1,5-Electrocyclisation of azomethine ylides leading to pyrrolo[2,1-a]isoquinolines—concise construction of the lamellarin skeleton

A new, general route to the 1,2-diaryl-substituted pyrrolo[2,1-a]isoquinolines has been developed via the 1,5-dipolar electrocyclisation reactions of azomethine ylides derived from readily available stilbenic acid derivatives. This method was applied to the concise construction of a lamellarin skeleton.     

Photo-dehydrogenation of 4,6-diaryl-2-oxo-1,2,3,4-tetrahydropyrimidines

Electron-transfer-induced photo-oxidation of 4,6-diaryl-substituted 2-oxo-1,2,3,4-tetrahydropyrimidines (THPMs) in chloroform under argon atmosphere results in the smooth formation of 4,6-diaryl-substituted 2-oxo-1,2-dihydropyrimidines. Sequentially, electron-transfer and proton removal processes in this oxidative reaction result in the occurrence of two different benzylic and allylic radical intermediates, which converted to each other via resonance. Preferably, capto-dative stabilized radical center stimulates the type of product. Based on the proposed oxidation reaction mechanism, the electron transfer from the excited THPMs to chloroform starts this oxidative reaction. The results of the computational study obtained at DFT-B₃LYP/6-311++G** level of theory indicate that the first electron is preferably removed from the N₁ atom of the heterocyclic ring. A comparison of the sum of the Mulliken spin densities of the radical intermediates supports the argument that the more stable capto-dative stabilized radical is involved in the reaction.     

Synthesis of polyaza macrocycles by palladium-catalyzed amination of 1,2-dibromobenzene and 2-bromo-1,3-dichlorobenzene

Palladium-catalyzed amination of 1,2-dibromobenzene with equimolar amounts of linear polyamines leads to the formation of polyaza macrocycles in low yields. The use of 2-bromo-1,3-dichlorobenzene as starting compound ensures considerably larger yields of the target macrocycles, and the reaction is accompanied by side formation of N-aryl- and N,N′-diaryl-substituted polyamines, as well as of cyclic oligomers. The yields strongly depend on the polyamine chain length. Reactions of excess 2-bromo-1,3-dichlorobenzene with a series of polyamines gave the corresponding N,N′-diarylpolyamines in high yields, and the latter reacted with the second polyamine molecule to form cyclic dimers. A relation between the yield of cyclic dimers and polyamine structure was revealed.     

Steric structure of some 1,2-diaryl-substituted ethanes

Conclusions In the investigated 1,2-diaryl-substituted ethanes, the content of the trans and gauche conformers relative to the C-C bond is practically identical; the trans form shows some predominance. In these compounds, the aromatic rings are orientated in parallel and are turned by an average of 120±10 relative to the central C-C bond.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 95–100, January, 1987.The authors are grateful to A. Kh. Plyamovatii for submitting the MAP-3 program.     

A pyridine promoted ‘weak base route’ to (NHC)2NiCl2 complexes with bulky N,N'-diaryl carbene ligands

A simple one-step synthesis of (NHC)₂NiCl₂ complexes containing bulky N-heterocyclic carbene (NHC) ligands relies on the C–H metallation of N,N'-diaryl-substituted azolium salts, NHC-precursors, with NiCl₂Py₂ in the presence of Cs₂CO₃ and pyridine. This procedure allows one to implement all synthetic manipulations in air.     

Modifications of 5,12-dihydroindolo[3,2-a]carbazole scaffold via its regioselective C2,9-formylation and C2,9-acetylation

The effective approaches for regioselective double formylation and acetylation of 5,12-dialkyl-6,7-diaryl-substituted 5,12-dihydroindolo[3,2-a]carbazoles by their treatment with dichloromethyl methyl ether in the presence of SnCl₄ or with acetyl chloride in the presence of AlCl₃ to afford the 2,9-diformyl or 2,9-diacetyl derivatives, respectively, were developed. Furthermore, new 2,9-bis(2,2-dicyanovinyl) derivatives were synthesized by the Knoevenagel condensation of diformyl-containing substrates with malononitrile, when new 2,9-bis(quinoxaline-2-yl)- and 2,9-bis(benzo[g]quinoxaline-2-yl) derivatives were formed via microwave-promoted oxidation of diacetyl-containing substrates with SeO₂ to the corresponding diglyoxals, followed by the reaction of these intermediates with o-phenylendiamine or 2,3-diaminonaphthalene, respectively. The basic optical and electrochemical properties of some 5,12-dihydroindolo[3,2-a]carbazoles were investigated.     

