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Katritzky salts have emerged as effective alkyl radical sources upon metal- or photocatalysis. These are typically prepared from the corresponding triarylpyrylium ions, in turn an important class of photocatalysts for small molecules synthesis and photopolymerization. Here, a flow method for the rapid synthesis of both pyrylium and Katrizky salts in a telescoped fashion is reported. Moreover, several pyrylium salts were tested in the photoinduced RAFT polymerization of vinyl ethers under flow and batch conditions.

A chemoselective method for the carbonylation of allylic substrates CH2=CHCH2X (X= OAc, OC(O)CH2CN, OPh, OEt, OC(O)OPh, OC(O)OiBu, N(H)C(O)Ph, N(Ph)C(O)Ph, N(H)Boc, N(Ph)Boc, Ph, CO2Bn, CN), leading to alkyl succinates with preservation of the X group, under Pd(II)-catalyzed oxidative carbonylation conditions, has been developed. Our method shows a completely different inverse chemoselectivity with respect to the "classical" substitutive carbonylation of the allyl compounds, which is known to provide beta,gamma-unsaturated carbonyl derivatives through the formation of a p-allylpalladium intermediate. An accurate study, carried out using allyl acetate as model substrate, allowed to maximize the selectivity in the envisioned 2-CH2X substituted succinates. The best catalyst is generated in situ by mixing Pd(TFA) 2 (TFA= trifluoroacetate) and the N,N'-di(anthracen-9-yl)butane-2,3-diimine ligand. pBenzoquinone was used as oxidant in presence of benzyl alcohol, which acts as a nucleophile and as a solvent, under 4 bar of CO at 20 degrees C. A combined effect of the ligand and the nucleophile, rationalized through DFT calculations, has been observed both in promoting the bis-alkoxycarbonylation process and in preventing p-allylpalladium-mediated side reactions, allowing the attainment of succinate derivatives with moderate to good yields.

We report the first example of successful heterogenization of the classical PdI42- carbonylation catalyst, achieved in two simple steps from ionic liquid-functionalized multi-walled carbon nanotubes (MWCNTs). The newly developed materials (PdI4@MWCNT-imi-X, X = Br, I) present the PdI42- anion supported on an imidazolium network (imi) grown on MWCNTs and have been fully characterized. The activity of PdI4@MWCNT-imi-X has been successfully tested in a paradigmatic carbonylation reaction, the oxidative monoaminocarbonylation of 1-alkynes with amines to give high value added 2-ynamides (obtained in good yields, 50–84%, starting from various substrates). The heterogeneous catalyst could be easily recycled and showed a good efficiency even after the fourth recycle, when deactivation began to occur owing to the formation of inactive Pd(0) species, as confirmed by XPS analysis. Hot and cold filtration tests were compatible with an essentially heterogeneous catalytic process, and limited metal contamination in the final organic compounds occurred, as assessed by ICP-MS analysis of representative carbonylation products.

The hydroamination reaction is a convenient alternative strategy for the formation of C–N bonds. Herein, we report a new versatile and convenient protocol for the hydroamination of arylacetylenes with anilines using palladium iodide in the absence of any added ligand as catalyst. Mild conditions, excellent regio- and stereoselectivity, and high functional group tolerance are the main features of this methodology. A subsequent reduction step gives access to a wide variety of secondary aromatic amines.

The first example of the bis-alkoxycarbonylation of acrylic esters and acrylic amides, leading to differently substituted 1,1,2-ethanetricarboxylate compounds and 2-carbamoylsuccinates respectively, is reported. The catalyst is formed in situ by mixing Pd(TFA)2 (TFA=trifluoroacetate) and the ligand bis(2,6-dimethylphenyl)butane-2,3-diimine. The reaction, that proceeds using p-benzoquinone as oxidant and p-toluenesulfonic acid as additive, has been applied to variously substituted electron-poor alkenes, employing different alcohols as nucleophiles, under very mild reaction conditions (4 bar of carbon monoxide at 20 °C). Remarkably, this catalytic system is able to promote the carbonylation of both the β- and the generally unreactive α-positions of acrylic esters and amides, allowing the formation of bis-alkoxycarbonylated products in good to excellent yields (up to 98%). The trend of reactivity, observed with the different electron-deficient olefins, has been rationalized on the basis of the proposed catalytic cycle and DFT calculations. (Figure presented.).

