Functionalized ynones can be activated by Tf2C=CH2, which was generated in situ, to form zwitterionic species. These species were trapped in an intramolecular fashion by several nucleophiles to generate two major types of triflones in a divergent manner. Through fine-tuning of the reaction temperature, bis(triflyl)-6-membered- or (triflyl)-5-membered-fused-heterocycles were achieved in reasonable yields in a totally selective manner. In this way, bis(triflyl)flavones, bis(triflyl)thioflavones, bis(triflyl)selenoflavones, (triflyl)benzothienopyrans, (triflyl)benzoselenophenopyrans, (triflyl)vinyl aurones, and (triflyl)pyranoindoles were constructed. Conceivable mechanistic pathways were suggested on the basis of the isolation of several intermediates and the results from control experiments. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

New azahelicenes having interesting photophysical properties have been prepared in a four-step sequence. These [7]helicenocarbazoles are efficient blue luminophores, demonstrating the utility of gold catalysis in the preparation of advanced materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Indole-tethered amino allenynes were chemodivergently cyclized for the controlled preparation of fused polycyclic indoles using gold catalysis. Double cyclization of terminal allenynes afforded hexacyclic 15 H-indolo[1,2,3-de]quinolino[3,2,1-ij]quinoxalines, in which allenynes bearing a substituted alkyne at the terminal end generated 12,13-dihydro-7 H-indolo[3,2-c]acridines, which are 5-membered cyclized adducts. Density functional theory calculations were performed to shed light on this difference in reactivity. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Several heterocycles reacted with shelf-stable 2-(2-fluoropyridinium-1-yl)-1,1-bis[(trifluoromethyl)sulfonyl] ethan-1-ide, a latent Tf2CCH2 source, to give rise in a mild and controllable way to adducts via direct C-H bis[(trifluoromethyl)sulfonyl]ethylation reactions. This metal- and irradiation-free protocol is convenient. Besides, the volatile side-product 2-fluoropyridine can be smoothly eliminated under vacuum, which facilitates purification. The substrate scope survey discloses that exquisite chemo- and regioselectivities are achieved in a variety of heterocyclic systems. Of particular interest are the late-stage structural modification of known pharmaceuticals, such as the marketed drugs Phenazone (Antipyrine) and Edaravone, and the development of a water soluble fluorescent dye. © 2018 the Partner Organisations.

Phosphorus 1,3- and 1,4-carbabetaines with ′P(+)−C−C(−)′ and ′P(+)−C−C−C(−)′ structures, respectively, in which the carbanion moiety was significantly stabilized by two trifluoromethylsulfonyl groups, have been synthesized and characterized. Analysis of their X-ray crystal structures revealed that any attractive interactions between the anionic and cationic moieties were negligibly weak. This result was corroborated by using natural bond orbital (NBO) and Bader′s quantum theory of atoms in molecules (QTAIM) models. In contrast, performing the same analysis of a known 1,3-carbabetaine equivalent, which can be drawn as a ′P(+)−C−C=C−O(−)′ resonance structure, revealed pronounced charge-transfer interactions between the anionic and cationic moieties. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

The room temperature radical cycloetherification/arylation cascade of allenols and diazonium salts has been accomplished via a combination of gold and photoredox catalysis to provide 2,3,4-trisubstituted-2,5-dihydrofurans. The functionalized oxacycle formation sequence is chemo- and regioselective for the cycloetherification and for the position that bears the aryl moiety after the cross-coupling. Mechanistic investigations revealed that this transformation proceeds through an initial oxidation of gold(I) to a phenyl gold(III) complex, which, upon coordination to the allene, catalyzes its cyclization and leads to the coupling product after a reductive elimination regenerating Au(I). (Figure presented.). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

The controlled metal-free synthesis of a vast variety of heteroatom-containing cyclobutene-triflones [bis(trifluoromethylsulfonyl)cyclobutenes] and cyclobutenones has been developed starting from heteroatom-substituted alkynes and a pyridinium salt (a latent Tf2C=CH2 source). This powerful methodology, involving cyclization reactions, allows for the selective preparation of oxygen-, nitrogen-, bromine-, chlorine-, iodine-, sulfur-, selenium-, tellurium-, phosphorus-, and silicon-functionalized cyclobutene derivatives. (Figure presented.). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Visible light-promoted and gold-photoredox-catalyzed reactions of heteroatom (N, S, Se, O) tethered alkynes with arenediazonium salts selectively proceeded to build vicinal diaryl-substituted 2H-benzo[e][1,2]thiazine 1,1-dioxides (benzosultams), benzoselenophenes, benzothiophenes, 4H-chromen-4-ones (flavones), 3H-indoles, 1H-isochromen-1-ones (isocoumarins), and 4H-thiochromen-4-ones (thioflavones). Moreover, the utility of functionalized 3H-indoles as precursors for further elaboration has been demonstrated with the switchable and facile preparation of 1H-indoles, 2-oxindoles, and 3-oxindolines. (Figure presented.). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

The β-lactam ring (2-azetidinone) is found in classical antibiotics such as penicillins and cephalosporins. In addition, this fragment is also detected in compounds with other pharmacological profile, such as antidiabetic, anticancer and cholesterol absorption inhibition among others. Besides, to its biological relevance, the β-lactam ring is a versatile building block for the synthesis of a huge amount of acyclic and cyclic structures by selective fragmentation or rearrangement of each single bond. This chapter is devoted to the synthesis of five-membered heterocycles by ring expansion of β-lactams. The contributions presented in this chapter have been selected from the developments achieved mainly in the last 20 years, in addition to some remarkable early reports. © Springer International Publishing AG 2017.

