Intramolecular photocyclization of N-[(2-haloaryl)methyl]pyridinium and n-(arylmethyl)-2-halopyridinium salts

Various N-[(2-haloaryl)methyl]pyridinium, N-(arylmethyl)-2-halopyridinium and N-(2-halobenzyl)iso-quinolinium salts have been synthesized and their intramolecular photocyclization reactions studied. Upon irradiation the aqueous solution of N-[(2-haloaryl)methyl]pyridinium, and N-arylmethyl-2-halopyridinium salts 1, 2 were cyclized to give isoindolium salts. In contrast to the pyridinium salts 1, 2 , the aqueous solution of N-(2-halobenzyl)isoquinolinium salts 3 appear not to undergo photocyclization. N-Benzyl-2-chloropyridinium salts 1c is more reactive than N-(2-chlorobenzyl)pyridinium salt 1a in the photocyclization. N-(2-Chlorobenzyl)-2-chloropyridinium salt 1d is three times more reactive than 1c . A mechanism of π-complex formation of the halogen moiety of the pyridinium ring with the phenyl ring is suggested for the reactive pyridinium salt. The triplet energy of the isoquinolinium salts 3 is tool low to photocyclize.     

Solid‐State Emissive Aroyl‐S,N‐Ketene Acetals with Tunable Aggregation‐Induced Emission Characteristics

N‐Benzyl aroyl‐S,N‐ketene acetals can be readily synthesized by condensation of aroyl chlorides and N‐benzyl 2‐methyl benzothiazolium salts in good to excellent yields, yielding a library of 35 chromophores with bright solid‐state emission and aggregation‐induced emission characteristics. Varying the substituent from electron‐donating to electron‐withdrawing enables the tuning of the solid‐state emission color from deep blue to red.     

Novel polyviologens: Photochromic redox polymers with film-forming properties

Several novel polyamides containing the N,N′-dialkyl-4,4′-dipyridinium (“viologen”) system were made by interfacial condensation of N,N′-bis(aminoalkyl)-4,4,-dipyridinium salts with di-, tri-, or tetrafunctional acid chlorides. These materials are useful redox polymers which turn deeply colored when reduced chemically or electrically, or when exposed to light.     

Synthesis of some isomeric quinoxaline derivatives with 6‐azauracil cycle

By diazotization of 3‐(2‐aminophenyl)‐1,2‐dihydroquinoxaline 1c, its 3‐(4‐aminophenyl)‐isomer 2c , 3‐(2‐aminobenzyl)‐1,2‐dihydroquinoxaline‐2‐one 3c and its 3‐(4‐aminobenzyl)‐isomer 4c and by azo coupling of formed diazonium salts with ethyl cyanoacetylcarbamate, corresponding hydrazones ld‐4d were prepared. Cyclization of these compounds afforded compounds containing two heterocyclic rings with acidic N‐H groups in their molecules: 3‐[2‐(5‐cyano‐6‐azauracil‐1‐yl)‐phenyl]‐1,2‐dihydroquinoxaline‐2‐one 1e , its 4‐isomer 2e , 3‐[2‐(5‐cyano‐6‐azauracil‐1‐yl)‐benzyl]‐1,2‐dihydroquinoxaline‐2‐one 3e and its 4‐isomer 4e . The aminoderivative 1c was prepared by the reaction of N‐acetylisatine with o‐phenylenediamine and by hydrolysis of prepared N‐acetylderivative 1a . The aminoderivative 2c was prepared by the condensation of 4‐acetylaminophenylglyoxylic acid with o‐phenylenediamine and by hydrolysis of prepared N‐acetylderivative 2a . The aminoderivative 3c was prepared by the condensation of 2‐nitrophenylpyruvic acid with o‐phenylenediamine and by the reduction of the formed nitroderivative 3b and finally starting aminoderivative 4c was obtained by the condensation of o‐phenylenediamine with 4‐aminophenylpyruvic acid.     

