Efficient metal-free hydrosilylation of tertiary, secondary and primary amides to amines

International audienceHydrosilylation of secondary and tertiary amides to amines is described using catalytic amounts of B(C6F5)3. The organic catalyst enables the reduction of amides with cost-efficient, non-toxic and air stable PMHS and TMDS hydrosilanes. The methodology was successfully extended to the more challenging reduction of primary amides

Recyclage du CO2 : Une alternative à la pétrochimie pour la synthèse de molécules azotées

The fossil carbon resources (oil, coal, gas) cover 85% of world energy portfolio and serve as raw materials for 95% of organic chemicals consumables (plastics, fertilizers, pesticides...). The decrease of oil resources and the accumulation of CO2 arising from their use thus pose environmental, energetic and availability of raw materials problems for the chemical industry. In this context, it is appropriate to propose new methods of chemical synthesis to build a sustainable industry based on the use of renewable carbon resources. Bypassing petrochemicals and valorize its carbon waste, CO2, to build molecular structures without energy purposes (polymers, fertilizers, synthetic textiles ...) represents a leading scientific challenge. From this perspective, new nitrogen molecules synthetic processes have been developed from CO2 as a carbon source, amines as nitrogen source and mild reductant such as hydrosilanes and hydroboranes as a hydrogen source. These processes are accelerated by the use of metal-free catalysts and enable the production of formamides, formamidines, aminals and methylamines, which are basic molecules of the chemical industry.Les ressources carbonées fossiles (pétrole, charbon, gaz) couvrent 85 % des besoins énergétiques mondiaux et servent de matières premières pour 95 % des consommables chimiques organiques (plastiques, engrais, pesticides…). L’amenuisement des ressources pétrolières et l’accumulation du CO2 résultant de leur utilisation posent donc un problème écologique, énergétique et de disponibilité en matières premières pour l’industrie chimique. Dans ce contexte, il convient de proposer de nouvelles voies de synthèse de consommables chimiques, de manière à construire une industrie durable basée sur l’utilisation de ressources carbonées renouvelables. Contourner la pétrochimie et valoriser au maximum son déchet carboné, le CO2, pour construire des édifices moléculaires sans vocation énergétique (polymères, engrais, textiles synthétiques…) représente donc un enjeu scientifique de premier plan. Dans cet optique, de nouveaux procédés de synthèse de molécules azotées ont été mis au point à partir de CO2 comme source de carbone, d’amines comme source d’azote et de réducteurs doux de type hydrosilanes et hydroboranes comme source d’hydrogène. Ces procédés sont accélérés par l’utilisation de catalyseurs sans métaux et permettent de produire des formamides, des formamidines, des aminals et des méthylamines, qui constituent des molécules de bases de l’industrie chimique

Reductive functionalization of CO2 with amines: an entry to formamide, formamidine and methylamine derivatives

International audienceCO2 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

CO2 recycling : An alternative to petrochemistry for synthesis of nitrogen molecules

Les ressources carbonées fossiles (pétrole, charbon, gaz) couvrent 85 % des besoins énergétiques mondiaux et servent de matières premières pour 95 % des consommables chimiques organiques (plastiques, engrais, pesticides…). L’amenuisement des ressources pétrolières et l’accumulation du CO2 résultant de leur utilisation posent donc un problème écologique, énergétique et de disponibilité en matières premières pour l’industrie chimique. Dans ce contexte, il convient de proposer de nouvelles voies de synthèse de consommables chimiques, de manière à construire une industrie durable basée sur l’utilisation de ressources carbonées renouvelables. Contourner la pétrochimie et valoriser au maximum son déchet carboné, le CO2, pour construire des édifices moléculaires sans vocation énergétique (polymères, engrais, textiles synthétiques…) représente donc un enjeu scientifique de premier plan. Dans cet optique, de nouveaux procédés de synthèse de molécules azotées ont été mis au point à partir de CO2 comme source de carbone, d’amines comme source d’azote et de réducteurs doux de type hydrosilanes et hydroboranes comme source d’hydrogène. Ces procédés sont accélérés par l’utilisation de catalyseurs sans métaux et permettent de produire des formamides, des formamidines, des aminals et des méthylamines, qui constituent des molécules de bases de l’industrie chimique.The fossil carbon resources (oil, coal, gas) cover 85% of world energy portfolio and serve as raw materials for 95% of organic chemicals consumables (plastics, fertilizers, pesticides...). The decrease of oil resources and the accumulation of CO2 arising from their use thus pose environmental, energetic and availability of raw materials problems for the chemical industry. In this context, it is appropriate to propose new methods of chemical synthesis to build a sustainable industry based on the use of renewable carbon resources. Bypassing petrochemicals and valorize its carbon waste, CO2, to build molecular structures without energy purposes (polymers, fertilizers, synthetic textiles ...) represents a leading scientific challenge. From this perspective, new nitrogen molecules synthetic processes have been developed from CO2 as a carbon source, amines as nitrogen source and mild reductant such as hydrosilanes and hydroboranes as a hydrogen source. These processes are accelerated by the use of metal-free catalysts and enable the production of formamides, formamidines, aminals and methylamines, which are basic molecules of the chemical industry

