Liquid Crystalline Esters of Alicyclic and Heterocyclic Acids

Karamysheva, L. A.; Geivandova, T. A.; Roitman, K. V.; Ljukmanov, N. F.; Kovshev, E. I.

doi:10.1080/00268948308072039

Cited by 23 publications

(1 citation statement)

References 7 publications

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“…Carbocyclic spiro compounds 1 are not only part of natural products such as sesquiterpenes, but can also be used as building blocks in thermotropic liquid crystals. 2 The required and characteristic molecular shape 3 of a calamitic liquid crystal 4 is a linear elongated structure as it is achieved by the bicyclohexyl compounds 1 synthesised by Eidenschinck et al 5 which show remarkable mesophases. The interest in new rodlike liquid crystals is due to their broad applicability in optical displays and screens.…”

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Synthesis of Rodlike Dispiro Hydrocarbon Skeletons for New Liquid Crystal Compounds

Feuerbacher¹,

Vögtle²,

Windscheidt³

et al. 1999

Synthesis

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A simple synthesis of the dispiro[5.2.5.2]hexadecane skeleton was developed. Starting from the cyclohexanedicarbaldehyde 6 the dispirane was prepared in one step. The synthesised dispirodiketone 4 is a key compound for the preparation of a number of new liquid crystalline compounds, as its linear molecular shape is proved by an x-ray structural analysis of the corresponding diketal 10 . Additionally the synthesis of the first dispirane 4 with a [5.2.3.2]-linkage is described.Carbocyclic spiro compounds 1 are not only part of natural products such as sesquiterpenes, but can also be used as building blocks in thermotropic liquid crystals. 2 The required and characteristic molecular shape 3 of a calamitic liquid crystal 4 is a linear elongated structure as it is achieved by the bicyclohexyl compounds 1 synthesised by Eidenschinck et al 5 which show remarkable mesophases. The interest in new rodlike liquid crystals is due to their broad applicability in optical displays and screens. In search of novel nematogenic compounds we synthesised several dispiranes and spiranes and investigated the influence of their molecular shape on the liquid crystalline behaviour. 6 We showed that the spiro linkage of cyclohexyl units only retain their required linearity if an even number of carbon atoms in the middle ring is given (cf. 2 ). In this contribution we have reported the synthesis of terminally substituted dispiro[5.1.5.1]tetradecanes 3 , which show enantiotopic mesophases over a large temperature range of more than 100¡C. 6b,c Now we report the facile synthesis of a dispiro-[5.2.5.2]hexadecane 2 (n = 2) as an excellent precursor for new liquid crystal compounds. The dispirodiketone 4 is a key intermediate which provides the possibility to investigate the consequences of different terminal substitution patterns on its physical properties.Additionally the synthesis of an alkyl substituted dispirotetradecane 5 which would be the first dispirane with a [5.2.3.2]-linkage allows further examinations of the influence of the molecule geometry on liquid crystal behaviour.Various methods of preparing polyspiro compounds consisting of cyclohexane rings are described in the literature. 7 However, to our knowledge, no preparation of a dispirohexadecane which can be twice terminally substituted has been discovered and the known syntheses of dispiro[5.2.5.2]hexadecanes are still very complex. 8 For this reason a simple and efficient synthesis is desirable. Following the acid-catalysed annelation of a -alkyl aldehydes and a,b -unsaturated ketones found by Flaugh et al. 9 we succeeded in performing a one-pot synthesis of cyclohexanedicarbaldehyde 7 . 10 Treatment of 6 with methyl vinyl ketone yields the desired dispirodiketenones 7 and 8 respectively. The synthesis was carried out by treating a mixture of the dialdehyde and methyl vinyl ketone in toluene with a catalytic amount of sulfuric acid and direct azeotropic removal of water.The dialdehyde 6 was prepared by a convenient TEMPOcatalysed oxidation of cyclohexanedimethanol with sodium h...

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