Electrochemically controlled hydrogen bonding. Redox-dependent formation of a 2:1 diarylurea/dinitrobenzene2- complex

[reaction: see text] The electrochemistry of 1,2-dinitrobenzene (1,2-DNB), 1,3-dinitrobenzene (1,3-DNB), and 1,4-dinitrobenzene (1,4-DNB) is strongly affected by the presence of 1,3-diphenylurea. In DMF, the second reduction potential of all three DNBs shifts substantially positive in the presence of the urea, indicating very strong hydrogen bonding to the dianions. With 1,2- and 1,3-DNB, the hydrogen bonding leads to irreversible chemistry, likely due to proton transfer from the urea to the dianions. No such irreversible behavior is observed with 1,4-DNB. Instead, the second reduction shifts into the first reduction, producing a single, reversible, two-electron cyclic voltammetric wave at high urea concentrations. Computer simulations show that the changes in wave shape accompanying this process are well accounted for by the stepwise formation of a 1:1 and 2:1 1,3-diphenylurea/DNB2- complex, with sequential binding constants of approximately 5.5 x 10(4) M(-1) and approximately 4.0 x 10(3) M(-1) in DMF.     

Detection of organic gunshot residues from human hands using direct sample analysis-time of flight-mass spectrometry

The organic gunshot residues (OGSRs), specifically methyl centralite (MC; 1,3-dimethyl-1,3-diphenylurea), ethyl centralite (EC; 1,3-diethyl-1,3-diphenylurea), 2,4-DNT (2,4-dinitrotoluene), and TNT (trinitrotoluene), are characteristic compounds for which forensic analysts test determining if a person has discharged a firearm. A set of 200 samples from 50 shooters were collected as part of the validation study. Pistol 9 mm and special revolver .38 were fired at indoor and outdoor shooting ranges. The development of a methodology based on direct analysis of samples-time of flight-mass spectrometry (DSA-TOF-MS) made it possible to identify the main components of organic shot residues, which gave the possibility to introduce a new method of analysis of shot residues in the Chilean supply area. The DSA-TOF-MS provided extensive information on the composition of the shot residues: MC, EC, 2,4-DNT, and TNT. Samples taken from the trigger hands required minimal sample preparation that reduced analyses time. With the implementation of new alternative analytical methodologies, a great step would be taken in the analysis of OGSRs, because now there is no such technique for its analysis in Chile, and the results would also complement the existing inorganic elemental analyses generated during a gunshot.     

Highly efficient synthesis of stereodefined multisubstituted 1,4-dicyano- and 1-cyano-1,3-butadienes and their reactions with organolithium reagents

Stereodefined multisubstituted 1-cyano- and 1,4-dicyano-1,3-butadiene derivatives were obtained in excellent yields of the isolated product from their corresponding monohalo- and dihalobutadienes and CuCN. This reaction proceeded with high stereoselectivity and retention of the stereochemistry of the starting halobutadienes. A study of the utility of the thus-obtained 1-cyano- and 1,4-dicyano-1,3-butadiene derivatives was demonstrated by their reactions with organolithium reagents. 2H-Pyrrole or iminocyclopentadiene derivatives were formed in high yields from 1-cyano-4-halo-1,3-butadienes and organolithium reagents. When 1,4-dicyano-1,3-butadienes were treated with organolithium reagents followed by trapping with electrophiles, a tandem process took place to afford 2H-pyrrolyl nitriles in excellent yields. Reduction of 1,4-dicyano-1,3-butadiene derivatives with LiAlH4 showed novel reaction patterns relative to normal nitriles.     

Reaction of 1,3-diaryl-2,3-dibromo-1-propanones with urea in basic and acidic medium. Synthesis of pyrimidine,imidazoline and imidazolidine derivatives

Reaction of 1,3-diaryl-2,3-dibromo-1-propanones 1 with urea in basic medium afforded 4,6-diaryl-5-bromo-5,6-dihydropyrimidine-2(1H)-ones 4 . Oxidation of these bromopyrimidines 4 in dimethylsulphoxide gave 4,6-diaryl-1,6-dihydropyrimidine-2,5-diones 6 , which were further converted to their thione analogues 7 . Reaction of 1,3-diaryl-2,3-dibromo-1-propanones 1 with urea, phenylurea and sym-diphenylurea in glacial acetic acid medium gave in appreciable yields 4-phenyl-5-α-(bromoarylmethyl)imidazolin-2-one 8 and 1,3-diphenyl-4-aroyl-5-arylimidazolidin-2-one 11 respectively.     

