Quantum chemical studies of mechanisms of organic reactions: VI. Reaction of ethane-1,2-dithiol with vinylidene chloride

A theoretical mechanism has been proposed for the reaction of vinylidene chloride with ethane-1,2-dithiol in the system hydrazine hydrate–potassium hydroxide on the basis of DFT quantum chemical calculations at the B3LYP/6-311++G(d,p) level of theory. The reaction includes two consecutive stages: dehydrochlorination of vinylidene chloride to chloroacetylene and nucleophilic addition of one thiol group of ethane-1,2-dithiol to the β-carbon atom of chloroacetylene, followed by closure of 2,3-dihydro-1,4-dithiine ring via nucleophilic substitution of chlorine by sulfur atom of the second thiol group.     

Quantum chemical study of mechanisms of organic reactions: V. Addition of ethane-1,2-dithiol to 4-hydroxy-4-methylpent-2-ynenitrile

The mechanism of nucleophilic addition of ethane-1,2-dithiol to 4-hydroxy-4-methylpent-2-ynenitrile has been studied at the DFT B3LYP/6-311++G(d,p) level of theory. The base-catalyzed reaction involves nucleophilic attack by deprotonated ethane-1,2-dithiol on the ß-carbon atom of the nitrile with formation of intermediate Z-vinylic carbanion which undergoes intramolecular cyclization with closure of 1,3-dithiolane ring. Further transformation of 2-[2-(2-hydroxypropan-2-yl)-1,3-dithiolan-2-yl]acetonitrile to 6,6-dimethyl-7-oxo-1,4-dithiaspiro[4.4]nonan-8-imine has also been studied.     

Quinoxaline-2,3-dithiol in reactions with propargyl bromide and 1,3-dibromopropyne

Propargyl bromide with quinoxaline-2,3-dithiol in DMSO in the presence of K₂CO₃ affords 2,3-bis-(2-propynylsulfanyl)quinoxaline in good yield whereas in absolute methanol in the presence of sodium methoxide at 20°C a 1:2 mixture of 2,3-bis(2-propynylsulfanyl)quinoxaline and 3-(2-propynylsulfanyl)-2(1H)-quinoxalinethione is formed. Individual 3-(2-propynylsulfanyl)-2(1H)-quinoxalinethione was obtained by crystallization of this mixture from ether. The reaction of 1,3-dibromopropyne with quinoxaline-2,3-dithiol in ethanol in the presence of NaOH at heating results in 2-bromomethylidene-1,4-(3H)-dithiino[2,3-b]quinoxaline in 77% yield. Performing this reaction in methanol in the presence of sodium methoxide during long heating (16 h) led to 2,3-bis[(3-bromo-2-propynyl)sulfanyl]quinoxaline in 72% yield.     

Rhodium-catalyzed hydrothiolation of alkynes with thiols for construction of sulfur-containing π-conjugated systems

To synthesize sulfur-containing π-conjugated polymers, reaction conditions for rhodium-catalyzed hydrothiolation of terminal alkynes with arenethiols are optimized in detail. Under the optimized conditions, rhodium-catalyzed hydrothiolation of terminal alkynes proceeds regio- and stereoselectively to afford the corresponding vinyl sulfides via an anti-Markovnikov and syn-addition process. Then, the rhodium-catalyzed hydrothiolation is applied to polymerization of 2,5-diethynylthiophene with benzene-1,4-dithiol, which successfully provides sulfur-containing π-conjugated polymers with excellent regio- and stereoselectivities.     

Synthesis of unsaturated 1,4-heteroatom-containing benzo-fused heterocycles using a sequential isomerization-ring-closing metathesis strategy

A small library of 1,4-benzodioxins and 4H-1,4-benzoxazines was synthesized from the corresponding bis-allyloxy precursors by way of an initial isomerization to the bis-vinyloxy compounds, followed by a ring-closing metathesis using the second generation Grubbs' catalyst (G2). A related strategy, starting from benzene-1,2-dithiol and 2-mercaptophenol, afforded benzodithiin and 1,4-benzoxathiin, respectively.     

