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A convenient, recyclable catalytic synthesis of benzofuran-2-acetic esters 2 by sequential Pd(0)-catalyzed deallylation—Pd(II)-catalyzed carbonylative heterocyclization of 1-(2-allyloxyphenyl)-2-yn-1-ols 1 in ionic liquids is presented. Reactions were typically carried out in BmimBF4 as the solvent at 100 °C and under 30 atm of CO, in the presence of catalytic amounts (1 mol %) of PdI2 in conjunction with KI (1 equiv), PPh3 (4 mol %), MeOH (28 equiv), and H2O (2 equiv). The solvent-catalyst system could be recycled several times without appreciable loss of catalytic activity.

New liquid crystalline stilbene derivatives containing 1,2-dienylalkoxy chains 1 (n = 7, 9, 11) have been synthesized and their mesomorphic properties have been measured by polarizing optical microscopy, differential scanning calorimetry, and absorption spectroscopy. The effect of terminal alkoxy chain length and polimerisable function on the mesomorphic behaviour is discussed.

A new kind of solid plastic electrochromic (EC) film, prepared by introducing EC molecules, belonging to a class of bipyridinium salts (viologens), and plasticizers into preformed solid thermoplastic polymers, is presented. The particularly easy preparation of this EC device makes it suitable for large-scale applications, by simple lamination of the film between conductive glasses. In this way it is possible to eliminate the disadvantages of fast EC films, due to the variation of the solvent organization around the EC molecules and to the onset of the hydrostatic pressure of the fluid layer which can break or separate from the glass supports. The electrochromic cells based on our solid films have undergone up to 105 operational cycles in which coloring, bleaching processes, and stationary state conditions have been adjusted by applying suitable electric pulse sequences.

The reactivity of 2-(prop-2-ynylthio)imidazoles under PdI2/KI-catalyzed oxidative aminocarbonylation conditions has been studied. Under relatively mild conditions, 0.33–1 mol % of catalyst at 100 °C in MeCN and under 20 atm (at 25 °C) of a 4:1 mixture of CO/air, and in the presence of an equimolar amount of a secondary nucleophilic amine, substrates that are unsubstituted or bear a single substituent on the imidazole ring were converted directly in a multicomponent fashion into functionalized imidazothiazinones. This transformation occurred through a new auto-tandem catalysis process that involves two concatenated catalytic cycles both catalyzed by PdI2: oxidative aminocarbonylation of the terminal triple bond/cyclocarbonylation. However, in the presence of an excess of secondary amine, 4,5-disubstituted substrates led selectively to functionalized imidazothiazoles through an oxidative aminocarbonylation/conjugate addition process.

Indanes and indenes are among the most important carbocycles. Many indane and indene derivatives have shown important pharmacological activities, and the indane and indene nuclei are structural motifs present in several natural products of biological relevance. In spite of their importance, only a few reviews on their preparation methods have appeared so far in the literature, the most recent ones being published about ten years ago. The present Review is aimed at filling this gap, presenting some of the most important and innovative approaches to indanes and indenes that have been published in the course of the last ten years (coverage: from 2005 to May, 2015).

The reactivity of 2-(prop-2-ynylthio)imidazoles under PdI2/KI-catalyzed oxidative aminocarbonylation conditions has been studied. Under relatively mild conditions, 0.33-1mol% of catalyst at 100 degrees C in MeCN and under 20atm (at 25 degrees C) of a 4:1 mixture of CO/air, and in the presence of an equimolar amount of a secondary nucleophilic amine, substrates that are unsubstituted or bear a single substituent on the imidazole ring were converted directly in a multicomponent fashion into functionalized imidazothiazinones. This transformation occurred through a new auto-tandem catalysis process that involves two concatenated catalytic cycles both catalyzed by PdI2: oxidative aminocarbonylation of the terminal triple bond/cyclocarbonylation. However, in the presence of an excess of secondary amine, 4,5-disubstituted substrates led selectively to functionalized imidazothiazoles through an oxidative aminocarbonylation/conjugate addition process.

