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Rhodium-catalyzed intramolecular [2 + 2 + 2] cycloaddition of linear chiral triynes having 4-atom tethers leads to, in a single step, complex tetrahydroisoquinolines having central chirality.

The Pauson–Khand reaction (PKR) is one of the key methods for the construction of cyclopentenone derivatives, which can in turn undergo diverse chemical transformations to yield more complex biologically active molecules. Despite the increasing availability of fluorinated building blocks and methodologies to incorporate fluorine in compounds with biological interest, there have been few significant advances focused on the fluoro-Pauson–Khand reaction, both in the inter- and intramolecular versions. Furthermore, the use of vinyl fluorides as olefinic counterparts had been completely overlooked. In this review, we collect the advances both on the stoichiometric and catalytic intermolecular and intramolecular fluoro-Pauson–Khand reaction, with special attention to the PKR of enynes containing a fluoride moiety.

Despite the great advances achieved in the Pauson-Khand reaction and the ever-increasing demand for fluorinated compounds, the use of vinyl fluorides as olefinic counterparts in the above-mentioned transformation had been completely overlooked. Herein, we describe, for the first time, the intramolecular Pauson-Khand reaction of enynes containing a vinyl fluoride moiety.

The addition of propargylmagnesium bromide to fluorinated aromatic sulfinyl imines gave homopropargyl amines with total regio- and diastereoselection. Complete reversal of diastereoselectivity can be achieved in some cases using coordinating (THF) or noncoordinating (DCM) solvents. Substituted propargylic magnesium reagents have been also tested toward fluorinated aryl sulfinyl imines affording chiral homoallenyl amines with good yields and selectivity control. DFT calculations helped to rationalize the origin of the experimental regio- and diastereoselectivities observed in each case.

Kinetic data by means of electrochemical techniques are used to characterize the reactivity of aryl bromides and activated alkyl bromides in oxidative addition to palladium(0) complexes generated from three precursors: Pd0(PPh3)4, {Pd0(dba)2 + 2 PPh3} and {Pd0(dba)2 + 2 P(o Tol)3} in DMF at 25 °C. It is established that, for the investigated substrates 1-6 and 7-11, the oxidative addition at the Csp3 Br bond is much faster than that at the Csp2 Br bond when the palladium(0) is ligated by two PPh3. This explains why the regioselectivity in Suzuki-Miyaura reactions performed from substrates bearing both Csp2 Br and Csp3 Br groups is in favour of the substitution at the Csp3 Br bond. It is in agreement with DFT calculations which propose a SN2-type mechanism from the bis-ligated Pd0(PPh3)2. The oxidative addition at the Csp2 Br bond is much faster when the palladium(0) is ligated by P(o-Tol)3 than by PPh3 in agreement with the DFT calculations which support a concerted mechanism involving the mono-ligated Pd0[P(o-Tol)3] as the reactive species. This explains why the regioselectivity in Suzuki-Miyaura reactions performed from substrates bearing both Csp2 Br and Csp3 Br groups might be in favour of the substitution at Csp2 Br bond when the ligand is P(o-Tol)3.

The authors are grateful to the Spanish MICINN and the AEI (CTQ2017-84249-P) for financial support, the SCSIE (Universitat de Valencia) for access to instrumental facilities, and M. ̀ R. Pedrosa (Universidad de Burgos) for providing us with MoO2Cl2. The technical and human support provided by SGIker (UPV/EHU, MINECO, GV/DJ, ERDF, and ESF) is also gratefully acknowledged. P.B. thanks the Spanish Ministry of Economy for a Ramon y Cajal contract (RyC-2016-20951). ́ The authors are also grateful to Jose Cabeza for assistance in the synthesis of certain starting materials.

Over the last two decades, fluorine substitution has become one of the essential structural traits in modern pharmaceuticals. Thus, about half of the most successful drugs (blockbuster drugs) contain fluorine atoms. In this review, we profile 17 fluorine-containing drugs approved by the food and drug administration (FDA) in 2018. The newly approved pharmaceuticals feature several types of aromatic F and CF3 , as well as aliphatic (CF2 ) substitution, offering advances in the treatment of various diseases, including cancer, HIV, malarial and smallpox infections.

The three component reactions of α-bromomethyl oxime ethers, carbon monoxide, and alcohols or aromatic amines give imino esters and amides, respectively.

Treatment of alkynylureas (I) with trifluoroethanol in the presence of a Au/Ag catalytic system provides N-6-exo-dig heterocyclization products (III) and in some cases open chain acetals as side products.

