Rabih Jahjah - Academia.edu (original) (raw)
Papers by Rabih Jahjah
Journal of Molecular Catalysis A-chemical, May 1, 2008
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Tetrahedron-asymmetry, Jun 1, 2007
Novel P-chirogenic anisylphenyl-HMOP derivatives have been synthesised from (R)-2, 2′-bis-(triflu... more Novel P-chirogenic anisylphenyl-HMOP derivatives have been synthesised from (R)-2, 2′-bis-(trifluoromethanesulfonyloxy) 1, 1′-binaphthyl. Preliminary results concerning the asymmetric hydrogenation of acetophenone and 3, 5-bis (trifluoromethyl) acetophenone ...
International Journal of Organic Chemistry, 2018
Chemistry - A European Journal, 2010
The stereo- and regioselectivity of triplet-sensitised radical reactions of furanone derivatives ... more The stereo- and regioselectivity of triplet-sensitised radical reactions of furanone derivatives have been investigated. Furanones 7a,b were excited to the (3)pipi* state by triplet energy transfer from acetone. Intramolecular hydrogen abstraction then occurred such that hydrogen was transferred from the tetrahydropyran to the beta position of the furanone moiety. Radical combination of the tetrahydropyranyl and the oxoallyl radicals led to the final products 8a,b. In the intramolecular reaction, overall, a pyranyl group adds to the alpha position of the furanone. The effect of conformation was first investigated with compounds 9a,b carrying an additional substituent on the tether between the furanone and pyranyl moiety. Further information on the effect of conformation and the relative configuration at the pyranyl anomeric centre and the furanone moiety was obtained from the transformations of the glucose derivatives 12, 14, 17 and 18. Radical abstraction occurred at the anomeric centre and at the 5'-position of the glucosyl moiety. Computational studies of the hydrogen-abstraction step were carried out with model structures. The activation barriers of this step for different stereoisomers and the abstraction at the anomeric centre and at the 6'-position of the tetrahydropyranyl moiety were calculated. The results of this investigation are in accordance with experimental observations. Furthermore, they reveal that the reactivity and regioselectivity are mainly determined in the hydrogen-abstraction step. Intramolecular hydrogen abstraction (almost simultaneous electron and proton transfer) in (3)pipi* excited furanones only takes place under restricted structural conditions in a limited number of conformations that are defined by the relative configuration of the substrates. It is observed that in the biradical intermediate, back-hydrogen transfer occurs leading to the starting compound. In the case of glucose derivatives, this reaction led to epimerisation at the anomeric centre.
International Journal of Organic Chemistry
Several types of solid acid catalysts were prepared based on oxides like (ZrO 2 , TiO 2 , HfO 2 ,... more Several types of solid acid catalysts were prepared based on oxides like (ZrO 2 , TiO 2 , HfO 2 , MCM-41 and SBA-15), using two main preparation methods: the precipitation and the sol-gel methods. Each catalyst was subjected to two types of impregnations: sulfate ions using sulfuric acid as precursor and niobium using niobium oxalate as precursor. These prepared catalysts were tested in the etherification reaction of 2-naphtol, where the catalysts showed both acidic and redox properties. The acidic character was manifested through the formation of 2-butoxynaphtalene (with moderate yields) when oxide is sulfated, and the redox character (when impregnated with niobium) manifested through the formation of the interesting product 2-ethylnaphtofuran (with low yields) and other products that were a result of oxidative coupling of two 2-naphtol molecules (binol and acetal of binol). However despite the effort, several attempts to increase the yield of 2-ethylnaphtofuran did not work. All products prepared were obtained in pure form and characterized by 1 H and 13 C NMR, GC and MS.
Main Group Chemistry, 2015
Tetrahedron: Asymmetry, 2007
Novel P-chirogenic anisylphenyl-HMOP derivatives have been synthesised from (R)-2, 2′-bis-(triflu... more Novel P-chirogenic anisylphenyl-HMOP derivatives have been synthesised from (R)-2, 2′-bis-(trifluoromethanesulfonyloxy) 1, 1′-binaphthyl. Preliminary results concerning the asymmetric hydrogenation of acetophenone and 3, 5-bis (trifluoromethyl) acetophenone ...
The Journal of Organic Chemistry, 2011
Journal of Molecular Catalysis A: Chemical, 2008
New chiral oxazoline-based ruthenium(II) complexes have been synthetized and fully characterised.... more New chiral oxazoline-based ruthenium(II) complexes have been synthetized and fully characterised. The corresponding grafted catalysts were prepared by anchoring the complexes onto SiO 2 or Pd/SiO 2 supports. 13 C CP-MAS NMR and XPS spectroscopies showed that the organometallic complexes remained unchanged when they were deposited on the support. High activity and enantioselectivity in the reduction of acetophenone were achieved with some homogeneous complexes.