The oxidative carbonylation of readily available (Z)-(2-en-4-ynyl)amines, catalyzed by the PdI 2 -KI system, selectively afforded in satisfactory yields (40-95 %) either pyrrole-2-acetic ester or (pyridine-2-one)-3-acetic amide derivatives, depending on the susbtitution pattern of the substrate and the reaction conditions. The presence of an excess of carbon dioxide proved in most cases to be beneficial to both the reaction rate and product selectivity.

The effect of CO 2 on the reaction of a terminal alkyne with CO and H 2 O in the presence of PdI 2 –KI was studied. With simple 1-alkynes such as alkyl- or arylacetylenes in the absence of added CO 2 a catalytic process takes place with formation of substituted furan-2(5 H )-ones 1 , deriving from a reductive carbonylation process. Oxidation of CO to CO 2 accounts for the stoichiometry of the reaction. The latter may occur through decarboxylation of a Pd–CO 2 H species with formation of a Pd–H species, which is in turn responsible for the reduction process. It has been found that working in the presence of added CO 2 the latter can also work as hydrogen acceptor, probably via its insertion into the Pd–H bond. In this way a catalytic synthesis of maleic anhydrides 2 , corresponding to an oxidative carbonylation process, can be obtained even in the absence of external oxidants. In contrast with simple 1-alkynes, the use of 2-methylbut-3-yn-2-ol in the absence of added CO 2 results in additive carbonylation with formation of teraconic anhydride 5 , formally deriving from the combination of oxidative dicarbonylation and reduction. No CO 2 effect is observed in this case, which rules out the intervention of Pd–H species in the catalytic cycle leading to 5 . As expected, however, carbon dioxide effect is felt by secondary products resulting from reductive carbonylation, their formation being curtailed by CO 2 addition to the reaction mixture.

We have found that carbon dioxide effectively promotes the Pd-catalyzed oxidative carbonylation of terminal alkynes to give maleic anhydrides in fair yields. Reactions were carried out in aqueous dioxane at 60−80 °C in the presence of catalytic amounts of PdI2 in conjunction with KI and under a 4:1:10 mixture of CO/air/CO2 (60 atm total pressure at 25 °C). By working in the presence of a large excess of water, maleic acids were formed selectively with unprecedented catalytic efficiencies for this kind of reaction. In the latter case, the use of an excess of carbon dioxide tended to inhibit, rather than promote, the reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Materials in which photoluminescence is modulated by redox processes are known as electrofluorochromic. Intrinsically switchable fluorophores, incorporating both redox and fluorescent moieties, could be ideal electrofluorochromic materials if they possess high fluorescence quantum yields in at least one of their redox states. Fluorescent liquid crystals with redox active centres could combine the above requirements with the advantage to work in bulk anisotropic phases. However, electrofluorochromic liquid crystals have not been reported yet because their synthesis is challenging due to aggregation-caused fluorescent quenching. Here we show the first examples of electrofluorochromic π-conjugated ionic liquid crystals based on thienoviologens. These ordered materials, combining ionic and electronic functions, are highly fluorescence in the bulk state (quantum yield>60%). Their direct electrochemical reduction leads to fast and reversible bulk electrofluorochromic response in both columnar and smectic phases allowing for fluorescence intensity modulation and colour tuning.

A novel, multicomponent and stereoselective approach to functionalized indane derivatives is reported. It is based on a tandem process consisting of Pd-catalyzed oxidative carbamoylation of 2-(2-ethynylbenzyl) malonates with carbon monoxide, a secondary amine, and oxygen (with formation of a propiolamide intermediate), followed by carbocyclization, occurring through intramolecular addition of an in situ formed carbanion to the propiolamide moiety.

