Convenient Preparation of N,N′‐Diphenyl‐N,N′‐bis(4‐aminophenyl)‐p‐phenylenediamine

Abstract

This article describes modified conditions to prepare N,N′‐diphenyl‐N,N′‐bis(4‐aminophenyl)‐P‐phenylenediamine in 60% overall yield.     

Amino Acids as a Chiral Pool: Synthesis of (S)‐and (R)‐2‐N‐Carbomethoxy‐5‐aminoindane from (S)‐ and (R)‐Phenylalanines

Enantioselective syntheses of (R)‐and (S)‐2‐N‐carbomethoxy‐5‐aminoindanes from (R)‐ and (S)‐phenylalanines, respectively, are described. A Friedel–Crafts reaction employing N‐carbomethoxy phenylalanine leads to chiral 2‐N‐carbomethoxy‐1‐indanone, which is diastereoselectively reduced to 1‐hydroxy‐2‐N‐carbomethoxyindane. After protection of the hydroxyl group, a regioselective nitration gives a 6‐nitroindane intermediate, which upon hydrogenation affords (R)‐or (S)‐2‐N‐carbomethoxy‐5‐aminoindane.     

Efficient Synthesis of 2‐(N‐Substituted)‐2‐imidazolines and 2‐(N‐Substituted)‐1,4,5,6‐tetrahydropyrimidines

A general method for the preparation of 2‐(N‐Substituted)‐2‐imidazolines and 2‐(N‐Substituted)‐1,4,5,6‐tetrahydropyrimidines is described. These heterocycles can be synthesized from their respective anilines with 2‐chloro‐2‐imidazoline or 2‐chloro‐1,4,5,6‐tetrahydropyrimidine, generated in situ from imidazolidin‐2‐one and tetrahydropyrimidin‐2(1H)‐one activated by dimethyl chlorophosphate, in good to excellent yields.     

Synthesis of Chiral Nitrones from N‐Fmoc Amino Acids and N‐Fmoc Dipeptides

Abstract

In this work is presented a synthetic procedure for the preparation of chiral nitrones from N‐Fmoc protected amino acids and dipeptides. The nitrone functional group can replace the carboxyl unit of amino acid and peptide systems and can be inserted into the peptide chain. The introduction of the 1,3‐dipole in peptide segments can improve the solubility and the stability toward enzymatic degradation.     

Electroanalytical performance of Cd(II) selective sensor based on PVC membranes of 5,5′‐(5,5′‐(benzo[c][1,2,5]thiadiazole‐4,7‐diyl)bis(thiophene‐5,2‐diyl))bis(N1,N1,N3,N3‐tetraphenylbenzene‐1,3‐diamine)

The construction and performance characteristics of polymeric membrane electrodes based on neutral ionophore 5,5′‐(5,5′‐(benzo[c][1,2,5]thiadiazole‐4,7‐diyl)bis(thiophene‐5,2‐diyl))bis‐(N1,N1,N3,N3‐tetraphenylbenzene‐1,3‐diamine) (L) for quantification of cadmium ions, are described. Effect of plastisizers dibutylpthalate (DBP), tri‐n‐butylphosphate (TBP), dioctylpthalate (DOP), o‐nitrophenyloctyl ether (o‐NPOE), 1‐chloronaphthalene (CN) and ionic additives sodium tetraphenylborate (NaTPB), potassium tetrakis p‐(chlorophenyl)borate (KTpClPB) was studied. Best performance was obtained with the membrane having a composition L?:?PVC?:?DBP?:?NaTPB?≡?2?:?37?:?59?:?2 (w/w; mg). The membrane electrode exhibits Nernstian response in the concentration range 6.3?×?10^?8 to 1.0?×?10?^?1?mol?L^?1 with detection limit 3.6?×?10^?8?mol?L^?1 and is not affected by H⁺ ions over a wide pH range 3.0–10.0. The electrode possess a fast response time of 10?s and shelf life period of 3 months. The analytical utility of the proposed electrode has demonstrated by its application in the determination of cadmium in water, medicinal plants and soil samples. It could also be used successfully as an indicator electrode in the potentiometric titration of Cd²⁺ with EDTA (ethylenediaminetetraacetic acid).     

