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This work describes an efficient process for the reduction of nitro compounds to the corresponding amines with a catalytic amount of Pd/C (0.6 mol%), and a mixture of sodium hypophosphite and hypophosphorous acid as a reducing agent in H2O/2-MeTHF at 60 °C. The reaction was optimized under silent conditions. The conditions for the in situ production of H2 using the mixture NaH2PO2/H3PO2 were studied. The influence of ultrasonic activation was investigated both in terms of efficiency and kinetics. The reaction was shown to be efficient in water, at 70 °C with a quantitative conversion and a maximal yield in only 15 min thanks to the ultrasonic activation. Finally, ultrasound was proved to act as a physical agent of phase transfer. [ABSTRACT FROM AUTHOR]

New alkyl ether carboxylates with a glyceryl spacer instead of ethylene glycol units have been synthesised using environmentally friendly methodology. A cascade synthesis of acetalisation and hydrogenolysis was developed to obtain products containing an alkyl chain linked to a glycerol unit bearing a polar carboxylate head. These products were methylated by using trimethyl phosphate to observe the influence of a free or methoxylated alcohol on the physicochemical properties. Finally, saponification gave the carboxylate anionic group of the new hydrotropes. Studying the amphiphilicity, the tolerance to sodium and calcium ions, and the solubilising power of these bio-based ionic/nonionic hydrotropes has shown that they exhibit significantly improved application properties compared to similar petro-based hydrotropes., (© 2022 Wiley-VCH GmbH.)

This article describes a part of the results obtained from the cooperation between the University of Lyon1 (France) and the University of Antananarivo (Madagascar). It shows (among others) that useful research can be carried out in developing countries of the tropics if their social, technical, and economic conditions are taken into account. The concepts and methods associated with so-called "green chemistry" are particularly appropriated for this purpose. To illustrate this approach, two examples are shown. The first deals with industrial ecology and concerns waste transformation from the production of cashew nut into an amphiphilic product, oxyacetic derivatives. This product was obtained with a high yield and in a single step reaction. It exhibited an important surfactant property similar to those of the main fossil-based ones but with a much lower ecological impact. The second talks about chemical ecology as an alternative to insecticides and used to control dangerous mosquito populations. New substituted chromones were synthesized and showed biological activities toward Aedes albopictus mosquito species. Strong repellent properties were recorded for some alkoxylated products if others had a significant attractant effect (Kairomone) depending on their stereochemistry and the length of the alkyl chain.

Vector-borne diseases cause around 700,000 deaths every year. Insect repellents are one of the strategies to limit them. Para -menthane-3,8-diol (PMD), a natural compound, is one of the most promising alternatives to conventional synthetic repellents. This work describes a diastereodivergent method to synthesize each diastereoisomer of PMD from enantiopure citronellal and studies their repellence activity against Aedes albopictus . We found that cis -PMD is the kinetic control product of the cyclization of citronellal, while trans -PMD is the thermodynamic control product. X-ray diffraction analysis of crystals highlighted some differences in hydrogen-bond patterns between cis or trans isomers. The present paper demonstrates that (1 R )-(+)- cis -PMD has the highest repellency index using a new evaluation system for 24 h. (1 S )-(-)- cis -PMD has somewhat lower and (1 S )-(+)- trans -PMD and (1 R )-(-)- trans -PMD have a slight effect. Volunteer tests show that (1 R )-(+)- cis -PMD is the most efficient. This effect could be ascribed to the interaction of PMD/insect odorant receptors and their physical properties, that is, the evaporation rate.

Dehydrogenative oxidation of vicinal alcohols catalyzed by a commercially 64 wt.% Ni/SiO 2 catalyst leads to the formation of α-hydroxyketone. This first step was developed without additional solvent according to two protocols: "under vacuum" or "with an olefin scavenger". The synthesis of ketols was carried out with good conversions and selectivities. The recyclability of the supported nickel was also studied. Acyloin was then cleaved with oxidative reagent "formic acid/hydrogen peroxide", which is cheap and can be used on a large scale for industrial oxidation processes. The global yield of this sequential system was up to 80 % to pelargonic acid and azelaic acid monomethyl ester without intermediate purification. By treating the acyloin intermediate with hydroxylamine, nitriles were obtained with a good selectivity., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Herein we report the reduction of aromatic nitriles into aldehydes with calcium hypophosphite in the presence of base and nickel(ii) complex in a water/ethanol mixture. This catalytic system reduced efficiently a series of aromatic nitriles bearing different functional groups such as -Cl, -CF3, -Br, -CH3, -OCH3, -COOCH2CH3, -OH and -CHO. The corresponding aldehydes were isolated in moderate to excellent yields (30-94%).