The Pd-catalyzed cross-coupling reaction of chloromethyl oxime ethers with a wide range of aryl-, heteroaryl-, and vinylboronic acids proceeds with good yields.

Alkenyl sulfoxide derivatives are obtained in high yields through a palladium-catalyzed Suzuki/Miyaura cross-coupling reaction of racemic and chiral 1-halo sulfoxides with aryl and alkenyl boronic acids. Chiral substrates react with no loss of optical purity and high optical yields. The reaction takes place with different palladium catalysts, such as Pd(PPh 3 ) 4 or Pd(OAc) 2 /DABCO. Although nitrogen ligands like DABCO lead to an active palladium catalyst, they are less effective than the phosphine ones.

A new PEG-tagged material, which was prepared by a threefold copper-catalyzed [3+2] cycloaddition (click chemistry), was found to act as an efficient stabilizer for palladium nanoparticles. The newly formed material proved to be active as a recyclable catalyst in Suzuki coupling; the presence of polyether chains allowed for the catalytic runs to be conducted in aqueous media.

3-Substituted 1-(o-ethynylaryl)ureas 1 selectively undergo either 6-exo-dig or 5-endo-dig cyclization (to give 4-methylene-3,4-quinazolin-2-ones 2 or indoles 3, respectively) depending on the choice of the metal, ligand, and reaction conditions. The best results (up to 96% yield) in the preparation of the hydroamination products 2 are achieved with the highly bulky NHC-stabilized cationic gold(I) complex [Au(IPr)](+). Conversely, ureas bearing an internal alkyne lead to the 5-endo-dig cyclization mode regardless of the gold(I) complex employed. Whereas the nature of the substituent at N-3 does not have any influence on the regiochemistry observed, it does, in some cases, affect the efficiency of these transformations.

A gold(I)-catalysed hydroaminative/arylative cascade for the efficient synthesis of a variety of indole-fused skeletons has been developed. Factors controlling the catalyst loading required in these transformations involving 1,3-unsubstituted indole intermediates have been revealed, allowing isolation of an unprecedented 1,3-dimetallated 3H-indole gold complex characterized by X-ray diffraction.

The three component reactions of α-bromomethyl oxime ethers, carbon monoxide, and alcohols or aromatic amines give imino esters and amides, respectively.

A general procedure for the title condensation of dimethylacetals derived from enolizable aldehydes with silyl enol ethers is developed using FeCl3 as the catalyst.

A series of optically pure γ-halogenated β-hydroxysulphoxides containing two stereogenic centers have been prepared, and the X-ray crystal structures have been determined. The conformational behavior in the solid state and the crystal packing of the different β-hydroxysulphoxide diastereoisomers have been determined. The intermolecular and intramolecular interactions present have been studied in both halogenated and nonhalogenated β-hydroxysulphoxides to establish the influence of the halogen atom in the supramolecular structure. The main intermolecular hydrogen bond OH···OS is always present and produces molecular chains. Self-assembly of these chains includes weak CH···F, C−F···F−C, and C−F···π interactions. While the C−F···F−C and C−F···π interactions present do not appear to drive the crystal packing, partially fluorinated methyl groups induce C−H···F−C hydrogen bridges within CF−H···F−C crystal homosynthons that clearly change the packing mode.

[reaction: see text] An unprecedented palladium-catalyzed three-component cross-coupling reaction between alpha-bromo sulfoxide, carbon monoxide, and aromatic boronic acids provides a new and efficient approach to the synthesis of beta-ketosulfoxides. The reaction takes place under mild conditions with a wide range of variously substituted aryl and heteroaryl boronic acids. The carbonylative cross-coupling reaction is strongly favored over competing direct cross-coupling and homocoupling processes, except with boronic acids carrying strong electron-withdrawing substituents.

The enantioselective protonation with 2-sulfinyl alcohols of lithium enolates of 2-arylcyclohexanones with different substituents on the phenyl group takes place with excellent enantioselectivities (89–99%). Chiral 2-phenylcyclohexanone and 2-arylcyclohexanones carrying electron donor substituents on the aromatic ring are converted into the corresponding trans -2-arylcyclohexanols by diastereoselective reduction with sodium naphthalenide in the presence of acetamide. The stereochemical integrity of the tertiary stereocenter is fully preserved using this reduction procedure. Interestingly, the chiral proton source is not consumed in the synthesis.

[reaction: see text] A new Suzuki-type palladium-catalyzed reaction of boronic acids with alpha-bromo sulfoxides has been developed using a protocol similar to the well-documented reaction of boronic acids with aryl halides. Both cross-coupling and homocoupling processes were observed. The best yields in cross-coupling products were obtained when the presence of oxygen was carefully excluded using degassed solvents. The oxidative addition palladium complex intermediate could be isolated and characterized by X-ray single-crystal diffraction.

