Formation of formal compounds in reaction of dimethyl phenols with formaldehyde

Formaldehyde was reacted with both 2,4-dimethylphenol(2,4-xyenol) and 2,6-dimethylphenol(2,6-xylenol), which are model compounds of monofunctional phenols, and the reaction products were subjected to HLC analysis to elucidate details of the formation process and bonding manner of a formal group, which can greatly affect the performance of phenol–formaldehyde resins. As a result, formal compounds of dimethylphenols were successfully separated by HLC. It was further found, as a result of tracing the reactions by HLC, that the formation of a formal group occurs at either position of the ortho and para positions, and that methylol compounds were formed following formation of the formal compounds. Furthermore, as a result of NMR analysis as well as consideration of solvation on the basis of the relative elution volumes of the nonacetylated and acetylated reaction products it was found that the formal group was added to the phenol nuclei.     

Modified Riemschneider Reaction of 3‐Thiocyanatoquinolinediones

The Riemschneider reaction of 3‐thiocyanatoquinoline‐2,4(1H,3H)‐diones with conc. H₂SO₄ was investigated. Using different reaction conditions, 13 types of reaction products were isolated. Compounds bearing a Me, Et, or Bu group at C(3) afforded mainly [1,3]thiazolo[5,4‐c]quinoline‐2,4‐diones and 1,9b‐dihydro‐9b‐hydroxythiazolo[5,4‐c]quinoline‐2,4‐diones. In the case of the 3‐Bu derivatives of the starting compounds, C‐debutylation was also observed. If a Bn group is present at C(3), rapid C‐debenzylation of the starting thiocyanates occurred, yielding [1,3]oxathiolo[4,5‐c]quinoline‐2,4‐diones, and mixtures of mono‐, di‐, and trisulfides derived from 4‐hydroxy‐3‐sulfanylquinoline‐2‐ones. The reaction mechanism of all of the transformations is discussed. All new compounds were characterized by IR, ¹H‐ and ¹³C‐NMR, and EI and ESI mass spectra, and in some cases, ¹⁵N‐NMR spectra were also used to characterize new compounds.     

Synthesis of amino-5-arylsulfonylpyrimidines

Several new 4-amino-5-arylsulfonylpyrimidines were prepared via the reaction of various α-(ethoxymethylene)arylsulfonylacetonitriles with guanidine or variously substituted amidines (Table II). 2,4-Diamino-5-(p-chlorophenylsulfonyl)pyrimidine (IIIg), a typical example, was prepared from the reaction of 2-(p-chlorophenylsulfonyl)-3-ethoxyacrylonitrile (IId) with guanidine in refluxing ethanol containing sodium ethoxide. With proper substitution of the ethoxymethylene intermediate, the method was found suitable for the preparation of other compounds having either a hydroxy or methyl group at the 4-position of the 5-arylsulfonylpyrimidine. The fluoro group in 2,4-diamino-5-(p-fluorophenylsulfonyl)pyrimidine (IIIx) was successfully replaced by nucleophilic reagents such as sodium ethoxide, N-methylpiperazine and N,N-diethylethylene-diamine. Attempts at direct displacement of fluorine by ammonia at 190° were unsuccessful.     

Preparation ofN-nitrohydroxylamines by direct nitration

The possibilities for stabilization of compounds with the A-B-NO₂ fragment, where A is an atom containing a lone electron pair, were examined. It was shown thatN-methyl-O-2,4-dinitro- and 2,4,6-trinitrophenylhydroxylamines undergo nitration with nitronium tetrafluoroborate or with a mixture of nitric acid and acetic anhydride to give the correspondingN-nitrohydroxylamines in high yields.N-Nitro-2,4-dinitrohydroxylamine that contains no methyl group at the nitrogen atom is unstable and forms a product ofO-alkylation upon reaction with diazomethane.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2276–2278, November, 1995.The work was supported by the International Science Foundation (Grant NGN 000).     

