Efficient synthesis of cis- and trans-3,4-dihydroxy-3,4-dihydromollugin

An efficient synthesis of naturally occurring compounds isolated from Pentas longiflora, cis-3,4-dihydroxy-3,4-dihydromollugin 2, and trans-3,4-dihydroxy-3,4-dihydromollugin 3 is described. The O-protected mollugins were dihydroxylated using OsO4 to achieve the corresponding cis-dihydroxy derivatives in excellent yield. The synthesis of trans-3,4-dihydroxy-3,4-dihydromollugin was achieved using Oxone in good yield. A mechanism for the formation of cis-3,4-dihydroxymollugin acetonide from the reaction of mollugin with Oxone is proposed.     

Aromatic fluorine chemistry. Part 1. 3,4-Difluorobenzoic acid and derivatives via 3,4-difluorobenzotrifluoride

The preparation of 3,4-difluorobenzotrifluoride from 3-4-dichlorobenzotrifluoride by a KF exchange reaction is described. The conversion of 3,4-difluorobenzotrifluoride to 3,4-difluorobenzoic acid and derivatives is also reported.     

One-pot oxidation and bromination of 3,4-diaryl-2,5-dihydrothiophenes using Br2: synthesis and application of 3,4-diaryl-2,5-dibromothiophenes

A class of 3,4-diaryl-2,5-dibromothiophenes (1b-5b) was synthesized by a one-pot reaction of 3,4-diaryl-2,5-dihydrothiophenes with Br2 reagent in excellent yield (83-92%). It was found that Br2 performed a double function (oxidation and bromination) during the conversion of 3,4-diaryl-2,5-dihydrothiophenes to 3,4-diaryl-2,5-dibromothiophenes. The application of 3,4-diaryl-2,5-dibromothiophenes used as building blocks was also investigated. Employing 3,4-diphenyl-2,5-dibromothiophene (1b) as a template, a class of 2,3,4,5-tetraarylthiophenes was prepared by the Suzuki coupling reaction. This provided a new and simple approach to the preparation of 2,3,4,5-tetraarylthiophenes.     

Visible Light-Induced Synthesis of 3,4-Diarylthiophenes from 3,4-Diaryl-2,5-dihydrothiophenes

Using a catalytic amount of platinum(II) terpyridyl complex 3, 3,4-diarylthiophenes (2a-f) could be synthesized from 3,4-diaryl-2,5-dihydrothiophenes (1a-f) under visible light (λ > 450 nm) irradiation in degassed CH(3)CN. Spectroscopic study and product analysis reveal that the reaction is initiated by photoinduced electron transfer from 3,4-diaryl-2,5-dihydrothiophenes to platinum(II) complex 3, leading to the formation of 3,4-diarylthiophenes.     

二亚(3,4-二甲基)苄基山梨糖醇的合成与表征

山梨糖醇与3,4-二甲基苯甲醛在酸催化下缩合成聚丙烯透明成核剂——二亚（3,4-二甲基）苄基山梨糖醇。实验结果表明,在3,4-二甲基苯甲醛66mmol,n（醇）：n（醛）=1．0：2．0,ω（催化剂）=0．6％-1.2％（以反应单体的质量计算）,ω（促进剂）=15％～18％（以反应物的总质量计算）,回流反应5h的最佳反应条件下,收率在96.5％以上。     

Reaction of functionally substituted vinyl ethers with 3,4-diaminofurazan and furazan-3,4-dicarboxylic acid dihydrazide

Enaminofurazans were obtained by reaction of vinyl ethers with 3,4-diaminofurazan. It was established by IR and PMR spectroscopy that enaminofurazans exist in the form of a chelate complex. The structure of the chelate complex is discussed. Enehydrazides were obtained by reaction with furazan-3,4-dicarboxylic acid dihydrazide. When there is a cyano group in the ether molecule, the reaction does not stop with the formation of the enehydrazide but continues with its cyclization to give a pyrazole ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 319–323, March, 1979.     

Mechanism of the reaction of 3,4-epoxysulfolanes with ammonia and amines

The corresponding hydroxyaminosulfolanes were isolated from the reaction of 3,4-epoxysulfolane and 3-methyl-3,4-epoxysulfolane with ammonia and amines. The mechanism of the reaction was studied by thermography. The reaction proceeds through the intermediate formation of the corresponding unsaturated alcohols and subsequent addition of the nucleophile to the double bond. The reaction of 3,4-dimethyl-3,4-epoxysulfolane with the same reagents terminates with isomerization of the oxide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 31–35, January, 1978.In conclusion, we sincerely thank A. A. Musina for her assistance in the interpretation of the PMR spectra.     

