Efficient Synthesis of Primary Nitrocarbamates of Sugar Alcohols: From Food to Energetic Materials

The synthesis of various new polyvalent nitrocarbamates derived from sugar alcohols was accomplished by an economically benign two‐step synthesis. The precursor carbamates were synthesized with the reagent chlorosulfonyl isocyanate (CSI) and further nitrated using mixed acid. The starting materials, sugar alcohols, are renewable biomass, mainly used in food and cosmetic industry. The structures of one carbamate and one nitrocarbamate were exemplary described by single‐crystal X‐ray‐analysis. The heat of formation is calculated by the use of isodesmic reactions and the energetic performance data were estimated. All compounds were fully characterized by elemental analysis, vibrational spectroscopy, ¹H, ¹³C, and ^14/15N NMR spectroscopy and thermal analysis (DSC). The nitrocarbamates exhibit good detonation performance and have significantly lower sensitivities compared to the commonly used nitrate ester explosive PETN.     

Acylation of Cellulose with N,N′‐Carbonyldiimidazole‐Activated Acids in the Novel Solvent Dimethyl Sulfoxide/Tetrabutylammonium Fluoride

Summary: Carboxylic acids were efficiently activated with N,N′‐carbonyldiimidazole (CDI) and applied for the acylation of cellulose under homogeneous conditions using dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride trihydrate (TBAF) as solvent. The simple and elegant method is a very mild and easily applicable tool for the synthesis of pure aliphatic, alicyclic, bulky, and unsaturated cellulose esters with degrees of substitution of up to 1.9. Products are soluble in organic solvents, e.g., DMSO or N,N‐dimethylformamide (DMF). The cellulose esters were characterized by elemental analysis, FT‐IR, ¹H and ¹³C NMR spectroscopy and show no impurities or substructures resulting from side reactions.

The esterification of cellulose using carboxylic acids activated in situ with N,N′‐carbonyldiimidazole.     

Azoles as Reactive Nucleophiles with Cyclic Perfluoroalkenes

Di‐ and multiazole‐substituted fluorocyclic products ( 2 – 13 ) were readily synthesized in good to high yields. These were synthesized by nucleophilic substitution reactions of perfluorocycloalkenes with azoles (i.e., imidazole, triazole) involving simple reaction procedures. Interestingly, these azoles were later found to be reactive not only with the vinylic, but also with the allylic fluorine atoms. This resulted in the substitution of up to six azoles on the fluorinated rings. Stoichiometry plays a key role in determining the degree of substitution. For comparison, the analogous reactions of N‐substituted 1‐(trimethylsilyl)‐imidazole and 1‐(trimethylsilyl)‐1,2,4‐triazole were also investigated. All of the new compounds were fully characterized by elemental, spectral (¹⁹F, ¹H, ¹³C NMR), and thermal differential scanning calorimetry (DSC) analyses.     

Serine and Threonine Schiff Base Esters React with β-Anomeric Peracetates in the Presence of BF3·Et2O to Produce β-Glycosides

Improved procedures are reported for the glycosylation of L-serine and L-threonine utilizing activated Schiff base glycosyl acceptors, which are less expensive and more efficient alternatives to published methods. L-serine or L-threonine benzyl ester hydrochloride salts were reacted with the diarylketimine bis-(4-methoxyphenyl)-methanimine in CH₃CN at rt to form the more nucleophilic Schiff bases 3a and 3b in excellent yield. These Schiff bases exhibited ring-chain tautomerism in CDCl₃ as shown by ¹H NMR. Schiff bases 3a and 3b, acting as glycosyl acceptors, reacted at rt with simple sugar peracetate donors with BF₃·OEt₂ promotion to provide the corresponding L-serine and L-threonine O-linked glycosides in excellent yields and purities. The dipeptide ester Schiff base Ar₂C = N-Ser-Val-OCH₃ 3e also reacted to provide β-glycosides in excellent yields, and without epimerization. With microwave irradiation the reactions were complete in 2 to 5 min. To investigate this reaction further, classical AgOTf-promoted Koenigs-Knorr reaction of D-glucopyranosyl, lactosyl, and maltosyl bromides were examined, providing the β-glycosides with yields ranging from 35% to 68%. The difference in reactivity between α- and β-carbohydrate peracetate donors was remarkable. The less configurationally stable D-xylopyranosyl tetra-acetate (a pentose) showed no selectivity (αvsβ-configuration) toward the Schiff bases.     

