Ketene Dithioacetals Research Articles

Copper‐Catalyzed Ring‐Expansion/Thiolactonization via Azidation of Internal Olefinic C–H Bond under Mild Conditions

AbstractA copper(I)‐catalyzed, (diacetoxyiodo)benzene [PhI(OAc)2]‐mediated ring‐expansion/thiolactonization of α‐oxo ketene dithioacetals was efficiently realized via azidation of the internal olefinic C−H bond with sodium azide under mild conditions. Sequential amination, ring‐expansion rearrangement, and thiolactonization occurred to form aminated thiolactones in the presence of acetic anhydride as the additive, while only C−H amination to afford the unprotected enamines occurred when using ammonium sulfide as a reducing additive. The in situ generated vinyl azides were confirmed as the reactive intermediates, which were captured by phenylacetylene to produce triazoles. This protocol provides a concise route to thiolactone derivatives and unprotected enamines.magnified image

ChemInform Abstract: DBSA‐Catalyzed Friedel—Crafts Alkylation of Cyclic Ketene Dithioacetals with Alcohols in Water.

Abstract A novel DBSA-catalyzed Friedel–Crafts alkylation of cyclic ketene dithioacetals, internal alkenes with highly nucleophilic carbon atom adjacent to the electron-withdrawing group, with alcohols in water has been developed. The reaction is efficient in the presence of catalyst loading as low as 10 mol % in water at reflux, and a wide range of alkylated ketene dithioacetals are synthesized in excellent yields.

An Efficient One‐Pot Four‐Component Synthesis of Some New Spirooxindole Dihydropyridine Using Alum as a Heterogeneous Green Catalyst

Abstract4‐Nitro‐2,3‐dihydrospiro[imidazo[1,2‐a]indeno[2,1‐e]pyridine‐5,3′‐indoline]‐2′,6(1H)‐dione derivatives have been synthesized in good yields in a one‐pot four‐component, and efficient process by reaction of corresponding isatins, 1,3‐indandione, diamine, and nitro ketene dithioacetal in the presence of KAl(SO4)2.12H2O (Alum) as a nontoxic and easily available heterogeneous green catalyst.

Pd-Catalyzed C-S Activation/Isocyanide Insertion/Hydrogenation Enables a Selective Aerobic Oxidation/Cyclization.

Unique imidoylation of thioorganics with isocyanides endows an unprecedented aerobic oxidation process. Catalyzed by Pd(Ph3P)2Cl2 in the presence of Ph3SiH under N2 then upon exposure to air, a wide range of α-acyl ketene dithioacetals react with isocyanides to afford 5-hydroxy-α,β-unsaturated γ-lactams via a C-S bond activation, isocyanide migratory insertion, hydrogenation, selective aerobic oxidation, and intramolecular nucleophilic addition sequence.

ChemInform Abstract: Copper(I)‐Catalyzed Heterocyclization of α‐Acyl‐α‐alkynyl Ketene Dithioacetals: Synthesis of 3‐Cyanofurans.

AbstractThe heterocyclization procedure generates a cyano moiety in situ with ammonium acetate as the nitrogen source providing 3‐cyanofuran derivatives in good to excellent yield.

Iron chloride hexahydrate-catalyzed Friedel-Crafts akylation of cyclic ketene dithioacetals with alcohols

A cost-effective and environmentally compliance FeCl3·6H2O catalyzed Friedel-Crafts alkylation of cyclic ketene dithioacetals with alcohols was developed. The reaction was efficient in the presence of catalyst loading as low as 5%(molar fraction) in CH2Cl2 solvent at room temperature or under reflux conditions. A wide range of alkylated ketene dithioacetals were synthesized in excellent yields.

DBSA-catalyzed Friedel–Crafts alkylation of cyclic ketene dithioacetals with alcohols in water

A novel DBSA-catalyzed Friedel–Crafts alkylation of cyclic ketene dithioacetals, internal alkenes with highly nucleophilic carbon atom adjacent to the electron-withdrawing group, with alcohols in water has been developed. The reaction is efficient in the presence of catalyst loading as low as 10mol% in water at reflux, and a wide range of alkylated ketene dithioacetals are synthesized in excellent yields.

Copper(I)-Catalyzed Heterocyclization of α-Acyl-α-alkynyl Ketene Dithioacetals: Synthesis of 3-Cyanofurans.

