An unusual cascade of <Emphasis Type="Italic">S</Emphasis><Subscript>N</Subscript> reactions of benzotetrazine 1,3-dioxide derivatives

An unusual cascade of S _NAr reactions was discovered in the series of benzo-1,2,3,4-tetrazine 1,3-dioxides containing two adjacent nucleofuges X and Y in the benzene ring. First, the 1,2,3-triazole anion displaces the anion X^s- from the more reactive site. Then the nucleo-phile X^s- displaces the adjacent group Y. For instance, 1,2,3-triazole reacts with 6-azido-5-nitrobenzotetrazine 1,3-dioxide to give 5-azido-6-(1,2,3-triazol-2-yl)benzotetrazine 1,3-dioxide, with 8-azido-7-nitrobenzotetrazine 1,3-dioxide to give 7-azido-8-(1,2,3-triazol-2-yl)benzotetrazine 1,3-dioxide and 7-azido-8-(1,2,3-triazol-1-yl)benzotetrazine 1,3-dioxide, and with 7-bromo-6-(phenylthio)benzotetrazine 1,3-dioxide to give 7-phenylthio-6-(1,2,3-triazol-2-yl)benzotetrazine 1,3-dioxide.     

Synthesis of 1-(1-aryl-1H-1,2,3-triazol-4-yl)-β-carboline derivatives

Reaction of 5-methyl-1-aryl-1H-1,2,3-triazole-4-carbocylic acid chlorides with tryptamine derivatives afforded substituted 1-aryl-N-[2-(1H-indol-3-yl)ethyl]-5-methyl-1H-1,2,3-triazole-4-carboxamides. At heating these compounds in toluene in the presence of POCl₃ and P₂O₅ Bischler-Napieralski cyclization occurs giving 1-(1-aryl-5-methyl-1H-1,2,3-triazol-4-yl)-4,9-dihydro-3H-β-carbolines that can be transformed into β-carboline and tetrahydro-β-carboline derivatives.     

Synthetic transformation of higher terpenoids 31. Synthesis of 1,2,3-triazolyl-containing furan labdanoids and studies of their cytotoxic activity

16-(1-R-1,2,3-Triazol-4-ylethyl)-, 16-(1-R-1,2,3-triazol-4-ylmethoxymethyl)-, and 16-{2-(1-R-1,2,3-triazol-4-yl)-1-[(1-R-1,2,3-triazol-4-ylmethoxy)ethyl]}-substituted derivatives of methyl lambertianate were synthesized by 1,3-cycloaddition of labdanoid alkynes with azides. The compounds obtained possess considerable cytotoxicity toward the human tumor cell lines CEM-13, MT-4, and U-937. The most active compound, methyl 16-(2-{2-[(1-benzyl-1H-1,2,3-triazol-4-yl)acetyl]furan-3-yl}ethyl)lambertianate, was found to inhibit the viability of the tumor cells by 50% (CCID₅₀) in the concentration of 7–12 μmol L^?1.     

Nitropyrazoles: XII. Transformations of the 4-Methyl Group in 1,4-Dimethyl-3,5-dinitropyrazole and Cyclization of the Transformation Products

A preparative procedure for the synthesis of 1,4-dimethyl-3,5-dinitropyrazole by nitration of 1,4-dimethylpyrazole was developed. The reaction of 1,4-dimethyl-3,5-dinitropyrazole with dimethoxymethyl- (dimethyl)amine (N,N-dimethylformamide dimethyl acetal) gave (E)-N,N-dimethyl-2-(1-methyl-3,5-dinitropyrazol- 4-yl)ethenylamine. Acid hydrolysis of the latter afforded (1-methyl-3,5-dinitropyrazol-4-yl)acetaldehyde, and the reaction with sodium nitrite in hydrochloric acid led to formation of 2-hydroxymino-2-(1-methyl- 3,5-dinitropyrazol-4-yl)acetaldehyde. The corresponding O-methyloxime and phenylhydrazone reacted with K₂CO₃ to give 6-methyl-4-nitropyrazolo[4,3-d]isoxazole-3-carbaldehyde O-methyloxime and 1-methyl-3-nitro-4-(2-phenyl-2H-1,2,3-triazol-4-yl)pyrazol-5-ol, respectively. Treatment of (1-methyl-3,5-dinitropyrazol-4-yl)-acetaldehyde with benzenediazonium chloride gave (1-methyl-3,5-dinitropyrazol-4-yl)acetaldehyde phenylhydrazone which underwent intramolecular cyclization with replacement of the 5-nitro group by the action of K₂CO₃ in acetonitrile; in the reaction with K₂CO₃ in ethanol, the 5-nitro group was replaced by ethoxy.     

