Reduction of tri(hetero)arylcarbinols to tri(hetero)arylmethanes

Summary A series of seven new tri(hetero)arylmethanes has been prepared by reduction of the corresponding carbinols using a mixture of lithium aluminium hydride/aluminium trichloride. The yields are excellent (77–98%) except in the case of the tri(2-benzothienyl)derivative (41%).¹H NMR spectra are discussed.

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Reduktion von Tri(hetero)arylcarbinolen zu Tri(hetero)arylmethanen

Zusammenfassung Durch die Reduktion der entsprechenden Carbinole mit Lithium-aluminiumhydrid/Aluminiumchlorid wurden sieben neue Tri(hetero)arylmethane in sehr guten Ausbeuten (77–98%) hergestellt. Eine Ausnahme bildet das Tri-(2-benzothienyl)-Derivat mit 41%. Die¹H-NMR-Spektren werden diskutiert.

     

Palladium-catalyzed direct (hetero)arylation of ethyl oxazole-4-carboxylate: an efficient access to (hetero)aryloxazoles

A straightforward route toward 2-(hetero)arylated and 2,5-di(hetero)arylated oxazoles through regiocontrolled palladium-catalyzed direct (hetero)arylation of ethyl oxazole-4-carboxylate with iodo-, bromo-, and chloro(hetero)aromatics followed by a two-step hydrolysis/decarboxylation sequence was described. The method was applied here to a neat synthesis of two 2,5-di(hetero)aryloxazole natural products, balsoxin and texaline.     

Palladium-catalyzed selective N-(hetero)arylation or N,N′-di(hetero)arylation of 1-aminoindoles

The selective synthesis of N-(hetero)aryl-1-aminoindoles 3 from the corresponding N-aminoindoles and (hetero)aryl halides using a catalyst combination of Pd₂(dba)₃ associated to Josiphos is described. By switching to Xantphos as the ligand, the alternate catalytic system allows the coupling to proceed efficiently for the preparation of symmetrical and unsymmetrical N,N′-diaryl-1-aminoindole derivatives in good yields.     

Palladium-catalysed 5-endo-trig allylic (hetero)arylation

A palladium-catalysed intramolecular allylic (hetero)arylation strategy for the synthesis of fused cyclopentenes incorporated with all-carbon quaternary and spiro centres is described. The method is straightforward, shows broad scope, proceeds in synthetically useful yields, and provides a rare means to construct complex cyclopentanoids. The reaction is believed to involve a kinetically unfavourable 5-endo-trig carbocyclisation of the tethered (π-allyl)palladium system. Further, this method was successfully applied as the key step in the total synthesis of diterpene natural products taiwaniaquinone H and dichroanone.

A palladium-catalysed intramolecular allylic (hetero)arylation strategy for the synthesis of fused cyclopentenes incorporated with all-carbon quaternary and spiro centres is described.     

Copper-mediated chelation-assisted ortho nitration of (hetero)arenes

A novel copper-mediated chelation-assisted ortho C-H nitration of (hetero)arenes has been developed for the first time, which used dioxygen as terminal oxidant and 1,2,3-TCP as solvent, leading to the synthesis of nitroaromatics with excellent regioselectivity and in good yields. Mechanistic investigations indicate a mechanism involving a four-centered transition state, with simultaneous cleavage of an ortho C-H bond and a N-O bond of the nitrate anion on the 2-arylpyridine-coordinated copper(II) complex.     

Decarboxylative homocoupling of (hetero)aromatic carboxylic acids

A variety of hetero(aromatic) carboxylic acids are shown to undergo decarboxylative homocoupling, mediated by a Pd/Ag system. This novel methodology for the synthesis of symmetrical biaryls avoids the use of haloarenes and organometallic compounds as starting materials.     