Chiral (S)‐(+) 1‐Substituted Aryl‐4‐(1‐phenyl) Ethylformamido‐5‐amino‐1,2,3‐triazole: A New Class of Chiral Ligands for the Silver(I)‐Promoted Enantioselective Allylation of Aldehydes

Some novel chiral ligands, (S)‐(+) 1‐substituted aryl‐4‐(1‐phenyl) ethylformamido‐5‐amino‐1,2,3‐triazoles, were prepared starting from 1‐substituted aryl‐4‐ethoxycarbonyl‐5‐amino‐1,2,3‐triazoles and other reagents. They were used as catalytic chiral ligands in the silver (I)‐promoted enantioselective allylation reaction of aldehydes with allyltributyltin.     

Efficient Synthesis of N‐Oxide Derivatives: Substituted 2‐(2‐(Pyridyl‐N‐oxide)methylsulphinyl)benzimidazoles

Different substituted 2‐chloromethylpyridyl derivatives (6a–d) were oxidized with mCPBA to give the respective 2‐chloromethylpyridine‐N‐oxide derivatives (7a–d) at low temperature, which on condensation with 2‐mercapto‐1H‐benzimidazole (8a–c) in the presence of aprotic solvents give the 2‐[[(pyridin‐2‐yl‐1‐oxide)methyl]sulfanyl]‐1H‐benzimidazole (9a–d) in good yield. Finally, 9a–d oxidized with mCPBA in chlorinated solvent gives a mixture of 2‐[[(pyridin‐2‐yl‐1‐oxide)methyl]sulfonyl]‐1H‐benzimidazole (3a–d, 10%) and 2‐[[(pyridin‐2‐yl‐1‐oxide) methyl]sulfinyl]‐1H‐benzimidazole (4a–d, 90%) derivatives.     

Facile Synthesis of 3‐Hydroxyglutamic Acids via Cyanation of Chiral N‐Acyliminium Cation Derived From (S)‐Malic Acid

Facile synthesis of 3‐hydroxyglutamic acids via cyanation of an N‐acyliminium intermediate derived from (S)‐malic acid is described. The chiral cyclic imide derived from (S)‐malic acid was converted to an acetoxylactam by reduction with sodium borohydride followed by acetylation. The obtained acetoxylactam was treated with trimethylsilyl cyanide in the presence of boron trifluoride etherate to give the corresponding cyanolactam in high yield, even though the diastereoselectivity of the cyanation reaction was moderate. The diastereomers of the cyanolactam were chromatographically separable and were independently converted to (2R,3S)‐ and (2S,3S)‐3‐hydroxyglutamic acids.     

Synthesis of 1,4‐Diaryl‐piperazine‐2,5‐diones: New Behavior of N,N‐Dimethylformamide Dimethyl Acetal (DMFDMA)

Reactions of chloroacetamides (5) with N,N‐dimethylformamide dimethyl acetal gave 1,4‐diaryl‐piperazine‐2,5‐diones 11a–e in good yield, rather than 1,5‐diaryl‐3,7‐dimethoxy‐1H,5H‐[1,5]diazocine‐2,6‐diones (9a–e).     

Synthesis of New 1,3‐bis(Heteroaryl)‐4,5‐imidazolidinediones Through Reaction of N,N′‐bis(Heteroaryl)methanediamines with Oxalyl Chloride

Reaction of N,N′‐bis(2‐pyridinyl, 3‐pyridinyl, 4‐pyridinyl, 2‐thiazolyl, 4‐nitrophenyl, and 2‐benzothiazolyl)methanediamines 1a–f with oxalyl chloride in dry dichloroethane in the presence of pyridine affords the corresponding 1,3‐bis (heteroaryl)‐4,5‐imidazolidinediones 3a–f in good to excellent yields. The essential role of pyridine in the reaction mixture is described, and reaction details as well as product characterization is discussed.     

