New ionic liquid crystal compounds having a 1,3-dithiane or 1,3-dioxane ring

New pyridinium type thermotropic ionic liquid crystal materials having a 1,3-dithiane ring in the central core N-substituted 4-(5-alkyl-1,3-dithian-2-yl)pyridinium bromides and the corresponding 1,3-dioxanes were synthesized and their mesomorphic behaviours compared. The principal feature of these compounds is to exhibit a smectic A phase over a very wide temperature range including room temperature.     

New 1,3-dioxan-type ionic liquid crystal compounds having a large dielectric constant

New pyridinium-type thermotropic ionic liquid crystal materials having a 1,3-dioxan ring in its central core: N-substituted-4-(5-alkyl-1,3-dioxan-2-yl)pyridinium bromides (6) were synthesized. The mesomorphic behaviour of these compounds and dielectric constant perpendicular to the molecular axis were measured. The principal features of these compounds are that they exhibit a smectic A phase over a wide temperature range including room temperature - for example 6f: g -9 SmA 181 I (°C)-and they have a large dielectric constant perpendicular to the molecular axis.     

Hetero-diels-alder reaction of N-cyanoaniline and pyridinium cyano-(ethoxycarbonyl)methylide with aroylketenes generated in situ in thermolysis of 6-aryl-2,2-dimethyl-1,3-dioxin-4-ones

We have used thermolysis of 6-aryl-2,2-dimethyl-1,3-dioxin-4-ones in the presence of N-cyanoaniline, pyridinium cyano(ethoxycarbonyl)methylide, and 4-hydroxybenzonitrile to obtain the corresponding 6-aryl-2-phenylamino-1,3-oxazin-4-ones, pyridinium ethoxycarbonyl(4-oxo-6-aryl-4H-1,3-oxazin-2-yl)methylides, and p-cyanophenyl esters of 3-aryl-3-oxopropanoic acids. We present the results of a preliminary investigation of the biological activity of these compounds. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 764–768, May, 2006.     

New 1,3-dioxan-type ionic liquid crystal compounds having a large dielectric constant

New pyridinium-type thermotropic ionic liquid crystal materials having a 1,3-dioxan ring in its central core: N-substituted-4-(5-alkyl-1,3-dioxan-2-yl)pyridinium bromides (6) were synthesized. The mesomorphic behaviour of these compounds and dielectric constant perpendicular to the molecular axis were measured. The principal features of these compounds are that they exhibit a smectic A phase over a wide temperature range including room temperature - for example 6f: g -9 SmA 181 I (°C)-and they have a large dielectric constant perpendicular to the molecular axis.     

Preparation of 2‐Amino‐1,3‐butadienes as N‐Pyridine Derivatives

2‐Amino‐1,3‐butadienes as pyridine derivatives have been prepared from corresponding dihydrothiazolo[3,2‐a]pyridinium salts in reactions with a strong base. The pyridinium salts were prepared from pyridine‐2(1H)‐thiones and trans‐1,4‐dibromo‐2‐butene by a vicinal and chemoselective formation of 3‐vinyldihydrothiazolo[3,2‐a]pyridinium salts. A strong base was used for selective proton removal from the vinyl‐substituted 3‐position. A subsequent ring opening provided 2‐substituted 1,3‐butadienes with the azine appended at the annular nitrogen. Simple S‐alkylation yielded a corresponding azinium salt, thereby introducing electrophilic character to the 1,3‐butadiene system. Hydrolysis of the sulfide function provided the corresponding pyridin-2(1H)‐one attached to the 1,3‐butadiene in the 2‐position.     

Synthesis of 4-tert-butylperoxy-4-methylpentan-2-one and 3-tert-butylperoxy-3-methylbutanoic acid

Alkylation of tert-butyl hydroperoxide with 1,3-diols gave the corresponding hydroxy-containing ditertiary peroxides which were oxidized with pyridinium chlorochromate to carbonyl-containing peroxides. 3-tert-Butylperoxy-3-methylbutanal was oxidized with oxygen at room temperature to obtain 3-tert-butylperoxy-3-methylbutanoic acid.     

