Photocatalyzed hydrodecarboxylation of fatty acids: a prospective method to produce drop-in biofuels.

A direct and practical method for photocatalyzed hydrodecarboxylation of fatty acids is reported herein. The catalytic system consists of a commercially available acridinium salt as the photocatalyst and thiophenol as the Hydrogen Atom Transfer (HAT) co-catalyst. Results evidenced that Cn-1 alkanes were obtained in yields up to 77%. Furthermore, the protocol was employed for a complex mixture of fatty acids bio-derived from a real sample of licuri oil to obtain hydrocarbons in the range of C9-C17 with high selectivity and excellent conversion (>90%). This work provides a powerful strategy for producing drop-in biofuels under mild conditions. Finally, an energetic assessment of our proposed protocol (∼22.9 kW h) reveals the benefit of a sustainable production of renewable hydrocarbons.

Sulphate-based electrochemical processes as an alternative for the remediation of a beauty salon effluent‡.

Beauty salons (BS) are places that deal with a wide range of cosmetics with potentially hazardous chemicals, and their effluent should be properly treated before going to the sewage system, once it represents characteristics of industrial wastewater. This work provides an extensive characterization of a BS effluent and its respective electrochemical treatment by comparing NaCl, Na2SO4, and Na2S2O8 as supporting electrolytes with a boron-doped diamond (BDD) as anode, applying 10 or 30 mA cm-2 of current density (j). The inclusion of UVC irradiation was also performed but the improvements achieved in removing the organic matter were null or lower. The analysis of chemical oxygen demand (COD) removal, energy consumption, and total current efficiency (TCE) was required to prove the efficacy of the processes and the comparative study of the performance of different technologies. Precipitate analysis was also done due to the high turbidity of the raw effluent and the appearance of a precipitate before and during the electrolysis, mainly with Na2S2O8. The precipitate confirmed the presence of silicates and small amounts of heavy metals. The results clearly showed that 6 h of treatment with Na2SO4 achieved 58% of COD removal with an energy consumption of about 0.52 kWh m-3, being the best electrolyte option for treating BS effluent by applying 10 mA cm-2. Under these experimental conditions, the final wastewater can be directly discharged into the sewage system with a lower amount of visible precipitate, and with 73% less turbidity. The treatment here proposed can be used as an alternative to decision-makers and governments once it can be a step further in the implementation of better and advanced politics of water sanitation.

Photocatalytic Hydrodecarboxylation of Fatty Acids for Drop-in Biofuels Production.

A mild, practical, and environmentally friendly method for the hydrodecarboxylation of fatty acids using an acridine-based photoredox catalyst and thiophenol was developed. Cn-1 alkanes were synthesized in good to excellent yields (up to 99 %) from C10-C18 saturated fatty acids under visible light irradiation (405 nm). The developed protocol was employed for a mixture of fatty acids obtained from the hydrolysis of Licuri oil, affording a mixture of C9-C17 hydrocarbons in quantitative yield, which demonstrates the potential application of the method to produce drop-in biofuels.

Nickel-catalyzed reductive decarboxylation of fatty acids for drop-in biofuel production.

An operationally simple and highly selective method for the decarboxylation of fatty acids under remarkably mild conditions is described herein. The activation of the aliphatic carboxylic acids by esterification with N-hydroxyphthalimide (NHPI) enabled efficient deoxygenation to synthesize n-alkanes in up to 67% yield, employing inexpensive PMHS as a hydrogen source, NiCl2·6H2O, bipyridine, and zinc in THF. In contrast to the conventional thermo-catalytic approaches, this protocol does not require high temperature and high pressure of hydrogen gas to deoxygenate biomass-derived carboxylic acids, thus representing an attractive alternative for producing drop-in biofuels.

Rutin-modified silver nanoparticles as a chromogenic probe for the selective detection of Fe3+ in aqueous medium.

The development of nanoprobes for selective detection of metal ions in solution has attracted great attention due to their impact on living organisms. As a contribution to this field, this paper reports the synthesis of silver nanoparticles modified with rutin in the presence of ascorbic acid and their successful use as a chromogenic probe for the selective detection of Fe3+ in aqueous solution. Limits of detection and quantification were found to be 17 nmol L-1 and 56 nmol L-1, respectively. The sensing ability is proposed to proceed via an iron-induced nanoparticle growth/aggregation mechanism. A practical approach using image analysis for quantification of Fe3+ is also described.

Photoredox Catalysis in Nickel-Catalyzed Cross-Coupling.

The traditional transition metal-catalyzed cross-coupling reaction, although well suited for C(sp2)-C(sp2) cross-coupling, has proven less amenable toward coupling of C(sp3)-hybridized centers, particularly using functional group tolerant reagents and reaction conditions. The development of photoredox/Ni dual catalytic methods for cross-coupling has opened new vistas for the construction of carbon-carbon bonds at C(sp3)-hybridized centers. In this chapter, a general outline of the features of such processes is detailed.

Electrophilic alkynylation of ketones using hypervalent iodine.