Enantioselective Phase Transfer Catalytic Reactions. A Comparative Study on the Use of Cinchonidine Salts and Glucose-Based Lariat Ethers Including Phosphinoxidomethyl Derivatives

Five model reactions including an epoxidation by alkylhydroperoxide or Darzens condensation, as well as Michael additions were accomplished under phase transfer catalytic conditions using cinchonidine salts or lariat ethers with side arms having HO or Ph₂P(O) endgroups as the catalysts. In almost all cases, the use of lariat ethers with either hydroxyalkyl- or phosphinoxido N-substituents led to better enantioselectivities than that of the three cinchonidine derivatives studied.     

Novel N‐methylbenzothiazolium salts as hardeners for epoxy and acrylate monomers

Novel N‐methylbenzothiazolium salts [N‐methyl‐2‐benzylthiobenzothiazolium, N‐methyl‐2‐(4‐nitrobenzylthio)benzothiazolium, N‐methyl‐2‐(1‐ethoxycarbonylethylthio)benzothiazolium, and N‐methyl‐2‐methylthiobenzothiazolium hexafluoroantimonates] were synthesized by the reaction of the corresponding 2‐substituted benzothiazole with dimethylsulfate, followed by anion exchange with KSbF₆. These benzothiazolium salts cationically polymerized an epoxy monomer by photoirradiation. They also polymerized an acrylate monomer via a photoradical process. The use of aromatic compounds such as 2‐ethyl‐9,10‐dimethoxyanthracene as photosensitizers was effective in enhancing the polymerization. These benzothiazolium salts also served as thermal cationic initiators. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3828–3837, 2003     

Synthesis of new derivatives of 1,5,9,13-tetraaza[16]annulene using 2-substituted vinamidinium salts

New 7,15-dibromo-, 7,15-di(bromomethyl)-, and 7,15-di[4-(bromomethyl)phenyl]-1,5,9,13-tetraaza[16]annulene derivatives are synthesized via the condensation reaction of 2-substituted vinamidinium salts [2-substituted 3-(dimethylamino)-N,N-dimethyl-2-propen-1-aminium salts] with 1,8-diaminonaphthalene in acetonitrile/acetic acid. The ultraviolet spectral behavior of these compounds is examined in DMSO.     

Synthesis and gas transport properties of random amide imide copolymers

Fully imidized random amide imide copolymers (rPAI) can be prepared in an aprotic solvent from trimellitic anhydride chloride (TMAc) and mixtures of various aromatic diamines via condensation polymerization. The polymers are soluble in a number of aprotic organic solvents including 1‐methyl‐2‐pyrrolidinone (NMP), N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), and dimethylsulfoxide (DMSO). The gas transport properties of the rPAI materials are governed by the local structure around both the amide and imide linkages and can be tuned by the choice and ratio of diamines used. Significant improvement in selectivity relative to polyimides can be achieved. When inorganic carbonate salts are used to scavenge byproduct hydrogen chloride, the amount of residual salt in the dense films has a substantial effect on their gas transport properties. A fugitive salt process was identified, which eliminated this problem of residual inorganic salts. The activation energy for O₂, N₂, He, CO₂, and CH₄ permeability was determined for one of the copolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1951–1965, 2000     

Towards the Synthesis of Azoacetylenes

The synthesis of azoacetylenes (=dialkynyldiazenes) 1 and 2 has been investigated. They represent a still elusive class of chromophores with potentially very interesting applications as novel bistable photochemical molecular switches or as antitumor agents (Fig. 1). Our synthetic efforts have led us alongside three different approaches (Scheme 1). In a first route, it was envisioned to generate the azo (=diazene) bond by photolysis of N,N′‐dialkynylated 1,3,4‐thiadiazolidine‐2,5‐diones that are themselves challenging targets (Scheme 2). Attempts are described to obtain the latter by alkynylation of the parent heterocycle with substituted alkynyliodonium salts. In a conceptually similar approach, the no‐less‐challenging dialkynylated 9,10‐dihydro‐9,10‐diazanoanthracene ( 29 ) was to be generated by alkynylation of the unsubstituted hydrazine 28 (Scheme 6). In a second route, the generation of the N?N bond from Br‐substituted divinylidenehydrazines (ketene‐azines) 35 was attempted in a synthetic scheme involving an aza‐Wittig reaction between azinobis(phosphorane) 36 and (triisopropylsilyl)ketene 37 (Scheme 7). Finally, a third approach, based on the formation of the central azo bond as the key step, was explored. This route involved the extrapolation of a newly discovered condensation reaction of N,N‐disilylated anilines with nitroso compounds (Scheme 11, and Tables 1 and 2) to the transformation of N,N‐disilylated ynamine 55 and nitroso‐alkyne 54 (Scheme 13).     