Pyridinium dichlorophosphinomethylides

Seven new pyridinium dichlorophosphinomethylides 2 have been obtained from dichlorophosphinylation of the pyridinium methylides generated in situ. 2 give 1,3‐bis(alkoxycarbonyl)‐2‐phosphaindolizines 4 through 1,5‐electrocyclization of the intermediate, bis(pyridinium ylidyl)phosphenium chloride 3 which is generated either from disproportionation of 2 or from the reaction of 2 with pyridinium methylide. Formation of 3 has been confirmed by carrying out a crossed reaction. 3‐Substituted 2 forms 4 regiospecifically. Intramolecular 1,5‐cyclocondensation of 2‐methylpyridinium dichlorophosphinomethylide is preferred over its disproportionation. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:602–609, 2001     

A Convenient Synthesis of 3-Benzoylindolizine-5-carbaldehydes

3-Benzoylindolizine-5-carbaldehydes (4a-f), which could be used as derivatization reagents for amino compounds in HPCE were synthesized based on the 1,3-dipolar cycloaddition of 1-phenacyl-2-(1,3-dioxolan-2-yl)pyridinium ylide with alkenes in the presence of TPCD.     

Organoselenium‐Catalyzed Regioselective C−H Pyridination of 1,3‐Dienes and Alkenes

An efficient approach for organoselenium‐catalyzed regioselective C−H pyridination of 1,3‐dienes to form pyridinium salts has been developed. This method was also successfully applied to direct C−H pyridination of alkenes. Fluoropyridinium reagents, or initially loaded pyridine derivatives, acted as pyridine sources in the pyridination reactions. The obtained pyridinium salts could be further converted under different conditions. This work is the first example of catalytic C‐2 direct C−H functionalization of 1,3‐dienes and the first case of organoselenium‐catalyzed C−H pyridination.     

Inverse electron‐demand 1,3‐dipolar cycloaddition reactions of cyclooctyne with pyridinium bis(methoxycarbonyl)methylides

Cyclooctyne underwent 1,3‐dipolar cycloaddition with pyridinium bis(methoxy‐carbonyl)methylides to afford the corresponding indolizines (8‐methoxycarbonyl‐7‐azatricyclo[7.6.0.0^2‐7]pentadeca‐1,3,5,8‐tetraenes) in good to moderate yields. Some molecular orbital considerations are also described on this reaction compared with the results on the reaction of pyridinium dicyanomethylides with cyclooctyne.     

Alkaloids of Siberia and Altai flora: XVIII. Alkyl 2-acetylamino-5-[2-(pyridin-3-yl)vinyl]benzoates in the synthesis of indolizines containing an anthranilic acid ester moiety

Methyl 2-acetylamino-5-[2-(6-methylpyridin-3-yl)vinyl]benzoate reacted with phenacyl bromide to produce quaternary 1-(2-aryl-2-oxoethyl)-2-methyl-5-(4-acetylamino-3-methoxycarbonyl)pyridinium bromides. 1,3-Dipolar cycloaddition of the latter to methyl propynoate and dimethyl but-2-ynedioate gave the corresponding indolizine derivatives containing an anthranilic acid ester moiety. Reactions of acetylenes with N-phenacylpyridinium salts obtained from a diterpene alkaloid derivative, 2-(pyridin-3-yl)vinyl-substituted lappaconitine afforded analogous compounds in which the indolizine fragment is conjugated to the aromatic ring of the alkaloid. 1,3-Dipolar cycloaddition of 1-(2-aryl-2-oxoethyl)-2-methyl-5-(4-acetylamino-3-methoxycarbonyl) pyridinium bromides with methyl propynoate was regioselective.     

Synthesis of N-substituted 4-aminomethyl-1,3-dioxanes

4-(R-Amino)methyl-1,3-dioxanes were synthesized from 4-chloromethyl-1,3-dioxanes. Some of these products were converted into water-soluble pyridinium chlorides by consecutive treatment with chloroacetyl chloride and pyridine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 21–23, January, 1995.     

gem-Difluorination of 2,2-diaryl-1,3-dithiolanes by Selectfluor and pyridinium polyhydrogen fluoride

2,2-diaryl-1,3-dithiolanes, readily obtainable from diaryl ketones, were transformed into the corresponding gem-difluoro compounds using a novel reagent combination involving Selectfluor and pyridinium polyhydrogen fluoride (PPHF) under mild conditions in moderate to good yields.     

γ-Trimethylsilyl(triphenylsilyl) pyridines in syntheses of silicon-containing pyridinium ylids and indolizines

Three N-phenacyl--trimethylsilyl (triphenylsilyl)pyridinium bromides were converted to stable silyl-substituted pyridinium ylids. Six previously unknown silicon-containing indolizines were obtained by two methods, viz., 1,3-dipolar cycloaddition of dimethyl acetylenedicarboxylate (DMAD) to the pyridinium ylids and the Chichibabin reaction. Spectral data that confirm the structures of the synthesized compounds are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 965–968, July, 1980.     