The alkylation of alcohols and polyols has been investigated with alkylphosphates in the presence of a Lewis or Brønsted acid catalyst. The permethylation of polyols was developed under solvent-free conditions at 100 °C with either iron triflate or Aquivion PW98, affording the isolated products in yields between 52 and 95 %. The methodology was also adjusted to carry out peralkylation with longer alkyl chains., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The development of new tools for the reduction of organic functions to reach high chemo- and stereo-selectivity is an important research domain. Although, aluminum and boron hydrides are commonly used, they suffer from environmentally and safety issues. In particular, at industrial scale, the search for more specific and efficient reagents with a lower ecological impact remains one of the main objectives of organic chemists. This review captures highlights from literature concerning phosphonic and phosphinic acid derivatives as reducing agents and evaluates their potential as alternatives, in particular to boron and aluminum hydrides.

A one-pot two-step reaction (Knoevenagel condensation - reduction of the double bond) has been developed using calcium hydride as a reductant in the presence of a supported noble metal catalyst. The reaction between carbonyl compounds and active methylene compounds such as methylcyanoacetate, 1,3-dimethylbarbituric acid, dimedone and the more challenging dimethylmalonate, affords the corresponding monoalkylated products in moderate to good yields (up to 83%) with minimal reduction of the starting carbonyl compounds.

We have established that bipyridinium radicals can be reversibly π-dimerized under the combined effects of chemical (proton transfer) and electrochemical (electron transfer) stimuli. Our investigations also led to the discovery that a bis-pyridinyl appended calixarene intermediate is involved in a fully reversible redox-triggered σ-dimerization process. The structure of the most stable intramolecular σ-dimer was provided by computational chemistry and its complete conversion into a noncovalent π-dimer could be triggered chemically by addition of protons, leading to the formation of protonated cation radicals. Theoretical data collected with the N-methylated and N-protonated π-dimers also support the existence of multivariant orientations in π-bonded dimers of viologen cation-radicals., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of redox-responsive architectures featuring two bipyridinium units introduced onto the lower rim of a calixarene skeleton has been synthesized. The redox-triggered intramolecular dimerization of the reduced bipyridiniums has been investigated by electrochemistry, spectroelectrochemistry and by theoretical chemistry. The spectroscopic signature of the intramolecular dimers was found to evolve significantly with the size of the alkyl linker introduced between the calixarene skeleton and the bipyridinium units. On account of experimental data supported by theoretical calculations, these differences have been attributed to the extent of the orbital overlap in the π-dimerized species, involving either four or only two of the pyridine rings of the bipyridinium radical cations stacked in eclipsed or staggered conformations, respectively.

(Poly)glycerol monoethers were synthesized in good yield and selectivity by the catalytic reductive alkylation of glycerol, diglycerol, and triglycerol with readily available, cheap and/or bio-sourced carboxylic acids. The reaction was catalyzed by 1 mol % of Pd/C under 50 bar H(2) using an acid ion-exchange resin as a recyclable cocatalyst. The catalytic system was recycled several times, and a mechanism is proposed for this transformation., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A variety of nucleophiles provided by activated methylenes have been added on 3-(2-nitrovinyl)-1H-indole in very good to excellent yields, under sonication and solvent-free conditions, using solid potassium carbonate or sodium acetate as a base. Direct synthesis avoiding preliminary NH protection is reported and exemplified to 15 molecules.

A selective palladium-catalyzed arylation and heteroarylation of 8-oxo-5,6,7,8-tetrahydroindolizines has been developed. Mechanistic studies assume an electrophilic substitution pathway for this transformation. This method provides an efficient one-step synthesis of 3-aryl-8-oxo-5,6,7,8-tetrahydroindolizines.

Iteration of a Pd-catalyzed reaction of alkynyl- and oligoynylzincs with (E)-ICH=CHCl followed by metalation-termination with electrophiles(E) has provided a linear route to conjugated tri- and tetraynes, and Pd-catalyzed monoalkynylation of 1,1-dibromoenynes accompanied by dehydrobromination has provided a convergent route to conjugated tri- , tetra- , and pentaynes. Both display unprecedented high efficiency and selectivity. [reaction: see text]