Formation of 1,2,5‐Oxadiazole,Isoxazole, Isothiazole, 1,2,3‐Triazole,and Pyrrole Rings from N‐(5,5‐Dimethyl‐3‐oxocyclohexenyl)‐S,S‐diphenylsulfilimine

Reactions of N‐(5,5‐dimethyl‐3‐oxocyclohexenyl)‐S,S‐diphenylsulfilimine, a kind of enaminone, with isopentyl nitrite, isocyanates, isothocyanates, benzenediazonium chloride, and 1,1,1‐trifluoro‐4‐ethoxy‐3‐buten‐2‐one gave 1,2,5‐oxadiazole, isoxazole, isothiazole, 1,2,3‐triazole, and pyrrole derivatives condensed with cyclohexane, respectively, in one pot.     

Improved Syntheses of N‐Desmethylcitalopram and N,N‐Didesmethylcitalopram

An improved and efficient synthesis of N‐desmethylcitalopram (2) and N,N‐didesmethylcitalopram (3) is presented. The method involved N‐demethylation of citalopram (1) using 1‐chloroethyl chloroformate to give 2 in 87% yield. Synthesis of 3 was accomplished by alkylation of 8 with 1‐(3‐bromopropyl)‐2,2,5,5‐tetramethyl‐1‐aza‐2,5‐disilacyclopentane (9).     

Practical Preparation of Z‐α‐(N‐Acetylamino)‐ and Z‐α‐(N‐Benzoylamino)‐α,β‐unsaturated Acids

An efficient two‐step synthetic procedure for the preparation of numerous variations of N‐protected α,β‐unsaturated α‐amino acids and their corresponding esters from N‐protected glycine and either aliphatic or aromatic aldehydes was developed. The reaction involved cyclization of the N‐protected glycine into oxazolone, condensation with the aldehyde, and ring opening with a base.     

Nanoporous Crosslinked Copolymers Prepared by Thermal Degradation of Poly(Methacryl‐N,N′‐diisopropylurea‐co‐ethylene Glycol Dimethacrylate)

Abstract

Copolymers of methacryl‐N,N′‐diisopropylurea (MA‐DiPrU) with ethylene glycol dimethacrylate (EDMA) at monomer‐to‐monomer ratios in the feed: 0.3/0.7; 0.5/0.5; 0.7/0.3; 0.8/0.2 were prepared in butanone in the presence of 2% of dibenzoyl peroxide (Bz₂O₂) at 70°C for 48?hr. Copolymers regardless of the ratio of comonomers in the feed decompose thermally at 200–250°C under the separation of isopropylisocyanate (iPrNCO). Residues after the removal of iPrNCO are thermally stable nanoporous crosslinked copolymers of methacryl‐isopropylamide (MA‐iPrA) with EDMA which decompose by a one‐step mechanism between 280°C and 450°C. Nonporous model copolymers poly(MA‐iPrA‐co‐EDMA) of similar composition, prepared by copolymerization of MA‐iPrA with EDMA, also decomposed by a one‐step mechanism as shown by TGA measurements.     

Dye Binding Characteristics of N,N′‐Methylene‐bis‐acrylamide (NNMBA)‐Crosslinked Polyacrylamide‐Supported Amine and its Photooxidizing Ability

The dye binding characteristics of 8 mol% NNMBA‐crosslinked polyacrylamide‐supported amine is investigated with Rose Bengal (RB), Methyl Orange (MO), Methylene Blue (MB) and Methyl Red (MR). The influence of the concentration of dye solution on dye binding, time course of dye binding and characterization were explored. It is observed that binding is higher in the case of Rose Bengal and dye binding depends on the polarity, as well as the size of the dye molecule. The photooxidation property of polymer bound RB was investigated towards the oxidation of benzoin to benzil. RB bound polymer acts as an efficient heterogenous photooxidizing agent.     

