A bis(triflyl)ethylation [triflyl = (trifluoromethyl)sulfonyl] inserted into a sequential cyclization cascade resulted in the direct formation of gem-bis(triflyl)ated cyclopenta[b]indolines from anilide-derived allenols and alkenols. This catalyst- and irradiation-free sequence facilitated the efficient preparation of functionalized tricyclic indoline cores bearing two contiguous stereocenters. The formed cyclopenta[b]indolines can be easily transformed into a wide variety of triflylated indolines, including the tetracycle ring system found in polyveoline. © 2021 American Chemical Society.

The allene functionality has participated in one of the most exciting voyages in organic chemistry, from chemical curiosities to a recurring building block in modern organic chemistry. In the last decades, a special kind of allene, namely, allenol, has emerged. Allenols, formed by an allene moiety and a hydroxyl functional group with diverse connectivity, have become common building blocks for the synthesis of a wide range of structures and frequent motif in naturally occurring systems. The synergistic effect of the allene and hydroxyl functional groups enables allenols to be considered as a unique and sole functionality exhibiting a special reactivity. This Review summarizes the most significant contributions to the chemistry of allenols that appeared during the past decade, with emphasis on their synthesis, reactivity, and occurrence in natural products. © 2021 American Chemical Society.

A selective palladium-catalyzed C(sp) arylation/carbocyclization/iodonium migration reaction sequence has been accomplished. Novel 2-iodo-1-aryl-9H-carbazoles are now easily available. As this result is contrary to the selectivity observed using gold catalysis, the formation of 2-iodocarbazoles is noticeable, suggesting a metal-controlled cyclization through chemo- and regioselective 1,2-alkyl migration and 1,4-iodonium migration. (Figure presented.). © 2021 Wiley-VCH GmbH

The synergy between metal catalysis and radical chemistry allows to surpass previous limitations of the reactions between allenols and sulfonylating reagents. Considering that previous studies of the reactivity of the allenol moiety with sulfonylating reagents have been limited to addition and rearrangement reactions lacking cyclization, we decided to modify the protocol for achieving a catalytic cyclization/functionalization. In this way, we accomplished a copper-catalyzed cascade cycloetherification/sulfonylation for the controlled preparation of 4-(arylsulfonyl)-2,5-dihydrofurans from allenols and sulfinates involving in situ-generated sulfur-centered radicals. The generality of our strategy was illustrated using various methyl- and phenyl-substituted allenes. (Figure presented.). © 2021 The Authors. Published by Wiley-VCH GmbH.

We report the sustainable and efficient synthesis of a new type of quinoline derivatives bearing one or two SO2CF3 groups. The protocol is metal-, catalyst- and irradiation-free, involves the use of readily available and stable precursors, and avoids the formation of side products. Also, the mild conditions of the process allow the tolerance of a wide range of functional groups. © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH

The carboarylation reaction of biphenyl-alkynes was successfully triggered by electrophilic attack of 1,1-bis(triflyl)ethylene on the alkyne moiety to give polycyclic aromatic hydrocarbons (PAHs) decorated by superacidic carbon acid functionality. Neutralisation of thus obtained acids with NaHCO3 yielded the corresponding sodium salts, which showed improved solubility in both aqueous and organic solvents. © 2021 Wiley-VCH GmbH

A synthesis of skipped 1,4-enynes through functionalization of the cyclobutene core with alkynes has been achieved, suggesting an unusual pathway of oxidative addition in tertiary iodoalkanes. This journal is © The Royal Society of Chemistry.

Herein, we report investigations embodying the first example of reversal of the native regioselectivity in the reaction of allenols with electrophiles. The effortlessness of C−C bond formation, mild reaction conditions, neither catalysts nor light irradiation, and exquisite selectivity, both in terms of functional-group tolerance and chemo-, site-, and stereo-selectivity, converts this trifluorosulfonylation-rearrangement sequence into an appealing protocol for the preparation of novel functionalized enones. The synthetic utility of this method has been validated by the conversion of the initially prepared bis(triflyl)enones into a variety of bis(triflyl)-functionalized molecules such as 1,3-dienes, allylic alcohols, pyrroles, pyrazoles, and chromenes. Besides, DFT calculations have provided a reliable understanding of observed selectivity. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

New (triflyl)cyclobutenes have been prepared by palladium-catalyzed hydrodetriflylation reaction using water and deuterium oxide as convenient hydrogen and deuterium sources. In addition, an investigation of the possible mechanism for this Tsuji-Trost type reaction of bis(triflyl)cyclobutenes has been facilitated by labelling studies and density functional theory (DFT) calculations. © The Royal Society of Chemistry 2020.

Supported silver nitrate in silica gel has been demonstrated as an excellent heterogeneous catalytic system for the selective hydroarylation of indole-tethered allenes, with a selectivity reversal in comparison with homogeneous gold catalysis. In this way, the controlled preparation of 1,2-disubstituted-9H-carbazoles, 1,2-disubstituted-4,9-dihydro-1H-carbazoles, and 2,4-disubstituted-spiro[cyclopentane-1,3′-indol]-3-enes has been accomplished. Control experiments supported by Density Functional Theory calculations strongly suggest that indole-tethered allenes react through a 5-endo-dig-carbometallation/rearrangement sequence, which contrasts to the previously reported 6-endo-dig-carbometallation pathway promoted by [Au(I)]-catalysts in related systems. © 2020 Elsevier Inc.

