- Nitrile ylide dimerization: Investigation of the carbene reactivity of nitrile ylides
-
A series of novel hexaaryl diazatrienes 5 ("nitrile ylide dimers") were synthesized directly from the corresponding diaryl ketimines 12 and dichlorotoluenes 13 in a facile one-pot synthesis. The carbene character of the nitrile ylides was investigated by varying the substituents on the aromatic ring adjacent to the carbene center. The isolation of the corresponding carbene dimers as stable crystalline materials with absorption maxima (λmax) from 363 to 422 nm was shown to be promoted by the absence of strongly electron-withdrawing substituents. The crystal structures indicate that the E-isomers were isolated when phenyl, 3-methylphenyl, and 3-chlorophenyl substituents are present at the carbene carbon; the Z-isomer was isolated when the more sterically hindered 2,4,6-trimethylphenyl substituent (Mes) is present. The 1H NMR spectra of the E-isomers demonstrate the nonequivalence of the aromatic rings, in which two of the aromatic rings of the imine moiety are pseudoaxial and the remaining aromatic rings are pseudoequatorial. The reactions proceed via the intermediate nitrile ylides 1 generated by the base-promoted 1,1-elimination of HCl from the intermediate chloroimine 14. The nitrile ylide was also generated by 1,3-elimination of HCl from the imidoyl chloride 18, confirming common pathways via the nitrile ylide as the dimer products obtained from these different routes were identical. The strongly electron-withdrawing 4-nitrophenyl substituent promotes the linear carbanion character of the 1,3-dipole and no dimer is formed.
- Fergus, Suzanne,Eustace, Stephen J.,Hegarty, Anthony F.
-
p. 4663 - 4669
(2007/10/03)
-
- A simple and efficient procedure for the preparation of benzal chlorides and benzal bromides
-
Benzal chlorides and benzal bromides were conveniently synthesized by reaction of aryl aldehydes with a Vilsmeier type reagent formed in situ by reduction of CCl4 or CBr4 in dimethylformamide (DMF) as solvent.
- Léonel, Eric,Paugam, Jean-Paul,Heintz, Monique,Nédélec, Jean-Yves
-
p. 4015 - 4024
(2007/10/03)
-
- New applications of tungsten hexachloride (WCl6) in organic synthesis. Halo-de-hydroxylation and dihalo-de-oxo-bisubstitution reactions
-
Tungsten hexachloride (WCl6) has been used for the halo-de-hydroxylation and dihalo-de-oxo-bisubstitution reactions of benzylic alcohols, benzaldehydes, acyloins, and epoxides to their chlorides, gem-dichlorides, vic-trichlorides, and vic-dichlorides respectively.
- Firouzabadi, Habib,Shiriny, Farhad
-
p. 14929 - 14936
(2007/10/03)
-
- CHARACTERISTICS OF THE INITIATED (RADICAL) CHLORINATION OF m-XYLENE
-
By GLC it was established that the composition of the products from initiated chlorination of m-xylene is determined by the molar ratio of the reagents (m-xylene and chlorine).An assessment of the reactivity of the individual chlorine derivatives of m-xylene is given.
- Kosheleva, L. M.,Rozenberg, V. R.,Motsarev, G. V.
-
p. 1607 - 1610
(2007/10/02)
-