3-(2-Cyanoethyl)-6-aryl- or 6-(trans-4-alkylcyclohexyl)cyclohex-2-enones: synthesis,transformations and mesomorphic properties

The synthesis and chemical transformations of 3-(2-cyanoethyl)-6-aryl- or 6-(trans-4-alkylcyclohexyl)cyclohex-2-enones into nematic and smectic liquid crystalline compounds are discussed. These 3,6-disubstituted cyclohex-2-enones were prepared by the condensation of appropriate Mannich salts or trans-4-alkylcyclohexyl 2-bromoethyl ketones with ethyl 2-(2-cyanoethyl)acetoacetate.     

New liquid crystalline cyclohexene and cyclohexane derivatives and compositions based upon them

The synthesis and chemical transformations of 3,6-disubstituted cyclohex-2-enones into new liquid crystalline cyclohexene and cyclohexane derivatives are discussed. 3,6-Disubstituted cyclohex-2-enones have been synthesized by the condensation of appropriate 2-bromoethyl ketones or Mannich salts with 2-[2-(trans -4-alkylcyclohexyl)ethyl]acetoacetic or 2-[2-(4-substituted phenyl)ethyl]acetoacetic esters.     

3-Aryl- or 3-(trans-4-alkylcyclohexyl)- 6-arylcyclohex-2-enones: synthesis, transformations and mesomorphic properties

The synthesis and chemical transformations of 3-aryl- or 3-(trans-4-alkylcyclohexyl)- 6-arylcyclohex-2-enones into liquid crystalline compounds are discussed. These 3,6-disubstituted cyclohex-2-enones were prepared by the condensation of appropriate Mannich salts or trans-4-alkylcyclohexyl 2-bromoethyl ketones with 4-substituted benzyl methyl ketones.     

3-(2-Cyanoethyl )-6-aryl- or 6-(trans-4-alkylcyclohexyl)cyclohex-2-enones: synthesis, transformations and mesomorphic properties

The synthesis and chemical transformations of 3-(2-cyanoethyl)-6-aryl- or 6-(trans-4-alkylcyclohexyl)cyclohex-2-enones into nematic and smectic liquid crystalline compounds are discussed. These 3,6-disubstituted cyclohex-2-enones were prepared by the condensation of appropriate Mannich salts or trans-4-alkylcyclohexyl 2-bromoethyl ketones with ethyl 2-(2-cyanoethyl)acetoacetate.     

New liquid crystalline cyclohexene and cyclohexane derivatives and compositions based upon them

The synthesis and chemical transformations of 3,6-disubstituted cyclohex-2-enones into new liquid crystalline cyclohexene and cyclohexane derivatives are discussed. 3,6-Disubstituted cyclohex-2-enones have been synthesized by the condensation of appropriate 2-bromoethyl ketones or Mannich salts with 2-[2-( trans -4-alkylcyclohexyl)ethyl]acetoacetic or 2-[2-(4-substituted phenyl)ethyl]acetoacetic esters.     

Liquid crystals of some new tolane derivatives containing a 1,2-ethylene linkage

Abstract

Three types of nematogenic compound, 4-[2-(trans-4-alkylcyclohexyl)ethyl]-4′-alkyltolanes, 2-fluoro-4-[2-(trans-4-alkylcyclohexyl)ethyl]-4′-alkyltolanes and 4-[2-(trans-4-alkylcyclohexyl)ethyl]-4′-halogenotolanes, have been synthesized and their transition temperatures and enthalpies determined. Their bulk viscosity and birefringence have been estimated from those of mixtures with other liquid-crystalline compounds. These compounds have been found to be excellent materials for twisted nematic displays, because of their wide nematic temperature range, high birefringence (Δn = 0·26), and low viscosity (η = 21 cP at 20°C). Several related compounds having other central linkages, namely -CH₂O-, a single bond or -COO-, in place of the 1,2-ethylene group, have also been studied.     