Metal-free reduction of CO2 using hydroboranes

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Metal-free reduction of CO2 using hydrosilanes and hydroboranes

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Bridging Amines with CO2: Organocatalyzed Reduction of CO2 to Aminals

International audienceThe 4-electron reduction of CO2 in the presence of secondary aromatic amines is described for the first time to access aminals. Under metal-free hydrosilylation conditions, the four CO bonds of CO2 are cleaved and the organocatalysts are able to balance the reactivity of CO2 to promote the selective formation of two C-N and two C-H bonds. The methodology enables the formation of various symmetrical and unsymmetrical aminals. Because CO2 is a renewable, cost-efficient and non-toxic resource, it is a desirable carbon feedstock for the production of value-added chemicals and a lot of groups have focused their attention on designing new transformations involving CO2 over the last few years. 1 In particular, the reductive func-tionalization of CO2 with nitrogen reagents has known tremendous developments using various types of reductants such as hydrosilanes, hydroboranes and dihydrogen. 2 These reactions have enabled the conversion of CO2 into formamides, 2b, 3 formamidines 4 and methylamines. 5 Notably, the carbon oxidation state in these products is either +2 or-2 and the formation of C 0 organic functional groups from CO2 remains a challenge. This trend reflects the higher electrophilicity of C 0 groups compared to C +II functions in carbonyl derivatives. It is indeed well established that upon hydrogenation of CO2, formate derivatives can be accumulated while formaldehyde is an elusive species because its reduction to methanol is more rapid than the hydrogenation of formic acid. 1a As a consequence of this limitation, only a few reports have tackled the formation of C 0 species from CO2. Under hydrosilylation conditions, the selective reduction of CO2 into a bis(silyl)acetal species with triethylsilane has been revealed. 6 Using a hydroborane reduct-ant, Bontemps, Sabo-Etienne et al. successfully trapped transient formaldehyde, obtained from CO2, with 2,6-diisopropylaniline, yielding the corresponding imine. 7 To unlock new 4-electron reduction transformations of CO2, one should focus on the use of well-balanced catalysts, able to finely control the kinetics of CO2 reduction. In nature, aceto-genic bacteria are able to produce over 10 9 tons of acetic acid annually, following the Wood-Ljungdahl pathway (Scheme 1). 8 In this biochemical cycle, CO2 is anchored to a diamine moiety and undergoes successive 2-electron reduction steps to yield a methylamine (C-II) after formation of the corresponding formamide (C +II), formamidine (C +II) and aminal (C 0) intermediates. While CO2 conversion to formamides, formaminides and methylamines has been described, the synthesis of aminals 9 directly from CO2 remains unknown and was only suggested as a possible intermediate in the Ru-based methylation of amines. 5b To open up the variety of products accessible from CO2, we describe herein the first catalytic synthesis of aminals by intermolecular coupling of two amines using CO2 as a C1-bridge. Scheme 1. Simplified mechanism of the Wood-Ljungdahl pathway for acetogenesis with CO2 Hydrosilanes are mild reductants, cheap, non-toxic with a redox potential well poised for CO2 reduction. Additionally, their slightly polar Si-H bond can be activated with metal-free catalysts, using either Lewis bases or Lewis acids. 10 Using phenylsilane as reductant, the reactivity between N-methylaniline (1a) and CO2 has been explored using a variet

Creating Added Value with a Waste: Methylation ofAmines with CO2 and H2

International audienceUnknown before 2013, a novel methodology utilizes CO2 as a carbon source for the methylation of amines, with water as the by‐product. This strategy offers a sustainable route to methylamines by converting CO2 to value‐added chemicals, using molecular hydrogen as a cheap and renewable reductant. The method may open novel applications for recycling CO2 to bulk and fine chemicals

Recycling of CO2: an alternative to petrochemistry for the synthesis of nitrogen compounds

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Catalytic hydrosilylation of CO2 for tjhe funtionalization of amines

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