5-烷氧基-4-环胺基-3-卤-2(5H)-呋喃酮的合成与表征

在氟化钾作用下,亲核试剂环状仲胺与5-烷氧基-3,4二卤-2(5H)-呋喃酮在室温下发生串联的迈克尔加成-消除反应,合成了17个新化合物.通过旋光度,UV-Vis,IR,1H NMR,13C NMR,MS,元素分析和X射线单晶衍射等表征方法,确定了目标化合物的化学结构和绝对构型.     

Intramolecular cyclization reactions of 5-halo- and 5-nitro-substituted furans

[reaction: see text] Intramolecular cyclization reactions of 5-halo- and 5-nitro-substituted furanylamides were examined. The 2-alkoxy-5-bromofuran derivative 2 produced the rearranged dihydroquinone 6 (36%), a product from the rearrangement of the intermediate oxabicycle 3. The 5-halo substituted furoyl amide 18 was converted to the polyfunctional oxabicycle 20 in 82% yield and at a much faster rate than the unsubstituted furanyl system 17. The 5-nitro-substituted furfuryl amide 33b underwent an unusual isomerization-cyclization reaction under microwave conditions to provide 1,4-dihydro-2H-benzo[4,5]furo[2,3-c]pyridin-3-one 34.     

Electrochemical reduction of 5-halo-5-nitro-1,3-dioxanes and 2-halo-2-nitro-1,3-propanediols

The character of the first stage of reduction of 5-X-5-nitro-1,3-dioxanes 1—10 and 2-X-2-nitro-1,3-propanediols 11 and 12 is independent of the nature of halogen (X = Br, Cl) and substituents in position 2 of the dioxane cycle. The transfer of two electrons to a molecule of compound 1—12 is accompanied by the anionoid elimination of halogen and formation of the anion of nitronic acid. The high mobility of halogen is mainly due to the acceptor nitro group capable of further transformations in the -position to halogen. The direction of further reduction involving the electron transfer to electrochemically active groups in the aromatic fragment of the molecule is determined by the nature of these groups. Chloro-, bromo-, and iodophenyl-substituted derivatives 4, 5, and 8—10 are reduced as typical halobenzenes. In the case of nitrophenyl-substituted compounds 3 and 7, the dioxane cycle opens to form dianions of p- and m-nitrobenzaldehydes along with the reduction of the nitroso group through the stages of formation of the radical anion and radical anion of the nitroso group. The radical anions of the nitro and nitroso derivatives were identified by ESR.     

Role of electron transfer in reactions involving substitution of halogen in 2-halo-5-nitrofurans

The replacement of the halogen in 2-halo-5-nitrofurans (Hal=C1, Br, I) in dimethylformamide (DMF) under the influence of tetra-n-butylammonium hydroxide to give 2-hydroxy-5-nitrofuran salts was studied. The intermediate anion radicals of the halonitrofurans were recorded by EPR spectroscopy; bromo- and iodonitrofurans can give 5,5-dinitro-2,2-difuryl anion radicals under the influence of Bu₄NOH. The polarographic reduction of halonitrofurans in the presence of hydrogen peroxide also leads to 2-hydroxy-5-nitrofuran. A mechanism for the transformation is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1604–1607, December, 1979Original article submitted March 17, 1977; revision submitted October 30, 1978.     

Thermal analysis of 5-halo-2'-deoxynucleosides

Heat may be a mutagenic agent which could be more important to evolution than are the ordinary errors in DNA replication. Therefore, it is necessary to know the stability of heredity determinants to thermal energy. Consequently, a thermal analysis, via differential scanning calorimetry (DSC), has been undertaken, using model compounds (crystalline 2'-deoxyribonucleosides and their 5-halo derivatives) to provide information regarding: 1. bond free energies maintaining the fibrous structure in nucleic acids e.g. H-bonding,π-complexing and dipole induced dipole interaction. 2. susceptibility to thermal degradation e.g. thermolytic cleavage of the glycosidic bond and deamination of the bases. Interpretation of the thermal curves has been facilitated and enhanced by utilization of a DSC-TLC analytical technique. Based on these data, a mechanism for the thermolysis of the glycosidic bond in the melt has been considered.     

Synthesis and Suzuki-Miyaura reactions of 5-halo-3,4-dihydropyrimidin-2(1H)-ones

A novel synthesis of 6-methyl-4-phenyl-5-substituted-3,4-dihydropyrimidin-2(1H)-ones from 6-methyl-4-phenyl-5-halo-3,4-dihydropyrimidin-2(1H)-ones via the Suzuki-Miyaura reaction is reported. These previously unknown heterocyclic halides are easily prepared using the Biginelli multicomponent reaction followed by halodecarboxylation. The effect of varied substitution at the C-4 position on the cross-coupling reaction is also examined.     

meta-Photoaddition reactions of 2-chloro-, 2,5-dichloro-, and 2-halo-5-isopropyl-tropones with 9,10-dicyanoanthracene

Photoreactions of 2-halotropones with the excited 9,10-dicyanoanthracene gave a meta-adduct and substitution products occurred at the C-2 position of troponoids. The mechanism of the meta-adduct was proved by the product analysis of the reaction of 3,7-dideuterio-2-bromo-5-isopropyltropone and 9,10-dicyanoanthracene. In the photoreaction of 2-chloro-5-isopropyltropone and 9,10-dicyanoanthracene in a mixed solvent of benzene and methanol, a benzaldehyde with a dibenzo-2-oxabicyclo[3.2.2]nonane system was obtained to support occurrence of an [8+4] cycloaddition reaction between them.     