Preparation of poly(2,4-dichloro-6-vinyl-1,3,5-triazine-co-styrene)s as polymer supports containing two replaceable groups in monomer unit

Poly(2,4-dichloro-6-vinyl-1,3,5-triazine-co-styrene)s were prepared by the reaction of poly(2,4-diamino-6-vinyl-1,3,5-triazine-co-styrene)s with hydrochloric acid, and followed by treatment with thionyl chloride and N,N-dimethylformamide. The chlorine atoms in the resulted polymers were replaced readily by several nucleophiles such as amide, alkoxide, and mercaptide to afford the corresponding polymers in moderate yields. Among these, polymers containing oligo (oxyethylene) groups at both 2 and 4 positions of 1,3,5-triazine ring worked effectively as phase transfer catalysts for the reaction of n-octyl bromide with alkali metal thiocyanates in toluene–water systems. However, polystyrenes containing only one oligo (oxyethylene) group in monomer unit scarcely exhibited the activity under these conditions although the degree of loading of the functional group was almost the same. The activity depended on the number of oxyethylene units, and the selectivity to alkali metal ions was also observed. © 1992 John Wiley & Sons, Inc.     

Dechlorination of 2,4-dichlorophenoxyacetic acid using biochar-supported nano-palladium/iron: Preparation,characterization, and influencing factors

In the present study, peanut shell, a green waste raw material, was used to prepare biochar (BC) and to obtain BC-supported nano-palladium/iron (BC-nPd/Fe) composites for removing 2,4-dichlorophenoxyacetic acid (2,4-D) from water. Characterization analysis demonstrated that nPd/Fe particles were well dispersed on the BC surface with weakened magnetic properties. The average particle diameter and specific surface area of nPd/Fe were 101.3 nm and 6.7 m² g⁻¹, whereas the corresponding values of the BC-nPd/Fe materials were 88.8 nm and 14.8 m² g⁻¹, respectively. Several factors were found to influence the dechlorination of 2,4-D, including the weight ratio of BC to Fe, Pd loading ratio, initial solution pH, 2,4-D concentration, and reaction temperature. Dechlorination results indicated that the 2,4-D removal and phenoxyacetic acid (PA) generation rates were 44.1% and 20.1%, respectively, in the nPd/Fe system, and 100.0% and 92.1%, respectively, in the BC-nPd/Fe system. The dechlorination of 2,4-D was well described by the pseudo-first-order kinetic model (R² > 0.97), and the observed rate constants k_obs were 0.0042 min (nPd/Fe) and 0.0578 min (BC-nPd/Fe), respectively. The reaction mechanism indicated that the dechlorination hydrogenation was the main process to remove 2,4-D from water in the BC-nPd/Fe system. In addition, BC inhibited the formation of a passivation layer on the particle surface during the reaction, thus maintaining the high reactivity of BC-nPd/Fe. The easy preparation technique, high 2,4-D dechlorination capacity, and mild reaction conditions suggest that BC-nPd/Fe may be a promising alternative composite to remove 2,4-D from water.     

A one-step preparation of pyrido[3,4-d]pyrimidine ring system by reaction of 5-formyl-1,3,6-trimethyl-pyrimidine-2,4(1H,3H)-dione with primary amines

6,7-Dihydropyrido[3,4-d]pyrimidine-2,4(1H,3H)-diones were obtained in high yields from the reaction of 5-formyl-1,3,6-trimethylpyrimidine-2,4(1H,3H)-dione ( 1 ) and primary amines. For this pyridopyrimidine synthesis the following reaction pathway is proposed; the [1,5]-hydrogen shift of 1 gives a 5,6-dihydro-5,6-dimethylenepyrimidine-2,4(1H,3H)-dione intermediate. The cycloaddition reaction of the intermediate with aldimines from 1 and the primary amines affords 5,6,7,8-tetrahydropyrido[3,4-d]pyrimidine-2,4(1H,3H)-diones, which are dehydrated to the final products.     

