Cu-Catalyzed Carbocyclization for General Synthesis of N-Containing Heterocyclics Enabled by BrCF2COOEt as a C1 Source.

A practical and efficient copper-catalyzed carbocyclization of 2-functionalized anilines with ethyl bromodifluoroacetate has been developed. Ethyl bromodifluoroacetate is employed as the C1 source via quadruple cleavage in this transformation. This reaction can afford a variety of N-containing heterocyclics with satisfactory yields and excellent functional group compatibility.

Tandem Sulfonylative Annulation/Halogenation of 1,7-Enynes with Sodium Sulfinate and TBAX for the Assembly of 4-Methylenechromanes.

An effective and stereoselective synthesis of halogenated (E)-4-methylenechromanes with a sulfonyl group was developed via the copper-catalyzed sulfonylative annulation/halogenation of 1,7-enynes, in which sodium sulfinates were used as the sulfonyl reagents and tetrabutylammonium halide provided the halogen sources. The formed alkenyl C-X bonds were valuable and can efficiently undergo the subsequent hydrolysis, alkenylation, alkynylation, arylation, alkylthiolation, and alkoxylation to furnish a series of highly functionalized 4-methylenechromanes.

Pd-Catalyzed Deacylative [4 + 1] Annulation of N-Arylimidoyl Chlorides with ß-Keto Esters Leading to 2-Fluoroalkyl Indoles.

A palladium-catalyzed [4 + 1] annulation of N-arylimidoyl chlorides with ß-keto esters has been developed. In the presence of Pd(OAc)2, PCy3, and K3PO4, a variety of fluoalkyl-containing N-arylimidoyl chlorides smoothly underwent the cascade C-H imidoylation/deacylative Heck-type reactions to afford biologically important 2-fluoroalkyl indoles in moderate to good yields.

Synthesis of Trifluoromethylated Dibenzoxepines via Palladium-Catalyzed Tandem C-O Bond Formation/C-H Arylation.

A palladium-catalyzed cyclization reaction of phenols with trifluoromethyl-containing ortho-bromo-ß-chlorostyrenes has been developed. In the presence of palladium(II) acetate, tricyclohexylphosphine, and cesium carbonate, a variety of 6-trifluoromethyldibenzo[b,d]oxepines were prepared in moderate to good yields through the tandem O-alkenylation of general phenols and subsequent C-H arylation.

TBAI-Mediated Cyclization and Methylsulfonylation of Propargylic Amides with Dimethyl Sulfite.

A tetramethylammonium iodide (TBAI)-mediated cyclization and methylsulfonylation of propargylic amides enabled by dimethyl sulfite as a SO2 surrogate and methyl source have been developed. The transition metal-free and oxidant-free reaction provides a practical and efficient approach for the selective synthesis of methylsulfonyl oxazoles in moderate to excellent yields with good functional group compatibility.

Palladium-Catalyzed Methylsulfonylation of Alkyl Halides Using Dimethyl Sulfite as SO2 Surrogate and Methyl Source.

A novel and efficient method for the synthesis of methyl sulfone derivatives via palladium-catalyzed methylsulfonylation of alkyl halides with dimethyl sulfite has been described. A variety of aryl and alkyl iodides underwent the sulfonylation smoothly to furnish methyl sulfites in moderate to excellent yields.

Synthesis of Isoselenazoles and Isothiazoles from Demethoxylative Cycloaddition of Alkynyl Oxime Ethers.

A general method for the synthesis of isoselenazoles and isothiazoles has been developed by the base-promoted demethoxylative cycloaddition of alkynyl oxime ethers using the cheap and inactive Se powder and Na2S as selenium and sulfur sources. This transformation features the direct construction of N-, Se-, and S-containing heterocycles through the formation of N-Se/S and C-Se/S bonds in one-pot reactions with excellent functional group tolerance.

Copper-Catalyzed Selective Defluorinative Sulfuration of Trifluoropropanamides Leading to α-Fluorothioacrylamides.

A practical and efficient method for the synthesis of α-fluorothioacrylamide was developed from selective defluorinative sulfuration of trifluoropropanamides with disulfides. The N-chelation-assisted copper-catalyzed defluorination and sulfurization reactions feature excellent functional group tolerance and incorporation of both sulfur atoms of disulfides into acrylamides.

