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A simple four-step route to a chiral tetrahydrofluorenyl rhodium catalyst from naturally occurring (-)-α-pinene was developed. Our approach does not use multistep and time-consuming procedures such as chiral HPLC or diastereomeric resolution. The key to success lies in the face-selective coordination of rhodium to the sterically hindered tetrahydrofluorenyl ligand, giving only one diastereomeric complex. This catalyst proved to be highly efficient for asymmetric C-H annulation of aryl hydroxamates with alkenes (yield up to 95%, 91% ee ) at low loading (up to 0.4 mol % based on Rh).

Currently, non-proteinogenic α-amino acids (α-AAs) have attracted increasing interest in bio- and medicinal chemistry. In this context, the first protocol for the asymmetric synthesis of artificial α-AAs featuring a 3,4-dihydroisoquinolone core with two stereogenic centers was successfully elaborated. A straightforward Rh(III)-catalysed C-H activation/annulation reaction of various aryl hydroxamates with a set of robust and readily available chiral Ni(II) complexes, which have allylic appendages derived from glycine (Gly), alanine (Ala) and phenylalanine (Phe), allowed incorporation of a 3,4-dihydroisoquinolone scaffold into the chiral amino acid residue. The reaction was performed in methanol and under mild conditions (at room temperature under air atmosphere), providing separable diastereomeric complexes with up to 94% total yield. The target α-AA with a 3,4-dihydroisoquinolone core in an enantiopure form was subsequently released from the obtained chiral Ni(II) complexes via an acidic decomposition in aqueous HCl, along with the recovery of the chiral auxiliary ligand.

A straightforward and selective way for the preparation of amides from nitroarenes and carboxylic acids using carbon monoxide as a reductant was developed. This protocol does not require any non-gaseous additives, thus simplifying product isolation. Aliphatic carboxylic acid was modified in the presence of aromatic ones, and reducible functional groups such as CC, Ar-Br, and R-NO 2 were saved.

A novel rhodium-catalyzed tandem C-H annulation of commercially available benzaldehydes and aminobenzoic acids with 2 equiv of alkyne is reported for the construction of isocoumarin-conjugated isoquinolinium salts that demonstrate diverse outstanding photoactivity. Depending on the substituents in the isoquinolinium moiety, they display either highly efficient fluorescence (up to 99% of quantum yield) or strong fluorescence quenching, which is provided by the transfer of the HOMO from the isoquinolinium to the isocoumarin moiety. Importantly, the functional groups in the benzaldehyde coupling partner also strongly affect the reaction selectivity, shifting the pathway to the formation of the photoinactive isocoumarin-substituted indenone imines and indenyl amines. Selective formation of the latter can be achieved by using a reduced amount of the oxidizing additive.

Efficient protocols for the synthesis of triphenylcyclopentadienyl rhodium halides [(1,2,4-C 5 Ph 3 H 2 )RhX 2 ] 2 ( 1a , b : X = Cl, I) starting from 1,2,4-triphenylcyclopentadiene or the cyclooctadiene derivative (1,2,4-C 5 Ph 3 H 2 )Rh(cod) ( 2 ) were developed. Iodide abstraction from 1b with thallium or silver salts allowed us to prepare rhodocenium [(1,2,4-C 5 Ph 3 H 2 )RhCp]PF 6 ( 3 PF 6 ) and mesitylene complex [(1,2,4-C 5 Ph 3 H 2 )Rh(mesitylene)](SbF 6 ) 2 ( 4 (SbF 6 ) 2 ). Halides 1a , b (at 0.5 mol % loading) showed high catalytic activity in the construction of C-C, C-O, and C-N bonds via the C(sp 2 )-H activation approach. Their efficiency was demonstrated in the synthesis of more than 40 examples of polycyclic organic compounds (such as isocoumarins and naphthalenes, as well as isoquinolinium and dibenzo[ a , f ]quinolizinium salts). The protocols developed tolerate a wide range of functional groups. In particular, they were successfully used for the atom- and step-economical synthesis of hydroxy-substituted isocoumarins, including the natural product oospalactone 7fe . The 6- or 8-hydroxy-substituted isocoumarins showed moderate antiproliferative activity against several human cell lines in vitro .

A general protocol for the asymmetric synthesis of artificial amino acids (AAs) comprising an isoquinolone skeleton was successfully elaborated via a straightforward Rh(III)-catalyzed C-H activation/annulation of various aryl hydroxamates with a series of robust chiral propargylglycine Ni(II) complexes derived from glycine (Gly), alanine (Ala) and phenylalanine (Phe) in a green solvent (methanol) under mild conditions (at room temperature under air). Notably, in the case of phenylalanine-derived complexes, the formation of unfavorable 4-substituted isoquinolone regioisomers was achieved by a catalyst control for the first time. The subsequent acidic decomposition of the obtained Ni(II) complexes provides the target unnatural α- and α,α-disubstituted AAs with an isoquinolone core in an enantiopure form.