Synthesis of New N‐(5‐Oxo‐2,5‐dihydro)pyrrol‐3‐yl Glycines and N‐(5‐Oxo‐2,5‐dihydro)pyrrol‐3‐yl Glycines Esters

Following our efforts towards the synthesis of new potential inhibitors of Xanthine Dehydrogenase (XDH), we describe here a general method for the preparation of N-(5-oxo-2,5-dihydro)pyrrol-3-yl glycines and N-(5-oxo-2,5-dihydro)pyrrol-3-yl glycine esters from glycine ethyl ester hydrochloride and various 4-hydroxy-5-oxo-2,5-dihydro-1H-pyrrole-3-carboxylic acid esters and carbonitriles.     

The Structure of N‐(1‐Deoxy‐β‐D‐fructopyranos‐1‐yl)‐L‐proline Monohydrate (“D‐Fructose‐L‐proline”) and N‐(1,6‐Dideoxy‐α‐L‐fructofuranos‐1‐yl)‐L‐proline (“L‐Rhamnulose‐L‐proline”)

Nano n-propylsulfonated γ-Fe₂O₃ was found to be a highly efficient, reusable heterogeneous catalyst for the conversion of a range of monosaccharides and some of their derivatives to the corresponding O-isopropylidene derivatives in good to excellent yields by refluxing the reaction mixture in dry acetone. The magnetic property of the catalyst enabled its separation from the reaction mixture by a simple process of filtration along with the aid of an external magnet. The efficiency of the catalyst was found to be largely unaffected for at least up to six cycles of reuse, thus proving the new methodology to be environmentally rewarding besides being simple and facile in operation.     

Synthesis and Crystallographic Study of1,6‐bis‐(N‐phenothiazinyl)‐2,4‐hexadiyne

1,6‐bis‐(N‐phenothiazinyl)‐2,4‐hexadiyne (I) was synthesized in high yield by oxidative coupling of N‐propargyl phenothiazine. Grown from methylene chloride‐hexane solution, I is a monoclinic crystal, space group C2/c a=14.9500(18) Å; b=13.5512(15) Å; c=12.0116(10) Å; β=102.628(9)° Å; V=2374.6(4) ų. The intermolecular distances and arrangement of I in the unit cell preclude the usual diacetylene reactivity. Nevertheless, heating of I at 145°C results in decomposition of I to phenothiazine and a dark brown solid. In addition, cation‐radicals of I were prepared by oxidation with nitrosonium tetrafluoroborate and iodine to give stable ion‐radical salts.     

A Novel Holmium(III) Membrane Sensor Based on N‐(1‐Thien‐2‐Ylmethylene)‐1,3‐Benzothiazol‐2‐Amine

Abstract

A novel plasticized membrane sensor for Ho(III) ions based on N‐(1‐thien‐2‐ylmethylene)‐1,3‐benzothiazol‐2‐amine (TBA) as a neutral carrier was prepared. The best performance was obtained with a membrane composition of 31% PVC, 61% benzyle acetate, 2% sodium tetra phenyl borate and 6% carrier. The electrode exhibits a Nernstian response for Ho(III) ions over a particular concentration range (1.0×10^?5?1.0×10^?2 M) with a slope of 19.7±0.2 mV decade^?1. The limit of the detection is 7.0×10^?6 M. The sensor has a response time of <15 s and a useful working pH range of 4.0–9.5. The proposed sensor discriminates relatively well towards Ho(III) ions with regard to common alkali, alkaline earth, and specially lanthanide ions. It was successfully applied as an indicator electrode in a potentiometric titration of Ho(III) ions with EDTA. It was also applied in determination of fluoride ions in a mouth wash preparation. The proposed sensor was applied for the determination of Ho(III) ion concentration in binary mixtures.     

N‐Glycosyl‐N′‐[p‐(isoamyloxy)phenyl]‐thiourea Derivatives: Potential Anti‐TB Therapeutic Agents

Thiocarlide (THC; N,N′‐bis[p‐(isoamyloxy)phenyl]‐thiourea; also known as Isoxyl^®) has been used in the past as an anti‐tuberculosis agent. In an effort to improve the therapeutic value of THC, several N‐glycosyl‐N′‐[p‐(isoamyloxy)phenyl]‐thiourea derivatives were synthesized by coupling an aniline derivative and glycosyl isothiocyanates. The minimum inhibitory concentration (MIC) values of the new products against M. tuberculosis were determined.