Metal-Free Selective Synthesis of α,ß-Unsaturated Aldehydes from Alkenes and Formaldehyde Catalyzed by Dimethylamine.

α,ß-Unsaturated aldehydes are important building blocks for the synthesis of a wide range of chemicals, including polymers. The synthesis of these molecules from cheap feedstocks such as alkenes remains a scientific challenge, mainly due to the low reactivity of alkenes. Here we report a selective and metal-free access to α,ß-unsaturated aldehydes from alkenes with formaldehyde. This reaction is catalyzed by dimethylamine and affords α,ß-unsaturated aldehydes in yields of up to 80 %. By combining Density Functional Theory (DFT) calculations and experiments, we elucidate the reaction mechanism which is based on a cascade of hydride transfer, hydrolysis and aldolization reactions. The reaction can be performed under very mild conditions (30-50 °C), in a theoretically 100 % carbon-economical fashion, with water as the only by-product. The reaction was successfully applied to non-activated linear 1-alkenes, thus opening an access to industrially relevant α,ß-unsaturated aldehydes from cheap and widely abundant chemicals at large scale.

One-Pot Synthesis of Polymers Containing PC Bonds in the Main Chain.

Placement of phosphorus in the polymer main chain leads to organophosphorus polymers with potentially unique chemical and physical properties. Herein, it is demonstrated that the Abramov phosphonylation reaction can be extended to the synthesis of such polymers, by reacting di- or tricarbaldehydes with phosphinic acid (PA) in the presence of N,O-bis(trimethylsilyl)acetamide (BSA). This technique affords polymers with main chain PC bonds, wherein phosphorus (V), aromatic rings, and hydroxymethylene moieties are linked by bis(α-hydroxymethylene)phosphinic acid (BHMPA) units. The resulting polymers are water soluble, display resilience against acid- and base-catalyzed hydrolysis, and exhibit superior thermal stability with high char yield in air (≈83%) and nitrogen (≈76%) atmosphere.

Sonochemically-Induced Reduction of Alkenes to Alkanes with Ammonia.

With the progressive defossilization of our industry, hydrogen (H2 ) has been identified as a central molecule to store renewable electricity. In this context, ammonia (NH3 ) is now rapidly emerging as a promising hydrogen carrier for the future. This game change indirectly impacts the field of fine chemistry where hydrogenation reactions are widely deployed. In particular, the possibility of performing hydrogenation reactions using ammonia directly instead of hydrogen has become highly desirable but it remains a very difficult scientific task, which we address in this communication. Here we show that the N-H bond of NH3 can be cleaved within cavitation bubbles, generated by ultrasonic irradiation at a high frequency, leading to the in situ formation of a diimide, which then induces the hydrogenation of alkenes. Advantageously, this work does not involve any transition metal and releases N2 as a sole co-product.

Conversion of Ammonia to Hydrazine Induced by High-Frequency Ultrasound.

Hydrazine is a chemical of utmost importance in our society, either for organic synthesis or energy use. The direct conversion of NH3 to hydrazine is highly appealing, but it remains a very difficult task because the degradation of hydrazine is thermodynamically more feasible than the cleavage of the N-H bond of NH3 . As a result, any catalyst capable of activating NH3 will thus unavoidably decompose N2 H4 . Here we show that cavitation bubbles, created by ultrasonic irradiation of aqueous NH3 at a high frequency, act as microreactors to activate and convert NH3 to NH species, without assistance of any catalyst, yielding hydrazine at the bubble-liquid interface. The compartmentation of in-situ-produced hydrazine in the bulk solution, which is maintained close to 30 °C, advantageously prevents its thermal degradation, a recurrent problem faced by previous technologies. This work also points towards a path to scavenge . OH radicals by adjusting the NH3 concentration.

Hydroamination of non-activated alkenes with ammonia: a holy grail in catalysis.

Alkyl amines represent an important class of chemicals with multiple applications in our daily life. Among the different routes to alkyl amines, the catalytic hydroamination of alkenes with amines is of high interest mainly because it occurs in a 100% atom-economical fashion. To circumvent thermodynamic limitations, activated alkenes or activated amines are essentially employed in such reactions. To date, the catalytic hydroamination of cheap and abundant non-activated (linear) alkenes with ammonia, the simplest amine, remains an unsolved reaction by catalysis. This tutorial review covers the advances reported so far in the intermolecular hydroamination of non-activated linear alkenes with simple alkyl amines, with special interest in ammonia. Focusing on thermodynamics, catalysis and emerging technologies, we aim at providing new perspectives to look at this challenging reaction from a different point of view. In particular, we highlight that the generation of amino radicals from NH3 using "physics activation" is a potential source of inspiration to (i) reduce energy barriers and (ii) reverse the regioselectivity to complete anti-Markovnikov addition.

Reductive Amination of Furanic Aldehydes in Aqueous Solution over Versatile Ni y AlO x Catalysts.

We disclose in this study a Ni6AlO x catalyst prepared by coprecipitation for the reductive amination of biomass-derived aldehydes and ketones in aqueous ammonia under mild reaction conditions. The catalyst exhibited 99% yield toward 5-aminomethyl-2-furylmethanol in the reaction of 5-hydroxymethyl furfural with ammonia at 100 °C for 6 h under 1 bar H2. The catalyst was further extended to the reductive amination of a library of aromatic and aliphatic aldehydes and ketones with a yield in the range 81-90% at optimized reaction conditions. Besides, 5-hydroxymethylfurfural could react with a library of primary and secondary amines with yields in the range 76-88%. The catalyst could be easily recycled and reused without apparent loss of activity in four consecutive runs.