A novel synthesis of 2-ynamides (3) by palladium-catalyzed oxidative aminocarbonylation of alk-1-ynes (1) is reported. Reactions are catalyzed by PdI2/KI and are carried out at 100°C in dioxane as the solvent in the presence of dialkylamines (2) as nucleophiles (amine/alk-1-yne molar ratio=1/1) using a 4/1 CO/air mixture (20 atm total pressure at 25°C).

A simple and economical synthesis of substituted furans and pyrroles, by ligand-free CuCl2-catalyzed heterocyclodehydration of readily available 3-yne-1,2-diols and N-Boc- or N-tosyl-1-amino-3-yn-2-ols, respectively, is presented. Reactions are carried out in MeOH at 80–100 °C for 1–24 h and afford the corresponding heterocyclic derivatives in 53–99% isolated yields.

A novel and convenient approach to furan-3-carboxylic esters 2 is presented, based on palladium-catalyzed direct oxidative carbonylation of readily available 3-yne-1,2-diols 1 . The process, corresponding to a sequential combination between a 5- endo - dig heterocyclodehydration step and an oxidative alkoxycarbonylation stage, is catalyzed by PdI 2 in conjunction with an excess of KI under relatively mild conditions (100 °C in ROH under 40 atm of a 4:1 mixture of CO-air).

CuCl2-catalyzed heterocyclodehydration of readily available 3-yne-1,2-diols and 1-amino-3-yn-2-ol derivatives afforded substituted furans and pyrroles, respectively, in good to high yields (53-99%) under mild conditions (MeOH as the solvent, 80-100 °C, 1-24 h). In the case of 2,2-dialkynyl-1,2-diols, bearing an additional alkynyl substituent at C-2, a cascade process, corresponding to copper-catalyzed heterocyclodehydration followed by acid-catalyzed hydration of the triple bond, was realized when the reaction was carried out in the presence of both CuCl2 and TsOH, leading to 3-acylfurans in one step and high yields (75-84%). Under the same conditions, N-Boc-2-alkynyl-1-amino-3-yn-2-ols were converted into the corresponding N-unsubstituted 3-acylpyrroles in low to fair yields (19-59%). However, working in the presence of added water and a large excess of CO2 (40 atm), in addition to CuCl2 and TsOH, caused a significant improvement of the yields of 3-acylpyrroles (68-87%), thus making the method of general synthetic applicability.

CuCl2-catalyzed heterocyclodehydration of readily available 3-yne-1,2-diols and 1-amino-3-yn-2-ol derivatives afforded substituted furans and pyrroles, respectively, in good to high yields (53-99%) under mild conditions (MeOH as the solvent, 80-100 °C, 1-24 h). In the case of 2,2-dialkynyl-1,2-diols, bearing an additional alkynyl substituent at C-2, a cascade process, corresponding to copper-catalyzed heterocyclodehydration followed by acid-catalyzed hydration of the triple bond, was realized when the reaction was carried out in the presence of both CuCl2 and TsOH, leading to 3-acylfurans in one step and high yields (75-84%). Under the same conditions, N-Boc-2-alkynyl-1-amino-3-yn-2-ols were converted into the corresponding N-unsubstituted 3-acylpyrroles in low to fair yields (19-59%). However, working in the presence of added water and a large excess of CO2 (40 atm), in addition to CuCl2 and TsOH, caused a significant improvement of the yields of 3-acylpyrroles (68-87%), thus making the method of general synthetic applicability.

The reaction provides a convenient, mild, and widely applicable method to prepare substituted thiophenes under either conditions A) or B).

A variety of readily available 1-mercapto-3-yn-2-ols 5 were conveniently converted into the corresponding thiophenes 6 in good to high yields in MeOH as the solvent at 50-100 °C in the presence of catalytic amounts (1-2%) of PdI(2) in conjunction with KI (KI:PdI(2) molar ratio = 10). The catalyst could be made recyclable employing an ionic liquid, such as BmimBF(4), as the solvent under suitable conditions.

A new and convenient method to prepare a number of pyrrole-3-carboxylic esters is reported.

