Aleksander V. Vasilyev

Alkenylation of Arenes and Heteroarenes with Alkynes

This review is focused on the analysis of current data on new methods of alkenylation of arenes and heteroarenes with alkynes by transition metal catalyzed reactions, Bronsted/Lewis acid promoted transformations, and others. The synthetic potential, scope, limitations, and mechanistic problems of the alkenylation reactions are discussed. The insertion of an alkenyl group into aromatic and heteroaromatic rings by inter- or intramolecular ways provides a synthetic route to derivatives of styrene, stilbene, chalcone, cinnamic acid, various fused carbo- and heterocycles, etc.

Transformations of Conjugated Enynones in the Superacid CF3SO3H. Synthesis of Butadienyl Triflates, Indanones, and Indenes

Conjugated 1,5-diarylpent-2-en-4-yn-1-ones add the superacid CF3SO3H to the acetylenic bond with formation of the corresponding butadienyl triflates. Under superacidic reaction conditions, these triflates are transformed into indanone or indene derivatives depending on which substituents on the aromatic ring are conjugated with the butadiene fragment. In a less acidic system (10% vol pyridine in CF3SO3H) only the formation of butadienyl triflates takes place. Cationic reaction intermediates were studied by means of NMR and DFT calculations.

Organic chemistry. History and mutual relations of universities of Russia

The review describes the history of development of organic chemistry in higher schools of Russia over a period of 170 years, since the emergence of organic chemistry in our country till now.

Reactions of trifluoromethyl-substituted arylacetylenes with arenes in superacids

Protonation of the C≡C bond in trifluoromethyl-substituted arylacetylenes ArC≡CCF3 by the action of superacids (CF3SO3H or HSO3F) generates vinyl cations ArC+=CHCF3 which react with arenes Ar′H to give alkenes Ar(Ar′)C=CHCF3. Protonation of the latter at the C=C bond in the reaction medium yields stable cations Ar(Ar′)C+-CH2CF3 which are converted into E/Z-isomeric alkenes Ar(Ar′)C=CHCF3 and/or alcohols Ar(Ar′)C(OH)CH2CF3 as a result of quenching of superacid reaction solution.

Contents of α-o-4 and β-o-4 bonds in native lignin and isolated lignin preparations

An analytical calculation method for the estimation of the contents of alkyl aryl ether bonds (α-O-4 and β-O-4) in lignin was developed. In the framework of the method, Alkyl–O–Aryl type bonds are described as coupled phenolic hydroxyls (OHphen). The method is based on the balance equation including the free and coupled OHphen contents in dissolved and residual lignins, on the one hand, and their respective contents in native lignin, on the other. The free OHphen content is calculated on the basis of the OHphen contents of dissolved and residual lignin, determined by the aminolysis method in the course of kraft cooking of softwood. The calculation results for soluble lignin preparations are in good agreement with the 13C NMR (nuclear magnetic resonance) spectral data for the solutions. The content of Alkyl–O–Aryl bonds in native softwood (pine, spruce) lignin was estimated at 79/100 PPU (phenylpropane unit). In isolated lignin preparations, the contents of these bonds decrease in the sequence: Freudenberg lignin (71/100 PPU)> Bjorkman lignin (61/100 PPU)> Pepper lignin (44/100 PPU). Dissolved alkaline lignin still contains small amounts of Alkyl–O–Aryl bonds (36/100 PPU in soda lignin and an average of 23/100 PPU in soda-AQ lignin, kraft lignin, and kraft-AQ lignin). Residual lignin which represents the fraction of native lignin with inter-unit bonds resistant to kraft pulping contains 66/100 PPU of such bonds. A relatively high content of Alkyl–O–Aryl bonds (61/100 PPU) is preserved in technical hydrolysis lignins.

1,4-Dihydrophosphinolines and their complexes with group 10 metals

Syntheses and characterizations of novel phosphaheterocycles, 1-phenyl-4,4-dimethyl-1,4-dihydrophosphinoline (2a) and 1-phenyl-2-bromo-4,4-dimethyl-1,4-dihydrophosphinoline (2b), and their complexes with Pd(II) and Pt(II) are described. Reduction of 1-phenyl-4,4-dimethyl-1,4-dihydrophosphinoline 1-oxide (1a) and 1-phenyl-2-bromo-4,4-dimethyl-1,4-dihydrophosphinoline 1-oxide (1b) using trichlorosilane in refluxing benzene gave the target phosphines in a yield of 83–87%. Reactions of phosphines with acetonitrile complexes of Pd(II) (3) and Pt(II) (4) yielded bis(phosphine) species [MCl2L2] (5–8). Complexes 5–8 were characterized by 1H, 13C, 31P, 195Pt NMR and HRMS. The structures of all these new complexes were determined with single crystal X-ray diffraction. The configuration of the complexes in a CDCl3 solution was investigated via comparing of 31P NMR data in solution and solid state.

Reactions of 1,1,1-trifluoro-4-phenylbut-3-en-2-one with arenes in trifluoromethanesulfonic acid

The synthesis and chemical properties of trifluoromethyl-containing enones are subjects of considerable attention [1–10]. A combination of strong electronwithdrawing power of the COCF3 group and C=C bond endows conjugated 1,1,1-trifluorobut-3-en-2ones with unique chemical properties. Taking into account electrophilicity of such structures, reactions with various O-, N-, S-, and C-nucleophiles involving the carbonyl group and/or double carbon–carbon bond have been developed, and new trifluoromethyl-substituted carboand heterocycles, as well as various polyfunctional compounds, have been synthesized [11–15]. However, reactions of 1,1,1-trifluorobut-3-en-2-ones with such π-nucleophiles as arenes have not been studied so far.

Modern Trends of Organic Chemistry in Russian Universities

This review is devoted to the scientific achievements of the departments of organic chemistry in higher schools of Russia within the past decade.

Brominated CF3-allyl alcohols as multicentered electrophiles in TfOH promoted reactions with arenes

Superacidic activation of CF3-substituted allyl alcohols, bearing one or two bromine atoms at the CC double bond, with TfOH was studied. These brominated alcohols were found to behave as highly reactive multicentered electrophiles. The obtained cationic intermediates were studied by means of NMR and DFT calculations. The protonation of dibromo derivatives with TfOH resulted in cyclization to form trifluoromethylated 1H-indenes and/or indan-1-ones in yields up to 90%. The reaction of dibromosubstituted CF3-allyl alcohols with arenes in the presence of TfOH gave rise to either CF3-alkenes (formal substitution of hydroxyl with an aryl group) or CF3-indenes, depending on the nucleophilicity and bulkiness of the starting arenes. The reaction of monobrominated CF3-substituted allyl alcohols with arenes in TfOH afforded two regioisomeric CF3-alkenes, as a result of arylation of both terminal carbons of the allyl system, in yields up to 95%. The obtained brominated CF3-alkenes can be converted efficiently into trifluoromethylated allenes by treatment with KOH in ethanol in yields up to 92%.

Metal-free hydroarylation of the side chain carbon–carbon double bond of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles in triflic acid

The metal-free reaction of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles with arenes in neat triflic acid (TfOH, CF3SO3H), both under thermal and microwave conditions, leads to 5-(2,2-diarylethyl)-3-aryl-1,2,4-oxadiazoles. The products are formed through the regioselective hydroarylation of the side chain carbon–carbon double bond of the starting oxadiazoles in yields up to 97%. According to NMR data and DFT calculations, N4,C-diprotonated forms of oxadiazoles are the electrophilic intermediates in this reaction.