Intramolecular C-H...O hydrogen bonding in 2-(N-pyridinia)indane-1,3-dione betaines

The existence of an intramolecular C-H...O hydrogen bond between the protons of the pyridinium ring and the oxygen atoms of the phthaloyl part of the molecule in 2-(N-pyridinia)-indane-1,3-dione betaines and their aza analogs was proved by their PMR spectra. This sort of intramolecular hydrogen bond is absent in pyridinium betaines of cyclohexane-1,3-dione and acetoacetic and malonic esters.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 379–383, March, 1979.     

Organogelation behavior and thermal properties of supramolecular polymer networks using pyridyl-terminated 4-arm star-shaped ε-caprolactone oligomers and disulfonic acids

As a tetrapyridyl compound, nicotinate-terminated 4-arm star-shaped ε-caprolactone oligomer (Tetra-NA-CLO) was synthesized by the esterification reaction of nicotinic acid and hydroxy-terminated 4-arm star-shaped ε-caprolactone oligomer (Tetra-OH-CLO) having the degree of polymerization per one oligocaprolactone chain, n?=?5. As disulfonic acids, 1,3-bis(sulfopropoxy)propane (BSP) and 1,6-bis(sulfopropoxy)hexane (BSH) were synthesized by the reactions of 1,3-propanesultone with 1,3-propanediol and 1,6-hexanediol, respectively. A mixture of Tetra-NA-CLO and BSP or BSH became a thermo-reversible organogel in methanol, ethanol, and N,N-dimethylformamide at the concentration not less than 20 wt%. The sol-gel transition temperature of the mixtures was at around 15–20 °C. The ¹H NMR analysis of the mixture in a solution revealed a complete ionization of the pyridyl ring by the formation of pyridinium sulfonate moiety. The dried Tetra-NA-CLO/BSP and Tetra-NA-CLO/BSH films had higher crystallinity and melting temperature than that of the dried Tetra-NA-CLO film. The FT-IR analysis of the mixture in a dried solid state revealed that both the ionic and hydrogen-bonding interactions contributed.     

Iodo- and bromo-enolcyclization of 2-(2-propenyl)cyclohexanediones and 2-(2-propenyl)cyclohexenone derivatives using iodine in methanol and pyridinium hydrobromide perbromide in dichloromethane

alpha-Allylcyclohexane-1,3-diones undergo one-pot iodine-methanol promoted iodocyclization and oxidative aromatization to afford variously substituted 2-iodomethyltetrahydrobenzofuran-4-ones (minor) and 2-iodomethyl-4-methoxydihydrobenzofuran derivatives (major). On the other hand, the alpha-allyl-1,3-cyclohexanediones react with pyridinium hydrobromide perbromide in dichloromethane to afford mixtures of 2-bromomethyltetrahydrobenzofuran-4-ones (major) and 3-bromomethyltetrahydrobenzopyran-5-ones (minor). The prepared products and their derivatives were characterized using a combination of NMR, FT-IR and mass spectroscopic techniques.     

1,3-Dipolar cycloaddition reactions of cyclooctyne with azomethine ylides

Cyclooctyne smoothly underwent 1,3-dipolar cycloaddition with aziridines and pyridinium ylides to afford the corresponding pyrroles and indolizines in moderate to good yields.     

1,3-Dipolar cycloaddition reactions of cyclooctyne with pyridinium dicynomethylides

Cyclooctyne smoothly underwent 1,3-dipolar cycloaddition with pyridinium dicyanomethylides to afford the corresponding indolizines (8-cyario-7-azatricyclo[7.6.0.0^2,7]pentadeca-1,3,5,8-tetraenes) in excellent yields.     

Regioselectivity in the 1,3-dipolar cycloaddition reaction of unsymmetric pyridinium dicyanomethylides with dimethyl acetylenedicarboxylate and methyl propiolate: An example of dipole-dipole control of regioselectivity?

A study of the cycloaddition behavior of a series of unsymmetric pyridinium dicyanomethylides with dimethyl acetylenedicarboxylate and methyl propiolate has been carried out. The 1,3-dipolar cycloaddition proceeds in good yield with high regioselectivity to produce the corresponding indolizines and 1:1 adducts. The reactions of isoquinolinium dicyanomethylide follow frontier orbital predictions. In contrast, polar 3-substituted pyridinium dicyanomethylides gave predominantly the corresponding 8-isomers regardless of the substituents. The results can be explained by dipole-dipole interactions.