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Stephan Enthaler - One of the best experts on this subject based on the ideXlab platform.

Thibault Cantat - One of the best experts on this subject based on the ideXlab platform.

  • Reductive functionalization of CO2 with amines: an entry to formamide, Formamidine and methylamine derivatives
    Green Chemistry, 2015
    Co-Authors: Anis Tlili, Enguerrand Blondiaux, Xavier Frogneux, Thibault Cantat
    Abstract:

    CO2 utilization for the production of C1-containing molecules is a desirable route to value-added chemicals. In this perspective, we summarize the recent results devoted to the formation of nitrogen compounds obtained by reductive functionalization of CO2 in the presence of amines. Using mild reductants, such as molecular hydrogen, hydrosilanes and hydroboranes, novel catalytic reactions have been designed in the last few years to facilitate the reductive functionalization of CO2 to formamide, Formamidine and methylamine derivatives. While early efforts were devoted to the formylation of N-H bonds, efficient organic and metal catalysts have been developed lately to promote the complete deoxygenation of CO2 to benzimidazoles, quinazolinones, Formamidines and methylamines. Finally, the opportunities and challenges facing the practical use of CO2 in the production of nitrogen-containing molecules are discussed.

  • pushing back the limits of hydrosilylation unprecedented catalytic reduction of organic ureas to Formamidines
    ChemInform, 2014
    Co-Authors: Jacky Pouessel, Olivier Jacquet, Thibault Cantat
    Abstract:

    A novel catalytic transformation is designed to prepare Formamidine derivatives by reduction of substituted symmetrical and unsymmetrical ureas with hydrosilane.

  • pushing back the limits of hydrosilylation unprecedented catalytic reduction of organic ureas to Formamidines
    Chemcatchem, 2013
    Co-Authors: Jacky Pouessel, Olivier Jacquet, Thibault Cantat
    Abstract:

    Catalytic hydrosilylation of carbonyl functional groups is gaining an increasing interest in synthetic organic chemistry because it circumvents important limitations of the more classical hydrogenation or metal-hydride mediated reduction methodologies. Indeed, hydrosilanes are practical reducing agents because they have a mild reduction potential and are less sensitive to moisture than LiAlH4, DIBAL or NaBH4. Moreover, the slightly polar and weaker Si–H bond (bond dissociation energy (BDE) 92 kcal/mol in SiH4) [2] is easier to activate than the strong non-polar H–H bond (BDE 104 kcal/mol) and hydrosilylation reactions can be promoted using noble metal-free catalysts or organocatalysts under mild reaction conditions, without the need for high-pressure apparatus. As a result, catalytic hydrosilylation can achieve highly chemoand regio-selective transformations and recent examples include the reduction of carboxylic acids, esters (to ethers and aldehydes) and amides. Nonetheless, the methodology still has limitations and, so far, the catalytic hydrosilylation of organic ureas to Formamidines remains unknown. Indeed, the C=O group in urea derivatives is the least electrophilic function within the series of carbonyl groups in aldehydes, ketones, esters, amides, carbonates, carbamates and ureas. This effect primarily results from strong resonance effects between the vacant π*C=O orbital and the vicinal nitrogen lone pairs in urea. As a result, strong reductants such as aluminoand boro-hydrides have been utilized so far for the reduction of urea derivatives to Formamidines. However, they also lead to over-reduction to the aminal derivative, because the Formamidine product is more easily reduced than the urea starting material. In 2011, Milstein and coworkers were the first to successfully promote the hydrogenation of organic ureas, utilizing tailor-made ruthenium catalysts. However, the ruthenium catalysts promote C–N over C–O bond cleavage and the resulting formamide intermediate is hydrogenated faster than the urea starting material, leading to the formation of methanol and free amines (Scheme 1).

Matthias Driess - One of the best experts on this subject based on the ideXlab platform.

Anne Petitjean - One of the best experts on this subject based on the ideXlab platform.