A P,N ligand with central and axial chiral elements: synthesis and application in allylic alkylation

Two epimers of 4-({5-[(diphenylphosphino)methyl]-2,2-dimethyl-1,3-dioxolan-4-yl}methyl)-4,5-dihydro-3H-dinaphtho[1,2-e:2′,1′-c]azepine were prepared starting from (2S,3S)-4-amino-2,3-O-isopropylidenebutane-1,2,3-triol and (R)- and (S)-binaphthol. These ligands, in association with Pd(0) gave enantioselectivities up to 89% (S) and 36% (R) ee for the (S_A,4S,5R) and the (R_A,4S,5R) ligands in the alkylation of racemic 1,3-diphenylprop-2-enyl acetate with dimethyl malonate, showing that the binaphthyl moiety is the most important structure in the enantioselective creation of the new stereogenic center.     

Synthesis of 1,2,3-triazolo-nucleosides via the post-triazole N-alkylation

2-Substituted-2H-1,2,3-triazolo-nucleosides with 3-phosphonopropyl, 2-hydroxyethyl, 2-cyanoethyl, carbamoylmethyl, or 1-deoxy-2,5-anhydro-d-mannitol-1-yl on the triazole N-2 nitrogen atom were obtained via the DBU-promoted N-alkylation of 3-(pivaloyloxymethyl)-1-[(NH-1,2,3-triazol-4-yl)methyl]thymine with diethyl 3-bromopropylphoshonate, 2-bromoethanol, acrylonitrile, methyl bromoacetate, or 3,4,6-tris(O-benzoyl)-2,5-anhydro-d-mannitol 1-tosylate. The N-2/N-1 regioselectivity of the alkylation varied from 57/43 (methyl bromoacetate) to 97/3 (diethyl 3-bromopropylphoshonate). The 1-substituted-1H-1,2,3-triazoles, when formed in the appreciated amount in the alkylation reaction, were converted into the corresponding 1-substituted-1H-1,2,3-triazolo-nucleosides. The substitution pattern of 2-substituted-2H-1,2,3-triazolo-nucleosides was confirmed by ¹H–¹⁵N HMBC NMR spectra; the triazole nitrogen atoms were identified through their correlations with the triazole exo-cyclic protons.     

Synthesis of poly(vinyl acetate) with fluorescence via a combination of RAFT/MADIX and “click” chemistry

A novel ω-azido-functionalized RAFT reagent, O-(2-azido-ethyl) S-benzyl dithiocarbonate (AEBDC), was synthesized and subsequently employed to mediate the reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc) to prepare end-functionalized polymers. The polymerization results showed that the RAFT polymerizations of VAc could be well controlled using AEBDC as the RAFT agent. Number-average molecular weights (M_n GPC) increased linearly with monomer conversion, and molecular weight distributions were relatively narrow. ¹H NMR spectrum of the poly(vinyl acetate) (PVAc) confirmed the existence of functional azido group at the end of the polymers chains. The ω-azido-terminated polymers were coupled by “click” chemistry with a fluorescent alkyne, 7-propinyloxy coumarin, to prepare fluorescent PVAc. The fluorescence properties of the PVAc homopolymers before and after coupling with 7-propinyloxy coumarin in CH₂Cl₂ solution were investigated.     

Theoretical and experimental studies on the structure and isomerization of isocyano and cyano cyclopolyenes

Quantum-chemical calculations in terms of the density functional theory showed that cyclopolyenyl isocyanides RNC are considerably less stable than the corresponding cyanides and that they are capable of undergoing RNC → RCN isomerization according to both 1,2-shift mechanism (cyclopropenyl and cyclopentadienyl isocyanides; ΔE ^≠ = 35.0 and 37.5 kcal/mol, respectively) and previously unknown 2,5-sigmatropic shift mechanism (cycloheptatrienyl isocyanide, ΔE ^≠ = 26.4 kcal/mol). Migration of cyano group in the cyclopentadiene and cycloheptatriene systems follows the 1,5-sigmatropic shift pattern. The activation barrier to 1,5-shift of cyano group around the cycloheptatriene ring was estimated by dynamic NMR in deuterated nitrobenzene (ΔG _190°C ^≠ = 26.5 kcal/mol).     