A convenient synthesis of novel pyridazino[3,4-b]quinoxaline and pyrazolo[3,4-b]quinoxaline utilizing 1,3-dipolar cycloaddition reaction

The reaction of 2,6-dichloroquinoxaline 4-oxide 4 with methylhydrazine gave 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 5, whose reaction with dimethyl acetylenedicarboxylate or 2-chloroacrylonitrile resulted in the 1,3-dipolar cycloaddition reaction to afford 7-chloro-3,4-bismethoxycarbonyl-1-methyl-1,2-dihydropyridazino[3,4-b]quinoxaline 6 or 6-chloro-3-hydroxymethylene-1-methyl-2,3-dihydro-1H-pyrazolo[3,4-b] quinoxaline hydrochloride 7, respectively.     

光敏剂存在下3,4-聚异戊二烯的光交联反应

本文研究了在敏化剂二苯甲酮存在下3,4-聚异戊二烯的光交联反应。发现在80W高压汞灯辐照下,二苯甲酮敏化的3,4-聚异戊二烯能够发生光交联反应,其凝胶含量、交联密度与光照时间、3,4-聚异戊二烯的分子量以及二苯甲酮的用量有关。用FTIR和C¹³NMR证实了该交联反应以外双键的2+2加成为主。     

Synthesis of 2,3-anti-3,4-anti and 2,3-anti-3,4-syn propionate motifs: a diastereoselective tandem sequence of Mukaiyama and free-radical-based hydrogen transfer reactions

[reaction: see text] Reported herein is a strategy employing a Mukaiyama reaction in tandem with a hydrogen transfer reaction for the elaboration of 2,3-anti-3,4-anti and 2,3-anti-3,4-syn propionate motifs. The mode of complexation is controlled through monodentate or chelate pathways for the Mukaiyama reaction to give access to either syn or anti aldol products, precursors of the free-radical reduction reaction. Boron Lewis acid is used to control the free-radical reaction through the exocyclic pathway.     

Simple one-step synthesis of 3,4-dimethoxythiophene and its conversion into 3,4-ethylenedioxythiophene (EDOT)

3,4-Dimethoxythiophene (2) was synthesized in one-step from readily available bulk chemicals via a ring closure reaction, and was then trans-etherified with ethylene glycol to give 3,4-ethylenedioxythiophene (3) (EDOT).     

Preparation and reactions of 3,4-dihydro-2H-pyran-2-ones

The Michael reaction of ethyl cinnamates with deoxybenzoin gave ethyl 3,4,5-triaryl-5-oxopentanoates which were hydrolysed to the corresponding acids. The latter could be cyclized to the respective 3,4-dihydro-2H-pyran-2-ones which underwent ring opening with several nucleophiles to the corresponding acid derivatives. However, their reaction with ammonium acetate led to the formation of 3,4-dihydro-2-pyridones. The 3,4-dihydro-2-pyrones and pyridones were dehydrogenated to the corresponding 2-pyrones and 2-pyridones by fusion with sulfur.     

Synthesis of pyridazino[3,4-b]quinoxalines and pyrazolo[3,4-b]-quinoxaline by 1,3-dipolar cycloaddition reaction

The pyridazino[3,4-b]quinoxalines 6a,b and pyrazolo[3,4-b]quinoxaline hydrochloride 9 were synthesized by the 1,3-dipolar cycloaddition reaction of 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 5 with dimethyl or diethyl acetylenedicarboxylate and 2-chloroacrylonitrile, respectively. The reaction mechanisms were postulated for the formation of 6a,b and 9 .     

