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The increasing attention towards environmentally friendly synthetic protocols has boosted studies directed to the development of green and sustainable methods for direct C−H bond arylation of (hetero)arenes. In this context, here the infrared (IR) irradiation‐assisted solvent‐free Pd‐catalyzed direct C−H bond arylation of (hetero)arenes was achieved. Several heteroaryl‐aryl coupling reactions were described, also involving heterocycles commonly used as building blocks for the synthesis of organic semiconductors. The reaction tolerated many functional groups on the aromatic nuclei. The IR‐irradiation as the energy source compared favorably with thermal heating and, in combination with solvent‐free conditions, provided an important contribution to the development of protocols fitting with the principles of green chemistry., No solvent needed: Pd‐catalyzed (hetero)aryl–aryl coupling via C−H bond activation is proven in solvent‐free conditions under IR irradiation as effective and convenient energy source. The reaction efficiently works on several conjugated cores and tolerates several functional groups on aryl iodides used as coupling partners. The protocol opens the way to energy‐effective solvent‐free methods in organic synthesis.

A fruitful switch from tert-butyl to cumene hydroperoxide was able to overcome a difficulty arose in the enantioselective oxidation of fluorinated aryl benzyl sulfide with hydroperoxides in the presence of a titanium/(S, S)-hydrobenzoin catalyst. New experiments show the complementarity of the old and the new protocols and indicate unequivocally the right choice leading to the corresponding highly enantioenriched sulfoxides. Moreover, in a totally unexpected way, the new protocol was able to overcome another difficulty arose in another field of research, that is the enantioselective oxidation of a fluorinated aryl phenacyl sulfide. Also in this case, the complementarity of behavior is acting. Finally, this investigation gives new support to the attribution of configuration of sulfoxides with ECD techniques, but only if the protocol outlined in our past research was followed thoroughly.

Along the lines of a systematic investigation of conformational constraints promoted by weak interactions, the aryl-stacked structures of some chiral cyclic phosphonamides synthesised with the aid of Betti bases as chirality inducers were investigated by X-ray diffraction analysis and NMR spectroscopy. The synthesised systems showed the stacked conformation between two of their aryl groups, leading to pre-organized structures. The pi-pi stacking motif between the aromatic rings was observed in solid state and in solution, suggesting that this supramolecular synthon could be used as a conformational constraining tool in the development of drug molecule candidates based on chiral cyclic phosphonamides. The disabling of the pi-pi stacking motif was pursued by adding an ortho-substituent on one aromatic ring.

Two crystalline benzyl phenyl sulfides, bearing at the same time both a pentafluorophenyl and a nitrophenyl moiety in two different assemblies, were investigated by means of single crystal X-ray diffraction. The main assembly interactions were recognized and compared with the different behaviors of analogous sulfides bearing only one of these two functional groups. Since short contacts involving fluorine atoms have been a source of controversy, their contribution to the stability of the crystal was analyzed both with the help of Hirshfeld surface analysis, and with a comparison with items in the Cambridge Structural Database. The situation of a gauche-conformed sulfide having two contemporary interactions involving electron poor aryl groups is of particular interest.

Direct arylation of 5-octylthieno[3,4-c]pyrrole-4,6-dione with a series of functionalized aryl iodides via C-H bond activation is demonstrated in a deep eutectic solvent made of choline chloride and urea in non-anhydrous conditions and without exclusion of air. This is the first demonstration of a thiophene-aryl coupling via direct arylation in deep eutectic solvents.

Direct arylation of thienopyrrolodione, diketopyrrolopyrroles, benzodithiophene derivatives, and fluorinated heteroarenes with functionalized aryl iodides is proven in solvent-free and non-anhydrous conditions. The reaction is performed in the presence of air and tolerates several functional groups on both the coupling partners, enabling a convenient synthesis of extended heteroaromatic conjugated molecules.