Formanilide and carbanilide from aniline and carbon dioxide

Earlier syntheses of formamides from the catalytic hydrogenation of CO₂ in the presence of amines were only successful for the preparation of dialkylformamides. After an analysis of the reason for the failure of the reaction using aniline as a starting material, formanilide has been prepared, for the first time, from CO₂, H₂ and aniline with the use of 1,8-diazabicyclo[5.4.0]undec-7-ene. Omission of the H₂ reductant causes the selectivity to switch to the production of carbanilide (1,3-diphenylurea).     

Reaction of <Emphasis Type="Italic">N</Emphasis>-phenyltriflamide with 1,2-dibromoethane and propargyl bromide. Unexpected cleavage of С–С and С–N bonds

Reaction of N-phenyltriflamide with 1,2-dibromoethane under basic conditions in DMSO unexpectedly results in N-methyl-N-phenyltriflamide and 1,3-diphenylurea. The presumed reaction mechanism includes the formation of unstable intermediate disubstitution product TfN(Ph)CH₂CH2N(Ph)Tf that suffers the the С–С bond cleavage resulting in TfN(Me)Ph and N,N′-methanediylbis(N-phenyltriflamide). The latter reacts with K₂CO₃ releasing two molecules of potassium triflinate and after hydrolysis of diphenylcarbodiimide PhN=C=NPh gives 1,3-diphenylurea. With propargyl bromide, N-phenyltriflamide affords N-propargyl-Nphenyltriflamide in high yield. The bromination of the latter results in a mixture of Z,E-isomers of N-(2,3-dibromoprop-2-en-1-yl)-N-phenyltriflamide which undergo dehydrobromination giving first N-(3-bromopropanedienyl)-N-phenyltriflamide and then the products of the C–N bond cleavage: N-phenyltriflamide and 3,3-dimethoxyprop-1-yne.     

Synthesis of Arsenical Adduct: Synthesis and Transformation of Dimercapto Compound to Arsenical Adduct

Reaction of isothiocyanates with thioamide in presence of pyridine afforded 1,3-dimercapto substrates in good yield. Adipoin reacts with phenylarsine oxide and triphenylarsine to give the bicyclic 1,3,2-dioxarsole derivatives. A variety of 1,3,2-arsadithiolane derivatives were obtained by reaction of 1,3-dimercapto substrate with arsenic trioxide, phenylarsine oxide, triphenylarsine triphenylarsine oxide in ethanol or better in chloroform.     

An efficient one‐pot synthesis of dispiropyrrolidine derivatives through 1,3‐dipolar cycloaddition reactions under ultrasound irradiation

A series of dispiropyrrolidine derivatives were synthesized via the three‐component 1,3‐dipolar cycloaddition reaction of isatin, sarcosine and 5‐arylidene‐1,3‐thiazolidine‐2,4‐dione or 5‐arylidene‐4‐thioxo‐1,3‐thiazolidine‐2‐one in ethanol under ultrasound irradiation. This protocol has the advantages of mild reaction conditions, higher yields, and shorter reaction time. J. Heterocyclic Chem., (2011).     

An easy access to novel steroidal dispiropyrrolidines through 1,3-dipolar cycloaddition of azomethine ylides

A facile one-pot synthesis of novel steroidal dispiropyrrolidines has been accomplished by 1,3-dipolar cycloaddition reaction of various azomethine ylides derived from isatin/acenaphthenequinone/ninhydrin and sarcosine with various estrone derivatives as dipolarophiles, in good yield. The effect of various solvents on the 1,3-dipolar cycloaddition reaction are also studied.     