Synthesis and Biological Activities of 3‐Substituted Analogues of Tenuazonic Acid

A series of tenuazonic acid analogues in which the acetyl group was replaced with electron‐withdrawing substituents have been synthesized with the aim of obtaining molecules with various bioactivities. Substituents such as cyano, sulfonyl, and amido were introduced at the 3‐position of the pyrrolidine‐2,4‐dione nucleus of tenuazonic acid. 3‐Cyano and sulfonyl pyrrolidine‐2,4‐dione compounds ( 2 and 6 ) were prepared via a Dieckmann cyclization as key step. 3‐Amido pyrrolidine‐2,4‐dione compounds ( 9 ) were prepared by a microwave‐assisted amidation reaction from corresponding 3‐carboxylate derivative. The target compounds were evaluated; their herbicidal, fungicidal, and insecticidal activities, and the preliminary bioassay data showed that some 3‐cyanopyrrolidine‐2,4‐diones 2 gave good insecticidal activity, whereas some 3‐amido compounds 9 exhibited moderate to strong fungicidal activity against Pythium dissimile at 20 mg/L.     

The Thermal Instability of 2,4 and 2,6‐N‐Alkylamino‐disubstituted and 2‐N‐Alkylamino‐substituted Nitrobenzenes in Weakly Alkaline Solution: sec‐Amino Effect

We report herein the preparation of two families of secondary amines by the reactions of two equivalents of monoamines with either 2,4 or 2,6‐difluoronitrobenzenes in N,N‐dimethylacetamide in the presence of anhydrous potassium carbonate, as precursors of biologically important nitric oxide donating N‐nitrosamines. In both instances, these compounds could be prepared in quantitative yield when the reaction temperature was held below 130°C. Above this reaction temperature, an unexpected cyclization reaction between the nitro and newly formed adjacent secondary amine group leads to the formation of benzimidazole or quinoxaline rings in low yields. Reasonable reaction mechanisms for the cyclization reaction are proposed.     

Formose Reactions. XXXII. Synthesis of Dl-2-C-Hydroxymethyl-3-Pentulose from Formaldehyde in N,N-Dimethylformamide-Water Mixed Solvent (II)

ABSTRACT

The carbon number of the main product and the total yield of products increased with an increase in the amount of triethylamine (TEA). Furthermore, the decrease of DL-2-C-hydroxymethyl-3-pentulose (2-H-3-P) was speeded up by increasing the TEA concentration and 2,4-bis(hydroxy-methyl)-3-pentulose (2,4-BH-3-P) increased smoothly along with the progress of the reaction. In the low formaldehyde (HCHO) concentration range (ca. 0.5 M), dihydroxyacetone (DHA) and DL-glycero-tetrulose were main products. 2-H-3-P and 2,4-BH-3-P increased with an increase in the formaldehyde concentration. Dihydroxyacetone, DL-glycero-tetrulose, 2-H-3-P and 2,4-BH-3-P were favorably obtained from a formose reaction by choosing a suitable [thiamine. HCl]/[HCHO] ratio. Under the reaction conditions reported in this paper, thiamine decomposed rapidly and lost its catalytic ability.     

Reactions of trifluoroacetic acid with poly(vinyl alcohol) and its model compounds. Effect of neighboring hydroxyl groups on the reaction

Reactions of trifluoroacetic acid with poly(vinyl alcohol) and various model alcohols were investigated by observing the fluorine and the proton magnetic resonance spectra of the reaction mixtures. At equilibrium the degree of conversion to ester under given conditions decreased in the order isopropanol, pentane-2,4-diol, heptane-2,4,6-triol and poly(vinyl alcohol). Therefore the equilibrium constant for esterfication of a hydroxyl group is depressed by the presence of neighboring hydroxyl groups. It was observed that the steric structures of the models and polymers also affect the equilibrium position of the reaction and this is mainly ascribable to the fact that meso (isotactic) molecules react more slowly with the acid than do racemic (syndiotactic) molecules. In acid-catalyzed acetylation of the model alcohols with acetic acid no similar dependence on the steric configuration was found. Therefore trifluoroacetylation seems to be specific in this respect.     