A new method for the synthesis of 3-cyanofurans via Cu(I)-catalyzed heterocyclization of α-acyl-α-alkynyl ketene dithioacetals in the presence of ammonium acetate has been developed. The procedure generates the cyano moiety in situ with ammonium acetate as the nitrogen source. Based upon experimental observations, a plausible reaction mechanism is proposed.

Synthesis, Characterization and Biological Evaluation of some Novel Pyrazolo[1,5-a]Pyrimidine Derivatives

A convenient synthesis of substituted Pyrazolo[1,5-a]pyrimidine was carried out by the reaction of different ketene dithioacetals with different aromatic amine in isopropanol in the presence of potassium carbonate. The newly synthesized compound were characterized by 1H NMR, IR, Mass and screened for their antimicrobial activity against various strains of bacteria and fungi. From the synthesized different NCEs, compounds 8a, 8d and 8e are broad spectrum drug which can inhibit the growth of gram positive, gram negative bacteria and fungi.

Synthesis, Characterization and Biological Evaluation of some Novel Pyrazolo[1,5-a]Pyrimidine Derivatives

A convenient synthesis of substituted Pyrazolo[1,5-a]pyrimidine was carried out by the reaction of different ketene dithioacetals with different aromatic amine in isopropanol in the presence of potassium carbonate. The newly synthesized compound were characterized by1H NMR, IR, Mass and screened for their antimicrobial activity against various strains of bacteria and fungi. From the synthesized different NCEs, compounds 8a, 8d and 8e are broad spectrum drug which can inhibit the growth of gram positive, gram negative bacteria and fungi.

Reactions of ketene dithioacetal for a new versatile synthesis of 4,5-substituted 3-aminothiophene-2-carboxylate derivatives

ABSTRACTPoly substituted 3-aminothiophenes were successfully synthesized in good yields by using a one-pot protocol via ketene S,S-acetal as an intermediate in basic medium (K2CO3/N,N-dimethylformamide) followed by Dieckmann condensation with ethyl bromoacetate. Further, chemistry of thiophenes was explored using active functional groups such as C3–NH2, C4–CN and C5–SCH3 on the thiophene nucleus.Synthesis of ethyl 3-acetamido-4-cyano-5-(methylthio)thiophene-2-carboxylate derivatives and ethyl 3-amino-4-carbamoyl-5-(methylthio)thiophene-2-carboxylate derivatives.

Understanding the Mechanism of the Lewis Acid Promoted [3 + 2] Cycloaddition of Propargylic Alcohol and α-Oxo Ketene Dithioacetals.

The mechanism and origin of selectivities in BF3·Et2O-catalyzed intermolecular [3 + 2] cycloadditions of propargylic alcohol and α-oxo ketene dithioacetals have been studied using density functional theory. Several possible reaction pathways were evaluated on the basis of two possible binding modes between the carbonyl or hydroxyl oxygen of substrates and catalyst. The preferred mechanism initiates dehydroxylation of propargylic alcohol by Lewis acid BF3 and generates active allenic carbocation species to provide the favorable electrophile. It then proceeds via four processes involving nucleophilic addition of C(α) on α-oxo ketene dithioacetals to the C1 of active allenic carbocation intermediate, [1,4]-alkylthio shift, H(α)-elimination, and intramolecular cyclization. This reaction sequence is in contrast to the mechanism by a previously published study, that is, [1,4]-alkylthio migration occurs prior to the cyclization. Our calculated results suggested that electrostatic attraction and hydrogen-bonding interactions between substrates and catalyst play a vital role in the [3 + 2] cycloaddition.

ChemInform Abstract: Et3N Mediated Synthesis of Polysubstituted Thiophenes from α‐Oxo Ketene Dithioacetals.

Abstract In this Letter, an efficient synthetic route to prepare polysubstituted thiophene derivatives was achieved via the Et 3 N-mediated (Claisen) rearrangement reaction from α-oxo S -methyl- S -propargyl ketenes, which were obtained through alkylation of β-oxodithioesters with propargylic bromides, followed by regioselective intramolecular cyclization.