Synthesis of 3-fluoroalkyl-2-aziridinyl ketones

Simple and efficient methods for the synthesis oftrans-3-fluoroalkyl-2-aziridinyl ketones from polyfluorinated α,β-enones have been developed.     

Ketalizations of aryl ω-(2-imidazolyl)alkyl ketones by glycerol and 3-mercapto-1,2-propanediol. synthesis and characterization of cis- and trans-{2-aryl-2-[ω-(2-imidazolyl)alkyl](1,3-dioxolan-4-yl and 1,3-oxathiolan-5-yl)}methanols

Aryl 2-[(2-imidazolyl)ethyl or 3-(2-imidazolyl)propyl]ketones were ketalized by glycerol or 3-mercapto-1,2-propanediol in boiling benzene in the presence of 4-toluenesulfonic acid to provide the title compounds. The aryl substituents are 4-chloro-, 4-bromo-, 4-fluoro-, or 2,4-dichlorophenyl. While aryl (2-imidazolyl)methyl ketones condensed with glycerol to form cis- and trans-{2-aryl-2-[(2-imidazolyl)methyl]-4-(hydroxymethyl)}-1,3-dioxolanes, related condensations with 3-mercapto-1,2-propanediol, under similar, or even more stringent reaction conditions, produced no 1,3-oxathiolane analogs, with the starting ketones being recovered. Separation and structure determination of these racemic cis and trans isomeric products are described. The structure of these stereoisomers was established by means of ¹H and ¹³C nmr correlation and nOe experiments. Selective methylation of the N-unsubstituted 2-imidazolyl alcohols with one equivalent sodium hydride and methyl iodide provided the corresponding N-methyl alcohols in excellent yields. With excess benzoyl chloride, N-unsubstituted 2-imidazolyl alcohols were initially converted to O, N-dibenzoates from which the N-benzoyl group was easily cleaved by ammonium hydroxide in ethanol to provide benzoate esters.     

Synthesis and mesomorphic properties of three- and four-ring liquid crystals containing cyclohexyl,phenyl and pyridyl units

Two series of 4-(3-alkoxycarbonylpyridyl-6-ethynyl)phenyl trans-4-n-alkylcyclohexylcarboxylates and 4-(3-alkoxycarbonylpyridyl-6-ethynyl)phenyl 4-(trans-4-n-alkylcyclohexyl)benzoates have been prepared. Their mesmorphic properties were observed and measured by polarizing optical microscopy and differential scanning calorimetry. The relationship between structures and properties is discussed, showing that the ferroelectric phase can be observed when chiral terminal chains exist.     

Regio-, Diastereo-, and Enantioselective Synthesis of Vicinal Diols via α-Silyl Ketones

A new versatile and efficient regio-, diastereo-, and enantioselective synthesis of vicinal diols s-trans- 4 , s-trans- 5 , and s-cis- 4 is described. Symmetrical ketones are converted into their SAMP-or RAMP-hydrazones which are then silylated with (isopropyloxy)dimethylsilyl chloride, followed by ozonolysis to afford the α-silyl ketones (R)- 2 of high enantiomeric purity (ee 90– ≥ 98%). On the other hand, methyl ketones, after conversion into the corresponding (?)–(S)-1-amino-2-(methoxymethyl) pyrrolidine (SAMP) hydrazones, are silylated and then alkylated with RI to afford unsymmetrical α-silyl ketones (S)- 3 of high enantiomeric purity (ee 90- ≥ 98%). The reduction of the above obtained α-silyl ketones with L -Selectride, followed by oxidative cleavage of the C? Si bond gives rise to s-trans-4, s-trans- 5 , and s-cis- 4 with high diastereoselectivity (de 95- ≥ 98%) and without racemization (ee ≥ 90– ≥ 98%).     

Synthesis and mesomorphic properties of four-ring liquid crystals containing cyclohexyl,phenyl and pyridyl units

Two series of chiral and achiral 4-[(3-n-alkoxycarbonylpyridyl)-6-ethynyl]phenyl 4-(trans-4-n-alkylcyclohexyl)benzoate liquid crystals have been synthesized. Their mesomorphic properties were observed and measured by polarizing optical microscopy and DSC. A broad chiral smectic C phase was observed when terminal chains contained a chiral centre.     