Photoinduced charge transfer affects the efficiency and selectivity of photochemical reactions. Incorporation of donating groups into the isoquinolinium core allowed us to overcome the photochemical inactivity of the corresponding dithienyl-substituted terarylenes, presumably by redirecting the charge transfer within the molecule, and gave access to a new family of thermally reversible photoswitches.

Three new benzothiadiazole (BTD)-containing luminophores with different configurations of aryl linkers have been prepared via Pd-catalyzed cross-coupling Suzuki and Buchwald-Hartwig reactions. Photophysical and electroluminescent properties of the compounds were investigated to estimate their potential for optoelectronic applications. All synthesized structures have sufficiently high quantum yields in film. The BTD with aryl bridged carbazole unit demonstrated the highest electrons and holes mobility in a series. OLED with light-emitting layer (EML) based on this compound exhibited the highest brightness, as well as current and luminous efficiency. The synthesized compounds are not only luminophores with a high photoluminescence quantum yield, but also active transport centers for charge carriers in EML of OLED devices.

On the basis of the 1,2,3,4-tetrahydrofluorenyl ligand, a simple approach was developed to new effective rhodium catalysts for the construction of C-C and C-N bonds. The halide compounds [(η 5 -tetrahydrofluorenyl)RhX 2 ] 2 (2 a: X=Br; 2 b: X=I) were synthesized by treatment of the bis(ethylene) derivative (η 5 -tetrahydrofluorenyl)Rh(C 2 H 4 ) 2 (1 a) with halogens. An analogous reaction of the cyclooctadiene complex (η 5 -tetrahydrofluorenyl)Rh(cod) (1 b) with I 2 is complicated by the side formation of [(cod)RhI] 2 . The reaction of 2 b with 2,2'-bipyridyl leads to cation [(η 5 -tetrahydrofluorenyl)Rh(2,2'-bipyridyl)I] + (3). The halide abstraction from 2 a,b with thallium or silver salts allowed us to prepare sandwich compounds with incoming cyclopentadienyl, dicarbollide and mesityleneligands [(η 5 -tetrahydrofluorenyl)RhCp] + (4), (η 5 -tetrahydrofluorenyl)Rh(η-7,8-C 2 B 9 H 11 ) (5), and [(η 5 -tetrahydrofluorenyl)Rh(η-mesitylene)] 2+ (6). The structures of 1 b, 2 b ⋅ 2I 2 , 3PF 6 , 4TlI 4 , 5, and [(cod)RhI] 2 were determined by X-ray diffraction. Compounds 2 a,b efficiently catalyze the oxidative coupling of benzoic acids with alkynes to selectively give isocoumarins or naphthalenes, depending on the reaction temperature. Moreover, they showed moderate catalytic activity in other annulations of alkynes with aromatic compounds (such as benzamide, acetanilide, etc.) which proceed through CH activation. Compound 2 b also effectively catalyzes the reductive amination of aldehydes and ketones in the presence of carbon monoxide and water via water-gas shift reaction, giving amines in high yields (67-99 %)., (© 2021 Wiley-VCH GmbH.)

An efficient protocol was developed for the synthesis of π-extended isocoumarins and polycyclic aromatic hydrocarbons based on the oxidative coupling of aromatic carboxylic acids with internal alkynes catalyzed by (cyclopentadienyl)rhodium complexes. The coupling chemoselectivity strongly depends on whether Cp or the methylated Cp* ligands are used. The pentamethyl derivative [Cp*RhCl 2 ] 2 predominantly gives isocoumarins, while the non-methylated complex [CpRhI 2 ] n produces naphthalene derivatives. The polyaromatic carboxylic acids (such as 1-naphthoic acid, 1-pyrenecarboxylic acid, fluorene-1-carboxylic acid, and dibenzofuran-4-carboxylic acid) are suitable for this approach. A mixture of Cp*H/RhCl 3 can be used as a catalyst instead of [Cp*RhCl 2 ] 2 . The structures of 3,4-diphenylindeno[1,2-h]isochromen-1(11H)-one and 7,10-dimethyl-8,9-diphenylbenzo[pqr]tetraphene were determined by X-ray diffraction. In addition, the optical properties of the prepared compounds were studied. 7,8-Diphenyl-10H-phenaleno[1,9-gh]isochromen-10-one was employed as an emissive layer for OLED manufacturing. The OLED emits yellow-green light with a maximum intensity 1740 cd ⋅ m -2 at 15 V., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An efficient method for the CF3-carbenoid C-H functionalization of 6-arylpurines has been developed. This protocol uses readily available methyl 3,3,3-trifluoro-2-diazopropionate as a cross-coupling partner and proceeds smoothly under chelation-controlled Rh(iii) catalysis. The reactions provide the corresponding carbene insertion products with high regioselectivity within a few hours and allow the introduction of both the CF3 and carboxylate functions into biologically important purine molecules including nucleoside derivatives.

