Synthesis of 2-(N-formyl)-5-aryl/aryloxymethyl-1,3,4-thiadiazoles with potential bioactivity in PEG-400

<正>An environmental benign procedure for synthesis of 2-(N-formyl)-5-aryl/aryloxymethyl-1,3,4-thiadiazoles has been developed by reaction of 2-amino-5-aryl/aryloxymethyl-1,3,4-thiadiazoles with formic acid in PEG-400.The key advantages of this protocol are the shorter reaction time,higher yields,lower cost,simple workup,and environment-friendly compared to conventional organic solvent reaction.The present method does not involve any hazardous organic solvent or catalyst.     

Heterocyclization of derivatives of thioncarboxylic acids to 1,3,4-thiadiazoles under the action of tert-butyl hypochlorite

A method for synthesis of 2-alkyl-5-aryl- and 2,5-diaryl-1,3,4-thiadiazoles by successive reaction of thioamides with tert-butyl hypochlorite and benzothiohydrazides was developed. The first step in the formation of 1,3,4-thiadiazoles consists of oxidation of thioamides with tert-butyl hypochlorite with O atom transfer to the S atom, which was established by transformation of N-methyl-thiobutanamide into N-(methylimino)butanesulfenic acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1843–1848, August, 1989.     

Propylphosphonic anhydride (T3P): an efficient reagent for the one-pot synthesis of 1,2,4-oxadiazoles, 1,3,4-oxadiazoles, and 1,3,4-thiadiazoles

Propylphosphonic anhydride (T3P^®) has been demonstrated to be an efficient and mild reagent for the one-pot synthesis of 1,2,4-oxadiazoles, 1,3,4-oxadiazoles, and 1,3,4-thiadiazoles from carboxylic acids.     

Synthesis of new diheteroarylcarbazoles: a facile and simple route of 3,6-di(pyrazol-4-yl)carbazoles

A short and facile route to the synthesis of new 3,6-di(pyrazol-4-yl)carbazoles is reported. Dipyrazolylcarbazoles were synthesized in two steps from 3,6-diacetylcarbazoles through a Vilsmeier reaction which led to the formation of carbazolyl-β-chlorovinyl aldehydes, followed by cyclization with hydrazine hydrate. The reaction of the Vilsmeier reagent with hydrazones of diacetylcarbazoles yielded the corresponding pyrazole dicarbaldehydes in good yields.     

De novo synthesis of 2,2-bis(dimethylamino)-3-alkyl or benzyl 2,3-dihydroquinazolin-4(1H)-one compounds

A new versatile and efficient strategy for the synthesis of 2,2-bis(dimethylamino)-3-alkyl or benzyl 2,3-dihydroquinazoline-4(1H)-one compounds has been developed by one-pot multicomponent reaction with isatoic anhydride, amines followed by in situ-generated Vilsmeier reagent. The reaction has also been studied with different amines and solvents.     

Synthesis and characterization of some heterocyclic derivatives by cyclization of carbohydrate thiosemicarbazones. Part I

We report the synthesis of 2,3-dihydro-1,3,4-thiadiazoles and 1,3,4-thiadiazoles from 1,2:3,4-di-O-iso-propylidene-α-D-galacto-1,6-hexodialdo-1,5-pyranose thiosemicarbazone. The physical and spectro-scopic characterizations of the heterocyclic derivatives as well as the intermediate product are described. We present the prefered conformation in solution using computational calculations and spectroscopic data. The possibilities of chiral induction of the cyclization reaction are discussed.     

Modified procedure for the synthesis of 2-chloroquinoline-3-carbaldehydes using phosphorus pentachloride

An alternative, convenient, and efficient procedure for the synthesis of 2-chloroquinoline-3-carbaldehyde was carried out by the action of Vilsmeier’s reagent on acetanilides using phosphorus pentachloride as chlorinating agent in place of phosphoryl chloride, obtaining good yields for activated acetanilides. The optimal conditions for this reaction requires only 4.5 equivalents of phosphorus pentachloride, 3 equivalents of N,N-dimethylformamide, and 1 equivalent of the corresponding acetanilide at 100 °C for approximately 4 h.     

Cyclization of functionalized ketene-N,S-acetals to substituted pyrroles: applications in the synthesis of marine pyrrole alkaloids

α-Oxoketene-N,S-acetals, prepared by the reaction of alkyl glycinates with β-oxodithiocarboxylates followed by alkylation, underwent cyclization in the presence of the Vilsmeier reagent to afford alkyl 3-aryl-4-formyl-5-(alkylsulfanyl)-1H-pyrrole-2-carboxylates in excellent yields. When the reaction was extended to β-oxodithiocarboxylates derived from deoxyanisoin, 3,4-diarylpyrrole-2-carboxylates, the key intermediates in the synthesis of lukianol A and lamellarin Q were formed.     

Parallel solution phase synthesis of a library of amino acid derived 2-arylamino-[1,3,4]-oxadiazoles

A mild method for the synthesis of peptidomimetic 2-arylamino 5-substituted 1,3,4-oxadiazoles from Boc-protected α-amino acid derived hydrazides has been developed, and applied in a parallel solution-phase synthesis. The optimized reaction conditions involve a one-pot reaction of Boc-protected amino acid hydrazides with arylisothiocyanates in the presence of either Hg(II) chloride, Mukaiyama’s reagent (2-chloro-N-methylpyridinium iodide) or polymer supported Mukaiyama’s reagent, with triethylamine in dichloromethane at ambient temperature. The 1,3,4-oxadiazole products were obtained in good to excellent yields without any detectable epimerization. The reactions proceed via initial formation of thiosemicarbazides, followed by dehydrothiolative cyclization to the 1,3,4-oxadiazoles.     

Solvent-Free Green Synthesis of Azines and Their Conversion to 2,5-Disubstituted-1,3,4-thiadiazoles

A solvent-free, clean, and efficient method has been developed for the synthesis of 2,5-disubstituted-1,3,4-thiadiazoles via azines. This approach exploits the synthetic potential of clean reactions and offers many advantages such as excellent product yields, easy isolation of products, and ecofriendly benign reaction conditions. The newly synthesized compounds were analyzed by infrared, ¹H NMR, ¹³C NMR, and elemental analysis.