In this contribution, we report novel palladium-catalyzed carbonylative cascade approaches to highly functionalized polyheterocyclic structures. The Pd-catalyzed carbonylative process involves the regioselective insertion of one to three CO molecules and the sequential ordered formation of up to eight new bonds (one C-O, two C-C, five C-N). The exclusive formation of six-membered heterocycles is elucidated by detailed modeling studies.

We report the first example of cooperative catalysis by DBU and CuCl2, which allows the carboxylation of homopropargylic amines to high value added 6-methylene-1,3-oxazin-2-ones. This reaction also represents the first efficient method for the catalytic incorporation of CO2 into an acyclic substrate to give oxazinones. DFT calculations are in agreement with a mechanism involving: a) deprotonation of the substrate by DBU; b) CO2 capture with formation of a copper carbamate; c) 6-exo-dig cyclization through intramolecular triple bond insertion; and d) protonolysis, with regeneration of DBU and CuCl2 catalysts. The structure of a representative product has been confirmed by XDR analysis.

The front cover picture supplied by Carla Carfagna and co‐workers depicts an efficient process for the diastereospecific bis‐alkoxycarbonylation of 1,2‐disubstituted olefins, leading to the synthesis of 2,3‐disubstituted‐succinic diesters. Using Pd(TFA)2 as palladium source, bis‐(2,6‐dimethylphenyl)‐2,3‐dimethyl‐1,4‐diazabutadiene as ligand and p‐benzoquinone as oxidant, aliphatic, aromatic, cyclic olefins and unsaturated fatty acid methyl esters, have been successfully converted in the presence of different alcohols, under mild reaction conditions (PCO =4 bar, T = 20 °C). Further details can be found in the full paper on pages 3507–3517 (D. Olivieri, F. Fini, R. Mazzoni, S. Zacchini, N. Della Ca′, G. Spadoni, B. Gabriele, R. Mancuso, V. Zanotti, C. Carfagna, Adv. Synth. Catal. 2018, 360, 3507–3517: DOI 10.1002/adsc.201701597).

A catalytic carbonylative double cyclization method for the synthesis of furo[3,4-b]benzofuran-1(3H)-ones is reported. It is based on the reaction between readily available 2-(3-hydroxy-1-yn-1-yl)phenols, CO, and oxygen carried out in the presence of catalytic amounts of PdI2 (1 mol %) in conjunction with KI (20 mol %) and 2 equiv of diisopropylethylamine at 80 degrees C for 24 h under 30 atm of a 1:4 mixture of CO-air. Interestingly, the process was not selective when carried out in classical organic non-nucleophilic solvents (such as MeCN or DME), leading to a mixture of the benzofurofuranone derivative and the benzofuran ensuing from simple cycloisomerization, whereas it turned out chemoselective toward the formation of the double cyclization compound in BmimBF(4) as the reaction medium. Moreover, the ionic liquid solvent containing the catalyst could be easily recycled several times without appreciable loss of activity.

The first example of the oxidative carbonylation of 2-ethynylbenzoic acid derivatives, leading to alkyl (Z)-2-[3-oxoisobenzofuran-1-(3H)-ylidene]acetates in a regio- and stereoselective manner, is reported. Under the catalytic action of PdI2 (2 mol%) in conjuction with KI (20 mol%), different 2-[(trimethylsilyl)ethynyl]benzoic acids were converted into the corresponding isobenzofuranones in high to excellent yields (70–98%). The proposed reaction mechanism involves syn 5-exo-dig cyclization, carbon monoxide insertion, and nucleophilic displacement by an alcohol. Desilylation occurred under the reaction conditions. The structure of a representative product, that is, methyl (Z)-2-[3-oxoisobenzofuran-1(3H)-ylidene]acetate, was confirmed by XRD analysis. (Figure presented.).

A practical homogeneous and gas‐liquid palladium‐catalyzed Catellani‐type reaction using a continuous‐flow platform is described. The implementation of continuous‐flow technology allowed the acceleration of the transformation and, for the first time, expansion of the chemical space to gaseous olefins (i.e., ethylene, propylene and 3,3,3‐trifluoropropene), thus providing a safe and practical approach to sterically hindered ortho‐disubstituted styrenes and vinyl arenes. The complete control over the stoichiometry of gaseous reagents through flow technology proved essential for directing the selectivity of the Catellani reaction to the desired products.