A new triarylamine derivative, N,N′-Bis(4-heptanoylamidophenyl)-N,N′-di(4-methoxyphenyl)-1,4-phenylenediamine, with stable electrochromism in near-infrared and visible light regions, has been synthesized and characterized at theoretical and experimental level. The detected and simulated spectra, with and without the presence of an external potential at different values, clearly show that this mixed-valence system undergoes ionization at a low value of the applied potential, and the formed radical cation absorbs in the near-infrared region with an intense peak located at 1,040 nm. Density functional computations give the geometrical structure and absorption properties in very good agreement with experiment, allowing assigning the electronic transition and contributing to an understanding of the electron-transfer process between the two redox centers.

Palladium-catalyzed oxidative heterocyclization—alkoxycarbonylation of in situ generated o-alkynylbenzylideneamines proceeds smoothly to afford isoquinoline derivatives (IV) in moderate yields.

Novel and convenient approaches to benzothiophene derivatives 3 and 5 have been developed, based on heterocyclization reactions of 1-(2-mercaptophenyl)-2-yn-1-ols 2 or 4, respectively, readily available from alkynylation of 2-mercaptobenzaldehydes or 1-(2-mercaptophenyl) ketones 1. In particular, 1-(2-mercaptophenyl)-2-yn-1-ols 2, bearing a CH2R substituent on the triple bond (R = alkyl, aryl), were conveniently converted in fair to good yields (55–82%) into (E)-2-(1-alkenyl)benzothiophenes 3 when allowed to react in the presence of catalytic amounts (2 mol %) of PdI2 in conjunction with KI (KI:PdI2 molar ratio =10) at 80–100 °C in MeCN as the solvent, through a heterocyclodehydration process. On the other hand, 2-alkoxymethylbenzothiophenes 5 were selectively obtained in fair to excellent yields (49–98%) via a radical-promoted substitutive heterocyclodehydration process, by reacting 1-(2-mercaptophenyl)-2-yn-1-ols 4 (bearing an alkyl or aryl substituent on the triple bond) in alcoholic media at 80–100 °C...

Isoquinoline-4-carboxylic esters 3 and isochromene-4-carboxylic esters 4 have been conveniently prepared by direct PdI2-catalyzed oxidative heterocyclization/alkoxycarbonylation of readily available (2-alkynylbenzylidene)amine derivatives. In particular, (2-alkynylbenzylidene)(tert-butyl)amines 2 selectively afforded isoquinoline derivatives 3 by N-cyclization, whereas N-(2-alkynylbenzylidene)-N′-phenylhydrazines 5 led to the formation of isochromenes 4 through O-cyclization ensuing from water attack on the imino group of the substrate. Reactions were carried out in alcoholic solvents at 80–100 °C and under 20–80 atm (at 25 °C) of a 4:1 mixture of CO/air, in the presence of PdI2 (2–10 mol-%) in conjunction with KI (KI/PdI2 molar ratio = 10). In the case of imines 2, the use of a dehydration agent, such as trialkyl orthoformate, was necessary to obtain satisfactory yields of isoquinolines 3.

Novel and convenient approaches to benzothiophene derivatives 3 and 5 have been developed, based on heterocyclization reactions of 1-(2-mercaptophenyl)-2-yn-1-ols 2 or 4, respectively, readily available from alkynylation of 2-mercaptobenzaldehydes or 1-(2-mercaptophenyl) ketones 1. In particular, 1-(2-mercaptophenyl)-2-yn-1-ols 2, bearing a CH(2)R substituent on the triple bond (R = alkyl, aryl), were conveniently converted in fair to good yields (55-82%) into (E)-2-(1-alkenyl)benzothiophenes 3 when allowed to react in the presence of catalytic amounts (2 mol %) of PdI(2) in conjunction with KI (KI:PdI(2) molar ratio =10) at 80-100 °C in MeCN as the solvent, through a heterocyclodehydration process. On the other hand, 2-alkoxymethylbenzothiophenes 5 were selectively obtained in fair to excellent yields (49-98%) via a radical-promoted substitutive heterocyclodehydration process, by reacting 1-(2-mercaptophenyl)-2-yn-1-ols 4 (bearing an alkyl or aryl substituent on the triple bond) in alcoholic media at 80-100 °C in the presence of a radical initiator, such as AIBN.

