2,5-二取代-1,3,4-噁二唑类化合物的合成及其昆虫生长调节活性的研究进展

2,5-二取代-1,3,4-噁二唑类化合物因其具有独特的生物活性和光学活性而广泛被人们研究, 并被应用在农业、医药、材料等多个领域. 综述了2,5-二取代-1,3,4-噁二唑类化合物的合成方法, 以及对其作为昆虫生长调节剂的研究进展.     

A facile procedure for the one-pot synthesis of unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles

Unsymmetrically 2,5-disubstituted 1,3,4-oxadiazoles were efficiently synthesized from the cyclization-oxidation reaction of acyl hydrazones. Also, the synthesis of the title compounds was achieved by the condensation of acyl hydrazides and aromatic aldehydes in the presence of ceric ammonium nitrate in dichloromethane.     

Trichloroisocyanuric Acid–Mediated One-Pot Synthesis of Unsymmetrical 2,5-Disubstituted 1,3,4-Oxadiazoles at Ambient Temperature

An efficient method for the one-pot synthesis of unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles has been developed using trichloroisocyanuric acid (TCCA) at ambient temperature. A wide variety of aromatic as well as heterocyclic aldehydes exhibit condensation with a variety of acylhydrazines followed by oxidative cyclization to yield corresponding unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles. The mild nature of the synthesis and short reaction time are notable advantages of the developed protocol.     

Effects of thiophene-based mesogen terminated with branched alkoxy group on the temperature range and electro-optical performances of liquid crystalline blue phases

A series of symmetrically thiophene-based bent-shaped molecules with branched terminal was synthesised and characterised. Then, their effects as dopants on the blue phase (BP) range of the chiral nematic liquid crystal (N*LC) host were investigated. It was found that the bent-shaped dopants with branched terminal had better miscibility in LC host than the bent-shaped dopants with straight terminal, and contributed to induce BP and enhance the BP temperature range, with the maximum BP temperature range about 20.4°C. Besides, the electro-optical (E-O) performances of the blue phase liquid crystal doped with Th-BC6 (a bent-shaped dopant with the widest induced BP range in N*LC) were also explored. It was found that the drive voltage reduced first and then increased with the doping amount of Th-BC6 increasing. When the doping amount of Th-BC6 was about 15 wt%, the hysteresis could be strikingly reduced.     

Synthesis of di- and trisubstituted 1,2,4-triazoles containing indole fragments

The reaction of imino esters of indole-series acids with acid hydrazides gave N₍₁₎-acylamidrazones, which, during heating, were converted to 3,5-disubstituted 1H-1,2,4-triazoles containing indole fragments. Compounds of this type were also synthesized by the reaction of indolyl-containing 2,5-disubstituted 1,3,4-oxadiazoles with formamide. Condensation of 2,5-disubstituted 1,3,4-oxadiazoles with aniline gave 3,4,5-trisubstituted 4H-1,2,4-triazoles containing indolyl radicals. Cyclocondensation of N₍₁₎-phenylamidrazones of indole-series acids with benzoyl chloride gave 1,3,5-trisubstituted 1H-1,2,4-triazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 189–196, February, 1993.     

Photochemistry of heterocyclic compounds—II : The photochemical reaction of 2,5-disubstituted 1,3,4-oxadiazoles with furan

The photochemical reaction of 2,5-disubstituted 1,3,4-oxadiazoles with furan has been studied. With or without benzophenone as a sensitizer, irradiation of 2,5-diphenyl-1,3,4-oxadiazole with furan in benzene solution gives the 1 : 1 cycloadduct, tetrahydrofuro[2·3-b]azetidino[2·1-b]-1,3,4-oxadiazole. However in the presence of iodine 3-acylfurans and their acylhydrazones are formed. A reaction pathway of this novel photo-induced acylation has been suggested.     

Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles by visible-light-mediated decarboxylation–cyclization of hydrazides and diketones

A visible-light-induced synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from simple diketones and hydrazides with the assistant of the photocatalyst eosin Y catalyzed decarboxylation and cyclization under mild conditions has been discovered. The reaction tolerates a wide range of functional groups and gives a variety of valuable 1,3,4-oxadiazoles in moderate to good yields. Finally, a plausible reaction mechanism was proposed.     