Determinative role of ring size and substituents in highly selective synthesis of functionalized bicyclic guanidine and tetra substituted thiophene derivatives based on salt adducts afforded by cyclic thioureas and ketene dithioacetal

The condensation of organic salt adducts generated by cyclic thioureas and 2-di(methylsulfanyl)methylenemalononitrile with dialkyl acetylenedicarboxylates selectively leads to either tetrasubstituted thiophenes (2 examples) or hitherto unreported bicyclic guanidine (13 examples) derivatives, with controlling factors being ring size, the substituent on the S-methylisothiourea and the bulk of the substituent on the dialkyl acetylenedicarboxylates. Green solvents, short reaction time; easy purification, high yield and selectivity, are key feature of this protocol in the condensation step. The performances of the reactions in the presence of free-base and a catalyst at room temperature is unprecedented in the synthesis of thiophene frameworks and functionalized bicyclic guanidine scaffolds.

ChemInform Abstract: Broensted Acid‐Mediated Annulation of α‐Oxo Ketene Dithioacetals with Pyrroles: Efficient Synthesis of Structurally Diverse Cyclopenta[b]pyrroles.

AbstractThe annulation of dithioacetals with pyrroles is accompanied by a migration of the ethylthio group to afford cyclopenta[b]pyrroles such as (III) and (VIII), which are converted into sulfones (IV) and (IX), resp., using MCPBA as oxidant.

Trimethylsilyloxide‐Catalysed Peterson Olefinations with 2,2‐Bis(trimethylsilyl)‐1,3‐dithiane

AbstractThe synthesis of the reagent 2,2‐bis(trimethylsilyl)‐1,3‐dithiane was directly achieved in an excellent yield from 1,3‐dithiane in one step. The bench‐stable reagent can be utilized for Peterson olefinations using either TMSOK/Bu4NCl or fluoride ion as promoter of α‐silyl carbanion formation, thereby generating ketene dithioacetals, which are versatile intermediates in organic synthesis. Olefination reactions were successfully achieved with aromatic, heteroaromatic, aliphatic aldehydes and ketones.

ChemInform Abstract: BF3·OEt2‐Mediated Alkenylation of Pyrroles with α‐Oxo Ketene Dithioacetals.

AbstractThe title reaction affords mono‐ and bispyrrole compounds.

Synthesis of Novel Highly Substituted Pyrimidines Bearing Furanyl Thiazole Nucleous

A series of novel highly substituted pyrimidines bearing furanyl thiazole nucleous have been synthesized. In which reaction of guanidine nitrate with ketene dithioacetals 3c produced substituted pyrimidines 4d which further treated with various aromatic aldehydes to afford title compounds 5(a-t). The chemical structures of the synthesized compounds were elucidated by 1H NMR, 13C NMR, FT-IR, elemental analysis, and mass spectral data.

Et3N mediated synthesis of polysubstituted thiophenes from α-oxo ketene dithioacetals

In this Letter, an efficient synthetic route to prepare polysubstituted thiophene derivatives was achieved via the Et3N-mediated (Claisen) rearrangement reaction from α-oxo S-methyl-S-propargyl ketenes, which were obtained through alkylation of β-oxodithioesters with propargylic bromides, followed by regioselective intramolecular cyclization.

2-Pyridone-based fluorophores containing 4-dialkylamino-phenyl group: Synthesis and fluorescence properties in solutions and in solid state

Novel highly emissive 2-pyridone-based compounds 3a,b and 4a–d were synthesized by a convenient one-pot method from 4-(dialkylamino)acetophenones (1a,b) and cyanoketene dithioacetal (2a) or sulfonyl ketene dithioacetals (2b,c), and their fluorescence properties were investigated. A simple structure modification of 2-pyridones significantly affected their optical properties including the emission wavelength and fluorescence intensity. All the 6-(4-dialkylamino)phenyl-2-pyridones showed positive solvatofluorochromism and intense blue-green fluorescence in nonpolar solvents such as chloroform (Ф: 0.80–0.92) and dichloromethane (Ф: 0.83–0.94). A hypsochromic shift of the fluorescence emission maxima and strong fluorescence in a polar solvent were observed by substituting the dimethylamino group with a diethylamino group. Introduction of a sulfonyl group disturbed the molecular planarity of compounds 4a, 4b, and 4d, resulting in a strong fluorescence in acetone (Ф: 0.86–0.95) and acetonitrile (Ф: 0.59–0.88). These results indicate that 2-pyridone-based compounds have great potential as fluorophores for various practical applications.