General synthesis of 2,5-dihydrothiophenes (3-thiolenes) from diketo sulfides

The intramolecular reductive coupling reaction of easily accessible diketo sulfides by a low-valent titanium reagent [prepared from titanium(IV) chloride and zinc powder] provides an efficient general synthesis of 2,5-dihydrothiophenes.     

A facile and convenient one-pot synthesis of polysubstituted thiophenes from 1,3-dicarbonyl compounds in water

A facile and convenient one-pot synthesis of polysubstituted thiophenes 2 and polysubstituted thieno[2,3-b]thiophenes 3 from 1,3-dicarbonyl compounds 1 has been achieved in high yields catalyzed by tetrabutylammonium bromide (TBAB) in the presence of K₂CO₃ in water. TBAB in the aqueous phase can be recycled after the separation of organic products.     

Regioselective synthesis of poly-substituted thiophenes from Baylis-Hillman adducts

The reaction of Baylis-Hillman acetates and ethyl mercaptoacetate in the presence of DBU in DMF produced 2,3,4-trisubstituted tetrahydrothiophenes at room temperature as a diastereomeric mixture via the sequential S_N2′ and Michael addition. Aromatization of tetrahydrothiophenes by DDQ oxidation produced 2,3,4-trisubstituted thiophenes in good yields.     

Sulfone-mediated synthesis of polysubstituted pyridines

Base-mediated and/or palladium(0)-catalysed bis(allylation) of alkyl 2-(tolylsulfonyl)acetates gives 1,6-dienes, which upon ozonolytic cleavage of the double bonds and ammonolysis give 2,6-disubstituted pyridine-4-carboxylic esters. Decarboxylation of one of the 1,6-diene intermediates followed by deprotonation-alkylation and ozonolysis-ammonolysis gives a 2,4,6-trisubstituted pyridine.     

General synthesis of metal sulfides nanocrystallines via a simple polyol route

In this report, a simple and easy polyol route for synthesizing many binary metal sulfides nanocrystallines is demonstrated. Powder X-ray electron diffraction and energy-dispersive X-ray spectrum are applied to investigate the crystallinity and composition of the nanoscale materials. The resulting particle size and morphology are examined by transmission electron microscopy, and the possible mechanism is also briefly discussed.     

One-pot synthesis of polysubstituted pyrimidines

A series of polysubstituted pyrimidines were synthesized from in situ generated α,β-unsaturated imines and the corresponding amidine or guanidine derivatives in a convenient one-pot procedure.     

The synthesis of polycyclic thiophenes derived from phenanthrene intermediates

The synthesis of benzo[b]triphenyleno[2,1-d]thiophene ( 9 ), benzo[b]triphenyleno[1,2-d]thiophene ( 13 ), 5-methylbenz[7,8]anthra[2,1-b]thiophene ( 17 ), l-methylchryseno[3,4-b]thiophene ( 18 ), triphenyleno[1,2-c]dibenzothiophene ( 22 ), triphenyleno[2,1-a]dibenzothiophene ( 26 ), triphenyleno[1,2-a]dibenzothiophene ( 29 ), and triphenyleno[2,1-b]dibenzothiophene ( 30 ) is described.     

Synthesis of substituted thiophenes based on fluorine-containing β-functionalized vinyl sulfides

Derivatives of fluorine-containing 3-(methoxycarbonylmethylthio)acrylic acids readily undergo base-catalyzed cyclization to form 3-hydroxy- and 3-aminothiophenes.     

A convenient one-pot synthesis of polysubstituted pyrroles from N-protected succinimides

The dienamine products formed by the reaction between polysubstituted succinimides and the Petasis reagent were subjected to isomerization under mild acidic conditions to give polysubstituted pyrroles in excellent yields (85–95%). The scope and limitations of this methodology are explored.     

Multicomponent synthesis of polysubstituted dihydroquinoline derivatives

A series of new poly-functionalized dihydroquinoline derivatives (26 examples) were synthesized via three-component reactions of aldehydes (1 equiv) and 1-arylethylidenemalononitriles (2 equiv) in ethylene glycol using NaOH as a base promoter under microwave irradiation. During these reaction processes, the domino construction of dihydroquinoline skeleton with concomitant formation of two new cycles was readily achieved in a one-pot operation and in an intermolecular manner.     

