Cyano-4-biphenyl

Fig. 5a and b. Clearing points of poly(p-biphenyl acrylate) (a) and biphenyl-cyano-containing polymers [-CH2-CX-]... 

DCZP/poly(ll-(4-cyano-4 -biphenyl)-l-undecano yl acrylate 10-" ate X 10" v/cm 60... 

Properties have been determined for a series of block copolymers based on poly[3,3-bis(ethoxymethyl)oxetane] and poly [3,3-bis(methoxymethyl)oxetane]- (9-tetrahydrofuran. The block copolymers had properties suggestive of a thermoplastic elastomer (308). POX was a good main chain for a weU-developed smectic Hquid crystalline state when cyano- or fluorine-substituted biphenyls were used as mesogenic groups attached through a four-methylene spacer (309,310). Other side-chain Hquid crystalline polyoxetanes were observed with a spacer-separated azo moiety (311) and with laterally attached mesogenic groups (312). 

CH2)4-C6H4-CgH4CN T8[OSiMe2H]g+4-cyano-4 -(5-hexenenyloxy)biphenyl 85 12.3, -108.8 280... 

C12H21N 773777-37-4) see Dicycloverine 2 -cyanobiphenyl-4-carboxaldehyde (C14Hc.NO 135689-93-9) see Valsartan 7V-[(2 -cyano[l,l -biphenyl]-4-yl)methyl]-L-valine methyl ester... 

The compound in Fig. 3b exhibits two smectic phases (Sm and Sm ) in addition to nematic, whereas the compound in Fig. 3a exhibits only a nematic phase. The substitution of an alkoxy for an alkyl tail is known to shift phase transition temperatures considerably. In the cyano-biphenyls (Fig. 4), substitution of an alkoxy tail raises the melting point from 24 to 48 °C and T from 35 to 68 °C [22]. 

In this section, we will describe the crystal structures of the mesogenic A -n-alkoxy-4-cyano-biphenyls (Fig. 1) [53-57]. The compounds have the phase sequences crystal-nematic-isotropic for CB05—CB07 and monotropic nematic for CB01-CB04 crystal-smectic A-nematic-isotropic for CB08. The crystal and molecular data of the investigated compounds CBOn are summarised in Table 2. 

Table II. Influence of the Main Chain Flexibility on Liquid Crystalline Phase Transitions for Polymers with Cyano-biphenyl as Nesogen...

The photodecarbonylation of a series of dibenzyl ketones was studied by Robbins and Eastman/63 The results of this study are presented in Table 4.5. The data in Table 4.5 indicate that the presence of a p-methyl or a p-methoxy group has little effect on the quantum yield for this reaction. p-Cyano groups, on the other hand, essentially totally eliminated the decarbonylation. Since the reaction could also be quenched (inefficiently) by benzonitrile or biphenyl, it was concluded that the decarbonylation occurs from a short-lived triplet state. The effect of the p-cyano groups then could result from internal triplet quenching. 

Bazan and co-workers [93] coupled four branches of stilbene chromophores to a central C atom, leading to tetrastilbenylmethane [C(STB)4, 46a] tetrakis (4-ferf-butylstyryIstiIbenyljmethane [C(f-BuSSB)4, 46b], and the higher homolo-gue tetrakis 4-[4 -(4"-terf-butyl-styryl)styryl]stilbenyl methane [C(4R—f-Bu)4, 46c]. For 46b, Tg is 190°C, and for 46c it is as high as 230°C. Tetrakis(4,4 -2,2-diphenyl-vinyl)-l,l -biphenyl]methane [C(DPVBi)4, 47a] and the cyano derivative 47b exhibit the glass transition at 142 and 174°C, respectively. Similar compounds to 46a and 46b have also been synthesized with silicon and adaman-tane as the tetrahedral center. 

Dawson, G. B., Matyska, M. T., Pesek, J. J., and Seipert, R. (2004). Electrochromatographic studies of etched capillaries modified with a cyano pentoxy biphenyl liquid crystal. /. Chromatogr. A 1047, 299-303. 