Electrochemically controlled hydrogen bonding. Nitrobenzenes as simple redox-dependent receptors for arylureas

Reduction of nitrobenzene derivatives in the presence of arylureas in aprotic solvents results in large positive shifts in potential of the nitrobenzene(0/)(-) cyclic voltammetry wave with little change in wave shape. This behavior is indicative of reversible hydrogen bonding between nitrobenzene radical anions and arylureas. Computer fitting of the cyclic voltammetry of 4-nitroaniline, NA, plus 1,3-diphenylurea in DMF shows essentially no binding between urea and NA in the oxidized state (K(ox) < 1 M(-)(1)), but very strong binding in the reduced state (K(red) = 8 x 10(4) M(-)(1)), along with very rapid rates of hydrogen bond formation (k(f)'s approximately 10(8)-10(10) M(-)(1) s(-)(1)), making this system a fast on/off redox switch.     

A novel[2 + 3]cycloaddition reaction: singlet oxygen mediated formation of 1,3-dipole from iminodiacetic acid dimethyl ester and its addition to maleimides

Sensitized photolysis of iminodiacetic acid methyl ester and maleimides follows a [2 + 3] cycloaddition pathway yielding pyrrolidine derivatives. This is similar to the photochemical reaction between C(60) and amines. A series of pyrrolidine derivatives are prepared by the method including multipyrrolidines from bis- and tris-maleimide starting materials. The yields range from 13% to 85%. The reaction is highly stereoselective. All the isolated products have the 1,3-dimethoxycarbonyl groups in the cis configuration. Various sensitizers may be used with slightly different yields. A plausible mechanism is proposed that involves the singlet oxygen abstraction of two alpha hydrogen atoms from the iminodiacetate and formation of a 1,3-dipole with a structure similar to the classical thermally generated 1,3-dipole.     

Synthesis and characterization of acrylated phosphonates and their polymers having 1,3-dioxolane and 1,3-dioxane moieties derived from brominated cyclic acetals of polyols through the Arbuzov reaction. II

Glycerol, D -mannitol, and D -sorbitol were converted into their mono- and di-O-1,3-dioxolane and 1,3-dioxane bromoethylidene derivatives through a transacetalation reaction with bormoacetaldehyde diethyl acetal under controlled conditions. These brominated dioxolane or dioxane derivatives were subsequently phosphonylated through the Arbuzov reaction. The phosphonylated cyclic acetals were used as precursors for the synthesis of acrylated phosphonate monomers. All these compounds have been characterized by elemental analysis and spectroscopic (IR, ¹H-,¹³C-, ³¹P-NMR and mass) methods. A mixture of 1,3-dioxane and 1,3-dioxolane derivatives was obtained with D -sorbitol, whereas the reaction products with glycerol and D -mannitol yielded primarily the 1,3-dioxolane derivatives. The acrylated phosphonates of glycerol and mannitol have been polymerized and studied on the basis of gel permeation chromatography and their spectral and thermal properties. The acrylated phosphonates, monomers, and polymers, were shown to have a large capacity to solvate and dissolve heavy metal salts. This results in a dramatic increase (> 100°C) of the glass transition temperature of these polymers.     

New and practical method for synthesis of 1- and 1,3-substituted xanthines.

[reaction: see text] A new and practical method for the synthesis of 1- and 1,3-substituted xanthines is reported. Direct base-promoted condensation of the imidazole precursor 1 with carbamates 2 gives 1-substituted 7-PMB xanthines 7 in good yields. Alkylation of these derivatives or their potassium salts proceeds under mild conditions to give functionalized 1,3-substituted 7-PMB xanthines 9 in good to excellent yields. The obtained 7-PMB-protected derivatives can be readily deprotected to give the parent 1- and 1,3-substituted xanthines.     

Catalytic enantioselective 1,3-dipolar cycloadditions of nitrones with propioloylpyrazoles and acryloylpyrazoles induced by chiral π-cation catalysts

A chiral copper(II) complex of 3-(2-naphthyl)-l-alanine amide successfully catalyzes the enantioselective 1,3-dipolar cycloaddition reaction of nitrones with propioloylpyrazole and acryloylpyrazole derivatives. The asymmetric environment created by intramolecular π-cation interaction gives the corresponding adducts in high yields with excellent enantioselectivity. This is the first successful method for the catalytic enantioselective 1,3-dipolar cycloaddition of nitrones with acetylene derivatives. The 1,3-dipolar cycloadducts can be stereoselectively converted to β-lactams via reductive cleavage of the N-O bond using SmI(2).     