Pentafluorobenzyl pentafluorophenyl sulfide is oxidised with moderate e.e. value and a low yield by the usually highly successful oxidation protocol based upon tert-butyl hydroperoxide (TBHP) in the presence of a titanium/hydrobenzoin complex. This disappointing result resisted until the present work, in which the switch of the oxidation agent (from TBHP to cumene hydroperoxide), suggested by our previous computations, yielded the enantiopure sulfoxide. This valuable chiral compound was obtained in good yields (76%) without resorting to a chromatographic separation. DFT computations uncovered that this favourable reactivity was originated by a stabilizing π−π−stacking between the phenyl group of the oxidant and the pentafluorophenyl moiety of the substrate.

A series of ten chiral aryl benzyl sulfoxides with perfluorinated aryl or benzyl rings, obtained by enantioselective oxidation of sulfides, has been investigated by means of electronic circular dichroism (ECD) spectroscopy and time-dependent DFT (TDDFT) calculations. The (per)fluorination of the aromatic rings has a large impact on the conformer population, the molecular orbitals shape, and the character of electronic transitions. In this series, the transition responsible for the “sulfoxide primary” CD band has a large charge transfer (CT) character, as demonstrated by the CT metric index ΓNTO. As a consequence, global DFT hybrids such as B3LYP are largely inaccurate in the prediction of excited states; nevertheless, a correct simulation of CD spectra may be achieved by using range-separated functionals such as CAM-B3LYP. The use of the empirical Mislow's rule for assigning the absolute configuration is strongly discouraged for this class of compounds.

Chiral nonracemic aminobenzylnaphthols were obtained by a Betti multicomponent reaction between 2-naphthol, aryl aldehydes and enantiopure arylethylamine. Moreover, some new aminobenzylnaphthols were synthesized by a similar reaction between 2-naphthol, aryl aldehydes and prolinol. These aminobenzylnaphthols, synthesized from different components and thus having different structural features, were tested as anti-yeast agents inhibiting Candida albicans. The effect towards the test strain was studied with a microdilution approach and three different concentrations (150, 300 and 450 ?g/mL) were tested. The best results were found for the aminobenzylnaphthols obtained from 1-naphthylethylamine and from natural prolinol. The use of the two-way ANOVA highlighted the better performances of the prolinol derivative among the differently structured aminobenzylnaphthols that were screened. The activity towards C. albicans of this prolinol derivative resulted to be interesting and could represent a promising alternative to overcome the problem of the strains resistant to the traditional antifungals. © 2014 by the authors; licensee MDPI, Basel, Switzerland.

A series of 13 enantiopure aryl benzyl sulfoxides (1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1l, 1m) with different substituents on the two aromatic rings has been previously analyzed by means of electronic circular dichroism (CD) spectroscopy. Most of these compounds are crystalline and their X-ray structure is established. For almost one-half of the series, CD spectra measured in the solid state were quite different from those in acetonitrile solution. We demonstrate that the difference is due to strong exciton couplings between molecules packed closely together in the crystal. The computational approach consists of time-dependent density functional theory (TDDFT) calculations run on “dimers” composed of nearest neighbors found in the lattice. Solid-state CD spectra are well reproduced by the average of all possible pairwise terms. The relation between the crystal space group and conformation, and the appearance of solid-state CD spectra, is also discussed. Chirality 26:462–470, 2013. © 2013 Wiley Periodicals, Inc.

Some aminophenyl benzyl sulfides or benzyl pyridyl sulfides were asymmetrically oxidized with tert-butyl hydroperoxide in the presence of a complex between titanium i-propoxide and (S, S)-hydrobenzoin, an oxidation system that works particularly well with a vast set of aryl benzyl sulfides. Notwithstanding the presence of nitrogen-containing moieties that, in principle, could interfere with the correct co-ordination of the sulfide to the metal center, satisfactory levels of enantioselectivity (up to 78%) were measured for this oxidation process. © 2013 Taylor & Francis.

The title reaction generally proceeds with high yields and provides the products with high stereoselectivity.