Luminescent rhenium(I)-gold(I) hetero organometallics linked by ethynylphenanthrolines

The first luminescent rhenium(I)-gold(I) hetero organometallics, Re{phenAu(PPh₃)}(CO)₃Cl (3) and Re{(PPh₃)AuphenAu(PPh₃)}(CO)₃Cl (4), have been prepared using the gold(I) complex AuCl(PPh₃) (PPh₃ = triphenylphosphine) and the novel rhenium(I) complexes Re(phenH)(CO)₃Cl (5) (phenH = 3-ethynyl-1,10-phenanthroline) or Re(HphenH)(CO)₃Cl (6) (HphenH = 3,8-bis(ethynyl)-1,10-phenanthroline). All the present rhenium(I) complexes 3-6 were revealed to possess a facial configuration (fac-isomer) with respect to the three carbonyl ligands. The main frameworks for these new gold(I) organometallics were constructed by the Au-C σ-bonding (with the η¹-type coordination) between the ethynylphenanthrolines and the Au(I) phosphine unit. Re(I)-Au(I) heterometallics 3 and 4 have shown single phosphorescence from the ³MLCT excited state and this observation can be interpreted in terms of the efficient intramolecular energy transfer from the Au(I) unit to the Re(I) unit.     

Efficient Suzuki-Miyaura mono-arylation of symmetrical diiodo(hetero)arenes

A reliable protocol for converting 1,4-diiodo-2,3,5,6-tetrafluorobenzene into 1-(hetero)aryl-4-iodo-2,3,5,6-tetrafluorobenzene derivatives has been lacking in the literature. We have identified optimal conditions to achieve this conversion in good yields and have minimized formation of the bis-coupling product. The newly identified protocol involving the use of a syringe pump has been extended to other symmetrical diiodo(hetero)arenes.     

Catalytic enantioselective addition of diethylzinc to (hetero)aromatic aldehydes

The asymmetric alkylation with diethylzinc of five heterocyclic aldehydes and benzaldehyde (for comparison) has been studied in the presence of two optically active amino alcohols: (S)-2-amino-1-butanol (AB) and (1S,2R)-N,N-dibutylnorephedrine (DBNE). A number of chiral (hetero)aromatic secondary alcohols were synthesized in high yields (95–98%) with enantioselectivity up to 92% enantiomeric excess (ee) in the presence of DBNE catalyst. Optically active thienyl and 4-pyridyl derivatives were prepared for the first time by catalytic asymmetric alkylation. The influence of the amount of DBNE on the enantioselectivity was investigated. In contrast to benzaldehyde, 2-furan- and 2-thiophene-carbaldehydes, in the case of 3- and 4-pyridinecarbaldehydes the ee values depend directly on the catalyst concentration. © 1998 John Wiley & Sons, Ltd.     

Multifunctional triphenylamine polymers synthesized via direct (hetero) arylation polymerization

The design rules for creating multifunctional organic electronic materials are currently limited. By copolymerizing twisted triphenylamine (TPA) and electron rich dioxythiophene (XDOT) monomers via Direct (Hetero) Arylation Polymerization (DHAP), a set of polymers are obtained that perform as yellow to transmissive electrochromic (EC) films with up to 45% contrast, as well as in electroluminescent (EL) applications, achieving a luminance of ∼450 cd/m² in yellow‐green polymer light‐emitting diodes (PLEDs). In addition, polymerizing TPA with a donor‐acceptor‐donor monomer results in a low‐bandgap polymer that achieves power conversion efficiencies up to 2.5% when blended with PC₇₁BM in conventional organic photovoltaic (OPV) devices. Incorporation of TPA units into the polymer backbone largely breaks any aggregation and ordering in the solid‐state, leading to highly soluble materials that form smooth, reproducible thin films. The TPA unit also serves to break conjugation throughout the polymer backbone, providing precise control over optical and electronic properties through choice of comonomer. These results suggest that TPA copolymers can be useful for achieving multi‐functionality without sacrificing facile solution processability, making them promising candidates for multifunctional devices like dual EC/EL displays. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 147–153     

Optically pure bulky (hetero)arylalkyl carbinols via kinetic resolution

Planar chiral nucleophilic catalyst Fc-PIP was employed in the kinetic resolution of bulky (hetero)arylalkyl carbinols delivering unreacted alcohols with extremely high enantiomeric excess (>99.0% ees) in ideal conversions ranging from 50.4-56.7%.     