Switchable reactivity through cationic gold-based catalyst control built on the oxidation state, namely cationic Au III versus Au I , has been achieved in the direct functionalization of 2-azetidinone-tethered alkynyl indoles. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

2-Pyrrolines and 6-oxo-hexa-2,4-dienals have been prepared through the divergent reactions of 1-benzenesulfonyl-4-aryl-1,2,3-triazoles with functionalized allenes. The rhodium-catalyzed reactions between allenols and 1-benzenesulfonyl-4-aryl-1,2,3-triazoles yielded 2-pyrrolines. This transformation is compatible with the presence of aliphatic, aromatic, heterocyclic, amide, and halogen functional groups. Interestingly, a reactivity switch took place when the allene-tethered alcohol substrate was replaced by its ketone counterpart. When the rhodium-catalyzed reaction of 1-benzenesulfonyl-4-phenyl-1,2,3-triazole was performed with allenones, acyclic 6-oxo-hexa-2,4-dienals were stereoselectively formed as (2Z,4E) isomers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

A selective and convenient synthesis of tri- and tetrasubstituted α,β-unsaturated ketones, as well as 2,3-diarylbenzofurans has been developed with the aid of light and taking advantage of a cooperative gold/photoredox-catalyzed 2-fold arylation reaction of TMS-terminated alkynols. The reaction of 3-(trimethylsilyl)prop-2-yn-1-ols was competent to generate diarylated α,β-unsaturated ketones; whereas the photoredox sequence involving 2-[(trimethylsilyl)ethynyl]phenol exclusively afforded 2,3-diarylbenzofurans. The reaction of terminal alkynes proceeded in poor yields while the use of bulkier silyl groups, such as TIPS, resulted unproductive. Apparently, the C(sp) arylation reaction is the first event on the domino bis-arylative sequence. These results could be explained through the intermediation of arylgold(III) species and several single electron transfer processes. © 2017 American Chemical Society.

An unprecedented metal-free direct preparation of unprotected α-hydroxy ketones from terminal alkynes under mild conditions with diazonium salts as the arene source and without the requirement of irradiation is described. The process is general and fully compatible with a wide variety of substitution in both reactants. Experimental and computational evidence strongly suggest the involvement of radical species in the transformation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

The present study provides insights into the manner in which the configuration of β-aminoallene precursors affects their gold-catalyzed cyclization reactions. The reactivity can be switched by using indolizidinone-tethered β-aminoallenes bearing the syn- or the anti-disposition of both protons at the α- and β-allenic stereocenters. Fused heterocycles (seven examples, 60-75\% yields) are obtained from the syn-precursors, while a dimerization-aminoketalization-spirocyclization sequence to afford benzo[b]pyrrolo[3,2,1-ij][1,7]naphthyridin-1-ones (four examples, 34-48\% yields) can be achieved starting from their anti-isomers. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlled preparation of 2,5-dihydro-1H-pyrroles, 3,6-dihydro-2H-pyrans, and pyrroles has been achieved through switchable chemo- and regioselectivity in the metal-catalyzed heterocyclization reactions of allenic amino alcohols. The gold-catalyzed cycloisomerization reaction of α-amino-β-hydroxyallenes was effective as 5-endo cyclization by addition of amino functionality to the distal allene carbon to yield enantiopure 2,5-dihydro-1H-pyrroles, whereas their palladium-catalyzed cyclizative coupling reactions furnished 3,6-dihydro-2H-pyrans through a chemo- and regioselective 6-endo cycloetherification. Conversely, the gold-catalyzed heterocyclization reaction of β-amino-γ-hydroxyallenes generated exclusively pyrrole derivatives. These results could be explained through a chemo- and regioselective 5-exo aminocyclization to the central allene carbon followed by aromatization. Chemo- and regioselectivity depend on both linker elongation as well as the type of catalyst. This behavior can be justified by means of density functional theory calculations. © 2016 American Chemical Society.

A method for the arylative coupling of alkynols or alkynyl hydroperoxides using equimolar amounts of diazonium salts at room temperature has been achieved through application of a gold/photoredox dual catalytic system. The excess of external reagents (oxidant or base) and high temperatures required by previous arylative Meyer-Schuster rearrangement protocols are avoided by exploitation of a visible light-mediated process. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A convenient ligand-free catalytic system has been developed for the chemoselective cyclization reaction of various α-allenol derivatives by palladium nanoparticles (PdNPs) in an aqueous reaction medium. (Figure presented.) . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The diastereoselective synthesis of strained adducts that show cage-like structures has been accomplished directly from allenyl-β-lactams through gold catalysis. © The Royal Society of Chemistry 2016.

The controlled metal-free preparation of fused δ-sultone derivatives has been developed starting from hydroxyallenynes. The use of 2-(3,3-diethyltriaz-1-enyl)-4-methylbenzene-1-sulfonyl chloride in a sulfonylation/rearrangement sequence gives access to 1,3-dien-2-yl arenesulfonates. These functionalized enynes suffered a direct cyclization/desaturation radical cascade, allowing the synthesis of a variety of enynyl [1,2]oxathiine 1,1-dioxides. Stereoselective cyclization of the readily formed core through intramolecular Diels-Alder reaction has also been demonstrated, affording β-lactam- and glucofuranoside-fused δ-sultone polycycles. These selective reactions have been studied experimentally and additionally, their reaction mechanisms have been investigated computationally by means of density functional theory calculations. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The synthesis of 2-allenyl-2-substituted-3,3-difluoroindolines has been accomplished, taking advantage of the reaction between N-allenyl-indoles and Selectfluor under iron catalysis. © 2016 The Royal Society of Chemistry.