2-Azido-1,3,4-thiadiazoles, 2-Azido-1,3-thiazoles,and Aryl Azides in the Synthesis of 1,2,3-Triazole-4-carboxylic Acids and Their Derivatives

Diazotization of 2-amino-1,3,4-thiadiazoles gave 1,3,4-thiadiazole-2-diazonium sulfates which were converted to 2-azido-1,3,4-thiadiazoles. The latter reacted with ethyl acetoacetate in the presence of sodium methoxide in methanol to produce 1-(5-R¹-1,3,4-thiadiazol-2-yl)-5-R²-1H-1,2,3-triazole-4-carboxylic acid derivatives. The reactions of 2-azido-5-methyl-1,3,4-thiadiazole and 2-azido-1,3-thiazole with ethyl 3-(1,3-benzodioxol-5-yl)-3-oxopropanoate led to the formation of 1,2,3-triazole ring under milder conditions (K₂CO₃, DMSO). Various 1,2,3-triazole-4-carboxylic acid derivatives were synthesized.     

Acidic N-dealkylation in nitrotriazolium salts

New selective synthesis of 1-alkyl-5-nitro-1,2,3-triazoles and 1-alkyl-4-nitro-1,2,3-triazoles has been developed, involving acid N-dealkylation of the relative 4-nitro-1,2,3- and 3-nitro- 5-R-1,2,4-triazolium salts. The assortment of novel 1-alkyl- 4(5)-nitro-1,2,3-triazoles has been thus essentially expanded. Treatment of relative 3-nitro-1,2,4-triazolium salts with HCl or HBr proceeds mostly as S_N^ipso-substitution of the nitro group.     

Electrochemical Fluorination of Dithiocarbonates Using a Triarylamine Mediator

Electrochemical oxidation of O-(4-chlorobenzyl) S-methyl dithiocarbonate using tris(2,4-dibromophenyl)amine as a redox mediator was studied by cyclic voltammetric measurements. The triarylamine mediated anodic fluorodesulfurization of O-(4-chlorobenzyl) and O-(4-bromobenzyl) S-methyl dithiocarbonates provided 4-chloro- and 4-bromobenzyl fluorides, respectively in moderate yields. On the other hand, similar anodic fluorination of O-(2-phenethyl) S-octyl dithiocarbonate and O-(4-bromophenyl) S-methyl dithiocarbonate afforded 2-phenethyl trifluoromethyl ether and difluoro(methylthio)methyl 4-bromophenyl ether, respectively. Mechanistic aspects are also discussed.     