Oxidation of 2-Chloro-1-phenylethane-1,1-dithiol

Oxidation of 2-chloro-1-phenylethane-1,1-dithiol with bromine, iodine, and elemental sulfur, as well as under UV irradiation, leads to formation of 1,4-bis(chloromethyl)-1,4-diphenyl-2,3,5,6-tetrathiane in 50–95% yield. Oxidation of the same substrate with selenium dioxide gives 1,5-bis(chloromethyl)-1,5-diphenyl-2,4-dithia-3-selenapentane-1,5-dithiol. On heating to 60°C, the latter loses selenium to afford 1,4-bis-(chloromethyl)-1,4-diphenyl-2,3-dithiabutane-1,4-dithiol.     

Synthesis of 3-hetaryl-1,5,3-dithiazepanes and 3-hetaryl-1,5,3-dithiazocanes in the presence of catalysts based on transition metals

Efficient procedure was developed for 3-hetaryl-1,5,3-dithiazepanes and 3-hetaryl-1,5,3-dithiazocanes preparation from hetarylamines, N,N,N′,N′-tetramethylmethanediamine, and α,ω-alkanedithiols (ethane-1,2-dithiol, propane-1,3-dithiol), and also by the reaction of the latter with N,N-bis(methoxymethyl)hetarylamines in the presence of catalytic quantities of transition metals salts.     

Addition of 1,2- and 1,3-Dithiols to 2-alkoxypropenals - a New Method for the Production of Substituted Dithiacycloalkanes

The reaction of 2-alkoxypropenals with ethane-1,2-dithiols and propane-1,3-dithiols under various conditions was studied by ¹H NMR and chromato-mass spectrometry. Under kinetically controlled conditions at 20° in the absence of catalysts the addition of dithiols takes place according to the Markovnikov rule. The primary adducts are unstable and are quickly converted into the corresponding substituted 1,4-dithiacycloheptane or 1,4-dithiane. The latter in turn can be converted under the reaction conditions or at high temperature into a thiolane derivative. The reaction of 2-ethoxypropenal with a twofold excess of ethane-1,2-dithiol at 60°C in the presence of p-toluenesulfonic acid leads to 2-methyl-2,2'-bi(dithiolane)     

1,4-Dithiafulvene aus der Umsetzung von 4,4-disubstituierten 1,3-Thiazol-5(4H)-thionen mit Acetylenderivaten

1,4-Dithiafulvenes, Products of the Reaction of 4,4-Disubstituted 1,3-Thiazol-5(4H)-thiones and Acetylenic Compounds On heating in toluene, 4,4-disubstituted 1,3-thiazol-5(4H)-thiones 1 and acetylenecarboxylates or acetylenecarbonitriles 2 undergo a cyclosubstitution reaction to yield 2-methylidene-1,3-dithiol derivatives 3 (1,4-dithiafulvenes) and a nitrile. Further heating of 3a and 3b in the presence of excess 2a leads to the isomeric 2,3-dihydrothiophene-2-thiones 4a and 4b , respectively. The benzodithiafulvene 14 has been formed in a similar reaction from 1a and in situ generate benzyne.     

Multicomponent reactions of amino alcohols with CH2O and dithiols in the synthesis of 1,3,5-dithiazepanes and macroheterocycles

A series of new hydroxyl-substituted 1,3,5-dithiazepanes and N,N′-(2-hydroxyethyl)tetrathiadiazacycloalkanes were synthesized by the multicomponent reactions ₍MCRs) of amino alcohols with formaldehyde and α,ω-dithiols. The MCR with 1,2-dithiol proceeds via a (1+2+1)-cyclocondensation with selective formation of 1,3,5-dithiazepanes. Stereochemistry of the dithiazepane ring was determined by X-ray diffraction. The reaction with higher α,ω-dithiols (1,3-propane-, 1,4-butane-, 1,5-pentane-, 1,6-hexanedithiol and 2-[2-(2-sulfanyletoxy)ethoxy]-1-ethanethiol) yielded OH-substituted macroheterocycles as a result of (2+4+2)-cyclocondensation. The structure of the latter was determined by NMR spectroscopy, MALDI–TOF and electrospray ionization methods. The doubly charged ions like [M+2H]²⁺ are found in the ESI spectra of the macrocycles.     

