Smectic polymorphism of the 4-butyl-4-alkoxyazobenzenes and 4-pentyl-4-alkoxyazobenzenes

Two families of liquid crystalline compounds have been synthesised, the 4-butyl-4- alkoxyazobenzenes and the 4-pentyl-4-alkoxyazobenzenes; for the second family results are presented for the first time for alkoxy chains longer than butyl. The results for both families have been obtained up to the octadecyl homologues. In both families, on the basis of DSC, polarizing microscopy and thermo-optical analysis, a rich polymorphism has been detected (maximum tetramorphism). The smectic properties start with the hexyl derivative (for the butyl family) and with the heptyl derivative (for the pentyl family). Strong odd-even effects for the temperatures of clearing in both groups of compounds were detected. Our results are compared with those of de Jeu et al. and of Adomenas et al. for the 4-butyl-4- alkoxyazobenzenes, for which only one smectic modification was described.     

Synthesis of 4H-pyrazolo- and 4H-pyrrolophenothiazin-4-one derivatives

5-Methyl- and 6-methyl-2-phenyl-2H-indazole-4,7-diones were condensed with 2-aminobenzenethiol or 6-substituted-3-aminopyridine-2(1H)thiones 4 to produce a new type of 5-methyl-2-phenyl-4H-pyrazolophenothiazin-4-ones or 8-substituted-7-aza-5-methyl-2-phenyl-4H-pyrazolophenothiazin-4-one derivatives. From 6-bromo-2,5-dimethyl-1,3-diphenyl-2H-isoindole-4,7-dione and 4 8-substituted-7-aza-2,5-dimethyl-1,3-diphenyl-4H-pyrrolophenothiazin-4-one derivatives were also prepared.     

Synthesis of 4-alkoxy-4-methyl- and 4-alkoxy-4-fluoromethyl-1,3-benzoxazinones

Cyclization of 2-hydroxyacetophenone hydrazones with triphosgene resulted in the formation of 4-methylene-1,3-benzoxazinones. These compounds were converted to 4-alkoxy-4-methyl-1,3-benzoxazinones and 4-fluoromethyl-4-methoxy-1,3-benzoxazinones upon treatment with alcohols under refluxing conditions and F-TEDA-BF₄ in acetonitrile and methanol, respectively.     

Synthesis and mesomorphic properties of 4-cyanophenyl and 4-nitrophenyl 4- n -alkoxytetrafluorobiphenyl-4'-carboxylates

Four homologous series of 4-cyanophenyl and 4-nitrophenyl 4- n -alkoxytetrafluorobiphenyl-4'carboxylates have been synthesized. Their mesomorphic properties were measured by polarizing optical microscopy and differential scanning calorimetry. The relationship between the properties and chemical structures of these compounds has been studied; the effects of terminal alkoxy chain length, polarizable end groups and the position of tetrafluorophenylene in the rigid core on mesomorphic behaviour are discussed in detail.     

Orientational Order in Nematic and Smectic A Phases of Three Closely Related Compounds 4 4-di-n-Heptylazobenzene 4 4-di-n-Heptyl- and 4 4-di-n-Octylazoxybenzene

The orientational ordering in the three related compounds 4,4-di-n-heptyl-d₂-azobenzene-d, (HB-d₁₂), 4,4'-di-n-heptyl-d₂-azoxybenzene-d, (HAB-d₁₂) and 4,4-di-n-octyl-d₂-azoxybenzene-d₈ (OAB-d₁₂) has been monitored using deuteron N.M.R. spectroscopy. In these non-rigid molecules it is possible to obtain only the elements of local order matrices. For the aromatic rings these are found to be axially symmetric within the precision of our measurements. The temperature dependences of the local order parameters for the aromatic rings are compared with those predicted by McMillan's theory of smectic A phases.     

Fluorination of 4-nitroisoxazoline salts. Synthesis of 4-fluoro-4-nitroisoxazolines and 4-fluoroisoxazoles

Methods for the synthesis of hitherto unknown 4-fluoro-4-nitroisoxazolines by fluorination of 4-nitroisoxazoline salts with FClO₃ in MeOH and 4-fluoroisoxazoles by treatment of fluoronitroisoxazolines bearing the hydrogen atom bound to the C(5) atom of the isoxazole ring with MeONa in MeOH were developed.     

Synthesis of 4-fluororesorcinol and 4-trifluoromethylresorcinol

Less expensive, safer, and easily scaled-up methods for the synthesis of 4-fluororesorcinol and 4-trifluoromethylresorcinol have been established, including two methods to give the former compound. One involves the reaction of Selectfluor™ reagent with 1,3-dimethoxybenzene to give 2,4-dimethoxy-1-fluorobenzene followed by hydrolysis to give 4-fluororesorcinol. The overall yield of this two-step reaction is 54%. In the second case, when Selectfluor reagent is reacted directly with resorcinol, under the best reaction conditions, 4-fluororesorcinol is obtained in 66% yield. It is, however, very difficult to separate the starting material from the mono- and difluororesorcinol products. Consequently, the two-step method is the method of choice to prepare 4-fluororesorcinol. The trifluoromethyl group was incorporated into 2,4-dimethoxy-1-iodobenzene to form 1,3-dimethoxy-4-trifluoromethylbenzene followed by mild hydrolysis to give 4-trifluoromethylresorcinol. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:229–239, 1998     

Synthesis and Reactions of 4-cis- and 4-trans-Hydroxy-2e-methyl-4-ethynyl-trans-decahydroquinolines

By treating 2e-methyl-4-oxo-trans-decahydroquinoline with lithium acetylide a mixture of stereoisomeric 4-cis-hydroxy-2e-methyl- and 4-trans-hydroxy-2e-methyl-4-ethynyl-trans-decahydroquinolines was obtained in 3:2 ratio. Their reaction with acetonitrile in the presence of sulfuric acid (Ritter's reaction) results in a mixture of stereoisomeric 4-cis-acetylamino-2e-methyl- and 4-trans-acetylamino-2e-methyl-4-ethynyl-trans-decahydroquinolines in the same ratio. The ethynyl group of alcohols synthesized is not hydrated under conditions of Kuchrerov's reaction. The boiling of the alcohols with formic acid furnished a mixture of 4-acetyl-2e-methyl and 2e-methyl-4-ethynyl-1,2,3,6,7,8,9,10-octahydroquinolines in 1:7 ratio. The former of these compounds under conditions of Ritter's reaction yielded a mixture (1:1.4) of stereoisomeric 4-acetyl-4-trans-acetylamino- and 4-acetyl-4-cis-acetylamino-2e-methyl-trans-decahydroquinolines. From 2e-methyl-4-ethynyl-1,2,3,6,7,8,9,10-octahydroquinoline under the same conditions were obtained both already mentioned stereoisomeric 4-acetylamino-2e-methyl-4-ethynyl-decahydroquinolines (53% of cis-isomer and 35% of trans-isomer in the mixture) and 4-acetyl-4-acetylamino-2e-methyldecahydroquinolines (7% of cis-isomer and 5% of trans-isomer).