The reactions of propargyl alcohols with carbon dioxide in supercritical carbon dioxide or in acetonitrile with gaseous carbon dioxide in the presence of organic bases as catalysts have been examined. Bicyclic guanidines are effective catalysts for the formation of α-methylene cyclic carbonates under mild reaction conditions. Oxoalkyl carbonates, oxoalkyl carbamates or α-methyleneoxazolidinones are obtained in high yields and good selectivities in one-step starting from propargyl alcohols and an external nucleophile (alcohols or amines) using bicyclic guanidines as catalysts in supercritical carbon dioxide. Propargylic diols under the same reaction conditions underwent a rearrangement process instead of carbon dioxide insertion whereas in the presence of an external nucleophile the formation of oxocarbonates, oxocarbamates or cyclic carbamates was achieved in satisfactory yields.

Crude alkynylaniline imines prepared from the condensation between anilines (I) or (VIII) with benzaldehydes, react with CO, O2 and an alcohol under palladium catalysis to give the desired indole derivatives.

The reaction proceeds via sequential dealyllation/carbonylative heterocyclization of a variety of substituted 1-(2-allyloxyphenyl)-2-yn-1-ols [cf.

A novel and convenient approach to furan-3-carboxylic esters 2 is presented, based on palladium-catalyzed direct oxidative carbonylation of readily available 3-yne-1,2-diols 1 . The process, corresponding to a sequential combination between a 5- endo - dig heterocyclodehydration step and an oxidative alkoxycarbonylation stage, is catalyzed by PdI 2 in conjunction with an excess of KI under relatively mild conditions (100 °C in ROH under 40 atm of a 4:1 mixture of CO-air).

A novel synthesis of 2-ynamides (3) by palladium-catalyzed oxidative aminocarbonylation of alk-1-ynes (1) is reported. Reactions are catalyzed by PdI2/KI and are carried out at 100°C in dioxane as the solvent in the presence of dialkylamines (2) as nucleophiles (amine/alk-1-yne molar ratio=1/1) using a 4/1 CO/air mixture (20 atm total pressure at 25°C).

A direct synthesis of (E)-3-(methoxycarbonyl)methylene-1,3-dihydroindol-2-ones 2 by palladium-catalyzed oxidative carbonylation of 2-ethynylanilines 1 is reported. Reactions were carried out in MeOH as the solvent at 50−70 °C in the presence of catalytic amounts of PdI2 in conjunction with KI under a 4:1 CO/air mixture (20 atm total pressure at 25 °C). When the reaction was applied to 2-alkynylanilines with internal triple bonds, the reaction course changed completely, with formation of carbamates 4.

A convenient and simple approach for the recyclable catalytic synthesis of substituted quinolines is presented. The method is based on CuCl 2 -catalyzed heterocyclization of readily available 1-(2-aminoaryl)-2-yn-1-ols in BmimBF 4 as the solvent at 100 °C for 15–24 h. The solvent–catalyst system could be successfully recycled up to six times without significant loss of activity.

A convenient and simple approach for the recyclable catalytic synthesis of substituted quinolines is presented. The method is based on CuCl 2 -catalyzed heterocyclization of readily available 1-(2-aminoaryl)-2-yn-1-ols in BmimBF 4 as the solvent at 100 °C for 15–24 h. The solvent–catalyst system could be successfully recycled up to six times without significant loss of activity.

