Cited by 6 publications

(3 citation statements)

References 420 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Inspired by the observation of competitive 1,2-alkyl migration during cycloisomerization of selenoalkynone 16a into 3-alkyl-furan 18 (Table , entries 1−3), we envisioned that development of a cascade transformation involving a 1,2-migration of an alkyl/aryl group 8k,,,, in allenylketones is also feasible. If successful, this approach may allow for the rapid assembly of fully carbon-substituted furans.…”

Section: Resultsmentioning

confidence: 99%

Metal-Catalyzed 1,2-Shift of Diverse Migrating Groups in Allenyl Systems as a New Paradigm toward Densely Functionalized Heterocycles

et al. 2008

View full text Add to dashboard Cite

A general, mild, and efficient 1,2-migration/cycloisomerization methodology toward multisubstituted 3-thio-, seleno-, halo-, aryl-, and alkyl-furans and pyrroles, as well as fused heterocycles, valuable building blocks for synthetic chemistry, has been developed. Moreover, regiodivergent conditions have been identified for C-4 bromo- and thio-substituted allenones and alkynones for the assembly of regioisomeric 2-hetero substituted furans selectively. It was demonstrated that, depending on reaction conditions, ambident substrates can be selectively transformed into furan products, as well as undergo selective 6-exo-dig or Nazarov cyclizations. Our mechanistic investigations have revealed that the transformation proceeds via allenylcarbonyl or allenylimine intermediates followed by 1,2-group migration to the allenyl sp carbon during cycloisomerization. It was found that 1,2-migration of chalcogens and halogens predominantly proceeds via formation of irenium intermediates. Analogous intermediate can also be proposed for 1,2-aryl shift. Furthermore, it was shown that the cycloisomerization cascade can be catalyzed by Brønsted acids, albeit less efficiently, and commonly observed reactivity of Lewis acid catalysts cannot be attributed to the eventual formation of proton. Undoubtedly, thermally induced or Lewis acid-catalyzed transformations proceed via intramolecular Michael addition or activation of the enone moiety pathways, whereas certain carbophilic metals trigger carbenoid/oxonium type pathway. However, a facile cycloisomerization in the presence of cationic complexes, as well as observed migratory aptitude in the cycloisomerization of unsymmetrically disubstituted aryl- and alkylallenes, strongly supports electrophilic nature for this transformation. Full mechanistic details, as well as the scope of this transformation, are discussed.

show abstract

Section: Resultsmentioning

confidence: 99%

Metal-Catalyzed 1,2-Shift of Diverse Migrating Groups in Allenyl Systems as a New Paradigm toward Densely Functionalized Heterocycles

et al. 2008

View full text Add to dashboard Cite

show abstract

“…Considering the enhanced electrophilicity of the sp 3 center 1b in intermediate i, we envisioned that incorporation of a suitable 1,2-migrating group (MG) in ii would provoke a subsequent 1,2-shift 6 into iii, which upon proton loss and protiodeauration would afford 1,3diene 7 3. It is reasonable to propose that the latter may undergo 6π-electrocyclization into naphthalene 8,9 2, analogously to the known cyclization of acyloxy-1,3,5-trienes 10 (eq 3).…”

mentioning

confidence: 99%

“…12,23,24 Successful cycloisomerization of 3e, obtained via 1,3-migration/elimination cascade, into naphthalene 2e provided an additional support for possible intermediacy of 1,3-dienes in this transformation (eq 6). (6) In summary, we have developed a novel gold(I)-catalyzed approach toward polysubstituted naphthalenes, which features an unprecedented tandem sequence of 1,3-and 1,2-migration of different migrating groups in propargylic esters. A more detailed investigation on the mechanism, as well as the scope of this cascade, is ongoing and will be reported in due course.…”

mentioning

confidence: 99%

Gold-Catalyzed Double Migration-Benzannulation Cascade toward Naphthalenes

2008

View full text Add to dashboard Cite

A novel gold(I)-catalyzed cycloisomerization of propargylic esters leading to unsymmetrically substituted naphthalenes has been developed. This cascade reaction involves an unprecedented tandem sequence of 1,3- and 1,2-migration of two different migrating groups. It is believed that this transformation likely proceeds via the formation of 1,3-diene intermediate or its precursor, which upon cyclization and aromatization steps transforms into the naphthalene core.

show abstract

Metal‐Catalyzed [1,2]‐Alkyl Shift in Allenyl Ketones: Synthesis of Multisubstituted Furans

Dudnik

Gevorgyan

2007

Angewandte Chemie

View full text Add to dashboard Cite

Sogar kondensierte Furane sind durch die Cycloisomerisierung substituierter Allenylketone zugänglich. Schlüsselschritt der Kaskadenreaktion ist die [1,2]‐Wanderung von Alkyl‐ oder Arylgruppen in Allenylketonen. Die einfache Reaktion in Gegenwart kationischer Komplexe sowie die Eignung für die Cycloisomerisierung unsymmetrisch substituierter Allene sprechen überzeugend für einen elektrophilen Mechanismus dieser Umwandlung.

show abstract

One or More CH and/or CC Bond(s) Formed by Rearrangement

Cited by 6 publications

References 420 publications

Metal-Catalyzed 1,2-Shift of Diverse Migrating Groups in Allenyl Systems as a New Paradigm toward Densely Functionalized Heterocycles

Metal-Catalyzed 1,2-Shift of Diverse Migrating Groups in Allenyl Systems as a New Paradigm toward Densely Functionalized Heterocycles

Gold-Catalyzed Double Migration-Benzannulation Cascade toward Naphthalenes

Metal‐Catalyzed [1,2]‐Alkyl Shift in Allenyl Ketones: Synthesis of Multisubstituted Furans

Contact Info

Product

Resources

About