Carbazoles possessing Tf2CHCH2 groups were obtained by the reaction of 1-(indol-2-yl)but-3-yn-1-ols with in situ-generated Tf2CCH2 through vicinal difunctionalisation of the alkyne moiety, where the vinyl-type carbocation intermediate was selectively attacked by the indole moiety and not by the carbanion moiety. This journal is © The Royal Society of Chemistry.

The controlled synthesis of 1,4-naphthoquinones and tetraphene-7,12-diones, which bear the ABCD-ring of landomycins, has been accomplished directly through oxidative rearrangement of common stable precursors, namely, previously non-isolable cyclobuta[a]naphthalen-4(2H)-ones. © The Royal Society of Chemistry.

α,β-Unsaturated α′-alkoxy ketones have been prepared under mild conditions from allenes using water as the oxygen source and without the necessity of metals. The organocatalytic oxygenation-rearrangement sequence displays an exquisite chemo-, stereo-, and site-selectivity as well as good functional group compatibility. DFT calculations suggest that stabilizing noncovalent Se···O interactions may be responsible for the observed reactivity. © 2020 American Chemical Society.

Since earlier work on the use of arenediazonium tetrafluoroborates under gold-photoredox co-catalyzed activation of alkynes has been developed using Ar3PAuCl salts, we focused on modifying the gold precatalyst. The use of the gold complex [Ph3PAuNTf2] allowed for a direct alkoxyarylation of alkynes to form enol ethers in a stereoselective manner, instead of the previously obtained ketones. The synthetic utility of these enol ethers was demonstrated with the controlled preparation of deuterated ketones and fluorinated ketals. Additionally, the mechanism of this alkoxyarylation variant has been explored with density functional theory (DFT) calculations. © 2020 Elsevier Inc.

Multidrug resistance of cancer cells to cytotoxic drugs still remains a major obstacle to the success of chemotherapy in cancer treatment. The development of new drug candidates which may serve as P-glycoprotein (P-gp) efflux pump inhibitors is a promising strategy. Selenium analogues of natural products, such as flavonoids, offer an interesting motif from the perspective of drug design. Herein, we report the biological evaluation of novel hybrid compounds, bearing both the flavone core (compounds 1–3) or a bioisosteric analogue core (compounds 4–6) and the triflyl functional group against Gram-positive and Gram-negative bacteria, yeasts, nematodes, and human colonic adenocarcinoma cells. Results show that these flavones and analogues of flavones inhibited the activity of multidrug resistance (MDR) efflux pump ABCB1 (P-glycoprotein, P-gp). Moreover, the results of the rhodamine 123 accumulation assay demonstrated a dose-dependent inhibition of the abovementioned efflux pump. Three compounds (4, 5, and 6) exhibited potent inhibitory activity, much stronger than the positive control, verapamil. Thus, these chalcogen bioisosteric analogues of flavones become an interesting class of compounds which could be considered as P-gp efflux pump inhibitors in the therapy of MDR cancer. Moreover, all the compounds served as promising adjuvants in the cancer treatment, since they exhibited the P-gp efflux pump modulating activity. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

The first coupling of α-allenols, sulfur dioxide, and arenediazonium salts is presented. The three-component reaction which is promoted by visible light can be easily accomplished using DABSO as a sulfur dioxide surrogate in the presence of a photoredox catalyst. In this manner, a broad range of electron-rich and electron-deficient aryl substituents are well accommodated in the sulfonylation-rearrangement cascade to afford the 2,2-disubstituted 3-(arylsulfonyl)but-3-enals in reasonable yields. Based on control experiments, a radical mechanism which does imply 1,2-aryl migration has been proposed. © 2020 American Chemical Society.

Tunable chemoselectivity (O- versus C-attack) in the rhodium-catalyzed reactions of allenols with 4-substituted-1-sulfonyl-1,2,3-triazoles has been achieved through the replacement of the 4-aryl substituent by a 4-acetyl moiety. (Figure presented.). © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

The controlled preparation of two types of α-seleno-α,β-unsaturated carbonyls, namely, α-selenoenals and α-selenoenones, has been accomplished directly from allenes through metal-free oxidative selenofunctionalization reactions. The decisive role of organoselenium and 1-fluoropyridinium reagents has been disclosed. The divergent reactivity due to the presence or absence of an ethoxycarbonyl moiety at the allene end has also been studied. A tentative pathway implying selective electrophilic addition of the selenium reagent to the allene moiety followed by adventitious water attack and concomitant oxidation has been proposed. © the Partner Organisations 2019.

A regioselective synthesis of general applicability has been designed for the one-pot preparation of 2,3-disubstituted-cyclobutenones from iodoalkynes through cyclobutenylation, Suzuki CC coupling, and ketone formation. This one-pot methodology has been applied to the selective synthesis of an orally active cyclooxygenase II inhibitor. Furthermore, the obtained cyclobut-2-en-1-ones were used as synthons in several transformations, such as, the preparation of β-lactams, phthalazines, cyclohexa-2,5-dien-1-ones, and cyclopent-3-en-1-ones. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

The divergent and selective syntheses of two types of annelated β-lactams, namely, furan- and tetrahydropyridine-fused 2-azetidinones, have been accomplished directly from 2-azetidinone-tethered oxazolidine-enynes through gold catalysis. The decisive effect of the presence or absence of substituents at the enyne end has been disclosed. The gold-catalyzed conditions are mild enough to tolerate the selective formation of condensed β-lactams without the erosion of the stereochemical integrity of the products and without damaging the sensitive 2-azetidinone nucleus. © The Partner Organisations.