Development of novel, sustainable catalytic methodologies to provide access to amines represents a goal of fundamental importance. Herein we describe a systematic study for the construction of a variety of amines catalyzed by a well-defined homogeneous iridium complex using carbon monoxide as a reducing agent. The methodology was shown to be compatible with functional groups prone to reduction by hydrogen or complex hydrides.

Cobalt pi-complexes, previously described in the literature and specially synthesized and characterized in this work, were used as catalysts in homogeneous oxidation of organic compounds with peroxides. These complexes contain pi-butadienyl and pi-cyclopentadienyl ligands: [(tetramethylcyclobutadiene)(benzene)cobalt] hexafluorophosphate, [(C₄Me₄)Co(C₆H₆)]PF₆ ( 1 ); diiodo(carbonyl)(pentamethylcyclopentadienyl)cobalt, Cp*Co(CO)I₂ ( 2 ); diiodo(carbonyl)(cyclopentadienyl)cobalt, CpCo(CO)I₂ ( 3 ); (tetramethylcyclobutadiene)(dicarbonyl)(iodo)cobalt, (C₄Me₄)Co(CO)₂I ( 4 ); [(tetramethylcyclobutadiene)(acetonitrile)(2,2'-bipyridyl)cobalt] hexafluorophosphate, [(C₄Me₄)Co(bipy)(MeCN)]PF₆ ( 5 ); bis[dicarbonyl(B-cyclohexylborole)]cobalt, [(C₄H₄BCy)Co(CO)₂]₂ ( 6 ); [(pentamethylcyclopentadienyl)(iodo)(1,10-phenanthroline)cobalt] hexafluorophosphate, [Cp*Co(phen)I]PF₆ ( 7 ); diiodo(cyclopentadienyl)cobalt, [CpCoI₂]₂ ( 8 ); [(cyclopentadienyl)(iodo)(2,2'-bipyridyl)cobalt] hexafluorophosphate, [CpCo(bipy)I]PF₆ ( 9 ); and [(pentamethylcyclopentadienyl)(iodo)(2,2'-bipyridyl)cobalt] hexafluorophosphate, [Cp*Co(bipy)I]PF₆ ( 10 ). Complexes 1 and 2 catalyze very efficient and stereoselective oxygenation of tertiary C-H bonds in isomeric dimethylcyclohexanes with MCBA: cyclohexanols are produced in 39 and 53% yields and with the trans / cis ratio (of isomers with mutual trans - or cis -configuration of two methyl groups) 0.05 and 0.06, respectively. Addition of nitric acid as co-catalyst dramatically enhances both the yield of oxygenates and stereoselectivity parameter. In contrast to compounds 1 and 2 , complexes 9 and 10 turned out to be very poor catalysts (the yields of oxygenates in the reaction with cis -1,2-dimethylcyclohexane were only 5%-7% and trans / cis ratio 0.8 indicated that the oxidation is not stereoselective). The chromatograms of the reaction mixture obtained before and after reduction with PPh₃ are very similar, which testifies that alkyl hydroperoxides are not formed in this oxidation. It can be thus concluded that the interaction of the alkanes with MCPBA occurs without the formation of free radicals. The complexes catalyze oxidation of alcohols with tert -butylhydroperoxide (TBHP). For example, tert -BuOOH efficiently oxidizes 1-phenylethanol to acetophenone in 98% yield if compound 1 is used as a catalyst.

According to spectroscopic (NMR, IR, UV/Vis) study, the interaction of pentaphosphaferrocene [Cp*Fe(η(5) -P5 )] with trimeric copper pyrazolate [(Cu{3,5-(CF3 )2 Pz})3 ] yields a new compound that is astonishingly stable in solution. Single-crystal X-ray analysis reveals unprecedented structural changes in the interacting molecules and the unique type of coordination [Cp*Fe(μ3 -η(5) :η(2) ,η(2) -P5 ){Cu(3,5-(CF3 )2 Pz)}3 ]. As a result of the 90° macrocycle folding, the copper atoms are able to behave both as a Lewis acid and as a Lewis base in the interaction with the cyclo-P5 ligand., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)