Base-promoted thioannulation of o-alkynyl oxime ethers with sodium sulfide for the general synthesis of isothiocoumarins.

A general and efficient strategy for the one-pot synthesis of isothiocoumarin-1-ones has been developed via the base-promoted 6-endo-dig thioannulation of o-alkynyl oxime ethers using the cheap and readily available Na2S as the sulfur source. Mechanistic studies disclosed that the reaction proceeded through two C-S bond formations, N-O bond cleavage and the final hydrolysis of imines.

DBU-Promoted Demethoxylative Thioannulation of Alkynyl Oxime Ethers with Sulfur for the Synthesis of Bisisothiazole-4-yl Disulfides.

An efficient synthesis of bisisothiazole-4-yl disulfides via the demethoxylative thioannulation of alkynyl oxime ethers with odorless elemental sulfur has been first developed. This transformation involves the N-O bond cleavage, the formation of multiple C-S and N-S bonds, providing an efficient way for constructions of both isothiazoles and disulfides. Straightforward elaboration of the products to isothiazole thioethers expands the synthetic utility of this reaction.

Copper-Catalyzed Tandem Sulfuration/Annulation of Propargylamines with Sulfur via C-N Bond Cleavage.

Copper-catalyzed aerobic oxidative sulfuration and annulation of propargylamines with elemental sulfur is described. The tandem reaction involves C-N bond cleavage and the formation of multiple C-S bonds, affording 1,2-dithiole-3-thiones in good to excellent yields with good functional group tolerance.

Palladium-Catalyzed Tandem Carbocyclization and Hetroarylation for the Synthesis of 2-(Trifluoromethyl)indenylmethyleneindoles.

A palladium-catalyzed tandem cyclization and cross-coupling reaction of o-(2-chlorovinyl)alkynylbenzenes with indoles/pyrroles is developed. The process proceeds via intramolecular carbocyclization and subsequent hetroarylation to afford previously unknown trifluoromethyl-containing indenylmethyleneindoles, which are potentially useful in drug design.

Copper-Catalyzed N-Formylation of Amines through Tandem Amination/Hydrolysis/Decarboxylation Reaction of Ethyl Bromodifluoroacetate.

Ethyl bromodifluoroacetate (BrCF2COOEt) was first used as the N-formylating reagent in the copper-catalyzed N-formylation of amines. A range of primary, secondary, cyclic arylamines, and aliphatic amines underwent the N-formylation smoothly to furnish the N-formamides in moderate-to-excellent yields.

Pd-Catalyzed C(sp2)-H aminocarbonylation using the Langlois reagent as a carbonyl source.

A Pd-catalyzed C(sp2)-H aminocarbonylation of aryl carboxamides assisted by an N,S-bidentate directing group was developed, in which cheap and stable sodium trifluoromethanesulfinate was first utilized as a carbonyl source. The reaction can be applicable to a wide range of carboxamides with good functional group tolerance and afford isoindole-1,3-diones in moderate to good yields.

Palladium-catalyzed dimerization of N-aryl propargylamines for the synthesis of 3-vinylquinolines.

A straightforward method for the synthesis of polyfunctionalized quinolines from readily available N-aryl propargylamines under aerobic conditions was developed. It provides convenient access to a variety of synthetically and pharmaceutically important quinolines in moderate to good yields. Control experiments suggest that the cascade reaction might proceed via the Pd-catalyzed electrophilic cyclization of N-aryl propargylamines followed by a hydroarylation process through trapping of the σ-quinolinylpalladium intermediate with a second molecule of the substrate.

Transition-Metal-Free Conversion of Trifluoropropanamides into Cyanoformamides through C-CF3 Bond Cleavage and Nitrogenation.

A new transition-metal-free transformation of trifluoropropanamides into cyanoformamides through a sequence of C-CF3 bond cleavage and nitrogenation using tert-butyl nitrite as the nitrogen source is described. The method features direct detrifluoromethylation, broad substrate scopes, and excellent selectivity control, representing a new shortcut for constructing the nitrile group involving C-CF3 σ-bond cleavage.