Solvent-free Suzuki and Stille cross-coupling reactions of 4- and 5-halo-1,2,3-triazoles

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Synthesis and reactions of β-(5-halo-3-uracyl) propionic acids

The reaction of elementary bromine and iodine with -(3-uracyl)-propionic acid has given the corresponding -(5-bromo-3-uracyl) and -(5-iodo-3-uracyl)propionic acids. The methyl esters and amides of the acids have also been synthesized for the first time.     

Palladium-catalyzed C,N-cross coupling reactions of 3-halo-2-aminopyridines

A simple approach toward N(3)-substituted-2,3-diaminopyridines is presented, based on Pd-catalyzed C,N-cross coupling. The use of RuPhos- and BrettPhos-precatalysts in combination with LiHMDS allows for C,N-cross coupling reactions of unprotected 3-halo-2-aminopyridines with primary and secondary amines.     

Synthesis of 6-halo-5-nitroquinoxalines

The 5-nitro derivatives of 6-haloquinoxalines have been efficiently synthesized by condensation of α-dicarbonyls with 4-bromo- or 4-chloro-3-nitro-1,2-benzenediamines. The novel diamines were readily obtained by reductive cleavage of 5-bromo- and 5-chloro-4-nitro-2,1,3-benzoselenadiazoles. As demonstrated by the synthesis of an imidazo-, a selenadiazolo- and a pyrazinoquinoxaline, the reactive halogen atom ortho to the nitro substituent renders the novel quinoxalines versatile intermediates to further heterocycles.     

Mechanism of the electrochemical reduction of 2-halo-5-nitrothiophenes in dimethylformamide

The reduction of 2-bromo-5-nitrothiophene and 2-iodo-5-nitrothiophene in dimethylformamide (DMF) was studied by means of classical and commutated polarography, EPR spectroscopy, a rotating platinum disk electrode with a ring, and preparative electrolysis. It was established that, depending on the nature of the halogen, their anion radicals may undergo further reduction to 2-nitrothiophene anion radicals or decomposition with splitting out of a halide anion and conversion to nitrothienyl radicals, which were identified on the ring electrode. The latter are capable of undergoing dimerization to 2,2-dinitro-5,5-dithienyl. The spectra of the anion radicals of 2-nitrothiophene and 2,2-dinitro-5,5-dithienyl were recorded by means of EPR. A mechanism for the reduction of halonitrothiophenes is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 195–198, February, 1981.     

Syntheses and nucleophilic reactions of N-alkyldiphenylsulfilimines

N-Alkyldiphenylsulfilimines, Ph₂S⁺N^?R, were prepared by treating diphenylsulfilimine with alkyl halides in refluxing chloroform. Reactions of N-benzyldiphenylsulfilimine with activated olefins and acetylenes were investigated and found to give products consistent with nuclephilic attack of ^?NCH₂Ph followed by SN bond cleavage with or without hydrogen transfer. In general, the reaction conditions had a pronounced effect on the product distribution.     

Syntheses and reactions of pyrimidine derivatives

By the NMR method, the chemical shifts characterizing the methyl groups in monohydroxymonomethyl derivatives of pyrimidine have been determined. The changes in the chemical shifts and the activities of the methyl groups are symbatic. It has been shown by the NMR method that when 6-hydroxy-2,4-dimethylpyrimidine reacts with benzaldehyde and with p-nitrobenzenediazonium salts reactions take place through the methyl group in position 2. A gradual decrease in the activity of the methyl groups is found in the sequence of 6-hydroxy-, 6-mercapto-, and 6-aminoderivatives of 2,4-dimethylpyrimidine.For part XVII, see [5].     

Syntheses and reactions of some 4,5-dihaloimidazole-2-carboxylic acid derivatives

The preparation of 5H,10H-diimidazo[1,2-a:1′,2′-d]pyrazine-5,10-dione ( 2a ) and its 2,3,7,8-tetrabromo- and 2,3,7,8-tetrachloro- analogs ( 2b and 2c , respectively) is reported. These dimers, when allowed to react with various anilines, afford imidazole-2-carboxamides ( 3a-c ).     

Syntheses in the field of 5-nitro-2-furylpolyalkenals and 5-nitro-2-furylpolyalkenones

A series of, -bis(5-nitro-2-furyl)poryalkenones has been synthesized by the condensation of 5-nitro-2-furylalkenones with 5-nitrofuran aldehydes in acetic acid (concentrated sulfuric acid catalyst). In the , -bis(5-nitro-2-furyl)polyalkenone series, the keto group acts as a partial insulator of conjugation, which is shown most clearly in the case of 1,3-bis(5-nitro-2-furyl)prop-2-en-1-one and 1,5-bis(5-nitro-2-furyl)-penta-2,4-dien-1-one, i.e. compounds having the keto group directly linked to a 5-nitrofuran ring. The electronic spectra of the semicarbazones of the, -bis(5-nitro-2-furyl)polyalkenones exhibit a stronger disturbing effect of the conjugation in the molecule than in the case of the ketones, which may be connected with a disturbance of coplanarity. In a number of cases, the infrared spectra of the, -bis(5-nitro-2-furyl)polyalkenones exhibit splitting of the symmetrical and antisymmetrical vibrations of the nitro group.For part VII, see [1].Preliminary results of the present investigation were given for the first time at the 2-nd All-union Scientific Conference on the Chemistry of Furan Compounds, Saratov, 23–26 January, 1962, see [2].