Aza‐2‐dienes‐1,3. Partie 5. Préparation de N‐aminoimidazoles, 3H‐pyrroles, triazolo[1,2,4][1,5‐a]pyrazines et imidazo[1,2‐a]pyrazines

Legroux, Didier; Schoeni, Jean-Paul; Pont, Christiane; Fleury, Jean‐Pierre

doi:10.1002/hlca.19870700123

Cited by 23 publications

(6 citation statements)

References 7 publications

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“…1 Electron-poor 2-azadienes bearing one or more electronwithdrawing substituents are of particular interest due to their high activity both in cycloadditions 2 and various thermal, 3 catalytic 4 and nucleophile-initiated heterocyclizations. 5 There are two different synthetic approaches to electron-poor 2-azadienes. The first involves the eliminative formation of double bonds in the saturated precursor to give the target azadiene, as, for example, by destruction of 2-aryl-4-thiazolidinecarboxylates under action of Ag 2 CO 3 /DBU 6 or dehydration of arylidene derivatives of serine esters.…”

Section: Introductionmentioning

confidence: 99%

4-Halo-2-azabuta-1,3-dienes as intermediates in the rhodium carbenoid-initiated transformation of 2-halo-2H-azirines into 2,3-dihydroazetes and 2,5-dihydrooxazoles

et al. 2015

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Section: Introductionmentioning

confidence: 99%

4-Halo-2-azabuta-1,3-dienes as intermediates in the rhodium carbenoid-initiated transformation of 2-halo-2H-azirines into 2,3-dihydroazetes and 2,5-dihydrooxazoles

et al. 2015

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“…Depending on the substituents, azapolyenes at ambient temperature can be both stable compounds and reactive intermediates that rapidly and selectively undergo 1,4-, 1,5-, or 1,6-cyclizations to form four-, five-, ,, and six-membered N- and N,O-heterocycles . The most convenient method for the preparation of the starting azapolyenes is the reaction of rhodium carbenoids with isoxazoles or 2 H -azirines (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

Switchable Synthesis of Pyrroles and Pyrazines via Rh(II)-Catalyzed Reaction of 1,2,3-Triazoles with Isoxazoles: Experimental and DFT Evidence for the 1,4-Diazahexatriene Intermediate

et al. 2016

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4-Aminopyrrole-3-carboxylates and pyrazine-2-carboxylates were synthesized from 5-alkoxyisoxazoles and 1-sulfonyl-1,2,3-triazoles by tuning the Rh(II) catalyst and the reaction conditions. The reaction in chloroform at 100 °C under Rh(OAc) catalysis provides 4-aminopyrrole-3-carboxylates in good yields. The use of Rh(Piv) in refluxing toluene results in the formation of 1,2-dihydropyrazine-2-carboxylates as the main products, which can be converted by a one-pot procedure to pyrazine-2-carboxylates by heating with catalytic amounts of TsOH. According to the NMR and DFT investigations of the reaction mechanism, pyrroles and dihydropyrazines are formed, respectively, via 1,5- and 1,6-cyclization of common (5Z)-1,4-diazahexa-1,3,5-triene intermediates. The influence of the nature of the catalyst on the product distribution is rationalized in terms of the Rh-catalyzed isomerization of a pyrrolin-2-ylium-3-aminide zwitterion, the primary product of 1,4-diazahexatriene 1,5-cyclization.

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“…Activation of 2-azabutadiene fragment by electron-withdrawing groups makes these compounds active substrates for (4 + 2)-, (2 + 3)-, (2 + 2)- and (2 + 1)-cycloadditions. These intermolecular reactions along with nucleophile-initiated cyclizations of activated 2-azabutadienes allow constructing a great variety of functionalized 3–6-membered heterocycles. In contrast, only few examples of intramolecular transformations of 2-azabutadienes are known and limited to 1,6- and 1,4-electrocyclizations.…”

Section: Introductionmentioning

confidence: 99%

Pseudopericyclic 1,5- versus Pericyclic 1,4- and 1,6-Electrocyclization in Electron-Poor 4-Aryl-2-azabuta-1,3-dienes: Indole Synthesis from 2H-Azirines and Diazo Compounds

et al. 2014

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Transformations of 2-azabuta-1,3-dienes, formed in Rh2(OAc)4-catalyzed reactions of diazo carbonyl compounds with 2H-azirines, dramatically depend on the nature of substituents. 4,4-Diphenyl-2-azabuta-1,3-dienes with two electron-acceptor substituents at C(1) undergo thermal 1,5-cyclization to give indoles in good yields. The increase in electron-withdrawing ability of C(1)-substituents facilitates the reaction that proceeds via pseudopericyclic 1,5-electrocyclization of 2-azabutadiene into 7aH-indolium ylide followed by prototropic shift. 3,4-Diphenyl-2-azabuta-1,3-dienes, resulting from reaction of 2,3-diphenyl-2H-azirine and diazo compounds, do not produce indoles via 1,5-cyclization due to the trans-configuration of the 4-Ph-group and the nitrogen, but undergo 1,4-cyclization to 2,3-dihydroazetes. 1,6-Cyclization into 2H-1,4-oxazines with participation of the oxygen of ester or amide group at C(1) of corresponding 2-azabuta-1,3-dienes does not take place due to kinetic and thermodynamic reasons. Instead of this, 1,6-electrocyclization with participation of phenyl substituent at C(4) of the 2-azabuta-1,3-dienes, providing isoquinoline derivatives, can occur at elevated temperatures. The DFT-calculations (mPWB1K/6-31+G(d,p)) confirm the dependence of 2-azabuta-1,3-diene transformation type on the nature of substituents.

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Aza‐2‐dienes‐1,3. Partie 5. Préparation de N‐aminoimidazoles, 3H‐pyrroles, triazolo[1,2,4][1,5‐a]pyrazines et imidazo[1,2‐a]pyrazines

Cited by 23 publications

References 7 publications

4-Halo-2-azabuta-1,3-dienes as intermediates in the rhodium carbenoid-initiated transformation of 2-halo-2H-azirines into 2,3-dihydroazetes and 2,5-dihydrooxazoles

4-Halo-2-azabuta-1,3-dienes as intermediates in the rhodium carbenoid-initiated transformation of 2-halo-2H-azirines into 2,3-dihydroazetes and 2,5-dihydrooxazoles

Switchable Synthesis of Pyrroles and Pyrazines via Rh(II)-Catalyzed Reaction of 1,2,3-Triazoles with Isoxazoles: Experimental and DFT Evidence for the 1,4-Diazahexatriene Intermediate

Pseudopericyclic 1,5- versus Pericyclic 1,4- and 1,6-Electrocyclization in Electron-Poor 4-Aryl-2-azabuta-1,3-dienes: Indole Synthesis from 2H-Azirines and Diazo Compounds

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