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26 results on '"Grosjean, Christophe"'

4. The Strecker reaction of benzaldehyde, amines and cyanide : some mechanistic and synthetic studies

Author

Grosjean, Christophe

Subjects
541.39
Abstract

The Strecker reaction involves the formation of aminonitriles by the reaction of an aldehyde with an amine in the presence of cyanide ions. In this work kinetic, equilibrium and synthetic measurements have been made using benzaldehyde, or 4-nitrobenzaldehyde, as the aldehyde and benzylamine or allylamine as the amine. A side reaction involves the formation of a cyanohydrin from benzaldehyde and cyanide ion. The equilibria involved m the reaction and their pH dependence have been examined. For comparison values for the equilibrium constants for the reaction of benzaldehyde with sulfite are also reported. The syntheses and structural characterisations of N-benzylidene benzylamine, N-benzylidene allylamine and N-(4-nitro)-benzylidene benzylamine are reported. A major part of the thesis is concerned with the kinetics and equilibria involved in the reaction of N-benzylidene benzylamine and N-benzylidene allylamine with cyanide in aqueous solutions. The results are compatible with the rate-determining step involving reaction of the corresponding iminium ions with cyanide ions. The pH profile is bell-shaped with a plateau between pH = 6.5 and 8.5 defined by the pK(_a) values of the iminium ions and hydrogen cyanide. pK(_a) values of 6.14 ± 0.1 and 6.05 ± 0.1 have been calculated for N- benzylidene benzyliminium and N-benzylidene allyliminium ions respectively. Rate constants for reaction of cyanide ion with these cations are 6.70x10(^3) and 1.03x10(^4) dm(^3)mol(^-1)s(^-1) respectively. The hydrolysis reactions of imines to yield benzaldehyde have also been quantitatively investigated. The relatively low reactivity found for those iminium ions may be attributed to charge delocalisation in the aromatic ring. An important aspect of the Strecker reaction is the possibility of forming enantiomerically pure products. The asymmetric catalysis by Salen metal complexes of the reaction of the imines with trimethylsilyl cyanide in organic solvents has been investigated. Various methods for the determination of the enantiomeric excess were tested and the most reliable was found to be use of camphorsulfonic acid. The reaction carried out in the presence of a Salen V(V) complex was optimised to yield aminonitriles in a 80% e.e. at -30 C and 69% e.e. at room temperature. Trifluoroacetic anhydride (TFFA) has been reported in the literature as a reagent for reaction with aminonitriles to allow the separation of enantiomers. Here the reaction of imines with TFAA in acetonitrile and in benzene has been investigated In each solvent there are strong reactions yielding hifluoroacetylated derivatives which are thought to exist in both ionic and covalentiy-bound forms.

Published
2004

8. A (-)-sparteine-directed highly enantioselective synthesis of boroproline: solid- and solution-state structure and properties

Author

Batsanov, Andrei S., Grosjean, Christophe, Schutz, Thorben, and Whiting, Andrew

Subjects
Enantiomers -- Chemical properties, Solid state chemistry -- Research, Proline -- Chemical properties, Biological sciences, Chemistry
Abstract

A two-step, (-)-sparteine-directed highly enantioselective synthesis of boroproline is being described. The methodology used gives better solid- and solution-state structure and properties to the compound.

Published
2007

10. Solvent Selection Methods and Tool

Author

Piccione, Patrick M., primary, Baumeister, Julia, additional, Salvesen, Thomas, additional, Grosjean, Christophe, additional, Flores, Yannick, additional, Groelly, Eliane, additional, Murudi, Vikrant, additional, Shyadligeri, Ashok, additional, Lobanova, Olga, additional, and Lothschütz, Christian, additional

Published
2019
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11. An effective approach to same sign top pair production at the LHC and the forward–backward asymmetry at the Tevatron

Author

UCL - SST/IRMP - Institut de recherche en mathématique et physique, Degrande, Céline, Gérard, Jean-Marc, Grosjean, Christophe, Maltoni, Fabio, Servant, Géraldine, UCL - SST/IRMP - Institut de recherche en mathématique et physique, Degrande, Céline, Gérard, Jean-Marc, Grosjean, Christophe, Maltoni, Fabio, and Servant, Géraldine

Abstract

We study the phenomenology of same sign top pair production at the LHC in a model-independent way. The complete set of dimension six operators involving two top (or anti-top) quarks is introduced and the connection with all possible t- or s-channel heavy particle exchanges is established. Only in the former case, same and opposite sign top pair production can be related. We find that while current Tevatron data disfavor t-channel models, other production mechanisms are viable and can be tested at the LHC.

Published
2011

25. A Catalytic Aldol Reaction and Condensation through In 4;Situ Boron “Ate” Complex Enolate Generation in WaterWe thank the EPSRC for research grants (GR/R24722/01, GR/S85368/01, and GR/T22759/01) and GlaxoSmithKline Pharmaceuticals for a CASE award (to A.R.B.). We also thank Dr. M. Crampton (Durham University) for helpful discussions and the EPSRC MS service, Swansea.

Author

Aelvoet, Karel, Batsanov, Andrei 4;S., Blatch, Alexandrea 4;J., Grosjean, Christophe, Patrick, Leonard 4;G. 4;F., Smethurst, Christian 4;A., and Whiting, Andrew

Abstract

No Abstract

Published
2008
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26. Catalytic, asymmetric Strecker reactions catalysed by titaniumIV and vanadiumV(salen) complexes

Author

Blacker, John, Clutterbuck, Lisa A., Crampton, Michael R., Grosjean, Christophe, and North, Michael

Subjects
*IMINES, *ORGANONITROGEN compounds, *NITROGEN compounds, *NITROGEN
Abstract

Abstract: VanadiumV(salen) complex 3 has been found to be an effective catalyst for the asymmetric addition of hydrogen cyanide (generated in situ from trimethylsilyl cyanide) to imines. The best results (up to 81% enantiomeric excess) were obtained for aromatic imines in which the nitrogen atom is protected with a benzyl group and in which the imine bond is not sterically encumbered. [Copyright &y& Elsevier]

Published
2006
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