Dithioacetal Research Articles

Influence of the Thiol Structure on the Kinetics of Thiol‐ene Photopolymerization with Time‐Resolved Infrared Spectroscopy

AbstractPhotopolymerization kinetics of difunctional thiols with alkenes were studied. Two of the thiols, trans‐1,4‐bis(mercaptomethyl)cyclohexane (CHDMT) and 1,4‐bis(mercaptomethyl)benzene (BDMT) were synthesized. The CHDMT was synthesized via a two step process using potassium thioacetate and hydrochloric acid as reagents. The BDMT was synthesized by a one step process using 1,4‐benzenedimethanebromine with thiourea and potassium hydroxide as reagents. Three types of alkenes (divinyl ether, diallyl ether, and dimethacrylate) were reacted with CHDMT, BDMT or 1,8‐octanedithiol (ODT). The photopolymerization was investigated with and without a photoinitiator. The kinetics of the thiol‐ene photopolymerization was investigated by time‐resolved infrared spectroscopy. It was proposed that the steric hindrance of the cyclohexane (CHDMT) resulted in a lower rate of photopolymerization compared to BDMT and ODT. The vinyl ether (alkene) exhibited the highest activity compared to allyl ether and acrylate which was attributed to a high electron density of the alkene. Incorporation of photoinitiator increased the reaction rate and final conversion of the system, particularly in the ODT system.magnified image

Synthesis and Reactivity of 4‐(2‐Chloro‐5‐nitrophenyl)‐1,2,3‐thiadiazole. A Novel One‐Pot Synthesis of N‐Substituted Indole‐2‐thiols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Efficient Preparation of S‐Aryl Thioacetates from Aryl Halides and Potassium Thioacetate.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis and Reactivity of 4-(2-Chloro-5-nitrophenyl)-1,2,3-thiadiazole. A Novel One-pot Synthesis of N-Substituted Indole-2-thiols

4-(2-Chloro-5-nitrophenyl)-1,2,3-thiadiazole undergoes ring opening to produce a thioketene intermediate that reacts with an O- or N-nucleophile, forming an ester or an amide of the aryl-substituted thioacetic acid. Intermolecular cyclization of the thioacetic acid derivative via nucleophilic substitution of halogen in the aromatic ring gives an N-substituted indole-2-thiol (in case of an N-nucleophile) or a 2-alkoxy-substituted benzo[b]thiophene (in case of an O-nucleophile). The reaction is also applicable to the synthesis of heterocyclic analogues of N-substituted indole-2-thiols: 1-butyl-1,3-dihydropyrrolo[2,3-b]pyridine-2-thione was synthesized as an example. In the presence of potassium thioacetate (an S-nucleophile) 4-nitro-2-(1,2,3-thiadiazol-4-yl)benzenethiol is formed more quickly than thiadiazole ring opening occurs, making the heterocyclic ring tolerant toward the base.

Unexpected Microwave Reaction of 1,3‐Disubstituted Imidazolium Salts: A Novel Synthesis of 1,3‐Disubstituted Imidazole‐2‐thiones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Efficient preparation of S-aryl thioacetates from aryl halides and potassium thioacetate

A method for the preparation of S-aryl thioacetates using palladium-mediated couplings of aryl bromides and aryl triflates with potassium thioacetate as an inexpensive thiol source was developed. Electron withdrawing groups, electron donating groups and heterocyclic substrates were tolerated in the reaction conditions, affording the corresponding products in good to excellent yields. This method was applied to the preparation of novel sulfone-containing DPP-IV inhibitors.

Allergic Contact Dermatitis from Luliconazole: Implication of the Dithioacetal Structure

This article does not have an abstract.

Unexpected Microwave Reaction of 1,3‐Disubstituted Imidazolium Salts: A Novel Synthesis of 1,3‐Disubstituted Imidazole‐2‐thiones

Microwave‐promoted reaction of 1,3‐disubstituted imidazolium salts with potassium thioacetate or potassium thiocyanate under solvent‐free conditions provided a rapid and efficient synthesis of 1,3‐disubstituted imidazole‐2‐thiones.

Ancillary Ligand Functionalization of Cyanide-Bridged S = 6 FeIII4NiII4 Complexes for Molecule-Based Electronics

Treatment of 1-chloro-6-iodohexane or 1-chloro-10-iododecane with lithium tris(pyrazolyl)methanide, followed by potassium thioacetate, affords bifunctional 1-S(acetyl)-tris(pyrazolyl)alkanes (L) (pz)3C(CH2)nSAc (n = 6, 1; 10, 2). Magnetic studies of {[(pzTp)Fe(III)(CN)3]4[Ni(II)L]4[OTf]4}.solvent (4, L = 1; 5, L = 2) boxes suggest that -(CH2)6 chains (4) limit intermolecular interactions while -(CH2)10 chains in 5 introduce crystallographic disorder and a distribution of relaxation times; 4 and 5 exhibit slow relaxation of the magnetization.