Synthesis and properties of furan derivatives. 4. Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles containing furan fragments

The condensation of hydrochloride sats of iminoesters of furan acids with hydrazides of carboxylic acids gives 2,5-disubstituted 1,3,4-oxadiazoles containing furan fragments. Such compounds are also formed in the condensation of hydrazides of 5-R-furan-2-carboxylic acids with hydrocloride salts of carboxylic acid iminoesters. The reaction of furan acids with hydrazine dihydrochloride in polyphosphoric acid gave symmetrically disubstituted 1,3,4-oxadiazoles containing furan fragments.Communication 3, see ref. [1].I. M. Gubkin State Petroleum and Natural Gas Institute, 117917, Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 238–249, February, 1995. Original article submitted January 24, 1995.     

A mild and efficient one pot synthesis of 1,3,4-oxadiazoles from carboxylic acids and acyl hydrazides

A convenient one pot method for the synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from acids and acyl hydrazides is reported. Acid activation with CDI, followed by coupling with the desired acylhydrazide and dehydration in the same pot with Ph₃P and CBr₄ affords the corresponding 1,3,4-oxadiazoles in good yield. The scope of the acid and acylhydrazide components is presented.     

An iodine-mediated green synthesis of 1,3,4-oxadiazoles under solvent-free conditions using grinding technique

Abstract

An eco-friendly efficient synthesis of symmetrical and unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles is described through the reaction of aromatic hydrazides with aryl aldehydes obtained by grinding them in the presence of catalytic amounts of molecular iodine in a mortar in a single step. The present method avoids the isolation of N-acyl hydrazones prior to their oxidative cyclization and avoids the use of organic solvents at any stage of the reaction.     

Synthesis of 2,5-disubstituted pyrazolyl-1,3,4-oxadiazoles by the Huisgen reaction

Russian Chemical Bulletin - We developed an approach to the synthesis of 2,5-disubstituted pyrazole-containing 1,3,4-oxadiazoles by acylation of 5-(nitropyrazolyl)tetrazoles with alkyl, aryl, and...     

RAPID SYNTHESIS OF 2,5-DISUBSTITUTED 1,3,4-OXADIAZOLES UNDER MICROWAVE IRRADIATION

A number of symmetrically 2,5-disubstituted 1,3,4-oxadiazoles are quickly prepared by the reaction of aromatic acids with hydrazine dihydrochloride in a mixture of orthophosphoric acid and phosphorus pentoxide under microwave irradiation.     

Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles containing a sterically hindered 4-hydroxy-3,5-di(tert-butyl)phenyl group

A series of 2,5-disubstituted 1,3,4-oxadiazoles containing one or two 4-hydroxydi(tert-butyl)phenyl groups has been synthesized. These sterically hindered compounds were prepared by condensation of acids containing the indicated fragment and their derivatives with hydrazine dihydrochloride, hydrazides, and hydrochlorides of iminoesters of acids, by the reaction of 4-hydroxy-3,5-di(tert-butyl)thiphenol with 2-chloromethylsubstituted 1,3,4-oxadiazoles in the presence of KOH, and by cyclodehydration of N-acyl-N-[4-hydroxy-3,5-di(tertbutyl)benzoyl]hydrazones under action of POCl₃.I. M. Gubkin State Oil and Gas Academy, Moscow 117917. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 822–828, June, 1997.     

A new synthesis of symmetrical 2,5-disubstituted 1,3,4-oxadiazoles

Several new 2,5-disubstituted 1,3,4-oxadiazoles have been synthesized in good yields by reaction of aromatic acids with hydrazine dihydrochloride in a mixture of orthophosphoric acid, phosphorus pentoxide and, in general, with addition of phosphorus oxychloride to the reaction mixture. The structures of new oxadiazoles derivatives were confirmed by analytical and spectral data.     