Treatment of alkynylureas (I) with trifluoroethanol in the presence of a Au/Ag catalytic system provides N-6-exo-dig heterocyclization products (III) and in some cases open chain acetals as side products.

The Pd-catalyzed cross-coupling reaction of chloromethyl oxime ethers with a wide range of aryl-, heteroaryl-, and vinylboronic acids proceeds with good yields.

Enantioselective protonation of 2-methyl tetralone enolate using a stoichiometric amount of 2-sulfinyl alcohol ( S , R s )- 1 as a chiral proton donor yields the corresponding chiral ketone with a high level of enantioselectivity, provided that the chiral proton donor (CPD) is regenerated with an achiral proton source (APS). In contrast, stereoselectivity was only moderate if catalytic CPD (0.2 equiv.) and an APS are used.

Complexes OsCl3{dbf(PiPr2)2} [1; dbf(PiPr2)2 = 4,6-bis(diisopropylphosphino)dibenzofuran], OsCl3{xant(PiPr2)2} [2; xant(PiPr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene], and OsCl3{xant(PPh2)2} [3; xant(PPh2)2 = 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene] have been obtained in high yield by the reaction of the corresponding diphosphine with OsCl3·3H2O. The ruthenium(III) counterparts RuCl3{dbf(PiPr2)2} (4), RuCl3{xant(PiPr2)2} (5), and RuCl3{xant(PPh2)2} (6) are similarly obtained from RuCl3·3H2O in moderate yields. The X-ray structures of dbf(PiPr2)2 and complexes 1−3 are also reported., Financial support was provided by the Spanish MICINN (Projects CTQ2008-00810 and CTQ2007-65720 and Consolider Ingenio 2010 CSD2007- 00006), Diputación General de Aragón (E35), and the European Social Fund.

A series of nine TADDOLs (=α,α,α′,α′-tetraaryl-1,3-dioxolane-4,5-dimethanols) 1a – 1i, have been tested as proton sources for the enantioselective protonation of the Li-enolate of 2-methyl-1-tetralone (=3,4-dihydro-2-methylnaphthalen-1(2H)-one). The enolate was generated directly from the ketone (with LiN(i-Pr)2 (LDA)/MeLi) or from the enol acetate (with 2 MeLi) or from the silyl enol ether (with MeLi) in CH2Cl2 or Et2O as the solvent (Scheme). The Li-enolate (associated with LiBr/LDA, or LiBr alone) was combined with 1.5 – 3.0 equiv. of the TADDOL at −78° by addition of the latter or by inverse addition. 2-Methyl-1-tetralone of (S)-configuration is formed (≤80% yield) with up to 99.5% selectivity if and only if (R,R)-TADDOLs (1d, e, g) with naphthalen-1-yl groups on the diarylmethanol unit are employed (Table). The reactions were carried out on the 0.1- to 1.0-mM scale. The selectivity is subject to non-linear effects (NLE) when an enantiomerically enriched TADDOL 1d is used (Fig. 1). The performance of TADDOLs bearing naphthalen-1-yl groups is discussed in terms of their peculiar structures (Fig. 2).

A suitable method for the preparation of the chiral mixed O/S ligands 1,2-sulfinyl thiols is described. These compounds have then been used as a chiral proton source in the enantioselective protonation of 2-methyl tetralone enolate and the results are compared with those obtained from the analogous alcohols. A theoretical model is proposed to explain the different behaviors exhibited in the protonation reaction for each of these proton sources. Configurational assignments for the new chiral thiols have been carried out by means of X-ray analysis.

A facile and efficient separation of mixtures of epimeric α-sulfinyl alcohols 2:3 can be accomplished by selective lipase-catalyzed acylation with neat vinyl acetate. Pseudomonas cepacia and Candida rugosa lipase showed opposite epimer differentiation in the esterification.

The effects of the solvent, temperature, presence of lithium salts in the medium, and acidity of the proton source on enantioselective protonation with α-sulfinyl alcohols 2a−e were studied. Stereoselectivity was generally enhanced when lithium bromide was present in the medium during enolization and also with the use of methylene chloride solutions. Conversely, the optimal reaction temperature varied with the α-sulfinyl alcohol used as a proton source, and its effect appears to be related to both the acidity of the proton source and the enolate structure. α-Sulfinyl alcohols 2a and 2b gave the best results when the reactions were carried out at −100 °C, while the optimal temperature with 2c was −78 °C. The same ee values were obtained with 2d and 2e at either −100 or −78 °C. In addition, an efficient synthesis of α-sulfinyl alcohols 2b and 2c is described.