Photoinduced Nucleophilic Substitution of Aryl Halides with Potassium Thioacetate – A One‐Pot Approach to Aryl Methyl and Diaryl Sulfides

AbstractAryl methyl sulfides and diaryl sulfides were prepared by photoinduced reactions of potassium thioacetate with aryl halides under entrainment conditions. Without isolation, the arene thiolates obtained by the aromatic substitution were quenched with methyl iodide to afford the aryl methyl sulfides in 26–59 % yields in a “one‐pot” procedure together with the diaryl sulfides in variable yields (3–31 %). By optimization of the reaction conditions it was possible to improve the formation of the Ar2S, going from moderate to good yields (64–83 %). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

SOLID STATE DEPROTECTION OF THIOACETALS AND THIOKETALS USING 1-BENZYL-4-AZA-1-AZONIABICYCLO[2.2.2]OCTANE PERIODATE AND ALUMINUM CHLORIDE

(2005). SOLID STATE DEPROTECTION OF THIOACETALS AND THIOKETALS USING 1-BENZYL-4-AZA-1-AZONIABICYCLO[2.2.2]OCTANE PERIODATE AND ALUMINUM CHLORIDE. Organic Preparations and Procedures International: Vol. 37, No. 3, pp. 298-303.

A Convenient Synthesis of Thioacetates and Thiobenzoates Using Silica-Gel Supported Potassium Thioacetate and Thiobenzoate

Abstract

First synthesis of 4,5- O-isopropylidene-6-thio- d-galactono-1,6-lactone as a precursor of d-galactothioseptanose

Displacement of the bromide group in methyl 6-bromo-6-deoxy-2,3:4,5-di- O-isopropylidene- d-galactonate 7, with potassium thioacetate gave methyl 6-( S)-acetyl-2,3:4,5-di- O-isopropylidene-6-thio- d-galactonate 8 in quantitative yield. Regioselective removal of the 2,3-ketal protecting group afforded methyl 6-( S)-acetyl-4,5- O-isopropylidene-6-thio- d-galactonate 11 in 70% yield. Saponification of compound 11 gave the 6-( S)-4,5- O-isopropylidene-6-thio- d-galactonic acid 12 in quantitative yield. Treatment of 12 with DIC/HOBt as coupling reagents gave, after cyclisation; the target compound: 4,5- O-isopropylidene 6-thio- d-galactono-1,6-lactone 13 in 49% yield.

Synthesis and cytotoxicity of 9-(2-deoxy-2-alkyldithio-beta-D-arabinofuranosyl)purine nucleosides which are stable precursors to potential mechanistic probes of ribonucleotide reductases.

A series of 2[prime or minute]-thionucleosides, as potential inhibitors of ribonucleotide reductases, has been synthesized. Treatment of the 3[prime or minute],5[prime or minute]-O-TPDS-2[prime or minute]-O-(trifluoromethanesulfonyl)adenosine with potassium thioacetate gave the arabino epimer of 2[prime or minute]-S-acetyl-2[prime or minute]-thioadenosine which was deacetylated to give 9-(3,5-O-TPDS-2-thio-[small beta]-d-arabinofuranosyl)adenine in high yield. Treatment of the latter with diethyl azodicarboxylate-C(3)H(7)SH-THF gave 2[prime or minute]-propyl disulfide which was desilylated to give 9-(2-deoxy-2-propyldithio-[small beta]-d-arabinofuranosyl)adenine. Subsequent tosylation (O5[prime or minute]) and displacement of the tosylate with pyrophosphate afforded the 5[prime or minute]-O-diphosphate in a stable form as propyl mixed-disulfide, which upon treatment with dithiothreitol releases 9-(2-thio-[small beta]-d-arabinofuranosyl)adenine 5[prime or minute]-diphosphate. The arabino 2[prime or minute]-mercapto group might interact with the crucial thiyl radical at cysteine 439 leading to the inhibition of ribonucleotide reductases via formation of a Cys439-2[prime or minute]-mercapto disulfide bridge. The 2,6-diamino-, 2-amino-6-chloro- and 2-amino-6-methoxypurine ribosides were also converted to the corresponding 2[prime or minute]-deoxy-2[prime or minute]-propyldithio-[small beta]-d-arabinofuranosyl nucleosides, which might serve as convenient precursors to the arabino epimer of 2[prime or minute]-thioguanosine. Analogously, 2[prime or minute]-deoxy-2[prime or minute]-propyldithioadenosine was prepared from 9-([small beta]-d-arabinofuranosyl)adenine. The nucleoside disulfides show modest cytotoxicity in a panel of human tumor cell lines.