Glyconothio-O-lactones. Part I. Preparation and reactions with nucleophiles

Furanoid and pyranoid glyconothio-O-lactones were prepared by photolysis of S-phenacyl thioglycosides or by thermolysis of S-glycosyl thiosulfinates, which gave better results than the thionation of glyconolactones with Lawesson's reagent. Thermolysis of the thiosulfinates obtained from the dimannofuranosyl disulfide 7 or the manofuranosyl methly disulfide 8 (Scheme 2) gave low yields of the thio-O-lactone 2 . However, photolysis of the S-phenacyl thioglycoside 6 obtained by in situ alkylation of the thiolato anion derived from 5 led in 78–89% to 2 . Similarly, the dithiocarbonate 10 was transformed, via 11a , into the ribo-thio-O-lactone 12 (79%). Thermolysis of the peracetylated thiosulfinates 14 (Scheme 3) led to the intermediate thio-O-lactone 15 , which underwent facile β-elimination of AcOH (→ 16 , 75%) during chromatography. The perbenzylated S-glucopyranosyl dithiocarbonate 18 (Scheme 4) was transformed either into the S-phenacyl thioglucoside 19 or into a mixture of the anomeric methyl disulfides 21a/b . Whereas the photolysis of 19 led in moderate yield to 2-deoxy-thio-O-lactone 20 , oxidation of 21b and thermolysis of resulting thiosulfinates gave the thio-O-lactone 4 (79%), which was transformed into 20 (36%) upon photolysis. The pyranoid manno-thio-O-lactone 26 was prepared in the same way and in good yields from 22 via the dithiocarbonate 24b and the disulfide 25 . The ring conformations of the δ-thio-O-lactones, flattened ⁴C₁ for 15 and 4 and B_2,5 for 26 , are similar to the ones of the O-analogous oxo-glyconolactones. The reaction of 2 (Scheme 5) with MeLi and then with MeI gave the thioglycoside 27 (29%) and the dimeric thio-O-lactone 29 (47%). The analogous treatment of 2 with lithium dimethylcuprate (LiCuMe₂) and MeI led to a 4:1 mixture (47%) of 31 and 27 . The structure of 2 was proven by an X-ray analysis, and the configuration at C(6) and C(5) of 29 was deduced from NOE experiments. Substitution of MeI by CD₃I led to the CD₃S analogues of 27 , 29 , and 31 , i.e. 28 , 30 , and 32 , respectively, evidencing carbophilic addition and ‘exo’-attack on 2 by MeLi and the enethiolato anion derived from 2 . The preferred ‘endo’-attack of LiCuMe₂ is rationalized by postulating a single-electron transfer and a diastereoselective pyramidalization of the intermediate radical anion.     

Synthesis of S,S-dialkyl-N-(9,10-dioxo-9,10-dihydroanthracen-1-yl)sulfoximides and specificities of their base-catalyzed intramolecular heterocyclizations into naphtho[1,2,3-cd]-indol-6(2H)-ones

Heating of 6H-anthra[1,9-cd][1,2]oxazol-6-ones with dialkyl sulfoxides in sulfolane gave S,S-dialkyl-N-(9,10-dioxo-9,10-dihydroanthracen-1-yl)sulfoximides which underwent cyclization to naphtho-[1,2,3-cd]indol-6(2H)-one derivatives on heating in boiling tetrahydrofuran in the presence of sodium methoxide. p-Toluenesulfinic acid was isolated as by-product in the cyclization of S-methyl-S-(4-methylphenyl)-N-(9,10-dioxo-9,10-dihydroanthracen-1-yl)sulfoximide. The heterocyclizations of S,S-dipropyl- and S,S-dibutyl-N-(9,10-dioxo-9,10-dihydroanthracen-1-yl)sulfoximides to 1-ethyl- and 1-propylnaphtho[1,2,3-cd]-indol-6(2H)-ones were accompanied by formation of the corresponding 1-[1-hydroxyethyl(propyl)]naphtho-[1,2,3-cd]indol-6(2H)-ones.     

Convenient Strategies for the Preparation of Modified 2(3H)-Benzothiazolethiones

4-Alkyl-2-bromoanilines and 4-alkoxy-2-chloroanilines were synthesized conveniently and submitted to cyclization reaction with potassium O-ethyl dithiocarbonate to afford 6-substituted 2(3H)-benzothiazolethiones in good yields.     

An Improved Preparation of Polymer-Type η3-Allylpalladiumchlorides

Five polymer-type new compounds-(η³-cyclopentadienyl)palladiumchloride ( 6 ), (η³-indenyl) palladiumchloride ( 7 ), (η³-cycloheptatrienyl)palladiumchloride ( 8 ), (η³-phenalenyl)palladiumchloride ( 9 ) and (1,2,3-η³-4,5,6,7-η⁴-cyclopheptatrienyl)(palladium-chloride)(tricarboryl Iron) ( 10 ) have been prepared from the reaction of Na₂PdCl₄ with 1-trimethylsilylcyclopentadiene ( 1 ), 1-trimethylsilylindene ( 2 ), 1-trimethylsilyl cycloheptatriene ( 3 ), 1-trimethylsilylphenalene ( 4 ) and 1-trimethylsilylcycloheptatriene tricarbonyl Iron ( 5 ) respectively. All the complexes( 6 )-(10) are obtained in excellent yield using the improved preparation route. Furthermore, a reaction mechanism is proposed.     

