Crystal Structure and Spectroscopic Characterization of Zinc(II) and Mercury(II) Complexes of N‐(Pyridin‐2‐ylmethylene)benzene‐1,4‐diamine

The behavior of N,N′‐bis(pyridin‐2‐ylmethylene)benzene‐1,4‐diamine (L) towards zinc(II), cadmium(II), and mercury(II) chlorides was studied in methanol solutions. In the presence of metal ions, the organic molecule was decomposed to N‐(pyridin‐2‐ylmethylene)benzene‐1,4‐diamine (L′), and complexes of general formula M(L′)Cl₂ were isolated from the mixture. The complexes were identified by elemental analysis, IR, ¹H NMR, and ¹³C NMR spectra, and their structures were further confirmed by single‐crystal X‐ray diffraction analysis of Zn(L′)Cl₂ and Hg(L′)Cl₂. In the solid state of both complexes, the molecules are stabilized by N–H ··· Cl hydrogen bonds and aromatic π–π stacking interactions.     

Reaktionsverhalten verschiedener Carbodiimide mit Ferrocen‐1, 1'‐dicarbonsäure

Reaction Behaviour of Several Carbodiimides with 1, 1'‐Ferrocenedicarboxylic Acid 1, 1'‐bis‐(1, 3‐dicyclohexylureidocarbonyl)‐ferrocene ( 1 ), 1, 1'‐bis‐(1, 3‐diisopropylureidocarbonyl)‐ferrocene ( 2 ) and ferrocene‐1, 1'‐bis‐N‐p‐tolylcarboxamide ( 6 ) were synthesized by melting down 1, 1'‐ferrocenedicarboxylic acid ( 7 ) together with N, N'‐dicyclohexylcarbodiimide (DCC), N, N'‐diisopropylcarbodiimide (DIC) or N, N'‐di‐p‐tolylcarbodiimide ( 8 ), respectively, without application of any solvent in a short space of time. Substance 1 , 2 , 1, 1'‐bis‐(1‐ethyl‐3‐tert‐butylureidocarbonyl)‐ferrocene ( 3 ), 1‐(1‐tert‐butyl‐3‐ethylureidocarbonyl)‐1'‐(1‐ethyl‐3‐tert‐butylureidocarbonyl)‐ferrocene ( 4 ) and 1, 1'‐bis‐(1‐tert‐butyl‐3‐ethylureidocarbonyl)‐ferrocene ( 5 ) were obtained in good yield by reacting 7 DCC, DIC, or N‐tert‐butyl‐N'‐ethylcarbodiimide ( 9 ), respectively, with in ethyl acetate for weeks. Transannular 1, 1'‐ferrocenedicarboxylic anhydride was not detectable or isolable in these reactions. All new compounds were characterized by ¹H‐NMR, ¹³C‐NMR, IR, MS and elementar analysis. In the case of 1 a single crystal structure analysis was made.     

Synthesis and characterization of alt‐bipyridinylene‐phenylene copolymers containing ruthenium(II) complexes

Poly{bis(4,4′‐tert‐butyl‐2,2′‐bipyridine)–(2,2′‐bipyridine‐5,5′‐diyl‐[1,4‐phenylene])–ruthenium(II)bishexafluorophosphate} ( 3a ), poly{bis(4,4′‐tert‐butyl‐2,2′‐bipyridine)–(2,2′‐bipyridine‐4,4′‐diyl‐[1,4‐phenylene])–ruthenium(II)bishexafluorophosphate} ( 3b ), and poly{bis(2,2′‐bipyridine)–(2,2′‐bipyridine‐5,5′‐diyl‐[1,4‐phenylene])–ruthenium(II)bishexafluorophosphate} ( 3c ) were synthesized by the Suzuki coupling reaction. The alternating structure of the copolymers was confirmed by ¹H and ¹³C NMR and elemental analysis. The polymers showed, by ultraviolet–visible, the π–π* absorption of the polymer backbone (320–380 nm) and at a lower energy attributed to the d–π* metal‐to‐ligand charge‐transfer absorption (450 nm for linear 3a and 480 nm for angular 3b ). The polymers were characterized by a monomodal molecular weight distribution. The degree of polymerization was approximately 8 for polymer 3b and 28 for polymer 3d . © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2911–2919, 2004     