Synthesis of hyperbranched poly(ester urethane isocyanates) and their derivatives

Hyperbranched poly(ester urethanes) containing end isocyanate groups have been synthesized via the reaction of hyperbranched aliphatic polyesterpolydiols of three generations with tolylene diisocyanate. The interaction of these compounds with N,N-dimethylaminoethanol yields their functional derivatives. The polymers are characterized by functional analysis, ¹H NMR and IR spectroscopy, and DSC. It has been demonstrated that the incorporation of urethane moieties leads to development of the microheterogeneous structure of hyperbranched polymers.     

Synthesis of Some Fluorinated Pyridines Using Tetrabutylammonium Fluoride

Some bromo- and chloromethyl pyridines were synthesized using radical substitution reactions. Further reaction of these halopyridines with activated tetrabutylammonium fluoride under mild conditions gave the related fluorinated pyridines. The yields of products following recrystallization were of the order of 30–93%. ¹ H, ¹³ C, and ¹⁹ F spectroscopies together with elemental analysis were used characterize products.     

Greening the organic chemistry laboratory: a comparison of microwave-assisted and classical nucleophilic aromatic substitution reactions

ABSTRACT

An experiment is described for the undergraduate organic chemistry lab which compares microwave-induced organic reaction enhancement (MORE) to that of more traditional synthetic procedures. MORE and traditional reflux procedures for substituting thiocyanate, ethylamine and diethylamine nucleophiles for bromide in nucleophilic aromatic substitution reactions on 1-bromo-2,4-dinitrobenzene are given. Recrystallization affords products of sufficient purity for characterization by ¹³C NMR, mass spectrometry and melting point. As students compare the two synthetic methods, MORE procedures are consistently observed to be quicker, easier, greener and result in higher yields. Student instructions, instructor notes and example NMR and mass spectra obtained by students are provided in Supplemental material.     

Sulfur-containing polymers. Synthesis and properties of novel poly(arylene thioether)s based on 2,2-bis(4-mercaptophenyl)propane

Novel poly(arylene thioether)s were synthesised using the one pot polymerisation method from the bis(N,N-dimethyl-S-carbamate) of 2,2-bis(4-mercaptophenyl)propane and activated difluoro aromatic compounds. Each of the polymers, obtained in good yields and with fairly high molecular weights, were characterised by IR, GPC and NMR analyses. In particular, the NMR characterisation was performed using ¹H NMR, ¹³C NMR, DEPT, 2D COSY and 2D HSQC experiments. To study the effect on the thermal properties of replacing the ethereal oxygen atoms with sulfur atoms, we have synthesised the counterparts, the poly(arylene ether)s, with similar molecular weights. We observed that the substitution of the ethereal oxygen atoms with sulfur atoms results in a slightly lower thermal stability for the poly(thioether ketone)s, both under nitrogen and in air, and does not modify the T_g values. For the poly(thioether sulfone), on the other hand, the thermal stability is equal to that of the poly(ether sulfone), while the T_g is 10 °C lower. Furthermore, each sample is completely amorphous, with the exception of one of the poly(thioether ketone)s (sample 1b), which shows the capacity to crystallise, even if with a very slow crystallisation kinetics.     