One-Pot Synthesis of Quinoxalinones via Tandem Nitrosation/Cyclization of N-Aryl Cyanoacetamides.

A new one-pot strategy for the synthesis of quinoxalin-2-ones from the tandem nitrosation/cyclization reaction of N-aryl cyanoacetamides with tert-butyl nitrite has been developed. The dehydrogenative N-incorporation is achieved through a sequence of nitrosation, tautomerization, and cyclization, affording quinoxalin-2-ones in moderate to good yields with good functional group tolerance.

[Development of Tianma HPLC fingerprint and discriminant analysis].

Tianma(the tuber of Gastrodia eleta) is a widely used and pricy Chinese herb. Its counterfeits are often found in herbal markets, which are the plant materials with similar macroscopic characteristics of Tianma. Moreover, the prices of Winter Tianma(cultivated Tianma) and Spring Tianma(mostly wild Tianma) have significant difference. However, it is difficult to identify the true or false, good or bad quality of Tianma samples. Thus, a total of 48 Tianma samples with different characteristics(including Winter Tianma, Spring Tianma, slice, powder, etc.) and 9 plant species 10 samples of Tianma counterfeits were collected and analyzed by HPLC-DAD-MS techniques. After optimizing the procedure of sample preparation, chromatographic and mass-spectral conditions, the HPLC chromatograms of all those samples were collected and compared. The similarities and Fisher discriminant analysis were further conducted between the HPLC chromatograms of Tianma and counterfeit, Winter Tianma and Spring Tianma. The results showed the HPLC chromatograms of 48 Tianma samples were similar at the correlation coefficient more than 0.848(n=48). Their mean chromatogram was simulated and used as Tianma HPLC fingerprint. There were 11 common peaks on the HPLC chromatograms of Tianma, in which 6 main peaks were chosen as characteristic peaks and identified as gastrodin, p-hydroxybenzyl alcohol, parishin A, parishin B, parishin C, parishin E, respectively by comparison of the retention time, UV and MS data with those of standard chemical compounds. All the six chemical compounds are bioactive in Tianma. However, the HPLC chromatograms of the 10 counterfeit samples were significantly different from Tianma fingerprint. The correlation coefficients between HPLC fingerprints of Tianma with the HPLC chromatograms of counterfeits were less than 0.042 and the characteristic peaks were not observed on the HPLC chromatograms of these counterfeit samples. It indicated the true or false Tianma can be identified by either the similarity or characteristic peaks on HPLC fingerprint. Comparing the Winter Tianma with Spring Tianma showed that the HPLC chromatograms of 15 winter Tianma samples and 11 spring Tianma samples were similar at the mean correlation coefficient of 0.908. But the intensity of the characteristic peaks were different between the two groups of Tianma samples, i.e. the intensity of gastrodin, paishin A and C in winter Tianma was lower than those in spring Tianma. The Winter Tianma and Spring Tianma could be discriminated by either the Fisher unstandardized discrimination function or Linear discriminant function, based on the peak areas of 11 common peaks on HPLC chromatograms as variate.

Copper-Catalyzed Three-Component Tandem Cyclization for One-Pot Synthesis of 1,4-Benzothiazines.

A copper-catalyzed three-component tandem reaction has been developed for the convenient and practical synthesis of 1,4-benzothiazines. A variety of terminal alkynes and 2-iodo/bromophenyl isothiocyanates underwent this one-pot cyclization with aqueous ammonia to afford 1,4-benzothiazines in moderate to good yields.

Synthesis of 2-Sulfenylindenones via One-Pot Tandem Meyer-Schuster Rearrangement and Radical Cyclization of Arylpropynols with Disulfides.

A tandem annulation of arylpropynols with disulfides has been developed for the synthesis of 2-sulfenylindenone derivatives. The reaction pathway involves one-pot tandem Meyer-Schuster rearrangement of arylpropynols and successive radical cyclization with disulfides. Various arylpropynols and disulfides with a number of functional groups are compatible in this reaction that affords the corresponding 2-sulfenylindenones in moderate to good yields.