One-pot synthesis of polysubstituted 1,2,3,4-tetrahydropyridines

Mono- and bicyclic 1,2,3,4-tetrahydropyridine derivatives have been synthesized in up to 98% yield by one-pot three-component condensation of ethyl acetoacetate with methoxymethanol and primary amines (diamines) in methanol in the presence of tert-butyl alcohol.     

Three-component synthesis of polysubstituted homoproline analogs

Tetrasubstituted pyrrolidines representing analogs of homoproline were synthesized by three-component condensation of aryl(heteroaryl)aldehydes, asparagine and N-methylmaleimide (NMM). Compounds with (1S*, 3R*, 3aS*, 6aR*)-configuration at the corresponding carbon positions of the bicyclic pyrrolidine ring could be isolated ona preparative scale.     

One-pot multicomponent synthesis of polysubstituted indolizines

Concise and efficient four-component tandem approaches to polysubstituted indolizines have been developed under metal-free and mild aerobic conditions in refluxing acetonitrile. The mechanism of the novel reactions was proposed involving the formation of pyridinium ylides and α,β-unsaturated ketones with subsequent 1,3-dipolar cycloaddition and aromatization reaction.     

A facile synthesis of polysubstituted pyrroles

alpha-Aminoalkylcuprates prepared from CuX.2LiCl (X = Cl, CN) and 1 equiv of an alpha-lithiocarbamate undergo conjugate addition reactions to alpha,beta-alkynyl ketones in moderate to good yields, affording E:Z mixtures of alpha,beta-enones. Treatment of the conjugate adducts with PhOH/TMSCl in CH(2)Cl(2) effected carbamate deprotection and cyclization to afford a flexible two-step synthesis of substituted pyrroles.     

Catalytic synthesis of dialkyl sulfides from dialkyl disulfides

Dialkyl disulfides R₂S₂ where R = Me, Et, or Pr, both as individual compounds and as their mixtures, isolated from petroleum products can turn into alkanethiols and dialkyl sulfides under the action of catalysts having strong acid sites and medium-strength basic sites on their surface. In a helium atmosphere, the main conversion products are alkanethiols, while dialkyl sulfides form in low yield at a selectivity of no higher than 20%. A much higher dialkyl sulfide selectivity is attained in the reaction involving methanol. The most efficient catalyst for this reaction is alumina, with which the dialkyl sulfide selectivity is up to 99%.     

A versatile one-pot synthesis of 2,3,5-tri-substituted thiophenes from thiomorpholides

An efficient method for the preparation of 2,3,5-trisubstituted thiophenes in a one-pot synthesis from thiomorpholides via the thio-Claisen rearrangement was developed.     

Regioselective synthesis of 2,4-disubstituted thiophenes

A highly regioselective route was established to 2-aryl-, 2-cyclohexyl-, and 2-(2-arylethyl)4-alkylthiophenes, which are potential candidates as liquid crystalline compounds of low viscosity. The key synthetic intermediates, 2-substituted-4-(chloromethyl)thiophenes 6, 14, and 20 were prepared respectively from the reactions of β, γ-epoxycarbonyl compounds 5, 13, and 19 with Lawesson's reagent in the presence of a catalytic amount of p -toluenesulfonic acid. The epoxycarbonyl compounds were obtained from the TiCl₄-mediated reactions of 2-(chloromethyl)-3-(trimethylsliyl)propene (10) with acid chlorides followed by epoxidation with m-chloroperoxybenzoic acid, or from prior epoxidation followed by oxidation with pyridinium dichromate of homoallylic alcohols 3. The homoallylic alcohols 3 were synthesized from the reactions of 2-(chloromethyl)-3-(trichlorosilyl)propene (2) with aldehydes in N, N-dimethylformamide. Copper (I) catalysed cross-coupling reactions of 2-substituted-4-(bromomethyl)thiophenes (which were prepared by transhalogenation of 2-substituted-4- (chloromethyl)thiophenes with NaBr in acetone) with Grignard reagents afforded 2,4-disubstituted thiophenes. Using this method, eleven 2,4-disubstituted thiophenes were synthesized and their potentials as liquid crystalline compound of low viscosity were examined. The synthesized 2-(4-cyanophenyl)-4-pentylthiophene was observed to have a lower melting point than the corresponding 2,5-disubstituted thiophene. This observation is consistent with the expectation from the basis of molecular linearity which can affect the viscosity and/or melting point of crystalline compounds.