Ar = alkyl, methoxy, nitre, cyano, halophenyl derivatives, 2-biphenyl... 

Bis(phenylazo)phenanthrene 174, for which the cyclic form 175 dominates reactivity at low concentrations, reacts with acrylonitrile in dry toluene at 55 °C for 48h to give the o o-adduct 2,4-diphenyl-3a,6a-(biphenyl-2,2 -yl)-6-exo-cyano-l,3a,4,5,6,6a-hexahydropyrrolo[2,3-r7 -2,3-triazol-2-ium-l-ide 176 (60% ) as the only product of cycloaddition. Reaction with other alkenes, for example, A -phenylmaleimide, leads to a mixture of endo- and o ti-products, cf. 177 and 178 <1996J(P1)1623>. 

Two para-substituents, phenyl and cyano depress and retard the rate of cyclization significantly (Table 11.2)." p-Phenyl and p-cyano are both radical stabilizing substituents. These conjugative substituents reduce the spin density on the carbon ortho to the nitrene nitrogen. The reduced spin density at carbons ortho to the nitrogen lowers the rate at which the 1,3-biradical cychzes. The effect with p-cyano and p-biphenyl singlet phenylnitrene is quite dramatic. The lifetimes of these singlet nitrenes at ambient temperature are 8 and 15 ns, respectively, and the activation barriers to cychzation are 7.2 and 6.8 kcal/mol, respectively. 

The sequence for the synthesis of l,3,6-triazacycl[3,3,3]azines (58) is based on the reaction of 2,6-diaminopyridine with ethoxymethylene-malononitrile or ethyl ethoxymethylenecyanoacetate, leading to compounds 56. These on acylation gave 57, which after cyclodehydration yielded the desired cyclazines (58). Small amounts of the unsubstituted parent triazacyclazine (58a) were observed when the cyclization of 57 was carried out in a refluxing mixture of biphenyl and diphenyl ether. Decyanation of 4-cyano-2-methyl-l,3,6-triazacycl[3,3,3]azine (58f) with polyphosphoric acid at 200° yields 2-methyl-l,3,6-triazacycl-[3,3,3]azine (58b).18-80 The synthesis of 58d was carried out by a closely related route.74... 

Upon addition of a terminal crown ether to the calamitic core unit, nematic phases were observed for 2, 3 in agreement with previous studies on substituted cyano biphenyls [25, 26]. 

There is only one example that fits into this section and it uses a spectacular way to form the crown ether in the polymer that is worth noting (Scheme 22). In contrast to all other procedures that use crown ethers pre-formed in the monomers, this example by Percec forms the crown ether [13]crown-4 during the polymerization reaction [59]. Cationic cyclocopolymerization of l,2-bis(2-ethenyloxyethoxy)ben-zene 37 with the mesogenic cyano biphenyl unit 38 gave copolymer 39 with a 1 1 ratio of 37 38 displaying a smectic phase. 

Alkoxy derivatives of biphenyl can be obtained either from alkoxy-anilines or by coupling with alkoxybenzenes. From diazotized p-bromo-aniline and anisole a 20% yield of 4-bromo-2 -methoxybiphenyl and a 7% yield of 4-bromo-4 -methoxybiphenyl are obtained. In connection with their studies on Cannabis Indica, Ghosh, Pascall, and Todd u prepared the highly substituted biphenyl compound, 2-cyano-5-methyl-2, 5 -dimethoxy-4 -n-amylbiphenyl (VII), in 27% yield from the nitrosoacetyl derivative of 2-cyano-5-methylaniline and 2,5-dimethoxy-n-amylben-zene. 

A vinyl ether with a mesogenic side group, 3-[4-cyano-4 -biphenyl)oxy]propyl vinyl ether, was polymerized at 0 °C in CH2C12 with trifluoromethanesulfonic acid as an initiator in the presence of dimethylsulfide [92]. 

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