Stilbene heterocyclic derivatives

Fig-1 General structure of a stilbene heterocyclic derivative (A), and two chalcone heterocyclic derivatives (B and C). (Dashed circles represent the location of the herocydic ring)... 

Many chemical compounds have been described in the Hterature as fluorescent, and since the 1950s intensive research has yielded many fluorescent compounds that provide a suitable whitening effect however, only a small number of these compounds have found practical uses. Collectively these materials are aromatic or heterocycHc compounds many of them contain condensed ring systems. An important feature of these compounds is the presence of an unintermpted chain of conjugated double bonds, the number of which is dependent on substituents as well as the planarity of the fluorescent part of the molecule. Almost all of these compounds ate derivatives of stilbene [588-59-0] or 4,4 -diaminostilbene biphenyl 5-membeted heterocycles such as triazoles, oxazoles, imidazoles, etc or 6-membeted heterocycles, eg, coumarins, naphthaUmide, t-triazine, etc. 

There are considerably fewer examples of heterocyclic chalcone analogs of combretastatin than in the heterocyclic stilbene derivative category. Of these,... 

The synthesis of biologically important heterocyclic stilbene and chalcone derivatives of combretastatins has been discussed. Combretastatins have been shown to be inhibitors of tubulin polymerization. In many cases the compounds described in this chapter were included because of an interesting synthesis or structure, although limited biological data were found. It is the author s opinion that a great number of the compounds contained within this review are worthy of further investigation as potential tubulin binders. 

The photolysis of donor-acceptor systems provides unique synthetic opportunities. Direct irradiation of the donor-acceptor systems, such as systems containing arene and amine components, leads to intramolecular electron transfer, that is, to amine cation-radical and arene anion-radical moieties. After generation, these moieties undergo cyclization reactions providing efficient synthetic routes to fV-heterocycles with a variety of ring sizes. Thus, direct irradiation of secondary amino-ethyl and aminopropyl stilbenes leads to benzazepines in improved yields (Hintz et al. 1996). As known, benzazepines are used in medicine as antidepressants. Scheme 7.44 illustrates ion-radical cyclization with the formation of benzazepine derivative (65% yield). 

In addition to benzene and naphthalene derivatives, heteroaromatic compounds such as ferrocene[232, furan, thiophene, seienophene[233,234], and cyclobutadiene iron carbonyl complex[235] react with alkenes to give vinyl heterocycles. The ease of the reaction of styrene with substituted benzenes to give stilbene derivatives 260 increases in the order benzene < naphthalene < ferrocene < furan. The effect of substituents in this reaction is similar to that in the electrophilic aromatic substitution reactions[236]. 

Bis-substitution of stilbene produces stronger fluorescence and the bis-triazine derivatives of diaminostilbenes have proved to be the most successful brighteners for cellulosics, in particular, and polyamides (60MI11200). The variety of substitution permutations in (90) is almost endless and many primary and secondary homocyclic and heterocyclic amines, thiols and phenols have been used. Synthesis of such compounds is straightforward and utilizes the convenient selectivity to substitution of cyanuric chloride. 4,4 -Diaminostilbene-2,2 -disulfonic acid condenses readily at 0-5 °C with cyanuric chloride, under slightly acidic conditions. In this case cyanuric chloride behaves as a monofunctional acid chloride and, although some by-products are unavoidable, two molecules of cyanuric chloride condense... 

Heterocyclic ring closure of o-hydroxylated or o-acylated styrene, stilbene, and stilbazole derivatives. This group includes miscellaneous methods, the final stage of which involves ring closure of compounds as in Eq. (2). Starting from o-acyloxystilbenes, the reaction provides... 

Photoinduced ring cleavage also occurs readily in heterocyclic systems containing both oxygen and nitrogen. A series of dihydro-oxadiazinones, for example, undergo decomposition, and the results obtained parallel those observed on thermal decomposition cis- and Jraras-stilbene are obtained from the diphenyl derivative (71), whereas cis-cyclooctene is the major product of photolysis of the fused cyclooctane (72).62... 

The previously available methods for the preparation of such compounds were somewhat limited in their application. First, the oxidative coupling of 2 molecules of a heterocyclic-substituted toluene derivative in lie presence of sulfur results in the formation of symmetrical stil-benes,4,5 as shown by the synthesis of 4,4 -bis(benzimidazol-2-yl)stilbene (2). The disadvantages of this method are the high reaction temperatures necessary and the difficulties often involved in product workup. 