One-pot synthesis of fluorinated terphenyls by site-selective Suzuki-Miyaura reactions of 1,4-dibromo-2-fluorobenzene

The Suzuki-Miyaura reaction of 1,4-dibromo-2-fluorobenzene with two equivalents of arylboronic acids gave fluorinated para-terphenyls. The reaction with 1 equiv of arylboronic acid resulted in site-selective formation of biphenyls. The one-pot reaction of 1,4-dibromo-2-fluorobenzene with two different arylboronic acids afforded fluorinated para-terphenyls containing two different terminal aryl groups.     

Phenylethinyl-[1,3,2]dithiaphospholan. Bis(dithiaphospholanyl)-[1,4]dithian

Phenylethinyl-[1,3,2]dithiaphospholane. Bis(dithiaphospholanyl)-[1,4]dithiane Nucleophilic substitution of the amino group but no cycloaddition occurs in the reaction of phenyl phenylethinyl phosphinous acid diethylamide, 5 , with 2-aminothiophenol forming compound 6 . By analogous reaction, phenylethinyl phosphonic bis(diethylamide), 7 , and ethane-1,2-dithiol form compound 8 . Cycloaddition besides nucleophilic substitution is observed, however, when acetylene bis(phosphonic diethyl-amide), 9 , and ethane-1,2-dithiol are reacted resulting in compound 11 . All new products are characterized by their nmr, mass, and i.r. spectra. Furthermore, the results of an X-ray structure analysis of 11 are reported.     

Two isomeric fourteen-membered bis-dithioacetals derived from (<Emphasis Type="Italic">Z</Emphasis>)- and (<Emphasis Type="Italic">E</Emphasis>)-but-2-ene-1,4-dithiols

(Z)-But-2-ene-1,4-dithiol was found to undergo isomerization into the E isomer. Condensation of (Z)- and (E)-but-2-ene-1,4-dithiols with acetaldehyde gave isomeric fourteen-membered bis-dithioacetals whose structure was determined by X-ray analysis.     

Novel sequence of two base-catalyzed 1,3 proton shifts and [1,2] Wittig rearrangement in the synthesis of 2,4-bis-(trifluoromethyl)-6-phenylpyridine

The reaction of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione with (R)-phenylglycinol was found to proceed via intermediate formation of (R, 4E, 6Z)-5,7-bis-(trifluoromethyl)-2,3-dihydro-3-phenyl-1,4-oxazepine which further underwent a base-catalyzed 1,3-proton shift reaction followed by [1,2] Wittig rearrangement giving rise to 2,4-bis-(trifluoromethyl)-6-phenylpyridine.     

Heterocyclization of dimethyl malonate with SH acids and formaldehyde in the presence of catalysts

Three-component heterocyclization of dimethyl malonate with SH acids (H₂S, ethane-1,2-dithiol) and formaldehyde in the presence of 5 mol % of transition metal chlorides (FeCl₃, CoCl₂, NiCl₂) gave dimethyl 1,3-dithiane-5,5-dicarboxylate and dimethyl 1,4-dithiepane-6,6-dicarboxylate. The reactions in the presence of transition metal chlorides hydrates were accompanied by Krapcho decarboxylation with formation of methyl 1,3-dithiane-5-carboxylate and methyl 1,4-dithiepane-6-carboxylate.     

One-pot synthesis of bis-1,5,3-dithiazepanes from ethane-1,2-dithiol, formaldehyde, and ammonium salts

An efficient one-pot procedure has been developed for the synthesis of bis-1,5,3-dithiazepanes by reaction of ethane-1,2-dithiol with formaldehyde and ammonium salts. According to the X-ray diffraction data, the heterorings in 3,3′-[ethane-1,2-diylbis(sulfanediylmethanediyl)]bis(1,5,3-dithiazepane) in crystal adopt a chair conformation with axial orientation of the substituent on the nitrogen atom.     