The efficient asymmetric protonation of lithium enolates of 2-alkylcycloalkanones (87–96% ee) with readily accessible chiral α-sulfinyl alcohols is described. Optimal stereoselection is achieved for each lithium enolate at a different reaction temperature in the range −40 to −100°C.

meso -Diols derived from the Diels–Alder adduct 1,4-bis(hydroxymethyl)furan/dimethyl acetylenedicarboxylate can be enantioselectively monoacetylated under CRL or PSL catalysis with very good yields and moderate to excellent ees. (+)-Monoacetates are always preferentially formed in the reactions catalyzed by CRL, and their (−)-enantiomers are the main products in the acetylations under PSL catalysis. Absolute configurations have been determined by X-ray analysis of a single crystal of an ( R )-α-methoxyphenylacetyl derivative.

The favourable effect of lithium bromide enhancing the facial enantioselectivity in the protonation of methyl tetralone enolate with α-sulfinyl alcohols is described. Theoretical calculations allow to propose a model to explain the stereochemical course of the protonation reaction.

The competition between π- and dual σ,π-gold-activation modes is revealed in the gold(I)-catalyzed heterocyclization of 1-(o-ethynylaryl)urea. A noticeable effect of various ligands in gold complexes on the choice of these activation modes is described. The cationic [Au(IPr)](+) (IPr=2,6-bis(diisopropylphenyl)imidazol-2-ylidene) complex cleanly promotes the π activation of terminal alkynes, whereas [Au(PtBu3 )](+) favors intermediate σ,π species. In this experimental and mechanistic study, which includes kinetic and cross-over experiments, several σ-gold, σ,π-gold, and other gold polynuclear reaction intermediates have been isolated and identified by NMR spectroscopy, X-ray diffraction, or MALDI spectrometry. The ligand control in the simultaneous or alternative π- and σ,π-activation modes is also supported by deuterium-labeling experiments.

Pd2(dba)3/ Xantphos-catalyzed coupling of the sulfoxides (I) and (V) with amines and carbon monoxide allows a new and efficient access to amides of type (IV) and (VI).

The palladium-catalyzed reaction of α-bromomethyl sulfoxides, carbon monoxide, and N-nucleophiles follows different reaction pathways according to the catalytic system and the reaction conditions. The Pd-xantphos catalyst affords high yields of α-sulfinyl amides by an aminocarbonylation process and is the first example of this type of transformation for a nonbenzylic sp(3)-hybridized carbon. On the other hand, the oxidative carbonylation of amines occurs with α-bromomethyl sulfoxides, carbon monoxide, and catalytic Pd(PPh(3))(4) under aerobic conditions, yielding ureas and oxalamides from either primary or secondary amines. The reaction with ambident nucleophiles such as amino alcohols was highly selective and took place exclusively at the amino group despite the presence of the alcohol functionality. In parallel to the reaction paths for simple amines, amino alcohols were converted into hydroxy sulfinyl amides when the reaction was catalyzed by Pd-xantphos, while Pd(PPh(3))(4) catalyst afforded cyclic carbamates. The alkoxycarbonylation reaction of bromomethyl sulfoxides with simple alcohols and CO leading to the corresponding sulfinyl esters is also described.

Phosphine ligands are shown to control the selectivity in the Suzuki—Miyaura coupling of dibromo sulfoxide (I).

Polyethylene glycol-tagged macrocycle (I) is prepared by a three-fold copper-catalyzed [3 + 2] cycloaddition reaction.

Alkenyl sulfoxide derivatives are obtained in high yields through a palladium-catalyzed Suzuki/Miyaura cross-coupling reaction of racemic and chiral 1-halo sulfoxides with aryl and alkenyl boronic acids. Chiral substrates react with no loss of optical purity and high optical yields. The reaction takes place with different palladium catalysts, such as Pd(PPh 3 ) 4 or Pd(OAc) 2 /DABCO. Although nitrogen ligands like DABCO lead to an active palladium catalyst, they are less effective than the phosphine ones.

Under the optimized gold catalysis, the less favored and more challenging 6-exo-dig cyclized products are formed in yields up to 96% from ureas bearing a terminal alkyne at the ortho-position.

The mechanism of the formation of 1-methyl-3H,9H-pyrano[3,4-b]indol-3-one (4) from the corresponding 3-indolacetic acid 1 is discussed. The suggested mechanism is substantiated by the isolation of a stable intermediate 2 and its transformations in the presence of acetic anhydride and/or Lewis acids.