Lanthanide ions emitting in the near-infrared (NIR) region possess an intrinsically small molar absorption coefficient in the ultraviolet (UV)–vis–NIR spectrum, which is unfavourable for pumping efficiency. On the contrary, using organic lanthanide complexes it is possible to populate the excited state levels of the emitting ion through an efficient intramolecular energy transfer from the optically excited ligands, which act as light-harvesting antennae. With the aim of studying and maximizing the transfer to lanthanide metals, we have synthesized oligothiophene and thiophenefluorene ligands bearing carboxylate clamps able to complex erbium and other lanthanide 3 + ions. The complexes of {4′-(hydroxycarbonyl)methyl-[2,2′;5′,2″]terthiophen-3′-yl}acetic acid and 9-(hydroxycarbonyl)-methyl-2,7-dithien-2-yl-[fluoren-9-yl-]acetic acid with Er 3+ and different ancillary ligands have been prepared and their optical properties were carefully studied. Moreover, relaxation dynamics measurements have been carried out on all complexes in order to determine emission lifetimes, which result to be of the order of magnitude 2 μs. Quantum chemical calculations have been performed to explain optical absorption data in terms of different coordination types. The complexes containing phenanthroline/pyridine are modelled by adding to the dianion of the ligand one univalent/divalent counterion. The absorption spectra computed in this way are in close agreement with experiment, and the univalent→divalent theoretical wavelength shift goes in the right direction. The addition of a counterion has an even bigger effect on the triplet states, and hence on their matching with the emitting states of the ion.

2-[(Dialkylcarbamoyl)methylene]-2,3-dihydrobenzo[1,4]dioxine and 3-[(dialkylcarbamoyl)methylene]-3,4-dihydro-2H-benzo[1,4]oxazine derivatives (3 and 5, respectively) were synthesized for the first time starting from readily available 2-prop-2-ynyloxyphenols 1 and 2-prop-2-ynyloxyanilines 4, respectively, through tandem oxidative aminocarbonylation of the triple bond-intramolecular conjugate addition. Reactions were carried out in the presence of catalytic amounts of PdI2 in conjunction with an excess of KI in N,N-dimethylacetamide (DMA) as the solvent at 80-100 degrees C and under 20 atm (at 25 degrees C) of a 4:1 mixture of CO-air. The reaction showed a significant degree of stereoselectivity, the Z isomers being formed preferentially or exclusively. The configuration around the double bond of the major stereoisomers was unequivocally established by X-ray diffraction analysis.

Here we report the synthesis and the liquid crystalline properties of a new class of thienoviologen salts of the dication series 4,4′-(2,2′-bithiophene-5,5′-diyl)bis(1-alkylpyridinium)++ (mV++s) having different alkyl-chain lengths (m = 9–11). As determined by DSC, polarized optical microscopy and X-ray diffraction analyses, the anion of the salt plays a crucial role in disclosing the liquid crystalline nature of the mV++s. It is shown that the bis(triflimide) salts, mV(NTf2)2s, exhibit a unique bimesomorphic behaviour, self-segregating into columnar rectangular and/or smectic phases. Despite the rod-like shape of these π-extended viologen dications, columnar phases are obtained by the self-assembly of disk-like structures formed by the association of dications into dimers through bridging interacting anions. Interestingly, the bimesomorphism allows “switching” from a columnar to a calamitic phase and vice versa by changing the temperature and/or the alkyl-chain length. In particular, as the length of the alkyl chains increases from m = 9, where a stable rectangular columnar mesophase is observed, to m = 10, an incipient calamitic mesomorphism takes place which manifests itself with the formation of a lamello-columnar mesophase. This ultimately evolves toward a smectic A phase for m = 11.

A direct synthesis of (E)-3-(methoxycarbonyl)methylene-1,3-dihydroindol-2-ones 2 by palladium-catalyzed oxidative carbonylation of 2-ethynylanilines 1 is reported. Reactions were carried out in MeOH as the solvent at 50−70 °C in the presence of catalytic amounts of PdI2 in conjunction with KI under a 4:1 CO/air mixture (20 atm total pressure at 25 °C). When the reaction was applied to 2-alkynylanilines with internal triple bonds, the reaction course changed completely, with formation of carbamates 4.