Synthesis of (arylselanyl)- and (arylsulfenyl)-alkyl-1,2,3-triazolo-1,3,6-triazonines via a copper-catalyzed multicomponent reaction

An efficient copper-catalyzed multicomponent reaction was developed for the synthesis of (arylselanyl)- or (arylsulfenyl)-alkyl-1,2,3-triazolo-1,3,6-triazonines. The products were obtained in moderate to excellent yields via the reaction of o-phenylenediamine, 2-azidobenzaldehyde and different arylchalcogenyl alkynes using catalytic copper iodide in 1,4-dioxane at 100?°C. The reactions tolerated a range of substituents on the arylchalcogenyl alkynes and proved to be an efficient methodology for the combinatorial synthesis of new selenium or sulfur-containing triazonine derivatives.     

Concentration-Dependent Seeding as a Strategy for Fabrication of Densely Packed Surface-Mounted Metal–Organic Frameworks (SURMOF) Layers

The layer-by-layer (LbL) method is a well-established method for the growth of surface-attached metal–organic frameworks (SURMOFs). Various experimental parameters, such as surface functionalization or temperature, have been identified as essential in the past. In this study, inspired by these recent insights regarding the LbL SURMOF growth mechanism, the impact of reactant solutions concentration on LbL growth of the Cu₂(F₄bdc)₂(dabco) SURMOF (F₄bdc²⁻=tetrafluorobenzene-1,4-dicarboxylate and dabco=1,4-diazabicyclo-[2.2.2]octane) in situ by using quartz-crystal microbalance and ex situ with a combination of spectroscopic, diffraction and microscopy techniques was investigated. It was found that number, size, and morphology of MOF crystallites are strongly influenced by the reagent concentration. By adjusting the interplay of nucleation and growth, we were able to produce densely packed, yet thin films, which are highly desired for a variety of SURMOF applications.     

Revisited synthesis of fused diazepines from 3-(3-aryl-3-oxopropenyl)chromen-4-ones and binucleophilic amino enones in a three-step domino process

The synthesis of tetracyclic 11,12,13,14b-tetrahydrodi-benzo[b, f]pyrido[1,2-d][1,4]diazepines was revisited via a catalyst-free three-step domino reaction involving a pyrone ring-opening/aza-Michael addition/intramolecular cyclization, the reactants having been o-arylenediamine–dimedone adducts and 3-(3-aryl-3-oxopropenyl)chromen-4-ones. The 3-positioned exocyclic α,β-enone fragment on the chromone moiety is involved in the cyclization into the final products at the last step of the process.     

Oxidations catalyzed by osmium compounds. Part 1: Efficient alkane oxidation with peroxides catalyzed by an olefin carbonyl osmium(0) complex

A carbonyl osmium(0) complex with π-coordinated olefin, (2,3-η-1,4-diphenylbut-2-en-1,4-dione)undecacarbonyl triangulotriosmium (1), efficiently catalyzes oxygenation of alkanes (cyclohexane, cyclooctane, n-heptane, isooctane, etc.) with hydrogen peroxide, as well as with tert-butyl hydroperoxide and meta-chloroperoxybenzoic acid in acetonitrile solution. Alkanes are oxidized to corresponding alcohols, ketones (aldehydes) and alkyl hydroperoxides. Thus, heating cyclooctane with the 1-H₂O₂ combination at 70 °C gave products with turnover number as high as 2400 after 6 h. The maximum obtained yield of all products was equal to 20% based on cyclohexane and 30% based on H₂O₂. The oxidation of linear and branched alkanes exhibits very low regio- and bond-selectivity parameters and this testifies that the reaction proceeds via attack of hydroxyl radicals on C-H bonds of the alkane. The oxygenation products were not formed when the reaction was carried out under argon atmosphere and it can be thus concluded that the oxygenation occurs via the reaction between alkyl radicals and atmospheric oxygen. In summary, the Os(0) complex is much more powerful generator of hydroxyl radicals than any soluble derivative of iron (which is an analogue of osmium in the Periodic System).