C-H bond functionalization in the synthesis of fused 1,2,3-triazoles

A highly modular approach to fused 1,2,3-triazoles has been developed featuring a one-pot procedure combining copper(I) catalyzed azide-alkyne cycloaddition and palladium-catalyzed C-H bond functionalization. A class of structurally unique heterocycles was synthesized in good yields.     

The reaction of 4,5-dichloro-1,2,3-dithiazolium chloride with DMSO: an improved synthesis of 4-chloro-1,2,3-dithiazol-5H-one

4,5-Dichloro-1,2,3-dithiazolium chloride 2 (Appel salt) reacts with either DMSO, diphenylsulfoxide 11 or methylphenylsulfoxide 12 to give 4-chloro-5H-1,2,3-dithiazol-5-one 1 in excellent yields. The use of catalytic amounts of DMSO (1 mol %) in MeCN in the presence of water (1 equiv) transforms Appel salt 2 into dithiazolone 1 in near quantitative yields (92%). Rational mechanisms are proposed to explain the catalytic nature of these reactions.     

The reaction of 4,5-dichloro-1,2,3-dithiazolium chloride with dimethylsulfonium dicyanomethylide: an improved synthesis of (4-chloro-1,2,3-dithiazolylidene)malononitrile

4,5-Dichloro-1,2,3-dithiazolium chloride 6 (Appel salt) reacts with dimethylsulfonium dicyanomethylide 11 to give 5-(4-chloro-1,2,3-dithiazolylidene)malononitrile 1 and a mixture of E/Z isomers of 3-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)-3-chloro-2-(methylthio)acrylonitrile 13. The reaction of 4-chloro-5H-1,2,3-dithiazole-5-thione 10 with dimethylsulfonium dicyanomethylide 11 gives (dithiazolylidene)malononitrile 1 in 92% yield. All new compounds are fully characterised and rational mechanisms are proposed for the formation of all key compounds.     

An improved and practical synthesis of 4-fluorobenzaldehyde by halogen-exchange fluorination reaction

A process which can afford a large quantity of 4-fluorobenzaldehyde was developed from halogen-exchange of 4-chlorobenzaldehyde with potassium fluoride in aromatic hydrocarbon solvents in the presence of tetraphenylphosphonium bromide plus polyethylene glycol dimethyl ether. The features of the reaction are discussed.     

Synthesis of fused tetrazole derivatives via a tandem cycloaddition and N-allylation reaction and parallel synthesis of fused tetrazole amines

A method for the synthesis of novel fused tricyclic tetrazoles from allylic bromides generated by the recently discovered DiazAll reaction has been developed. This new tandem reaction comprises a cycloaddition between a nitrile and (TMS)N(3) followed by an intramolecular N-allylation. The variation of functionalities in the benzene moiety was well-tolerated, and only a moderate difference in yield and degree of purity was noticed. An exo-methylene group in these new compounds permitted further derivatization. Structural resemblance with substances which possess important pharmacological properties motivated the synthesis of a series of ketones and a small library of amines.     

An improved Larock synthesis of quinolines via a Heck reaction of 2-bromoanilines and allylic alcohols

A modified Larock method has been developed for the one-pot synthesis of substituted quinolines via a Heck reaction of 2-bromoanilines and allylic alcohols followed by dehydrogenation with diisopropyl azodicarboxylate (DIAD).     

An application of the ireland reaction to the stereospecific synthesis of fused carbocyclic systems.

The sequence: group transfer Michael addition, aldol / lactonization and Claisen rearrangement provides access to the title compounds.     

对Niementowski反应的改进

在三氯氧磷存在下,以甲酰胺和邻氨基苯甲酸类化合物为原料,用改进的Niementowski反应合成了5种喹唑啉酮化合物：6-X-4(3H)-喹唑啉酮(X=NO2,Cl,Br,I)和1-(呋喃-2-甲基)-6-磺酰胺基-7-氯-4(1H)-喹唑啉酮,并对该反应的历程进行了初步探讨。     

An improved Pfitzinger reaction: Eco-efficient synthesis of quinaldine-4-carboxylates by TMSCl-mediated

We report herein an improved Pfitzinger reaction for the synthesis of highly functionalized quinaldines from 1,3-dicarbonyl compounds, isatins and alcohols mediated by TMSCl. This synthesis involves cyclization and esterification in one-step cascade process for the formation of a carboxylate (CO₂R) at the 4-position of quinaldine ring. Moreover, this procedure shows highly efficient, good functional group tolerance, operational simplicity, environment-friendly and feasibility of scale up.     

4-(2-R-Aryl)-1,2,3-chalcogenadiazoles in the synthesis of fused heterocycles

The review generalizes and systemizes published data on the synthesis and chemical transformations of 4-(2-R-aryl)-1,2,3-thia- and -selenadiazoles. Powerful synthetic potential of 4-(2-R-aryl)-1,2,3-chalcogenadiazoles ensures their use in the synthesis of various heterocyclic compounds, such as 1-benzofurans, indoles, 1-benzothiophenes, 1-benzoselenophenes, and their more complex derivatives.     

An improved synthesis of resveratrol

In this article we report an improved total synthesis of resveratrol, increasing the overall yield from 22 to 71%. The synthesis reported in our previous publication was made up of two fundamental steps: a Wittig reaction and a Heck coupling. Here we studied these steps separately to increase the individual yields. The yield of the Wittig reaction was increased up to 98%; however, we could not find better reaction conditions for the Heck coupling than those reported in the previous article.     

An improved synthesis of norcocaine

An improved, high yielding procedure for the preparation of norcocaine from cocaine is described. The synthesis is accomplished by controlling the pH during the potassium permanganate oxidation. A quantitative conversion of N-benzoylecgonine methyl ester into norcocaine by dry, hydrogen chloride-dioxane is also included.     

An improved synthesis of galanthamine

Modifications in the total synthesis of the Amarylidaceae alkaloid of galanthamine from commercially available isovanillin and tyramine have resulted in a shortened reaction sequence, which is amenable to upscaling and in improved product yield.     

An improved synthesis of cyclohexenothioxanthenones

An improved synthesis of cyclohexanothioxanthenones in high yield (70-90%) by treatment of thiosalicylic acid ( 4 ) or 2,2′-dithiosalicylic acid with 1,2,3,4-tetrahydronaphthalene ( 5 ) in the presence of concentrated sulfuric acid or a mixture of 95% sulfuric acid with 27-30% fuming sulfuric acid (in 5:1 to 2:1 v/v ratio) was described. The crude product consisted of three isomers which were isolated and identified. These isomers are 1,2-, 2,3- and 3,4-cyclohexanothioxantenone ( 1, 2 , and 3 ).     

An improved synthesis of diiodonoradamantane

Τhe synthesis of 3,7-diiodo-tricyclo[3.3.1.0^3,7]nonane, the main precursor of noradamantene, by iodination of the corresponding diol via its dimesylate affords a threefold higher yield than the direct iodination of the diol. Neither the dimesylate nor the cyclic sulfate of the diol yields noradamantene upon reduction with sodium amalgam.     

An improved synthesis of pennogenin

An improved synthesis of pennogenin, a bioactive component of Chinese herb “Chonglou” (Paris), is described. A ring-switching process opened the ring E of diosgenin and allowed the use of a hydroxyl-directed diboration/oxidation to introduce C17α-OH, hence eliminating the use of OsO₄. This strategy might be rendered to synthesize similar steroids with C17α-OH.