Ring transformations of heterocyclic compounds. XVI. Spiro[cyclohexadiene-dihydroacridines]. A novel class of spirodihydroacridines by ring transformation of pyrylium salts with 9-methylacridine and its quaternary salts

2,4,6-Triarylpyrylium salts 1 react with the in situ generated anhydrobase of 9,10-dimethylacridinium methosulfate ( 2a ) in the presence of anhydrous sodium acetate in ethanol by a 2,5-[C₄+C₂] pyrylium ring transformation to give the hitherto unknown 6-aroyl-3,5-diaryl-10′-methylspiro[cyclohexa-2,4-diene-1,9′-9′,10′-dihydro-acridines] 3 . When the pyrylium perchlorate 1a is treated under the same conditions with the N-ethyl, N-allyl or N-benzyl substituted acridinium salts 2b-d a dealkylation of these salts occurs and the N-unsubstituted spiro[cyclohexadiene-dihydroacridine] 4a is formed. The same compounds 4 can also be obtained by transformation of the pyrylium salts 1 with 9-methylacridine ( 7 ) and triefhylamine/acetic acid in ethanol. Structure elucidation is performed by an X-ray crystal structure determination of the spiro[cyclohexadiene-dihydroacridine] 3a . Spectroscopic data of the transformation products and their mode of formation are discussed.     

Investigation of the Effect of Various Substituents on the Density of Tetrazolium Nitrate Salts as Green Energetic Materials

The substitution effect of various functional groups such as –NO₂, –CN, –N₃, –NF₂, and –NH₂ on the density of tetrazolium nitrate salts is investigated through multiple linear regression method. The methodology of this work introduces a new model, which related density of tetrazolium nitrate salts to the number of fluorine and nitrogen atoms, the presence of NF₂ groups, NO₂ groups, as well as CH₃ groups in the structural formula. The new reliable correlation shows that the NF₂ and NO₂ group can cause increasing the density of tetrazolium nitrate salts, especially NO₂, whereas the CH₃ group can decrease their density. The new proposed relationship has good reliability and predictability, so it can be used to design new rich nitrogen compounds based on tetrazolium nitrate salts as green energetic materials. These results are also tested for N,N′‐azo‐1,2,4‐triazolium nitrate salts, which is caused to derive another correlation. This correlation shows that the presence of NF₂ functional groups increases the density of N,N′‐azo‐1,2,4‐triazolium nitrate salts as well as the value of n_O/n_C.     

Amidine als Zwischenprodukte bei Umamidierungsreaktionen. 9. Mitteilung über Umamidierungsreaktionen

Amidines as Intermediates in Transamidation Reactions By loss of water in the presence of p-toluenesulfonic acid/xylole N-aminoalkyllactames form bicyclic amidines. The corresponding N-alkylaminoalkyl-lactames' react to bicyclic amidinium salts or to transamidated products, ring-enlarged by the N-alkylamino residue, respectively (s. Scheme 1). The bicyclic amidines and amidinium salts are partially hydrolyzed by KOH/H₂O to lactames (s. Scheme 2). Which of the two possible isomeric lactames are formed is discussed.     