(S)-4-Isopropyl-5,5-diphenyloxazolidin-2-one has been synthesized for the first time by the enantiospecific oxidative carbonylation of commercially available (S)-2-amino-3-methyl-1,1-diphenylbutan-1-ol. The cyclocarbonylation reaction was carried out at 100 °C in 1,2-dimethoxyethane (DME) as the solvent for 15 h, under 20 atm of a 4:1 mixture of CO–air and in the presence of the catalytic system PdI2/KI (substrate:KI:PdI2 molar ratio = 100:10:1), to give the oxazolidinone derivative in 81% isolated yield.

Readily synthesized aryl α-diimine derivatives have been used as efficient ligands for the palladium-catalyzed oxidative bis-alkoxycarbonylation reaction of 1,2-disubstituted olefins. The most active catalyst A was formed insitu from bis-(2,6-dimethylphenyl)-2,3-dimethyl-1,4-diazabutadiene and Pd(TFA)2(TFA=trifluoroacetate). This catalytic system was able to selectively convert 1,2-disubstituted olefins into 2,3-disubstituted-succinic diesters with total diastereospecificity, in good yields (up to 97%) with 2mol% of catalyst loading, under mild reaction conditions (4bar of CO at 20°C in presence of p- toluenesulfonic acid as additive and p-benzoquinone as oxidant). The optimized reaction conditions could be successfully applied to 1,2-disubstituted aromatic, aliphatic, cyclic olefins and to unsaturated fatty acid methyl esters, employing methanol or benzyl alcohol as nucleophiles. The use of the bulky, less reactive isopropyl alcohol has allowed to better understand the mechanisms involved in the catalytic process. The geometry of the carbonylated products can be explained as a consequence of a concerted syn addition of the Pd-alkoxycarbonyl moiety to the olefin C=C bond. Catalyst A was isolated, characterized and analyzed by single crystal X-ray diffraction analysis.

Dihydrodibenzo[b,f]azepines and dibenzo[b,f]azepines can be efficiently synthesized from aryl bromides, o-bromoanilines and norbornene or norbornadiene by means of palladium catalysis. This protocol gives access to dibenzo[b,f]azepine core containing a variety of electron-withdrawing substituents on both aromatic rings and complements the previously reported methodology where electron rich aryl iodides were preferentially used. The presence of KI, even in sub-stoichiometric amount, is crucial for this three-component reaction. The proper addition of iodide anions has a dramatic effect on reaction rate and selectivity. A formal three-step synthesis of the tricyclic antidepressant Clomipramine (Anafranil (R)) is also described.

The title compound, (Z)-4-(carbomethoxymethylene)-2-(4-fluorophenyl)-4H-benzo[d][1,3]oxazine, was synthesized in 68% isolated yield by palladium-catalyzed oxidative cyclization-methoxycarbonylation of 4-fluoro-N-(2-((trimethylsilyl)ethynyl)phenyl)benzamide. This new heterocyclic derivative was fully characterized by IR, 1H-NMR, 13C-NMR spectroscopies, MS spectrometry, and elemental analysis. The Z configuration around the double bond was unequivocally established by 2D NOESY experiments.

The direct syntheses of ureas, oxamides, 2-oxazolidinones, and benzoxazolones by the oxidative carbonylation of amines, β-amino alcohols, and 2-aminophenols allows us to obtain high value added molecules, which have a large number of important applications in several fields, from very simple building blocks. We have found that it is possible to perform these transformations using the PdI2 /KI catalytic system in an ionic liquid, such as 1-butyl-3-methylimidazolium tetrafluoroborate, as the solvent, the solvent/catalyst system can be recycled several times with only a slight loss of activity, and the product can be recovered easily by crystallization.

6 H-Dibenzopyrans are prepared starting from ORTHO-substituted aryl iodides, O-bromophenols and activated olefins, in the presence of a catalytic system based on palladium acetate and norbornene by means of a simple and efficient, one-pot, three-component procedure under mild conditions.

The first example of palladium-catalysed oxidative carbonylation of unprotected α-amino amides to hydantoins is described here. The selective synthesis of the target compounds was achieved under mild conditions (1 atm of CO), without ligands and bases. The catalytic system overrode the common reaction pathway that usually leads instead to the formation of symmetrical ureas.