Synthese,Struktur, Elektrochemie und optische Eigenschaften von alkinylfunktionalisierten 1,3,2‐Diazaborolen und 1,3,2‐Diazaborolidinen

Syntheses, Structures, Electrochemistry and Optical Properties of Alkyne‐Functionalized 1,3,2‐Diazaboroles and 1,3,2‐Diazaborolidenes The reaction of 2‐bromo‐1,3‐ditert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborole ( 3 ) with lithiated tert‐butyl‐acetylene and lithiated phenylacetylene affords the 2‐alkynyl‐functionalized 1,3,2‐diazaboroles 4 and 5 as a thermolabile colorless oil ( 4 ) or a solid ( 5 ). Similarly 2‐bromo‐1,3‐diethyl‐2,3‐dihydro‐1H‐1,3,2‐benzodiazaborole ( 6 ) was converted into the crystalline 2‐alkynyl‐benzo‐1,3,2‐diazaboroles 7 and 8 by treatment with LiC≡C–tBu or LiC≡CPh, respectively. 2‐Ethynyl‐1,3‐ditert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborole ( 2 ) was metalated with tert‐butyl‐lithium and subsequently coupled with 2‐bromo‐1,3,‐ditert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborole ( 3 ) to afford bis(1,3‐ditert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborol‐2‐yl)acetylene ( 9 ) as thermolabile colorless crystals. Analogously coupling of the lithiated species with 6 or with 2‐bromo‐1,3‐ditert‐butyl‐1,3,2‐diazaborolidine ( 11 ) gave the unsymmetrically substituted acetylenes 10 or 12 , respectively, as colorless solids. Compounds 4 , 5 , 7 – 10 and 12 are characterized by elemental analyses and spectroscopy (IR, ¹H‐, ¹¹B{¹H}, ¹³C{¹H}‐NMR, MS). The molecular structures of 5 , 8 and 9 were elucidated by X‐ray diffraction analyses.     

1,3‐Bis(trimethylsilyl)‐1,3,2‐diazaphospha‐[3]ferrocenophanes

The 2‐tert‐butyl, 2‐phenoxy, and 2‐diethylamino derivatives of 1,3‐bis(trimethylsilyl)‐1,3,2‐diazaphospha‐[3]ferrocenophane were prepared, and the molecular structure of the latter was determined by X‐ray diffraction. The phosphines could be oxidized by their slow reactions with sulfur or selenium, and the molecular structures of three sulfides and one selenide were determined. In contrast, the synthesis of oxides was less straightforward. All new compounds were characterized in solution by multinuclear magnetic resonance methods (1D and 2D ¹H, ¹³C, ¹⁵N, ²⁹Si, ³¹P, and ⁷⁷Se NMR spectroscopy).     

Hydrogen‐bonded thermotropic liquid‐crystalline polyester–amides from bis(hydroxy alkamido)aranes: Synthesis and properties