Treatment of 2- or 4-(p-formylphenyl)-2/f-l,2,3-triazoles with p-tolyl-substituted heterocycles such as benzo[6]furans,58,63 benzol-thiophenes,56,63 benzoxazoles,63,64 benzisoxazoles,54 oxazoles,63 isoxa-zoles,63 oxadiazoles,63,65 benzotriazoles,63 and y-triazolo [ 1,5-a]-pyri-dines19 has led to the formation of a number of new stilbene derivatives some of which are shown in Table XI. 

Heterocyclic variations on the basic stilbene — phenanthrcne theme are provided by many systems in which one or both of the phenyl groups of stilbene is replaced by a heteroaromatic group, or in which there is a pair of phenyl groups on adjacent positions in a heterocyclic ring. An example of the latter is seen in 1,2,6-triphenylpyridinium salts, which undergo photochemical cyclization to give a bridgehead aza-derivative of triphenylene (3.67). 

Aryl halides which are rather inert in usual organic reactions can undergo reactions by means of palladium catalysts. Thus, styrene and stilbene derivatives are obtained by reaction of olefins with aryl bromides at 125 °C using Pd(0Ac)2 (1 mol%) and tri-(o-tolyl)phosphine (2 mol%)83. The palladium-catalyzed vinylic substitution reaction is applicable to a variety of heterocyclic bromides including pyridine, thiophene, indole, furan, quinoline and isoquinoline84. Thus, reaction of 3-bromopyri-dine with l-(3-butenyl)phthalimide at 100 °C gives l-[4-(3 -pyridyl)-3-butenyl]-phthalimide (yield of mixed amine 57%, selectivity 68%) at 100 °C. This phthalimide is subsequently converted to nornicotine (188) (Scheme 59). The reaction of acrylic... 

These are added to paper, plastics and detergents to increase the whiteness by absorbing UV light and emitting blue light. Many optical brighteners are stilbene derivatives, but a number of heterocyclic ring types are also important, for example the oxazole and triazole derivatives shown below, 1,3,5-triazines and... 

One substituent is usually insufficient to facilitate condensation mono-nitrotoluenes react poorly with benzaldehyde, but condensation between the dinitrotoluenes and benzaldehyde leads to the corresponding stilbene derivatives.952 However, methyl groups attached to heterocyclic systems have been much more often used for such condensations Ladenburg953 showed that 2-methylpyridine and acetaldehyde at 250° give 2-propenylpyridine and 4-methylpyridine reacts similarly.954... 

The hrst example is insertion of styrene to Ar,AT-dimethylbenzylamine complex (416) to form the stilbene derivative 417, which takes place smoothly at room temperature in AcOH [14]. Alkynes insert smoothly. Two moles of diphenylacetylene insert into the benzyl methyl sulfide complex 418 to afford the eight-membered heterocycle 419 [175]. 

Stilbene-related heterocyclic compounds including benzalphthalide, phthalazi-none, imidazoindole, and pyrimidoisoindole derivatives were tested for their anti-HIV activity [174]. Assays based on recombinant vfruses were used to evaluate HIV replication inhibition, and stably transfeded cell lines were used to evaluate inhibition of Tat and NF-kB proteins. Some of the stilbene-related heterocyclic compounds analyzed displayed anti-HIV activity through interference with NF-kB and Tat fundion. Near-IR spectroscopy (NIRS) and artificial neural networks were employed for quantitative detedion of four active constituents in rhubarb ... 

Hano, Y., M. Itoh, and T. Nomura Structures of Kuwanols A and B, Two Novel Stilbene Derivatives from the Cultivated Mulberry Tree Morus bombycis Koidz.). Heterocycles 23, 819 (1985). 

Nonflavonoid compounds comprise simple phenols, phenolic acids, coumarins, xanthones, stilbenes, lignins, and lignans. Phenolic acids are further divided into benzoic acid derivatives, based on a C6-C1 skeleton and cinnamic acid derivatives, which are based on a C6-C3 skeleton [6], The conmarins are phenolic acid derivatives composed of a benzene ring fnsed with an oxygen heterocycle. Xanthones consist of a C6-C1-C6 basic structure, and stilbenes are composed of a C6-C2-C6 skeleton with various hydroxylation patterns [13], Lignins are polymers of C6-C3 units, whereas lignans are made up of two phenylpropane units [13]. The structures of each of these classes are shown in Table 16.1. 

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