Fluorescent properties and resonance energy transfer of 3,4-bis(2,4-difluorophenyl)-maleimide

A fluorescent compound 3,4-bis(2,4-difluorophenyl)-maleimide from the 3,4-diaryl-substituted maleimides was synthesized and determined to have a Stokes shift of 140 nm (λ(abs) 341 nm, λ(em) 481 nm), a high fluorescent quantum yield (Φ(fl) 0.61) and an extinction coefficient ε((340)) of 48?400 M(-1) cm(-1) in dichloromethane. For the first time we demonstrated the successful implementation of a 3,4-diaryl-substituted maleimide molecule as a donor component in FRET experiments.     

The magic effect of endocyclic but non-sterically hindering biisoquinoline chelates: From fast-moving molecular shuttles to [3]rotaxanes

The use of 8,8′-diaryl-substituted 3,3′-biisoquinolines allows the construction of new multi-component assemblies that are inaccessible with the 2,9-diaryl-substituted 1,10-phenanthroline ligands previously developed by the Sauvage group. This is due to the sterically non-hindering nature of the new chelates, which makes three-component entanglements around octahedral metal centres such as iron(II), cobalt(II) and ruthenium(II) readily possible. Among the newly synthesized molecular assemblies are [3]rotaxanes and [3]pseudorotaxanes in which two molecular strings pass through a single macrocycle, as well as molecular shuttles that exhibit greatly improved shuttling kinetics when compared to previously investigated molecular machines that are based on copper(I)/copper(II) redox chemistry.     

Synthesis of novel substituted diaryl-1,4-diazepines

In this paper a convenient route to new 2,3-diaryl-substituted 1,4-diazepines is described through cyclization of ethanedione derivatives and 1,3-propanediamine. The ethanedione derivatives required were synthesized by microwave-assisted oxidation from ethanones. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1042–1047, July, 2006.     

Sonication-assisted supramolecular nanorods of meso-diaryl-substituted porphyrins

Supramolecular nanorods of 5,15-diaryl-substituted porphyrins prepared by sonication method exhibit a broad absorption property, which is confirmed by photocurrent generation measurement in a photoelectrochemical cell.     

A quantitative study of substituent effects on oxidative cyclization of some 2-aryl-substituted aldehyde thiosemicarbazones induced by ferric chloride and cupric perchlorate

As a development of our previous work, we performed a kinetic study of the oxidative cyclization reaction of some 2,4-diaryl-substituted aldehyde thiosemicarbazones 1a-n induced by ferric chloride and by cupric perchlorate. The results of cyclization of 1a-n were compared to those of the corresponding 2-methyl derivatives. The kinetic data were analyzed by means of the Hammett's equation.     

Practical synthesis of β-isothiocyanato ketones from chalcones

Practical synthesis of 1,3-diaryl-substituted 3-isothiocyanatopropan-1-ones based on the reaction of chalcones with thiocyanic acid generated in situ by treatment of thiocyanate ammonium with dilute sulfuric acid has been developed.     

Determination of the configuration of piperidin-4-ol silyl ethers by mass spectrometry with chemical ionization

Mass spectrometry with chemical ionization (isobutane as reactant gas) can be used for the determination of the configuration of the chiral center at the C(4) atom in molecules of silyl ethers of 2,6-diaryl-substituted piperidin-4-ols. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1625–1627, September, 2006.     

Insights into the reaction of trans-diarylethenes with thionyl chloride: a practical synthesis of chlorobenzo[b]thiophenes

The reactivity of a variety of trans-1,2-diarylethenes with thionyl chloride has been investigated. All the substrates could readily afford 3-chlorobenzo[b]thiophenes in moderate yields and a pair of threo- and erythro-1,2-dichloro-1,2-diarylethanes as the minor products under mild condition. The diastereoisomers of 1,2-dichloro-1,2-diarylethanes with a methoxy group on the benzene ring were found for the first time to be also converted into cholobenzo[b]thiophenes under treatment of thionyl chloride. The chemical transformations have been mechanistically rationalized and successfully applied to a one-pot synthesis of novel fluorescent liquid crystalline compounds containing benzo[b]thiophene and 1,3,4-oxadiazole units. Their spectroscopic and mesogenic behaviours are also described.     