Synthesis of 1H-pyrazolo[3,4-e]-s-triazolo[3,4-c]-as-triazines, 8H-pyrazolo[3,4-e]tetrazolo[5,1-c]-as-triazine and 1,7-dihydro-8H-pyrazolo[3,4-e]-as-triazine derivatives

3-Hydrazino-7-methyl-5-phenyl-5H-pyrazolo[3,4-c]-as-triazine 1 underwent ring closure and/or condensation reaction with formic acid, acetic acid, acetic anhydride and benzoyl chloride to afford 1H-pyrazolo-[3,4-d]-s-triazolo[3,4-c]-as-triazines 2, 5 and 7a and/or N-acyl derivatives 3, 4 and 6 . N-Acyl derivatives 3 and 6 underwent cyclisation reaction on treatment with phosphoryl chloride to give 5 and 7a . 3-Methyl-1-phenyl-8-aryl-1H-pyrazolo[3,4-e]-s-triazolo[34,-c]-as-triazines 7 were also prepared by the reaction of the hydrazono derivatives 8 wit thionyl chloride. On treatment of 1 with nitrous acid gave the 8H-pyrazolo[3,4-e]tetrazolo-[5,1-c]-as-triazine 9 . Compound 1 underwent ring closure with carbon disulphide or ethyl chloroformate to 1,7-dihydro-8H-pyrazolo[3,4-e]-s-triazolo[3,4-c]-as-triazine derivatives 10 and 12 . Reaction of 1 with ethyl acetoacetate or acetylacetone gave 3-pyrazolo derivatives 13 and 14 .     

Synthesis and anticonvulsant activity of 2-aryl-3,4-dialkyltetrahydro-1,3,4-oxadiazines and 2-aryl-3,4-dialkyltetrahydro-1,3,4-oxadiazin-5-ones

Several 2-aryl-3,4-dialkyltetrahydro-1,3,4-oxadiazines have been synthesized from 2-(1,2-dialkylhydrazino)ethanol (2) and aromatic aldehydes. Also, three 2-aryl-3,4-dialkyltetrahydro-1,3,4-oxadiazin-5-ones were obtained from the reaction of 1,2-dialkylglycolylhydrazine (5) and aromatic aldehydes. These compounds exhibited activity in the maximal electroshock seizure test.     

3,4-二硝基吡唑的合成

吡唑经硝化、重排、硝化三步反应合成了潜在的TNT替代物——3,4-二硝基吡唑,其结构经1H NMR和IR确证。并对第三步硝化反应条件进行了优化,单步收率41%。     

Formylation of 3,4-Dihydropyrrolo[1,2-a]pyrazines

Formylation of 3,4-dihydropyrrolo[1,2-a]pyrazines containing alkyl or aryl substituents at position 1 has been studied under the conditions of the Vilsmeier reaction. The direction of the reaction depends on the structure of 3,4-dihydropyrrolo[1,2-a]pyrazine starting materials. Formylation of 1-methyl-substituted 3,4-dihydropyrrolo[1,2-a]pyrazines occurs at the methyl group.     

The Syntheses and Reactions of 3,4-Bisphosphono-1,2,4,5-Tetraenes

Abstract: 3,4-Bisphosphono- 1,2,4,5-hexatetraenes, prepared from the reaction of chlorophosphine/phosphite with 2,4-hexadiyne-1,6-diols,underwent an intramolecular [2+2]-cycloaddition to form 1,2-bis(diethylphosphonyl)-3,4- bis(isopropyleny1)cyclobutene.     

Reaction of 3,4-dicyano-5-aminopyrazole with ethyl orthoformate

The condensation of 3,4-dicyano-5-aminopyrazole with ethyl orthoformate was studied. Under severe conditions (150 °C) the principal reaction product is N-ethyl-3,4-dicyano-5-ethoxymethylaminopyrazole. Alkylation of the pyrazole ring does not occur at 100 °C, but 3,4-dicyano-5-ethoxymethyleneaminopyrazole is formed. Isomeric 1- and 2-ethyl-4-aminopyrazolo[2,4-d]pyrimidine-3-carboxylic acid methyl imino esters were obtained by the action of a methanol solution of ammonia on the principal reaction product. This constitutes evidence that N-ethyl-3,4-dicyano-5-ethoxymethyleneaminopyrazole is a mixture of 1- and 2-ethyl-3,4-dicyano-5-ethoxymethyleneaminopyrazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1682–1685, December, 1982.     

A Novel Synthesis of 3,4-Discubstituted-1H-pyrazolo[3,4-b]quinolines

A simple and efficient synthesis of pyrazolo[3,4-b] quinolines is described. The synthesis involves reaction of 2-amino-3-cyanoquinoline-4-carboxylates(1) with hydrazine hydrate to give regioselectively only pyrazolo[3,4-b]quinolines (2). No formation of pyridazino quinolines (3) is observed.