Novel pyridinium salts as cationic thermal and photoinitiators and their photosensitization properties

Novel pyridinium salts [N‐(α‐phenylbenzyl)‐, N‐(1‐naphthylmethyl)‐, or N‐cinnamyl p‐ or o‐cyanopyridinium hexafluoroantimonates] were synthesized by the reaction of p‐ or o‐cyanopyridine and the corresponding bromides followed by anion exchange with KSbF₆. These pyridinium salts polymerized epoxy monomers at lower temperatures than previously reported for N‐benzyl‐2‐cyanopyridinium hexafluoroantimonate. The o‐substituted pyridinium salts showed higher activity than the p‐substituted ones, and the crosslinked epoxy polymers cured with these initiators showed higher glass‐transition temperatures. These pyridinium salts photoinitiated radical polymerization as well as cationic polymerization. The photopolymerization was accelerated by the addition of aromatic ketones as photosensitizers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1037–1046, 2002     

Transition metal ion complexes of thiosemicarbazones derived from 2-acetylpyridine. Part 4. The 3-piperidinyl derivative

Summary Metal ion complexes of the thiosemicarbazone, 3-piperidinyl-3-thiocarboxylic acid-2-[1-(2-pyridyl)ethylidene]hydrazide (HLpip) have been prepared and spectrally characterized. HLpip coordinates both as the deprotonated ligand (i.e., pyridylN, azomethineN, and thione sulphur) and the neutral ligand (i.e., pyridylN and azomethineN) with the sulphur possibly weakly coordinating in [Ni(HLpip)₂](BF₄)₂. All three preparative cobalt(II) salts yielded cobalt(III) cationic complexes. The nickel(II) and copper(II) chloride salts gave [M(Lpip)Cl] solids while complexes involving the neutral ligand were prepared with the corresponding bromide salts. Significant differences in the spectral properties of the various complexes are observed when compared to other thiosemicarbazones prepared from 2-acetylpyridine.     

Influence of N‐Alkyl Substituents and Counterions on the Structural and Mesomorphic Properties of Guanidinium Salts: Experiment and Quantum Chemical Calculations

A series of N‐4‐(4′‐alkoxybiphenyl)‐N′,N′,N”,N“‐tetramethylguanidinium salts was synthesized with varying alkoxy chain lengths and additional N‐alkyl substituents, each with a number of different counterions. X‐ray crystal‐structure analyses of 1b I , 1b PF₆ , 2a I , and 4a I reveal bilayer structures in the solid state and, for the 1b and 1b PF₆ salts, a hydrogen‐bond‐type connectivity between the guanidinium N‐H group and the anion is found. For the N‐alkyl homologues 2a I and 4a I the anion is still oriented close to the head group, although at a larger distance. Ion pairs are present also in solution, as demonstrated by ¹H NMR: the N‐H chemical shift shows a good linear correlation with the radius, and hence the hardness, of the anion. The intramolecular conformational flexibility of 1b I , 2b I , 3b I, and 4b I was studied by temperature‐dependent ¹H NMR spectroscopy and discrete activation barriers were determined for rotations about each of the three C? N partial double bonds of the guanidinium core. The relative heights of the individual barriers change between the N‐H and the N‐alkylguanidinium salts. A fourth barrier is observed for the rotation about the N? biphenyl bond. DFT calculations of charge densities show that the positive charge resides primarily on the central carbon atom. Rotational barriers were calculated for N′‐substituted 2‐amino‐1,3‐dimethylimidazolidinium cations as models, and are in qualitatively good agreement with the NMR data. Mesomorphic properties were studied by differential‐scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction (WAXS/SAXS). All liquid‐crystalline guanidinium salts exhibit smectic A mesophases. Clearing temperatures show a linear correlation with the anionic radius. Substitution of the N‐H group with methyl, ethyl, or propyl results in decreasing mesophase widths and a concomitant shrinkage of the layer spacings.     

Design and synthesis of some new thiophene and 1,3,4-thiadiazole based heterocycles

Abstract

The reaction of 3-oxopropanenitriles with phenyl isothiocyanate in DMF containing KOH afforded the corresponding potassium salts. The latter salts were converted into ketene N,S-acetals upon acidification with hydrogen chloride. The reaction of the ketene N,S-acetals with 2-bromo-1-[5-methyl-1-(p-tolyl)-1H-1,2,3-triazol-4-yl]ethan-1-one or 3-(2-bromoacetyl)-2H-chromen-2-one gave novel thiophenes in good yields. Treatment of the ketene N,S-acetals with hydrazonyl halides afforded 1,3,4-thiadiazoles in good yields. The stereochemistry of the synthesized compounds was studied.     