Highly selective synthesis of 2,5-bis(aminomethyl)furan via catalytic amination of 5-(hydroxymethyl)furfural with NH3 over a bifunctional catalyst.

The development of facile protocols for the selective synthesis of biomass-derived diamine is a highly desirable pursuit in the field of heterogeneous catalysis. Herein, a simple and highly efficient bi-functional CuNiAlO x catalyst was developed for the one pot transformation of 5-(hydroxymethyl)furfural (5-HMF) into 2,5-bis(aminomethyl)furan (BAF) using a two-stage reaction process. Cu4Ni1Al4O x was found to be the most effective catalyst for this reaction, affording BAF in 85.9% yield. Our results could promote controllable conversion and utilization of biomass resource.

Search for the most 'primitive' membranes and their reinforcers: a review of the polyprenyl phosphates theory.

Terpenoids have an essential function in present-day cellular membranes, either as membrane reinforcers in Eucarya and Bacteria or as principal membrane constituents in Archaea. We have shown that some terpenoids, such as cholesterol and α, ω-dipolar carotenoids reinforce lipid membranes by measuring the water permeability of unilamellar vesicles. It was possible to arrange the known membrane terpenoids in a 'phylogenetic' sequence, and a retrograde analysis led us to conceive that single-chain polyprenyl phosphates might have been 'primitive' membrane constituents. By using an optical microscopy, we have observed that polyprenyl phosphates containing 15 to 30 C-atoms form giant vesicles in water in a wide pH range. The addition of 10 % molar of some polyprenols to polyprenyl phosphate vesicles have been shown to reduce the water permeability of membranes even more efficiently than the equimolecular addition of cholesterol. A 'prebiotic' synthesis of C10 and C15 prenols from C5 monoprenols was achieved in the presence of a montmorillonite clay. Hypothetical pathway from C1 or C2 units to 'primitive' membranes and that from 'primitive' membranes to archaeal lipids are presented.

"Primitive" membrane from polyprenyl phosphates and polyprenyl alcohols.

Polyprenyl phosphates, as well as polyprenyl alcohols bearing different isopentenyl C(5) units, have been synthesized. The pH range of spontaneous vesicle formation of polyprenyl phosphates with or without polyprenyl alcohols was defined by fluorescence microscopy. A variety of the acyclic or monocyclic polyprenyl phosphates studied formed stable vesicles in water over a wide range of pHs, and the addition of polyprenyl alcohols allowed the vesicle formation of polyprenyl phosphates at higher pHs. Osmotic swelling of a suspension of unilamellar vesicles using the stopped-flow/light-scattering method enabled us to evaluate the water permeability of polyprenyl phosphate vesicles with or without 10 mol% of free polyprenyl alcohol. The addition of many polyprenyl alcohols to polyprenyl phosphate vesicles decreased the water permeability, and some reduced it even more efficiently than cholesterol.

Enantioselective synthesis of (+)(R)- and (-)(S)-nicotine based on Ir-catalysed allylic amination.

The synthesis of nicotine with enantiomeric excess of >99% ee was accomplished by asymmetric Ir-catalysed allylic amination followed by ring closing metathesis and racemization-free double bond reduction.

Carbocycles via enantioselective inter- and intramolecular iridium-catalysed allylic alkylations.

Carbocycles with > 90% ee were prepared via Ir-catalysed asymmetric allylic alkylation/ring closing metathesis sequences or enantioselective Ir-catalysed intramolecular allylic alkylations.

Highly enantioselective syntheses of heterocycles via intramolecular Ir-catalyzed allylic amination and etherification.

[reaction: see text] Enantioselective Ir-catalyzed intramolecular allylic aminations and etherifications are described. Up to 97% ee was achieved using catalysts prepared by in situ activation of mixtures of phosphorus amidites and [Ir(COD)Cl]2. Sequential aminations of bis-allylic carbonates, involving an inter- followed by an intramolecular reaction, gave trans-N-benzyl-2,5-divinylpyrrolidine and trans-N-benzyl-2,6-divinylpiperidine with > or = 99% ee. New phosphorus amidites as well as improved conditions for intermolecular aminations are reported.

Synthesis of allylsilanes by reductive lithiation of thioethers.

Although much work in reductive lithiation has been done, the utilization of allylthioethers bearing various substituents to prepare allylsilanes has not been explored. The main reason clearly stems from the anticipated lack of regioselectivity. We describe herein the first study on the regioselectivity of the reductive silylation involving dissymmetric allylthioethers. We surveyed a broad spectrum of parameters and showed that this process displays a great dependence of the reaction conditions. We also discovered that an electron transporter, DBB or naphthalene, can cleave THF at room temperature by sonication, to generate a strong base, 4-lithiobutoxide. This feature was successfully exploited to the straightforward synthesis of bis-silanes in one pot. Examples are provided for maximizing both the chemical yield and the regioselectivity of the reductive silylation through the tuning of the reaction conditions. By changing these conditions, several allylsilanes can be selectively synthesized from one thioether.

A novel type of membranes based on cholesteryl phosphate.

Mixtures of the rigid amphiphile disodium cholesteryl phosphate (DCP) with the non-phosphorylated diacyl amphiphile dimyristoylglycerol (DMG) give self-organized systems in a wide range of pH, as demonstrated by differential microcalorimetry. These systems can be closed bilayer vesicles, as shown by optical microscopy (Nomarski and confocal). Neither DMG nor DCP, taken alone, give vesicles in these conditions but 10% DMG is enough to lead to the formation of vesicles from pH 5.8 to 9.3. These novel self-organized systems are akin to the classical eucaryotic ones, built on a phosphorylated diacylglycerol and free cholesterol (or analogues), the only difference being the site of the phosphate head-group.