Friedel-crafts cyclisations. II. Further studies of polyphosphoric acid-catalysed cyclisations of N-cinnamoyl derivatives of aromatic amines

Further studies of the effects of substituents in the N-phenyl nucleus on the polyphosphoric acid-catalysed cyclisation of cinnamanilide to 4-phenyl-3,4-dihydrocarbostyril have confirmed that the isomerisation is prevented by a nitro group and retarded by other substituents in the ortho position to the NH- group. Although a methyl group ortho to the only position at which cyclisation can occur was also shown to retard the reaction, N-cinnamoyl-2,4,5-trichloroaniline was cyclised in moderate yield after prolonged heating, but the 2,4-dibromo and 2,5-dimethoxy analogues were not isomerised. Isomerisation of 2-cinnamamidobiphenyl to 4,8-diphenyl-3,4-dihydrocarbostyril was accompanied by cyclodehydration to 6-styrylphenanthridine. Five new derivatives of cinnamanilide and eight new derivatives of 4-phenyl-3,4-dihydrocarbostyril are described.     

Synthesis of polyamides from rigid and sterically hindered dicarboxylic acids and diamines under mild conditions

The rate of polycondensation of piperazine with the 2,4-dinitrophenyl, succinimido, phthalimido, and 4-nitrophenyl esters of bicyclo[2.2.2]octane-trans-2,3-dicarboxylic acid was measured and found to decrease in this sequence. In the reaction of two moles of piperazine with one mole of diester, the reactivity of both ester groups was equal. In equimolar mixtures, the second ester group reacts with the second group about ten times slower because of steric hindrance. In the reaction of the esters with N,N′-dimethylethylenediamine no such effects were observed. The aminolysis of the N-hydroxyphthalimido ester stops at low conversions unless a very large excess of triethylamine is added. The catalytic effect of 1,2,4-triazole on the aminolysis was proportional to the triazole concentration. From the rate of ester consumption in the presence of pure triethylamine, the extent of possible racemization of the optically active dicarboxylic acid was estimated. In view of the rate data, the extent of polycondensation, and side reactions, only 2,4-dinitrophenyl and N-hydroxysuccinimido diesters are suitable for the synthesis of polyamides derived from rigid and sterically hindered dicarboxylic acids.     

Triazine dendrimers by divergent and convergent methods

Two types of dendrimers with a 1,3,5‐triazine ring at the branch point were synthesized by divergent and convergent methods. The divergent method began with 2,4,6‐tris(p‐nitroanilino)‐1,3,5‐triazine as a trifunctional core. Each cycle involved the reduction of the peripheral NO₂ group followed by a reaction with 2‐chloro‐4,6‐bis(p‐nitroanilino)‐1,3,5‐triazine. The synthetic cycle was completed by the coupling with 2,4‐dianilino‐6‐chloro‐1,3,5‐triazine (DACT) to eventually accomplish second‐generation dendrimers ([G2]₃‐C) bearing 12 benzene rings at their edge. The convergent approach started with the reaction of DACT with p‐nitrophenol to give rise to 2,4‐dianilino‐6‐(p‐nitrophenoxy)‐1,3,5‐triazine. The synthetic cycle consisted of reduction of the NO₂ group and coupling with 2,4‐dichloro‐6‐(p‐nitrophenoxy)‐1,3,5‐triazine. The final step was the connection of each monodendron with cyanuric chloride to produce tridendron; in this way, the second‐generation dendrimer ([EG2]₃‐C) was obtained. Gel permeation chromatography analyses indicated the aggregation of dendrimers in solution. Ultraviolet spectroscopic analyses revealed that the larger dendrimer had a more conjugated electron system from the core to the periphery. The thermal properties were evaluated by thermogravimetric analysis (TGA); excellent heat resistance was indicated, especially in [G1]₃‐C, which included alternately imine‐like nitrogen‐linked 1,3,5‐triazine and benzene rings. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4385–4395, 2000     

Highly Selective Room Temperature Monoreduction of Dinitro‐arenes by Hydrogen Sulfide under Liquid–Liquid Biphasic Catalysis