The effects of azo-oxadiazole-based bent-shaped molecules on the temperature range and the light-responsive performance of blue phase liquid crystal

A series of light-responsive azo-oxadiazole-based bent-shaped molecules was synthesised and characterised. Their effects as dopants on the blue phases (BPs) range of the chiral nematic liquid crystal (N*LC) matrix and light-responsive properties including the photo-inducing change of UV absorption properties, photo-adjusting the BP structure as well as the temperature range were investigated. It was found that the azo-oxadiazole-based bent-shaped molecules with branched terminal had better miscibility in LC host than the molecules with straight terminal, and that increasing the length of rigid core of bent-shaped molecules will greatly improve the effect of widening the BP temperature range.     

Synthesis and spectral-luminescence properties of stilbene derivatives with two unconjugated fluorophores

Compounds that contain 2,5-diphenyloxazole and 2,5-diphenyl-1,3,4-oxadiazole fluorophore groupings that are not conjugated with one another were obtained by the phosphonate modification of the Wittig reaction from 2-[4 (3)-bromomethylphenyl]-5-(2-tosylaminophenyl)-1,3,4-oxadiazoles and 2-phenyl-5-[4(3)-formylphenyl]-1,3-oxazoles. The absorption and fluorescence spectra of the compounds obtained and the individual fluorophores that constitute the molecules of these compounds were investigated. Intramolecular nonradiating transfer of the electronic excitation energy between the fluorophores that make up the compounds and in binary mixtures of the corresponding luminophores was observed in solutions and in polymeric matrices.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1188–1191, September, 1982.     

Novel syntheses of symmetrical 2,5-diaryl-1,3,4-oxadiazoles and 1,4-phenylenebis-1,3,4-oxadiazoles

The reactions of trichloromethylarenes with excess hydrazine hydrate in ethanol gives symmetrical 2,5-diaryl-1,3,4-oxadiazoles in 68–96% yields. The reaction of 1,4-bis(trichloromethyl)benzene with acylhydrazines in an ethanol-pyridine mixture gives the corresponding substituted or unsubstituted 1,4-phenylenebis-1,3,4-oxadiazoles in 35–51% yields. The mass spectra of 2,5-diaryl-1,3,4-oxadiazoles and 1,4-phenylenebis-1,3,4-oxadiazoles were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2309–2316, November, 1998.     

Polyethylene glycol (PEG) mediated green synthesis of 2,5-disubstituted 1,3,4-oxadiazoles catalyzed by ceric ammonium nitrate (CAN)

Abstract

Ceric ammonium nitrate in polyethylene glycol has been used as a sustainable, non-volatile, and ecofriendly catalytic medium for the green synthesis of 2,5-disubstituted 1,3,4-oxadiazoles. This protocol is effective toward various substrates having different functionalities. The easy recyclability of the reaction medium makes the reaction economically and potentially viable for commercial applications.     

Visible-light-promoted aerobic oxidative cyclization to access 1,3,4-oxadiazoles from aldehydes and acylhydrazides

A novel and practical access to symmetrical and unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles directly from aldehydes and acylhydrazides using visible light irradiation under an air atmosphere in the presence of eosin Y as an organophotoredox catalyst at rt is reported. This is the first example of oxidative cyclization of acylhydrazones employing air and visible light as inexpensive, readily available, non-toxic, and sustainable reagents.     

Zur acylierung von 5-aryl-tetrazolen; ein duplikationsverfahren zur darstellung von polyarylen

We have found that the thermolysis of 5-substituted-2-acyl-tetrazoles (I) at 60–110° leads to quantitative loss of nitrogen and formation of an N-acyl-nitrilimine (III) as a hypothetical intermediate. This immediately reacts via ring closure to form 1,3,4-oxadiazoles (IV) in excellent yields. By an elegant reaction series it is possible to form polyaryles with alternating phenyl and 1,3,4-oxadiazole rings by repeated reaction of 5-phenyltetrazole with p-cyano-benzoylchloride followed by treatment with lithium azide. Starting with terephthalonitrile polyaryles possessing 9 rings were synthesized in 4 steps. The ultra-violet absorption of the 2,5-disubstituted 1,3,4-oxadiazole systems resembles very closely the absorption curve of a p-disubstituted phenyl-group.