Acylation,cyanoethylation and alkylation of methyl and phenyl indolylmagnesium salts: Influence of the substituents on the c- and N-reaction products

Analysis of the influence of the substitution on indolylmagnesium salts in the reaction with benzoyl chlo ride, acrylonitrile and methyl iodide, giving the C- and N-derivatives, have been carried out. The yield in the C- and N-product depends upon the electronic character and position of the substituent (methyl or phenyl) on the indole ring and of the ethereal solvent as well as the concentration and molar ratio of the reagents. The 2- or 3-phenyl substituted indolylmagnesium salts with acrylonitrile always gave the 1-(2-cyanoethyl)indole derivative.     

Novel High Energy Intermediate Analogues with Triazasterol-Related Structures as Potential Inhibitors of the Ergosterol Biosynthesis II [1]. Optimization of the Synthesis of 1,6,7,11b-Tetrahydro-2 H pyrimido[4,3- a ] isoquinolin-4-amines as Parent Compounds of Novel 8,13,15-Triazasteroids

Various routes for an effective synthesis of 1,6,7,11b-tetrahydro-2H-pyrimido[4,3-a]isoquinolin-4-amine and its 9-methoxy derivative, which were designed as tricyclic triaza-analogues with stable positive charge to mimic carbocationic high energy intermediates (HEI) of the ergosterol biosynthesis, were investigated. Starting from β-phenylethylamines the corresponding 3-chloro-N-phenethylpropionamides were prepared and transformed into N-phenethyl-3-phthalimidopropionamides. These amides were cyclized via Bischler-Napieralski reaction to yield after hydrolytic deprotection 1-(aminoethyl)tetrahydroisoquinolines. The 1,6,7,11b-tetrahydro-2H-pyrimido[4,3-a]isoquinoline ring system was then built up by condensation of the bicyclic diamines with various carbonic acid derivatives (carbon disulfide, nitroguanidine, tetraethyl orthocarbonate). Along with the applied reaction sequences unexpected side reactions took place. The structures of all isolated compounds were proven and completely assigned on the basis of homo- and heteronuclear correlated 1D and 2D NMR experiments. The in vitro antifungal susceptibility tests with a standard panel of eight pathogenic fungi revealed only weak antimycotic effects of the pyrimidoisoquinolinamine salts, but strong inhibitory activity of the intermediate 1-(aminoethyl)-3,4-dihydroisoquinoline.     

New Synthetic Approach to 4-N-Arylaminoazuleno[2,1-d]pyrimides

1-Cyano-2-N,N-dimethylformamidinylazulenes as new synthons directed to heterocycle-fused azulenes were obtained by the condensation of 2-amino-1-cyanoazulenes and N,N-dimethylformamide dimethyl acetal (DMFDMA). 1-Cyano-2-N,N-dimethylformamidinylazulene (2a) and 1-bromo-3-cyano-2-N,N-dimethylformamidinylazulene (2b) reacted with anilines (3a–h) to give 4-N-arylaminoazuleno-[2,1-d]pyrimidines in moderate yields. This reaction provides a new procedure for synthesis of pyrimidine-fused azulenes.     

A new synthesis of imidazo[1,2-a]pyridine and imidazo[2,1-a]isoquinoline derivatives

A new synthesis of imidazo[1,2-a]pyridine and imidazo[2,1-a]isoquinoline derivatives 4 and 8 , respectively by 1,5-dipolar cyclization reactions of stabilized pyridinium N-ylides 3a-e or isoquinolinium N-ylide 7 is described. The starting N-ylides 3a-e and 7 are prepared by the reaction of the corresponding pyridinium salts 1a-e or isoquinolinium salts 6 with N-bis(methylthio)methylene-p-toluenesulfonamide (2) .