Selective reduction of one of the nitro group present in dinitro aromatic compounds by a novel Zinin reagent, H₂S‐laden N‐methyldiethanolamine (MDEA) solution, has been explored in the presence of tetra‐n‐butyl phosphonium bromide as a phase transfer catalyst under the liquid–liquid mode of reaction. Under the room temperature reaction condition, reduction of 2,4‐dinitrotoluene (2,4‐DNT) with H₂S‐laden MDEA leads to the selective reduction of one nitro group present either at the fourth position to obtain 4‐amino‐2‐nitrotoluene (4A2NT) or at the second position to get 2‐amino‐4‐nitrotoluene (2A4NT). The reaction was very fast to achieve 100% conversion, and the selectivity of 4A2NT is much higher than the 2A4NT. A detailed parametric study was performed to analyze the effect of parameters on 2,4‐DNT conversion and selectivity of both the isomers. The apparent activation energy was found to be as high as 46.25 kJ/mol, and the reaction was found to be kinetically controlled. An empirical kinetic model has been developed to correlate with the conversion version time data obtained experimentally. The present system dealt with an industrial problem in dealing with H₂S, present in by‐product gaseous streams of many petroleum and natural gas industries. Novelties in the selective monoreduction lie in that fact that the reaction was done at room temperature (303 K), with a novel reagent, H₂S‐laden MDEA solution. Therefore waste‐minimization was effected to yield value‐added fine chemicals, that is, amines.     

Chemie von a-Aminonitrilen. Aldomerisierung von Glycolaldehyd-phosphat zu racemischen Hexose-2,4,6-triphosphaten und (in Gegenwart von Formaldehyd) racemischen Pentose-2,4-diphosphaten: rac-Allose-2,4,6-triphosphat und rac-Ribose-2,4-diphosphat sind die Reaktionshauptprodukte

Chemistry of α-Aminonitriles. Aldomerisation of Glycolaldehyde Phosphate to rac-Hexose 2,4,6-Triphosphates and (in Presence of Formaldehyde) rac-Pentose 2,4-Diphosphates: rac-Allose 2,4,6-Triphosphate and rac-Ribose 2,4-Diphosphate Are the Main Reaction Products Glyclaldehyde phosphate aldomerizes in aqueous NaOH solution to a product mixture containing the racemates of the two diastereoisomeric tetrose 2,4-diphosphates and eight hexose 2,4,6-triphosphates. At room temperature in the absence of air and after 7 days, a solution 0.08M in glycolaldehyde phosphate (=formylmethyl dihydrogenphosphate)and 2M in NaOH gives products, in up to 80% yield, with a tetrose/hexose derivative ratio of ca 1:10 and with rac-allose, 2,4,6-triphosphate comprising up to 50% of the mixture of sugar phosphates. When the reaction is run under the same conditions but in the presence of 0.5 mol-equiv. of formaldehyde, sugar phosphates are formed in up to 45% yield, with pentose 2,4-diphosphates now predominating over hexose triphosphates by a ration f 3:1 rac-Ribose 2,4-diphosphate is found to be the major component, the ratios am ribose, arabinose, lyxose, and xylose 2,4-diphosphates being 52:14:23:11 in a representative experiment. The pentose diphosphates are constitutionally stable under the reaction conditions (observed for 23 weeks), but the diastereoisomeric ratios slowly change with time (tc 22:34:30:14 after 23 weeks), showing that ribose 2,4-diphosphate is not the thermodynamically favored diastereoisomer. The observed product distributions in both the pentose and the hexose series (after 1 week) reveal an aldolization mode that is preferentially erythro in the product-determining step (the reaction of glycolaldehyde phosphate as its enolate with glycerinaldehyde 2-phosphate and tetrose 2,4-diphosphate, respectively). An attempt is made to rationalize both this fact and the kinetic predominance of ribose 2,4-diphosphate in the pentose series and allose 2,4,6-triphosphate in the hexose series. Their configuration along the C-chain can be interpreted as corresponding to a minimum number of 1-5 repulsions in the packing of phosphate and OH substituents and minimal steric interaction between substituents at the reaction centers in the transition state of the product-determining step. The aldomerization of glycolaldehyde phosphate in the presence of formaldehyde is a variant of the formose reaction, It avoids the formation of complex formose product mixtures, largely as a consequence of the fact that aldoses which are phosphorylated at the C(2)     