Synthesis and characterizations of 1,2,3-triazole containing polymers via reversible addition-fragmentation chain transfer (RAFT) polymerization

A novel monomer containing triazole and naphthalene ring, 2-(1-naphthalen-1-ylmethyl-1H-[1,2,3]triazol-4-yl)-ethyl methacrylate (NTEMA), was designed and synthesized via “click” chemistry method. The RAFT polymerization of NTEMA was successfully carried out using 2-cyanoprop-2-yl dithiobenzoate (CPDB) as a RAFT agent, 2,2′-azobisisobutyronitrile (AIBN) as an initiator in tetrahydrofuran (THF) solution. The results showed that the polymerizations exhibited “living”/controlled characteristics. The obtained poly(2-(1-naphthalen-1-ylmethyl-1H-[1,2,3]triazol-4-yl)-ethyl methacrylate) homopolymers, PNTEMAs, were further coordinated with samarium ion to prepare rare earth containing polymers (PNTEMA-Sm(III) complexes) which were characterized by FT-IR, DSC and ICP-AES. The characterization data confirmed that triazole in side chain of the polymer could coordinate with Sm(III). The fluorescence property of the polymers and polymer Sm(III) complexes were investigated in solution and in film.     

Synthesis,antioxidant activity,and α-glucosidase enzyme inhibition of α-aminophosphonate derivatives bearing piperazine-1,2,3-triazole moiety

A novel series of piperazine-1,2,3-triazole bearing dimethyl(((2-(4-((1H-1,2,3-triazole-4-yl)methyl)piperazin-1-yl)ethylamino)(2-hydroxyaryl)methyl)phosphonate derivatives have been prepared via copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) (Click Reaction) and Schiff base reactions. The synthesized compounds were confirmed by spectral characterization (¹H, ¹³C and ³¹P NMR, and mass). The title compounds were evaluated for in vitro alpha glucosidase enzyme inhibition and in vitro antioxidant activity using DPPH and H₂O₂ methods.     

Synthesis of novel 1-(2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)-uracil and -thymine, and their corresponding S-oxidized derivatives

On the basis of molecular variations on isosteric replacements from the prototype 1-(2,3-dihydro-5H-1,4-benzodioxepin-3-yl)-5-fluorouracil a series of 3-(2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)-uracil or -thymine O,N-acetals was prepared. The nature of the cis- and trans-sulfoxide isomers was established by means of their conformational analyses carried out with Sybyl and after comparing the theoretical results with the ¹H NMR responses of the target molecules. (RS)-3-(1,1-Dioxo-2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)thymine and (1S*,3S*)-1-(1-oxo-3,5-dihydro-2H-4,1-benzoxathiepin-3-yl)thymine were found to be inhibitors of the MCF-7 cell growth.     

A simple and convenient synthesis of 3-[5-(trifluoromethyl)-1,2,3-triazol-4-yl]cinnamic acids from 4-aryl-6-(trifluoromethyl)-2H-pyran-2-ones and sodium azide

4-Aryl-6-(trifluoromethyl)-2H-pyran-2-ones and ethyl 4-aryl-6-(trifluoromethyl)-2-oxo-2H-pyran-3-carboxylates react with sodium azide to produce highly functionalized CF₃-1,2,3-triazoles: 3-[5-(trifluoromethyl)-1,2,3-triazol-4-yl]cinnamic acids and monoethyl esters of [5-(trifluoromethyl)-1,2,3-triazol-4-yl]arylmethylidene malonic acids.     

Synthesis of nitro,nitroso, azo,and azido derivatives of (4-R<Superscript>1</Superscript>-5-R<Superscript>2</Superscript>-1,2,3-triazol-1-yl)-1,2,5-oxadiazoles by oxidation and diazotization of the corresponding amines

Nitro-, nitroso-, and azo-1,2,5-oxadiazoles with 4-R¹-5-R²-1,2,3-triazol-1-yl substituents were synthesized by oxidation of amino-(1,2,3-triazol-1-yl)-1,2,5-oxadiazoles (aminotriazolylfurazans). Azido-1,2,5-oxadiazole was prepared by diazotization of amino(triazolyl)furazan followed by treatment of the diazonium salt with sodium azide. Depending on the nature of the substituents and the reagent, triazolylfurazans can undergo destruction to give amino-R-furazans (R = NO₂, N₃, aminofurazanylazo), the amino group being formed from the triazole ring. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1859–1865, August, 2005.