Synthesis of new derivatives of carbo(hetero)cyclospirobutanoic lactones

The diethyl esters of 2-oxo-1-oxaspiro[4,4]nonan-3,4-dicarboxylic, 2-oxo-1-oxaspiro[4,5]decan-3,4-dicarboxylic and 7,7-di-methyl-1,8-dioxaspiro-[4,5]decan-3,4-dicarboxylic acids (la-c) are transformed by hydrochloric acid into 2-oxo-1-oxa-spiro[4,4]nonan-, 2-oxo-1-oxaspiro-[4,5]decan-, and 7,7-dimethyl-1,8-dioxaspiro[4,5]decan-4-carboxylic acids (Ila-c), which are converted into the acyl chlorides IIIa-c, and the latter into the chloromethyl ketones IVa-c. Reaction of the acyl chlorides of IIa and IIb with thiosemicarbazide gives the acid thiosemicarbazides Va and Vb, which form the triazoles VIa and VIb in potassium hydroxide solution, and the thiadiazoles VIIa an VIIb in sulfuric acid. Reaction of the chloromethyl ketones IVa-c with formamide gives the imidazoles VIIIa-c. The diesters Ia-creatwithbenzylamine to form the N-benzylimides IXa-c.     

Cobalt-catalyzed aminocarbonylation of (hetero)aryl halides promoted by visible light

The catalytic aminocarbonylation of (hetero)aryl halides is widely applied in the synthesis of amides but relies heavily on the use of precious metal catalysis. Herein, we report an aminocarbonylation of (hetero)aryl halides using a simple cobalt catalyst under visible light irradiation. The reaction extends to the use of (hetero)aryl chlorides and is successful with a broad range of amine nucleophiles. Mechanistic investigations are consistent with a reaction proceeding via intermolecular charge transfer involving a donor–acceptor complex of the substrate and cobaltate catalyst.

An aminocarbonylation of (hetero)aryl halides using a simple cobalt catalyst under visible light irradiation is presented.     

Recent advances in (hetero)cyclizations of N-vinylazoles (microreview)

Chemistry of Heterocyclic Compounds - Recent advances in chemistry of N-vinylazoles are surveyed in this microreview, including results published in the last decade. In particular, reactions...     

Friedel-Crafts trifluoromethylthiolation of electron-rich (hetero)arenes with trifluoromethylthio-saccharin in 2,2,2-trifluoroethanol (TFE)

A promoter-free Friedel-Crafts trifluoromethylthiolation of electron-rich arenes and heteroarenes with N-trifluoromethylthiosaccharin 5 using 2,2,2-trifluoroethanol (TFE) as the solvent was described.     

Pd-catalyzed decarboxylative cross-coupling of sodium pyrimidinecarboxylates with (hetero)aryl bromides

A straightforward method for the synthesis of functionalized 4- or 5-(hetero)arylpyrimidines via decarboxylative cross-coupling reaction from readily available pyrimidine-4- and pyrimidine-5-carboxylates was described. In the presence of dual-catalyst system of Pd(PPh₃)₄/Cu₂O, the reaction proceeds smoothly, tolerates a variety of functional groups, and provides easy access to the synthesis of different (hetero)arylpyrimidines compounds.     

Friedel-Crafts trifluoromethylthiolation of electron-rich (hetero)arenes with trifluoromethylthio-saccharin in 2,2,2-trifluoroethanol (TFE)

A promoter-free Friedel-Crafts trifluoromethylthiolation of electron-rich arenes and heteroarenes with N-trifluoromethylthiosaccharin 5 using 2,2,2-trifluoroethanol (TFE) as the solvent was described. The reactions were conducted at 40 °C and a variety of common functional groups were compatible.     

One-pot propagation of (Hetero)Arylamines: Modular synthesis of diverse Amino-di(hetero)arylamines

Formal propagation of (hetero)arylamine is achieved via a one-pot Buchwald–Hartwig C–N cross-coupling and nitro reduction sequence, enabling a rapid modular synthesis of diverse amino-di(hetero)arylamines from (hetero)arylamines and halogenated nitrobenzenes. Various functionalized aromatic amines with different electronic and steric environments can be efficiently prolongated to formally incorporate another arylamino fragments. This approach has been successfully applied in the synthesis of more than forty amino-di(hetero)arylamines. The applicability of this method has also been demonstrated in the synthesis of oligoanilines and the tyrosine-kinase inhibitor Imatinib.