Dibenzyl Structuresin a Macromolecular Chain. III. Dibenzyldiisocyanates Reactivity

The reactivity of the 2,2′-, 2,4′-, 4,4′-dibenzyldiisocyanate (2,2′-, 2,4′-, 4,4′-DBDI) with n-butanol in benzene has been studied. The concentrations of all species were monitored by using high performance liquid chromatography (HPLC). The reactivity of 4,4′-DBDI is similar to that of 4,4′-diphenylmethanediisocyanate (4,4′-MDI). Very strong intramolecular catalytic effects were noticed in the case of 2,2′-DBDI, probably due to the variable molecular geometry. These effects are responsible for the whole reaction pattern. The 2,4′-DBDI NCO ortho and para groups reactivities are different and comparable to that of 2,4-toluylenediisocyanate (2,4-TDI).     

The Oxidation of Hexahydrotriazines

Summary. N-Alkyl-2,4-dioxohexahydro-1,3,5-triazines oxidize readily with oxygen to the corresponding cyanuric acid derivates. The oxidation of 1,3,5-trimethyl-2,4-dioxohexahydro-1,3,5-triazine resulted in a stable form of hydroperoxide. During the oxidation of 1,3,5-trimethyl- 6-phenyl-2,4-dioxohexahydro-1,3,5-triazine this hydroperoxide could not be identified, however, the result was the stable reaction product bis-[6-phenyl-1,3,5-trimethyl-2,4-dioxohexahydro-1,3,5-triazin]peroxide.     

Pyrimidines. 20. Novel reactions of 5-cyano-1,3-dimethyluracil. A simple synthesis of pyrido[2,3-d]pyrimidines

A reaction of 5-cyano-1,3-dimethyluracil (1, R = CN) with acetone in base afforded 1,3,7-trimethylpyrido-[2,3-d]pyrimidine-2,4(1H,3H)dione ( 9a ) in a moderate yield. From a reaction mixture of 1 (R = CN) with butanone, 1,3,6,7-tetramethyl- and 7-ethyl-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione ( 9b and 9c , respectively) were isolated in low yields. When ethyl cyanoacetate or malononitrile was used in place of the ketone in the above reaction, 7-amino-6-ethoxycarbonyl- and 7-amino-6-cyano-1,3-dimethylpyrido[2,3-d]-pyrimidine-2,4(1H,3H)-dione ( 14a and 14b , respectively) were obtained in quantitative yields. A plausible mechanism for the formation of bicyclic compounds is discussed.     

Synthesis of 1H‐quinazoline‐2,4‐diones from 2‐aminobenzonitriles by fixation of carbon dioxide with amidine moiety supported polymer at atmospheric pressure

1H‐Quinazoline‐2,4‐diones, which are key intermediates in the synthesis of medicines, were successfully synthesized from 2‐aminobenzonitriles by the fixation of CO₂ in the presence of a polystyrene derivative bearing amidine moiety [poly(amidine)]. A model reaction, that is, the reaction of 2‐aminobenzonitrile ( 1a ) with CO₂ in the presence of N‐methyltetrahydropyrimidine ( MTHP ) revealed that a catalytic amount of MTHP afforded 1H‐quinazoline‐2,4‐dione ( 2a ) quantitatively at atmospheric pressure. Several 1H‐quinazoline‐2,4‐diones ( 2a ‐ 2c ) were successfully synthesized from the corresponding 2‐aminobenzonitriles ( 1a ‐ 1c ) in the presence of poly(amidine). The poly(amidine) could easily be separated from the reaction mixture by filtration and reused in subsequent reactions owing to the heterogeneous system. These demonstrated that poly(amidine) is a useful heterogeneous polymer‐supported reagent for the synthesis of 1H‐quinazoline‐2,4‐diones from CO₂. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 653–657, 2009