Facile synthesis of oxaspirobicyclic butenolides via a domino Michael addition/aldol reaction/γ-lactonization sequence

A three-component domino reaction approach between a primary amine, a dialkyl acetylenedicarboxylate, and 1,3-dimethylalloxan that affords novel oxaspirobicyclic γ-butenolidobarbiturate derivatives is reported. The reaction sequence consists of an initial Michael-addition of primary amines to dialkyl acetylenedicarboxylates, followed by aldol-like reaction with 1,3-dimethylalloxan, and then γ-lactonization to afford the products. This cascade reaction sequence represents a rapid and unprecedented route to the described biologically interesting molecules.     

Synthesis of Spiro Pyrrolobenzothiazole Derivatives via a Three‐Component Reaction

A novel three‐component reaction involving 2‐methylbenzothiazole or 2,5‐dimethylbenzothiazole, acetylenic esters and 1,3‐dicarbonyl compounds such as (1,3‐dimethylbarbituric acid or 1,3‐indanedione) leading to the synthesis of spiro pyrrolobenzothiazole derivatives. The reactions proceeded smoothly at room temperature without using any catalyst. This method is very useful to functionalize benzothiazole derivatives in a one‐pot operation. The structures of the synthesized compounds have been characterized by spectral studies.     

Synthesis and stabilization mechanism of novel stabilizers for fullerene-malonamide derivatives in nitrocellulose-based propellants

Nitrocellulose (NC)-based propellants require stabilizers to avoid early decomposition or even explosion during storage. A series of novel fullerene-malonamide derivatives with different carbon chain lengths on the p-position of the benzene ring was synthesized as stabilizers for NC-based propellants through the Bingel reaction because of the excellent thermal stability and strong ability of these derivatives to eliminate free radicals. The molecular structures of these fullerene-malonamide derivatives were verified via ¹H nuclear magnetic resonance (NMR) spectroscopy, ¹³C NMR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet–visible spectroscopy, and high-resolution mass spectrometry. Meanwhile, their stability was investigated using methyl violet, vacuum stability, and weight loss tests. Results indicated that the stability of the novel fullerene-malonamide derivatives was considerably better than that of traditional stabilizers, such as N,N′-dimethyl-N,N′-diphenylurea and diphenylamine. Moreover, these derivatives exhibited excellent thermal stability at high temperatures. The stability of the fullerene-malonamide derivatives also improved as the carbon chain length on the p-position of the benzene ring on C₆₀ increased. In addition, the stability mechanism of the fullerene-malonamide derivatives was studied through electron paramagnetic resonance spectroscopy, FT-IR spectroscopy, and liquid chromatography-mass spectrometry. Results turned out that the fullerene-malonamide derivatives could react with nitroxide radicals released from the pyrolysis of NC. Hence, these novel fullerene-malonamide derivatives can be used as promising stabilizers for NC-based propellants.     

Reaction of 2-substituted 4,4-dimethyl-5-methylene-1,3-dioxolanes with dichlorocarbene and certain transformations of adducts obtained

A series of derivatives of 4,4-dimethyl-5-methylene-1,3-dioxolane has been synthesized, and their reaction with dichlorocarbene, obtained under interphase catalysis conditions, has been studied. The adducts obtained undergo thermal isomerization into dichloroethylidene derivatives.     

1,3-Dipolar cycloaddition of arynes with azomethine imines: synthesis of 1,2-dihydropyrazolo[1,2-a]indazol-3(9H)-ones

A [3+2] 1,3-dipolar cycloaddition reaction of arynes with stable azomethine imines has been developed. The reaction rapidly assembles tricyclic pyrazoloindazolone derivatives in moderate yields under mild reaction conditions.     

PEG-400介质中固载硫酸氢钠催化氧杂蒽二酮类衍生物的合成

聚乙二醇(PEG)具有低毒、可生物降解、不易挥发、不易燃、价廉易得等优点.将PEG用作绿色反应介质已引起人们的广泛关注~([1-2]).含吡喃环的化合物许多都具有重要的生物活性和药理活性,如抗发育不良、抗菌、抗癌活性等~([3]).