Synthesis of 4- C-sulfoaminosugar derivatives: isomerization of 4- C-sulfogalactosamine to its gluco epimer

Methyl 2-benzamido-3,6-di- O-benzoyl-2,4-dideoxy-α- d-glucopyranoside-4- C-sulfonate sodium salt 9 and its galacto epimer 10 were prepared by oxidation with hydrogen peroxide in acetic acid of methyl 4- S-acetyl-2-benzamido-3,6-di- O-benzoyl-2-deoxy-4-thio-α- d-glucopyranoside 7 and its galacto epimer 8, respectively. The 4-thioglucoside 7 was prepared from methyl 2-benzamido-3,6-di- O-benzoyl-2-deoxy-α- d-glucopyranoside by double inversion through triflation, inversion at C-4 with NaNO 2, triflation of the resulting methyl 2-benzamido-3,6-di- O-benzoyl-2-deoxy-α- d-galactopyranoside, followed by displacement with potassium thioacetate. Deacylation of 9 with refluxing aqueous sodium hydroxide followed by deionisation yielded methyl 2-amino-2,4-dideoxy-α- d-glucopyranoside-4- C-sulfonic acid 11. Deacylation of the galactopyranoside 10 under the same conditions also gave 11, due to base catalysed isomerisation of galacto to the more stable gluco configuration. The structure of 11, crystallized as the monohydrate, was confirmed by X-ray crystallographic analysis. The asymmetric unit contains two sugar molecules in two unique but similar conformations and two water molecules. The sulfo and the amino groups form a zwitterion, with each ammonium group hydrogen bonded to the sulfonate groups of two other molecules related by symmetry.

A Convenient Synthesis of Thioacetates and Thiobenzoates Using Silica-Gel Supported Potassium Thioacetate

A simple and efficient procedure has been developed for the synthesis of thioesters by a reaction of alkyl halides with silica-gel supported potassium thioacetate or thiobenzoate under mild conditions.

Synthesis and Tin(IV) Coordination Chemistry of the Novel Tripod N(CH2CH2CH2SH)3

The novel tetradentate ligand N(CH2CH2CH2SH)3, H3 - 5 was synthesized from tripropanolamine via the trichloride, subsequent reaction with potassium thioacetate and reduction with LiAlH4. Ligand H3 -5 reacts with MeSnCl3 under formation of the centrosymmetric dinuclear complex [MeSn(5)]2, 6, which was shown by X-ray structure analysis to contain two tetrahedrally coordinated tin atoms and two bridging thiolato functions.

Siloxane-anchored thin films on silicon dioxide-modified stainless steel

Siloxane-anchored self-assembled monolayers have been obtained on stainless steel. Initially the surface of the material was treated with tetraalkylorthosilicate in order to obtain a thin layer of SiO 2 (<3 nm). This layer effectively anchors the subsequent attachment of alkyl trialkoxysilanes like octadecyltrimethoxysilane. Some of the versatility of this approach was demonstrated by depositing thioacetate (TA)–hexadecyltrimethoxysilane on SiO 2-modified stainless steel and forming a TA functionalized film. In situ oxidation of the TA groups yielded a sulfonate-functionalized surface that was used to promote deposition of an adherent, pore-free, TiO 2 layer from aqueous solution onto the stainless steel substrate.

Preparations of Heterospirostanols and Their Pharmacological Activities.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Preparations of heterospirostanols and their pharmacological activities

(3β,20 S,22 S,25 R)-22-Thiospirosol-5-en-3-ol ( 9) and (3β,20 S,22 S,25 R)-22-seleno-spirosol-5-en-3-ol ( 11) were prepared from diosgenin ( 3) via 26-iodopseudodiosgenin ( 6) as a key intermediate. Diosgenone ( 15), solasodinone ( 16), (20 S,22 S,25 R)-22-thio-spirosol-4-en-3-one ( 17), (20 S,22 S,25 R)-22-selenospirosol-4-en-3-one ( 18) and (20 R,22 S,25 R)-spirosol-4-en-3-one ( 19) were prepared by Oppenauer oxidation of 3, solasodine 4, 9, 11 and (3β,20 R,22 R,25 R)-spirosol-5-en-3-ol 14, respectively. Oxidations of 15 and 16 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) provided corresponding dienone products, (20 S,22 S,25 R)-spirosol-1,4-dien-3-one ( 20) and (20 S,22 S,25 R)-22-thiospirosol-1,4-dien-3-one ( 21), respectively, while oxidation of 19 (C-20 diastereoisomer of 15) gave no dienone product but 21-exo vinyl product 22. 26-Thioacetylpseudodiosgenone ( 24) and 26-cyanoselenopseudodiosgenone ( 25) were prepared by treatment of 26-iodopseudodiosgenose ( 23), which was obtained by Oppenauer oxidation of 6, with potassium thioacetate and potassium selenocyanate, respectively. Compounds 15 and 19 exhibited more than 80% inhibitions in INF-γ productions at 10.0 μM. Compounds 4 and 25 showed cytotoxic activities (IC 50=6 and 5 μM, respectively) against cancerous HCT 116 cell lines. Compounds 12 and 25 had antiurease activities (IC 50=12.4 and 11.4 μM, respectively), in which only the latter showed an inhibition zone (mean zone diameter=12.2 mm) formed by Bacillus subtilis 168 trp.