Polyanhydrides. XI. Poly(Ester-anhydride)s Derived from 4-Hydroxybenzoic Acid,Vanillic Acid,and Aliphatic Dicarboxylic Acids

ABSTRACT

Poly(ester-anhydride)s, PEA's, built up by 50 mol% ester and 50 mol% anhydride groups were prepared by polycondensation of 0,0′-bistrimethylsilyl 4-hydroxybenzoic acid and various α,ω- alkane-dicarbonylchlorides. The polycondensations were conducted either in bulk or in 1-chloronaphthalene. High yields (up to 94%) were obtained under both reaction conditions, but the higher inherent viscosities resulted from polycondensations in 1- chloronaphthalene. IR- and ¹³C NMR spectroscopy revealed that reaction temperatures above 200°C cause side reactions such as transacylation and transesterification. Analogous series of polycondensations were conducted with 0,0′-bistrimethylsilyl vanillic acid. The resulting PEA's were amorphous, whereas the PEA's derived from 4-hydroxybenzoic acid are semicrystalline.     

Aminophosphine ligands: synthesis,coordination chemistry,and activity of their palladium(II) complexes in Heck and Suzuki cross-coupling reactions

The reaction of 4-aminodiphenylamine or 2-aminofluorene with two equivalents of PPh₂Cl in the presence of Et₃N gives new bis(diphenylphosphino)amines N,N-bis(diphenylphosphino)-4-aminodiphenylamine 1 and N,N-bis(diphenylphosphino)-2-aminofluorene 2 in good yields. Oxidation of 1 or 2 with hydrogen peroxide, elemental sulfur or gray selenium affords the corresponding chalcogen derivatives. The palladium and platinum complexes of these P–N–P donor ligands were prepared by the reaction of the bis(phosphino)amines with MCl₂(cod) (M = Pd or Pt, cod = cycloocta-1,5-diene). All the new compounds have been characterized by analytical and spectroscopic methods, including ¹H-³¹P NMR, ¹H-¹³C HETCOR, or ¹H-¹H COSY correlation experiments. The Pd(II) complexes were investigated as catalysts in the Suzuki and Heck reactions; both showed good catalytic activity affording high yields of the desired products.     

Synthesis of Benzofuryl Substituted Unsymmetrical Ureas Under Microwave Irradiation

A series of 2-benzofuryl substituted unsymmetrical ureas were synthesized by reactions of benzofuroyl isocyanate, which was prepared from benzofuroyl azide by Curtius rearrangement, with various aromatic amines, 2-amino-5-(benzo-2-furyl)-1,3,4-thiadiazole, and 2-amino-5-aryloxymethylene-1,3, 4-thiadiazoles under microwave irradiation. Compared to conventional methods, this synthesis has the advantages of mild reaction conditions, easy handling, and high yields. The products have been characterized by analytical and spectral (IR and ¹ H NMR) data.     

Syntheses and structural characterizations of 2-pyridyl(N/O)spirocyclotriphosphazene derivatives

The Cl exchange reaction of hexachlorocyclotriphosphazene, N₃P₃Cl₆ (1), with one equimolar amount of sodium salt of N/O donor type bidentate ligand containing a 2-pyridyl pendant arm (2) afforded, regioselectively, the partly substituted 2-pyridyl(N/O)spirocyclotriphosphazene (3; with a yield of 65%) in THF. The reactions of 3 with excess pyrrolidine, morpholine and 1,4-dioxa-8-azaspiro[4,5]decane (DASD) led to the formation of the tetraamino-2-pyridyl(N/O)spirocyclotriphosphazenes (3a-3c) in high yields. Compound 3 also gave both tetrapiperidino (3d) and gem-bispiperidino (3e) products with excess piperidine. The structures of all the compounds were determined by elemental analyses, ESI-MS, FTIR, HSQC, HMBC and ¹H, ¹³C, and ³¹P NMR techniques. The crystal structure of 3c was identified by single crystal X-ray crystallography. Besides, the compound 3e had one stereogenic P atom, and its chirality was verified by ³¹P NMR spectroscopy in the presence of (S)-(+)-2,2,2-trifluoro-1-(9’-anthryl)-ethanol (CSA).     