Chemistry - A European Journal, 2010
Journal of Molecular Catalysis A-chemical, May 1, 2008
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Tetrahedron-asymmetry, Jun 1, 2007
Novel P-chirogenic anisylphenyl-HMOP derivatives have been synthesised from (R)-2, 2′-bis-(triflu... more Novel P-chirogenic anisylphenyl-HMOP derivatives have been synthesised from (R)-2, 2′-bis-(trifluoromethanesulfonyloxy) 1, 1′-binaphthyl. Preliminary results concerning the asymmetric hydrogenation of acetophenone and 3, 5-bis (trifluoromethyl) acetophenone ...
International Journal of Organic Chemistry, 2018
Chemistry - A European Journal, 2010
The stereo- and regioselectivity of triplet-sensitised radical reactions of furanone derivatives ... more The stereo- and regioselectivity of triplet-sensitised radical reactions of furanone derivatives have been investigated. Furanones 7a,b were excited to the (3)pipi* state by triplet energy transfer from acetone. Intramolecular hydrogen abstraction then occurred such that hydrogen was transferred from the tetrahydropyran to the beta position of the furanone moiety. Radical combination of the tetrahydropyranyl and the oxoallyl radicals led to the final products 8a,b. In the intramolecular reaction, overall, a pyranyl group adds to the alpha position of the furanone. The effect of conformation was first investigated with compounds 9a,b carrying an additional substituent on the tether between the furanone and pyranyl moiety. Further information on the effect of conformation and the relative configuration at the pyranyl anomeric centre and the furanone moiety was obtained from the transformations of the glucose derivatives 12, 14, 17 and 18. Radical abstraction occurred at the anomeric centre and at the 5'-position of the glucosyl moiety. Computational studies of the hydrogen-abstraction step were carried out with model structures. The activation barriers of this step for different stereoisomers and the abstraction at the anomeric centre and at the 6'-position of the tetrahydropyranyl moiety were calculated. The results of this investigation are in accordance with experimental observations. Furthermore, they reveal that the reactivity and regioselectivity are mainly determined in the hydrogen-abstraction step. Intramolecular hydrogen abstraction (almost simultaneous electron and proton transfer) in (3)pipi* excited furanones only takes place under restricted structural conditions in a limited number of conformations that are defined by the relative configuration of the substrates. It is observed that in the biradical intermediate, back-hydrogen transfer occurs leading to the starting compound. In the case of glucose derivatives, this reaction led to epimerisation at the anomeric centre.
International Journal of Organic Chemistry
Several types of solid acid catalysts were prepared based on oxides like (ZrO 2 , TiO 2 , HfO 2 ,... more Several types of solid acid catalysts were prepared based on oxides like (ZrO 2 , TiO 2 , HfO 2 , MCM-41 and SBA-15), using two main preparation methods: the precipitation and the sol-gel methods. Each catalyst was subjected to two types of impregnations: sulfate ions using sulfuric acid as precursor and niobium using niobium oxalate as precursor. These prepared catalysts were tested in the etherification reaction of 2-naphtol, where the catalysts showed both acidic and redox properties. The acidic character was manifested through the formation of 2-butoxynaphtalene (with moderate yields) when oxide is sulfated, and the redox character (when impregnated with niobium) manifested through the formation of the interesting product 2-ethylnaphtofuran (with low yields) and other products that were a result of oxidative coupling of two 2-naphtol molecules (binol and acetal of binol). However despite the effort, several attempts to increase the yield of 2-ethylnaphtofuran did not work. All products prepared were obtained in pure form and characterized by 1 H and 13 C NMR, GC and MS.
Main Group Chemistry, 2015
Tetrahedron: Asymmetry, 2007
Novel P-chirogenic anisylphenyl-HMOP derivatives have been synthesised from (R)-2, 2′-bis-(triflu... more Novel P-chirogenic anisylphenyl-HMOP derivatives have been synthesised from (R)-2, 2′-bis-(trifluoromethanesulfonyloxy) 1, 1′-binaphthyl. Preliminary results concerning the asymmetric hydrogenation of acetophenone and 3, 5-bis (trifluoromethyl) acetophenone ...
The Journal of Organic Chemistry, 2011
Journal of Molecular Catalysis A: Chemical, 2008
New chiral oxazoline-based ruthenium(II) complexes have been synthetized and fully characterised.... more New chiral oxazoline-based ruthenium(II) complexes have been synthetized and fully characterised. The corresponding grafted catalysts were prepared by anchoring the complexes onto SiO 2 or Pd/SiO 2 supports. 13 C CP-MAS NMR and XPS spectroscopies showed that the organometallic complexes remained unchanged when they were deposited on the support. High activity and enantioselectivity in the reduction of acetophenone were achieved with some homogeneous complexes.
Chemistry - A European Journal, 2010