Approaches to the preparation of (Z)-1,2-difluorostilbenes

Methodology directed at the preparation of (Z)-1,2-difluorostilbenes has been evaluated. For symmetrical (Z)-1,2-difluorostilbenes, photochemical isomerization of the isomeric (E)-1,2-difluorostilbenes, and HPLC separation of the mixture of stilbene isomers is a reasonable route to a particular (Z)-stilbene. An alternative approach to both symmetrical and/or unsymmetrical (Z)-1,2-difluorostilbenes has been developed via stereospecific Pd(0) coupling of (E)-1,2-difluoro-aryl-ethenyltributylstannanes under Stille-Liebiskind conditions with aryl idodies. The requisite arylstannanes can be obtained via the reported route developed by Davis or via (E)-1,2-difluorovinyltributylstannane - a new route described in this work. The methodology tolerates almost any functionality in the aryl ring, is easily carried out, is stereospecific and provides the first general route to (Z)-1,2-difluorostilbenes.     

Catalytic asymmetric epoxidation of alkenes with arabinose-derived ketones containing a cyclohexane-1,2-diacetal

The effect of diol blocking groups, cyclohexane-1,2-diacetal verses butane-1,2-diacetal, on the asymmetric epoxidation of trans- and cis-alkenes by arabinose-derived ketones is reported. The ketone catalysts with a cyclohexane-1,2-acetal display similar asymmetric induction as those catalysts with a butane-1,2-diacetal in most cases. For (E)-1-benzyloxy-4-hexene, the ee of the enantioselective epoxidation has reached 61% with the cyclohexane-1,2-dineopentyl acetal ketone catalyst.     

Straightforward synthesis of 4,5-bifunctionalized 1,2-oxazinanes via Lewis acid promoted regio- and stereo-selective nucleophilic ring-opening of 3,6-dihydro-1,2-oxazine oxides

Functionalized 1,2-oxazinanes are interesting and valuable heterocycles with potential applications in synthetic and medicinal chemistry. A straightforward strategy for quick access to unprecedented trans-4-hydroxyl-5-azido/cyano/amino 1,2-oxazinanes are developed: N-COR 3,6-dihydro- 1,2-oxazine oxides are prepared with ease from related dihydro- 1,2-oxazines and opened by nucleophiles TMSN₃, TMSCN and aryl/alkyl amines. Appropriate Lewis acid catalysts are found playing a vital role for both reaction rate and regioselectivity. The N-COR group can be removed under mild conditions to provide highly desirable NH 1,2-oxazinanes inaccessible via previous methods.     

Synthesis and oxidation of (E)-1,2-diphenyl-2-(arylimino) ethanol derivatives

The compounds (E)-1,2-diphenyl-2-(phenylimino)ethanol, (E)-1,2-diphenyl-2-(p-tolylimino)ethanol, and (E)-2-((4-chlorophenyl)imino)-1,2-diphenylethanol) were synthesized by reaction of a p-substituted aniline with benzoin then oxidized with chromium trioxide–triethylamine in chloroform to give (E)-1,2-diphenyl-2-(phenylimino)ethanone, (E)-1,2-diphenyl-2-(p-tolylimino)ethanone, and (E)-2-((4-chlorophenyl)imino)-1,2-diphenylethanone in very high yield. The products were characterized by IR and NMR spectral analysis.     

Copper-catalyzed asymmetric reduction of 3,3-diarylacrylonitriles

CuH-catalyzed enantioselective conjugate reduction of 3,3-diaryl-substituted acrylonitriles is described. A range of 3-aryl-3-pyridylacrylonitriles were reduced with high levels of enantioselectivity under optimal conditions employing a copper/Josiphos complex in the presence of polymethylhydrosiloxane (PMHS).     

Enantioselective addition of diethylzinc to aromatic aldehydes catalyzed by C2-symmetric chiral diols

Optically pure C₂-symmetric diols have been synthesized with moderate yields in a straightforward manner, and are used as catalysts in the enantioselective alkylation of aromatic aldehydes with diethylzinc. The addition of diethylzinc to benzaldehyde and sterically hindered 1-naphthaldehyde was achieved with excellent enantioselectivities (97–99% ee) under catalysis with (1R,2R)-1,2-bis(3,5-dibromophenyl)-ethane-1,2-diol and (1R,2R)-1,2-bis(3,5-diphenylphenyl)-ethane-1,2-diol.