Highly Enantioselective Reactions of Configurationally Labile Epimeric Diamine Complexes of Lithiated S‐Benzyl Thiocarbamates

Substitution reactions that employ primary‐carbamoyl‐protected arylmethanethiols are described. The enantiodetermining step was found to occur in the post‐deprotonation step as a dynamic thermodynamic resolution with a chiral bis(oxazoline) ligand. The configurationally labile lithium complexes were trapped with various electrophiles to yield different substitution products in good to excellent yields and enantiomeric excesses. The absolute configurations of the substitution products were determined, and the stereochemical pathway of the substitution reaction was elucidated for different classes of electrophiles. The temperature‐dependent epimerization process was monitored by ¹H and ⁶Li NMR spectroscopy.     

Thianthrene as an activating group for the synthesis of poly(aryl ether thianthrene)s by nucleophilic aromatic substitution

A method for the preparation of poly(aryl ether thianthrene)s has been developed in which the aryl ether linkage is generated in the polymer‐forming reaction. The thianthrene heterocycle is sufficiently electron‐withdrawing to allow fluoro displacement with phenoxides by nucleophilic aromatic substitution. The monomer for this reaction, 2,7‐difluorothianthrene, can be synthesized in a moderate yield by a simple reaction sequence. Semiempirical calculations at the PM3 level suggest that 2,7‐difluorothianthrene is sufficiently activated, whereas NMR spectroscopy (¹H and ¹³C) indicates that the monomer is only slightly activated or (¹⁹F) not sufficiently activated for nucleophilic aromatic substitution. Model reactions with p‐cresol have demonstrated that the fluorine atoms on 2,7‐difluorothianthrene are readily displaced by phenoxides in high yields, and the process has been deemed suitable for polymer‐forming reactions. High‐molecular‐weight polymers have been produced from bisphenol A, bisphenol AF, and 4,4′‐biphenol. The polymers have been characterized with gel permeation chromatography, NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. The glass‐transition temperatures for the polymers of different compositions and molecular weights range from 138 to 181 °C, and all the polymers have shown high thermooxidative stability, with 5% weight loss values in an air environment approaching 500 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6353–6363, 2004     

Multicomponent Molecular Systems Based on Porphyrins, 1,3,5-Triazine and Carboranes: Synthesis and Characterization

2,4,6-Trichloro-1,3,5-triazine (cyanuric chloride) is an excellent coupling reagent for the preparation of highly structured multifunctional molecules. Three component systems based on porphyrin, cyanuric chloride and carborane clusters were prepared by a one-pot stepwise amination of cyanuric chloride with 5-(4-aminophenyl)-10,15,20-triphenylporphyrin, followed by replacement of the remaining chlorine atoms with carborane S- or N-nucleophiles. Some variants of 1,3,5-triazine derivatives containing porphyrin, carborane and residues of biologically active compounds such as maleimide, glycine methyl ester as well as thioglycolic acid, mercaptoethanol and hexafluoroisopropanol were also prepared. A careful control of the reaction temperature during the substitution reactions will allow the synthesis of desired compounds in a good to high yields. The structures of synthesized compounds were determined with UV-vis, IR, ¹H NMR, ¹¹B NMR, MALDI-TOF or LC-MS spectroscopic data. The dark and photocytotoxicity as well as intracellular localization and photoinduced cell death for compounds 8, 9, 17, 18 and 24 were evaluated.     

REACTIONS OF DERIVATIVES OF PHOSPHORUS ACIDS WITH CARBONYL COMPOUNDS ACTIVATED BY ELECTRONEGATIVE GROUPS

Abstract

The Arbuzov reaction results in the synthesis of various phosphonic esters and is of great importance for the further development of the chemistry of organophosphorus compounds. Investigations of recent decades have shown that, besides halogen-containing organic compounds, different types of organic compounds of the electrophilic type which do not contain halogen atoms are capable of entering this reaction. Reactions with carbonyl compounds are especially interesting. This report presents the results of reactions of derivatives of tricoordinated phosphorus (trialkyl phosphites, amidophosphites, ester anhydrides, isocyanate phosphites) with carbonyl compounds. Special emphasis was placed on studying the reactions with carbonyl compounds activated by some electronegative groups. The regularities and mechanisms of these reactions were investigated depending on the structure of the carbonyl compounds, the derivatives of tricoordinated phosphorus and the reaction conditions.     