A new method for the electrophilic α-alkynylation of ketones was developed using hypervalent iodine under mild and metal-free conditions. Carbonyl compounds containing an α-acetylene group were obtained in good to excellent yields for several ketones using 1-[(trimethylsilyl)ethynyl]-1,2-benziodoxol-3(1H)-one (TMS-EBX) as an alkynylation agent in the presence of t-BuOK and TBAF in THF as solvent. Under the same conditions, an aldehyde was alkynylated.

Nickel-catalyzed borylation of halides and pseudohalides with tetrahydroxydiboron [B2(OH)4].

Arylboronic acids are gaining increased importance as reagents and target structures in a variety of useful applications. Recently, the palladium-catalyzed synthesis of arylboronic acids employing the atom-economical tetrahydroxydiboron (BBA) reagent has been reported. The high cost associated with palladium, combined with several limitations of both palladium- and copper-catalyzed processes, prompted us to develop an alternative method. Thus, the nickel-catalyzed borylation of aryl and heteroaryl halides and pseudohalides using tetrahydroxydiboron (BBA) has been formulated. The reaction proved to be widely functional group tolerant and applicable to a number of heterocyclic systems. To the best of our knowledge, the examples presented here represent the only effective Ni-catalyzed Miyaura borylations conducted at room temperature.

Synthesis of trifluoromethylated isoxazolidines: 1,3-dipolar cycloaddition of nitrosoarenes, (trifluoromethyl)diazomethane, and alkenes.

Isoxazolidines have proven to be important substrates in synthetic organic chemistry. Limited examples in the literature that provide trifluoromethylated versions of these compounds have prompted us to investigate a 1,3-dipolar cycloaddition route providing access to N-functionalized isoxazolidines containing a trifluoromethyl group. Thus, a 1,3-dipolar cycloaddition of nitrosoarenes, (trifluoromethyl)diazomethane, and alkenes was developed. The starting materials can be synthesized from easy to handle and accessible reagents. The reaction proved to be tolerant of a variety of electron-deficient alkenes and nitrosoarenes.

Nitrosation of aryl and heteroaryltrifluoroborates with nitrosonium tetrafluoroborate.

Organotrifluoroborates have emerged as an alternative to toxic and air- and moisture-sensitive organometallic species for the synthesis of functionalized aryl and heteroaryl compounds. It has been shown that the trifluoroborate moiety can be easily converted into a variety of different substituents in a late synthetic stage. In this paper, we disclose a mild, selective, and convenient method for the ipso-nitrosation of organotrifluoroborates using nitrosonium tetrafluoroborate (NOBF(4)). Aryl- and heteroaryltrifluoroborates were converted into the corresponding nitroso products in good to excellent yields. This method proved to be tolerant of a broad range of functional groups.

Metal-free chlorodeboronation of organotrifluoroborates.

A mild and metal-free method for the chlorodeboronation of organotrifluoroborates using trichloroisocyanuric acid (TCICA) was developed. Aryl-, heteroaryl-, alkenyl-, alkynyl-, and alkyltrifluoroborates were converted into the corresponding chlorinated products in good yields. This method proved to be tolerant of a broad range of functional groups.

Oxidation of organotrifluoroborates via oxone.

A method for the oxidation of organotrifluoroborates using Oxone was developed. A variety of aryl-, heteroaryl-, alkenyl-, and alkyltrifluoroborates were converted into the corresponding oxidized products in excellent yields. This method proved to be tolerant of a broad range of functional groups, and in secondary alkyl substrates it was demonstrated to be completely stereospecific.

Efficient hydrolysis of organotrifluoroborates via silica gel and water.

A general, mild, and efficient method for the hydrolysis of organotrifluoroborates to unveil boronic acids using silica gel and H(2)O was developed. This method proved to be tolerant of a broad range of aryl-, heteroaryl-, alkenyl-, and alkyltrifluoroborates as well as structurally diverse aminomethylated organotrifluoroborates. As anticipated, electron-rich substrates provided the corresponding boronic acids more readily than electron-poor substrates, owing to the resonance-stabilized difluoroborane intermediate. The method developed was expanded further for the conversion of organotrifluoroborates to the corresponding boronate esters.

Aqueous Barbier allylation of aldehydes mediated by tin.

The aqueous tin-mediated Barbier reaction affords good to excellent yields and moderate syn diastereoselectivity under basic and acidic conditions. The high yields and stereoselectivity observed in the case of o-substituted aldehydes suggest a cyclic organotin intermediate or transition state in K2HPO4 solution. A practical and efficient aqueous tin allylation of methoxy- and hydroxybenzaldehydes can be carried out in HCl solution in 15 minutes to afford the corresponding homoallylic alcohols in high yields. Aliphatic aldehydes give moderate to excellent yields with reaction times ranging from 30 to 60 minutes. Under these conditions, crotylation gives exclusively the gamma-product and the syn isomer is formed preferentially. For 2-methoxybenzaldehyde, an equilibration of the isomers to a syn/anti ratio of 1:1 can be observed after several hours. Control experiments with radical sources or scavengers give no support for radical intermediates. NMR studies suggest a mechanism involving an organotin intermediate. The major organotin species formed depends on the reaction medium and the reaction time. The use of acidic solution reduces the reaction times, due to the acceleration of the formation of the allyltin(IV) species.