  • alkoxyamine derived Formamidines configurational control and molecular folding
    Organic Letters, 2011
    Co-Authors: Weiwen Zhao, Ruiyao Wang, Nicholas J. Mosey, Anne Petitjean
    Abstract:

    N,N′-Disubstituted Formamidines, and amidines in general, have very rich configurational, conformational, and tautomeric diversities. As part of an effort to incorporate alkoxyamine-derived Formamidine units into foldamers, the first evidence for the isolation of the up-to-now unknown E isomer, the conditions for its exclusive formation, its stability and self-assembly properties, and its configurational isomerization to its much more common Z counterpart are reported. Considering the distinctly different H-bonding patterns displayed by both E and Z isomers, such configurational control may find applications in self-assembly, molecular recognition, and biomimetic systems.

  • amine exchange in Formamidines an experimental and theoretical study
    Chemistry: A European Journal, 2011
    Co-Authors: Marinha Df Capela, Liyan Xing, Ruiyao Wang, Nicholas J. Mosey, Anne Petitjean
    Abstract:

    : N-H-containing Formamidines combine a reasonably strong association to carboxylic acids to form complexes of well-defined geometries with a simultaneous proton-induced electrophilicity enhancement that allows for the exchange of their amine portion. The N=C(H)-NH fragment, therefore, undergoes "imine-like" exchange with N-containing nucleophiles. Because of the prototropic equilibrium, the N=C(H)-NH fragment may behave as a "bisimine" centred on the same carbon, in which both N-containing fragments can be exchanged. Considering the proton-induced sensitisation of both C-N units and the well-defined Formamidine-carboxylic acid complex geometry, it should be possible to use carboxylic acids as templates for the synthesis of defined architectures by dynamic amine exchange within Formamidines. This study highlights three exchange regimes based on the nature of the incoming amine (aliphatic amines, aromatic amines and alkoxyamines), as well as exchange rules based on the amine leaving groups. Following this analysis, a proof of concept for carboxylic acid templated macrocycle formation through dynamic exchange is provided.

  • functional Formamidines pyridine substituents make an exception in the usual doubly hydrogen bonded Formamidine dimer
    CrystEngComm, 2010
    Co-Authors: Anne Petitjean, Liyan Xing, Ruiyao Wang
    Abstract:

    N,N′-DipyridylFormamidine isomers crystallize differently depending on the position of the pyridyl nitrogen. The 2-pyridyl isomer self-assembles into a quadruply hydrogen-bonded dimeric macrocycle, whereas the 4-pyridyl isomer forms a hydrogen-bonded polymer. It is therefore possible to control the formation of the traditional Formamidine dimer based on the positioning of basic residues.

  • stereochemical and conformational exchanges in n n di 2 pyridyl Formamidines an x ray and 1h nmr study
    Journal of Organic Chemistry, 2009
    Co-Authors: Liyan Xing, Charline Wiegert, Anne Petitjean
    Abstract:

    The solid state structure of N,N′-di(2-pyridyl)Formamidine displays a four-hydrogen-bonded dimer. In solution, two isomers are observed, one of which is selected and amplified either by crystallization or by adding protons. Solution state analysis of N,N′-di(2-pyridyl)Formamidines reveals the presence of the uncommon Z Formamidine isomer, which equilibrates with the E-isomer with an activation energy of 90 kJ mol−1 in CDCl3.

  • Stereochemical and Conformational Exchanges in N,N′-Di(2-pyridyl)Formamidines: An X-ray and 1H NMR Study
    The Journal of organic chemistry, 2009
    Co-Authors: Liyan Xing, Charline Wiegert, Anne Petitjean
    Abstract:

    The solid state structure of N,N'-di(2-pyridyl)Formamidine displays a four-hydrogen-bonded dimer. In solution, two isomers are observed, one of which is selected and amplified either by crystallization or by adding protons. Solution state analysis of N,N'-di(2-pyridyl)Formamidines reveals the presence of the uncommon Z Formamidine isomer, which equilibrates with the E-isomer with an activation energy of 90 kJ mol(-1) in CDCl(3).

Matthias Beller - One of the best experts on this subject based on the ideXlab platform.