After the discovery of a few cases of lower enantioselectivity in the oxidation of aryl benzyl sulfides with hydroperoxides in the presence of a complex between titanium isopropoxide and (S, S)-hydrobenzoin, a screening of the oxidation of new substrates that are related to the structures that gave low ee values, was performed. From this screening, we confirmed that only a few sulfides remain as exceptions within a framework of exceptionally high stereoselectivity of the oxidation reaction. Moreover, the exceptions are clearly identified and are connected to particular coordinating moieties present on the aryl groups. (C) 2015 Elsevier Ltd. All rights reserved

Single crystal X-ray structure determination of four crystals of alkyl or aryl p-haloaryl sulfoxides is reported. Intramolecular short contacts between the ortho-hydrogen of the aryl ring and the oxygen of the sulfinyl group were found to determine the conformations of the sulfoxides. On the other hand, in the absence of classical hydrogen bond donors, crystal packing arrangements are the results of intermolecular aryl hydrogen-oxygen short contacts and of interactions involving halogen atoms. From a comparison of the structures of the investigated sulfoxides with other literature data, the crystal packings of these types of compound appear to derive from a complex balance among different interactions.

A series of enantiopure crystalline aryl benzyl sulfoxides, bearing different substituents on both the aryl groups, were synthesized by an enantioselective oxidation of the corresponding sulfides. Structural investigations, achieved by means of single-crystal X-ray diffraction, allowed us to recognize the main assembling interactions. The same procedure was repeated for some corresponding fluorinated aryl benzyl sulfoxides. The synthesis of the enantiomers of a new fluorinated compound, which shows unusual structural patterns, prompted us to compare the structural motifs of the two families of sulfoxides (fluorinated and unfluorinated) and to investigate the changes due to the fluorine substitution. Some short contacts involving the fluorine atom were discussed in more details, taking into account the recent interest in these sometimes controversial interactions. (Chemical Equation Presented).

A series of experiments was performed to test a theoretical model that we have recently proposed to explain the highly enantioselective oxidation of aryl benzyl sulfides with tert-butyl hydroperoxide in the presence of a complex between titanium and (S,S)- or (R,R)-hydrobenzoin. The studied variations involved the sulfides, the ligands, and the order of addition of reactants. The reaction path predicted by our model was confirmed in every experiment. In particular, aryl benzyl sulfides behaved as the ideal substrate for this type of asymmetric oxidation, which yields synthetically useful, enantiopure aryl benzyl sulfoxides in a straightforward manner. The theoretical model of the enantioselective oxidation of aryl benzyl sulfides in the presence of chiral titanium catalysts was tested with a series of experiments in which the reagents and conditions were varied. It was confirmed that aryl benzyl sulfides are an ideal substrate for this oxidation protocol, which yields the synthetically useful chiral non-racemic aryl benzyl sulfoxides. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enantiopure aryl benzyl sulfoxides were easily obtained by an enantioselective oxidation of the corresponding sulfides with tert-butyl hydroperoxide in the presence of a complex between titanium and (S, S)-or (R, R)-hydrobenzoin. Theoretical and experimental investigations confirmed that these aryl benzyl sulfides represent an ideal substrate for the asymmetric oxidation system. Copyright © Taylor and Francis Group, LLC.

An experimental investigation of the enantioselective oxidation of aryl benzyl sulfides by tert-butyl hydroperoxide in the presence of a titanium/hydrobenzoin catalyst has shown that these sulfides are ideal substrates for this catalytic system, with negligible interference by the substituents on the aryl groups. A reaction mechanism based on DFT computations has been proposed. The DFT MPWB1K functional was used in the theoretical investigation to account for weak hydrogen-bonding and pi interactions. The computed reaction profile explains the experimentally observed enantioselectivity, which is determined by the thermodynamics of the first phase of the reaction. A detailed discussion of the hydrogen-bonding and pi interactions that drive the reaction along the observed stereochemical path is given.