4625-23-4Relevant articles and documents
Rhodium- N-Heterocyclic Carbene Catalyzed Hydroalkenylation Reactions with 2-Vinylpyridine and 2-Vinylpyrazine: Preparation of Nitrogen-Bridgehead Heterocycles
Azpíroz, Ramón,Di Giuseppe, Andrea,Passarelli, Vincenzo,Pérez-Torrente, Jesús J.,Oro, Luis A.,Castarlenas, Ricardo
, p. 1695 - 1707 (2018)
Dinuclear rhodium-NHC complexes of formula [Rh(μ-Cl)(NHC)(η2-coe)]2 react with 2-vinylpyridine to yield the chelate compounds RhCl(NHC)(κ-N,η2-CH2=CHC5H4N) {NHC = IPr, 1,3-bis(2,6-diisoprop
Preparation of Butadienylpyridines by Iridium-NHC-Catalyzed Alkyne Hydroalkenylation and Quinolizine Rearrangement
Azpíroz, Ramón,Castarlenas, Ricardo,Greger, Ingo,Oro, Luis A.,Pérez-Torrente, Jesús J.,Passarelli, Vincenzo
, p. 11868 - 11878 (2021)
Iridium(I) N-heterocyclic carbene complexes of formula Ir(κ2O,O’-BHetA)(IPr)(η2-coe) [BHetA=bis-heteroatomic acidato, acetylacetonate or acetate; IPr=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-carbene; coe=cyclooctene] have been prepared by treating Ir(κ2O,O’-BHetA)(η2-coe)2 complexes with IPr. These complexes react with 2-vinylpyridine to afford the hydrido-iridium(III)-alkenyl cyclometalated derivatives IrH(κ2O,O’-BHetA)(κ2N,C-C7H6N)(IPr) through the iridium(I) intermediate Ir(κ2O,O’-BHetA)(IPr)(η2-C7H7N). The cyclometalated IrH(κ2O,O’-acac)(κ2N,C–C7H6N)(IPr) complex efficiently catalyzes the hydroalkenylation of aromatic and aliphatic terminal alkynes and enynes with 2-vinylpyridine to afford 2-(4R-butadienyl)pyridines with Z,E configuration as the major reaction products (yield up to 89 %). In addition, unprecedented (Z)-2-butadienyl-5R-pyridine derivatives have been obtained as minor reaction products (yield up to 21 %) from the elusive 1Z,3gem-butadienyl hydroalkenylation products. These compounds undergo a thermal 6π-electrocyclization to afford bicyclic 4H-quinolizine derivatives that, under catalytic reaction conditions, tautomerize to 6H-quinolizine to afford the (Z)-2-(butadienyl)-5R-pyridine by a retro-electrocyclization reaction.
A new access to 4 h-quinolizines from 2-vinylpyridine and alkynes promoted by rhodium-N-heterocyclic-carbene catalysts
Azpíroz, Ram?n,Di Giuseppe, Andrea,Castarlenas, Ricardo,Pérez-Torrente, Jesús J.,Oro, Luis A.
supporting information, p. 3812 - 3816 (2013/04/10)
Forging the lock that autolocks! Rh-NHC catalysts promote a new access to 4 H-quinolizine species from 2-vinylpyridine and terminal and internal alkynes through C-H activation and C-C coupling reactions (see figure). N-Bridgehead heterocycle formation is favored for internal- over terminal-substituted butadienylpyridine derivatives in a thermal 6π-electrocyclization process. Copyright
A highly tunable stereoselective olefination of semistabilized triphenylphosphonium ylides with N -Sulfonyl imines
Dong, De-Jun,Li, Hai-Hua,Tian, Shi-Kai
supporting information; experimental part, p. 5018 - 5020 (2010/06/13)
The Wittig reaction involving direct olefination of triphenylphosphonium ylides (Ph3PCHR) with aldehydes is arguably the most often used method for alkene synthesis, but in general it yields mixtures of Z- and E-alkenes for semistabilized triphenylphosphonium ylides (R = aryl or vinyl). We have developed a simple and efficient protocol to improve the stereoselectivity significantly by replacing the aldehydes used in the Wittig reaction with N-sulfonyl imines, which possess distinct electronic and steric properties relative to aldehydes. A broad range of aromatic, α,β-unsaturated, and aliphatic imines bearing appropriate N-sulfonyl groups smoothly undergo olefination reaction with various benzylidenetriphenylphosphoranes or allylidenetriphenylphosphoranes under mild reaction conditions to afford an array of both Z- and E-isomers of conjugated alkenes in good to excellent yields and with greater than 99:1 stereoselectivity. Moreover, this tunable protocol has been successfully applied to the highly stereoselective synthesis of two anticancer agents, DMU-212 and its Z-isomer.
Photoisomerization mechanisms and photoselectivity of the stereoisomers of 1-(pyrid-n-yl),4-phenylbuta-1,3-diene
Bartocci,Galiazzo,Latterini,Marri,Mazzucato,Spalletti
, p. 2911 - 2916 (2007/10/03)
The positional isomers of 1-(pyrid-n-yl),4-phenylbuta-1,3-diene (n = 2, 3 and 4) have been synthesized and characterized by spectrometric techniques. All the four expected stereoisomers (EE, EZ, ZE and ZZ) were prepared for n = 2 while only three and two geometrical isomers were obtained for the positional isomers with n = 3 and 4, respectively. Their excited state properties were investigated by stationary and pulsed fluorimetric techniques and by laser flash photolysis. This paper describes the photochemical behaviour under direct and triplet sensitized excitation. The selective formation of photoproducts and the role of diabatic/adiabatic mechanisms are reported and compared with the results on the direct photoisomerization of the EE and ZE isomers in the singlet manifold described in a previous paper (G. Bartocci, G. Galiazzo, U. Mazzucato and A. Spalletti, Phys. Chem. Chem. Phys., 2001, 3, 379-386).
Photophysics and photochemistry of the EE and ZE isomers of 1-(n-pyridyl)-4-phenyl-1,3-butadiene (n = 2, 3 and 4)
Bartocci,Galiazzo,Mazzucato,Spalletti
, p. 379 - 386 (2007/10/03)
The positional isomers of 1-(n-pyridyl)-4-phenyl-1,3-butadiene (n = 2, 3 and 4) have been synthesized in the EE and ZE geometries by common routes and characterized by spectrometric techniques. Their excited state properties were investigated by stationary and pulsed fluorimetric techniques and by laser flash photolysis. This paper reports the spectral, photophysical and photochemical behaviour of the EE and ZE isomers in a non-polar solvent. The photoisomerization proceeds through singlet, diabatic and/or adiabatic mechanisms with generally low quantum yield, owing to the role of internal conversion (markedly more important for n = 2). The role of intramolecular hydrogen bonds on the excited state properties of the ZE isomer of the 2-pyridyl derivative is particularly described.
STEREOSPECIFIC SYNTHESIS OF (E)-ALKENYLPYRIDINES VIA α-SILYL CARBANION
Konakahara, Takeo,Takagi, Yukio
, p. 2073 - 2076 (2007/10/02)
(E)-2-Alkenylpyridines were stereospecifically prepared from 2-(trimethylsilylmethyl)pyridine and the corresponding (E)-aldimines of anilines by an analogous reaction to the Peterson reaction.