FRIEDEL-CRAFTS-Reaktionen der C7-, C8- und C12-Cycloalkane mit Kohlenmonoxid

The reaction of cycloheptane, cyclooctane, and cyclododecane with carbon monoxide under pressure in the presence of anhydrous aluminium chloride has been investigated. Cycloheptane leads to acetylcyclohexane and trans-2-methyl-cyclohexane carboxylic acid as main products. Cyclooctane yields 3- and trans-4-acetyl-methylcyclohexane and various dimethylcyclohexane carboxylic acids. From cyclododecane a mixture of numerous ketones has been obtained besides a mixture of acids.     

Synthesis of 6-(N-azolyl)cyclohex-2-enones fromN-acetonylazoles

N-Acetonylazoles react with chalcones in the presence of a base to givetrans-3,5-disubstituted 6-(N-azolyl)cyclohex-2-enones. Usually, the reactions are fast and high-yielding. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 557–561, March, 1999.     

Furylcyclohexenones. 3. Synthesis and properties of 6-acetyl-3(5)-furylcyclohex-2-enones. Molecular and crystal structure of 6-acetyl-3-(2-furyl)-5-phenylcyclohex-2-enone

6-Acetyl-3(5)-furylcyclohex-2-enones were prepared by condensation of furan-containing chalcones with acetylacetone. Acetylcyclohex-2-enones were subjected to C-methylation. Studies by IR and ¹H NMR spectroscopy demonstrated that the resulting compounds occur predominantly in the enol form both in solutions and in the crystalline state. The molecular structure of 6-acetyl-3-(2-furyl)-5-phenylcyclohex-2-enone was established by X-ray diffraction analysis.     

Novel polycyclic heterocycles. XII. Reactions of 1,2-dihydro-11-(trifluoromethyl)-3H-7H-quino[8, 1-cd] [1,5]-benzoxazepin-3-one with aromatic aldehydes

The Claisen-Schmidt condensation between 1,2-dihydro-11-(trifluoromethyl)-3H,7H-quino-[8,1 -cd][1,5]benzoxazepin-3-one, 1 , and aromatic aldehydes has been investigated. The acid catalyzed reactions yielded the trans-2-benzylidene derivatives, 4 ; the structures and configurations of the group of compounds represented by 4 have been confirmed by pmr in conjunction with the Eu(fod)₃ shift reagent. In contrast, catalysis with sodium hydroxide gave the isomeric 2-benzyl-endocyclic α,β-unsaturated ketones, 3. Finally, the 4 could be isomerized to the corresponding 3 by means of sodium hydroxide. The ir, uv, and pmr spectra of these compounds are discussed.     

Structure of 2(5)-alkyl-4-hydroxy-3,4-diphenylcyclopent-2-en-1-ones,cyclocondensation products of benzil with aliphatic ketones

The reaction of benzil with methyl alkyl ketones gave three isomeric cyclopentenone derivatives, 2-substituted and cis- and trans-5-substituted 4-hydroxy-3,4-diphenylcyclopent-2-en-1-ones. cis- and trans-2,5-Disubstituted 4-hydroxy-3,4-diphenylcyclopent-2-en-1-ones were formed in analogous reaction of benzil with dialkyl ketones. The structure of the products was confirmed by ¹H NMR spectroscopy and molecularmechanics calculations.     