Synthesis and antitumor activity evaluation of some novel pyrazolotriazine derivatives

6-Aminopyrazolo[1,2-a][1,2,4]triazine-4,8-dione derivative 3 was obtained upon the reaction of the acid hydrazide derivative 2a with ethyl cyanoacetate. The reactions of 3 with several electrophiles such as aldehydes, isatin, acetic anhydride, phenyl isocyanate, benzoyl isothiocyanate, and p-toluenesulfonyl chloride were studied. The structures of the newly synthesized compounds were established on the basis of IR, ¹H NMR, mass spectra, and elemental analyses. The antitumor activities of some selective compounds were examined against two cell lines as liver carcinoma cell line (HEPG-2) and human breast cancer cell line (MCF7).     

Synthesis of chiral calix[4]arenes bearing tartaric ester moieties

The synthesis of chiral calix[4]arenes with tartaric acid ester moieties has been achieved by the reactions of tartaric ester chloroacetates with calix[4]arenes in moderate yields. All the chiral calix[4]arene derivatives are in a cone conformation according to the ¹H NMR doublet–doublet pattern of the protons of the methylene groups between the phenol rings. The results of NMR and specific rotations indicate that the molecules have C₂ symmetry with asymmetric features.     

Mechanisms for the Formation of Diamides and Polyamides by Aminolysis of d‐Glucaric Acid Esters

¹H and ¹³C NMR were employed to chart the conversion of the five‐membered lactone esters methyl d‐glucarate 1,4‐lactone (1) and ethyl d‐glucarate 6,3‐lactone (5) to N,N′‐dipropyl‐d‐glucaramide with n‐propylamine in DMSO‐d₆. These experiments were carried out to model the amide forming steps in polycondensation reactions between esterified d‐glucaric acid and diamines to give poly(d‐glucaramides). It was clear from the resulting NMR spectra that the lactones 1 and 5 were each converted in three consecutive steps to the product diamides; aminolysis of the lactone ester to the corresponding acyclic N‐propyl‐d‐glucaramide monoester, followed by lactonization to a five‐membered lactone amide, and concluding with aminolyis of the lactone amide to N,N′‐dipropyl‐d‐glucaramide (4). Comparison of the reaction pathways from 1 and 5 by ¹H NMR analysis suggests that ring opening of the 1,4‐lactone ester (1) and 1,4‐lactone amide (7) is faster than ring opening of the corresponding 6,3‐lactone ester (5) and 6,3‐lactone amide (3). Aminolysis of dimethyl l‐tartrate, which cannot form a five‐membered lactone, with n‐propylamine in DMSO‐d₆ was much slower than aminolysis of esterified glucaric acid, indicating that the lactone forming/lactone aminolysis steps are the dominant aminolysis rate enhancing steps from glucarate.     

A novel synthesis and herbicidal activity of fluorine-containing pyrazolo[3,4-d]pyrimidin-4-one derivatives

The 6-(4-alkoxycarbonylalkoxy)phenoxy-3-alkylthio-5-(fluoro-substituted)phenyl-1-phenylpyrazolo[3,4-d]pyrimidin-4-ones 6 have been successfully synthesized via a tandem aza-Wittig and annulation reactions of the corresponding iminophosphorances 4, aromatic isocyanate, and substituted phenols 2 in 59-69% isolated yields using actonitrile as solvent. These novel compounds 6 could be oxidized to sulfones 7 by hydrogen peroxide in satisfactory yields (57-93%). Their structures were clearly verified by spectroscopic data (IR, ¹H NMR, ¹³C NMR, MS, Elemental analysis or X-ray diffraction crystallography). The results of preliminary bioassay indicated that these compounds possess herbicidal activity against the root of rape and barnyard grass.