Die thermische Umlagerung von 2-(Buta-1′,3′-dienyl)-phenolen in 2-Alkyl-2H-chromene; Beispiele für aromatische [1,7a]- und [1,5s]sigmatropische Wasserstoffverschiebungen

2-(1′-cis,3′-cis-)- and 2-(1′-cis,3′-trans-Penta-1′,3′-dienyl)-phenol (cis, cis- 4 and cis, trans- 4 , cf. scheme 1) rearrange thermally at 85–110° via [1,7 a] hydrogen shifts to yield the o-quinomethide 2 (R ? CH₃) which rapidly cyclises to give 2-ethyl-2H-chromene ( 7 ). The trans formation of cis, cis- and cis, trans- 4 into 7 is accompanied by a thermal cis, trans isomerisation of the 3′ double bond in 4. The isomerisation indicates that [1,7 a] hydrogen shifts in 2 compete with the electrocyclic ring closure of 2 . The isomeric phenols, trans, trans- and trans, cis- 4 , are stable at 85–110° but at 190° rearrange also to form 7 . This rearrangement is induced by a thermal cis, trans isomerisation of the 1′ double bond which occurs via [1, 5s] hydrogen shifts. Deuterium labelling experiments show that the chromene 7 is in equilibrium with the o-quinomethide 2 (R ? CH₃), at 210°. Thus, when 2-benzyl-2H-chromene ( 9 ) or 2-(1′-trans,3′-trans,-4′-phenyl-buta1′,3′-dienyl)-phenol (trans, trans- 6 ) is heated in diglyme solution at >200°, an equilibrium mixture of both compounds (～ 55% 9 and 45% 6 ) is obtained.     

Photorearrangement of 4,4-Dimethylcyclohex-2-enones with Alkyl or Fluoro Substituents at C(5) and C(6): In Search of the Mechanism

The photorearrangement of cyclohex-2-enones 4a-h to bicyclo[3.1.0]hexan-2-ones 5 and cyclopent-2-enones 6 (λ = 350 nm, MeCN) was investigated. Both the quantum yield (Φ_?4 = 0.004– 0.024) and the product ratio ( 5/6 = 65:35–31:69) vary only over a rather small range, indicating the rearrangement to be relatively insensitive to substituents on C(5) or C(6). Compounds 4b, 4c , and 4g with just one alkyl group at either C(6) or C(5) rearrange selectively to the diastereoisomer 5 with alkyl group and three-membered ring in trans-configuration, while 6-fluorocyclohex-2-enones 4d and 4f afford mixtures of diastereoisomeric bicyclohexanones. Mechanistic conclusions regarding an intermediate trimethylene biradical are presented.     

Pyridinethiones. XI. Diastereoselective aldol condensations with 2(1H)-pyridones, 2(1H)-pyridinethiones,and the crystal structure of 3-(1-hydroxy-2-methyl-3-oxo-3-(4-chlorophenyl)propyl-1-isoprpyl-2(1H)-pyridinethione

Aldol condensation of 3-formyl-2(1H)-pyridinethiones and the corresponding pyridones with ketones such as acetophenones in aqueous base yields 3-hydroxy-1-propanones in high yields. Reaction with propiophenone showed this reaction to be highly diastereoselective as only the erythro-isomer is formed at room temperature. This assignment was based on an X-ray crystallographic investigation of the compound given in the title. Aldol condensations of a number of related 3-acetyl-2(1H)-pyridinethiones with benzaldehyde yielded the corresponding trans-vinyl ketones.     

Haloacetylated enol ethers. 13. Synthesis of N-[1-aryl(alkyl)-3-oxo-4,4,4-trichloro-1-buten-1-yl]-o-phenylenediamines and 2-trichloromethyl-4-aryl-3H-1,5-benzodiazepines

The synthesis and isolation of the intermediates N-[1-aryl(alkyl)-3-oxo-4,4,4-trichloro-1-buten-1-yl]-o-phenylenediamines 2a-f and the corresponding 2-trichloromethyl-4-aryl-3H-1,5-benzodiazepines 3c-g or benzimidazoles 4a-b derivatives obtained from the intramolecular cyclization of 2a-f or from direct cyclo-condensation reaction of β-alkoxyvinyl trichloromethyl ketones 1a-g with o-phenylenediamine, is reported. Depending of the structure of the β-alkoxyvinyl trichloromethyl ketones or the N-[1-aryl(alkyl)-3-oxo-4,4,4-trichloro-buten-1-yl]-o-phenylenediamines and the reactions conditions, benzimidazoles or 3H-1,5-benzodiazepines were obtained.