Hydrogen‐bonded aromatic–aliphatic polyester–amides (PEAs) were prepared by solution/melt polycondensation of aromatic–aliphatic amidodiols 1,4‐bis(4‐hydroxybutyramide)benzene (BHBB), 1,4‐bis(5‐hydroxy pentamide)benzene, 1,4‐bis(6‐hydroxyhexamide)benzene, 1,4‐bis(4‐hydroxybutyramidexylene), 1,4‐bis(5‐hydroxypentamidexylene, 1,4‐bis(4‐hydroxybutyramide)benzene, and 1,4‐bis(6‐hydroxyhexamidexylene) with terephthaloyl chloride/dimethyl terephthalate. Aromatic–aliphatic amido diols were prepared by the aminolysis of γ‐butyrolactone, δ‐valerolactone, and ?‐caprolactone with aromatic diamines such as paraphenylene diamine and paraxylene diamine. The monomers and polymers were characterized by chemical analysis (hydroxyl value and elemental analysis), Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR. The thermal‐ and phase‐transition behaviors of the polymers were investigated by differential scanning calorimetry in combination with hot‐stage optical microscopy. Crystallinity of polymers was examined with wide‐angle X‐ray diffraction. The polymers exhibited liquid crystallinity with layered structures formed by self‐organization of the hetero intermolecular hydrogen‐bonded networks indicating smectic phases except for PEAs prepared from BHBB. The hydrogen atom of the phenyl‐substituent group forces the neighboring carbonyl groups out of plane of the rings preventing formation of layered structures in the case of BHBB. The PEAs retained intermolecular hydrogen bonding even in the mesomorphic state, and variations in the hydrogen‐bonded lamellae/micelles might be responsible for the variations from one smectic to another texture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 335–346, 2003     

Syntheses,Crystal Structures,and Photocatalytic Activities of Three Copper Coordination Polymers Based on Bis(1H‐imidazol‐4‐yl)benzene/3‐(2‐Pyridyl)pyrazole

Three copper(II) coordination polymers (CuCPs), namely, [Cu_0.5(1,4‐bib)(SO₄)_0.5]_n ( 1 ), {[Cu(1,3‐bib)₂(H₂O)] · SO₄ · H₂O}_n ( 2 ), and [Cu(bpz)(SO₄)_0.5]_n ( 3 ), were assembled from the reaction of three N‐donors [1,4‐bib = 1,4‐bis(1H‐imidazol‐4‐yl)benzene, 1,3‐bib = 1,3‐bis(1H‐imidazol‐4‐yl)benzene, and Hbpz = 3‐(2‐pyridyl)pyrazole] with copper sulfate under hydrothermal conditions. Their structures were determined by single‐crystal X‐ray diffraction analyses and further characterized by elemental analyses (EA), IR spectroscopy, powder X‐ray diffraction (PXRD), and thermogravimetric analyses (TGA). Structure analyses reveal that complex 1 is a 3D 6‐connected {4¹² · 6³}‐ pcu net, complex 2 is a fourfold 3D 4‐connected 6⁶‐ dia net, whereas complex 3 is a 1D snake‐like chain, which further expanded into 3D supramolecular architectures with the help of C–H ··· O hydrogen bonds. Moreover, the photocatalytic tests demonstrate that the obtained CuCPs are photocatalysts in the degradation of MB with the efficiency is 86.4 % for 1 , 75.3 % for 2 , and 91.3 % for 3 after 2 h, respectively.     

Palladium‐mediated Cleavage of S–C Bonds: Preparation and Characterization of Palladium(II) Complexes of 2, 6‐Diformyl‐4‐tert‐butylthiophenol Dioxime

The synthesis of air‐sensitive 2, 6‐diformyl‐4‐tert‐butylthiophenol dioxime H₃L3 was achieved by a Pd‐mediated S–C cleavage of the corresponding S‐tert‐butyl protected thioether. The novel ligand forms a dinuclear, neutral Pd^II₂ complex, which is stabilized by two N ··· HO hydrogen bonds to give a pseudo‐macrocyclic structure. The crystal structure of a Pd^II complex of an oxidized isothiazole derivative of H₃L3 is also reported.     

2‐(Dinitromethylene)‐1‐nitro‐1, 3‐diazacyclopentane‐Based Energetic Salts

Energetic salts that contain nitrogen‐rich cations and the 2‐(dinitromethyl)‐3‐nitro‐1, 3‐diazacyclopent‐1‐ene anion were synthesized in high yield by direct neutralization reactions. The resulting salts were fully characterized by multinuclear NMR spectroscopy (¹H and ¹³C), vibrational spectroscopy (IR), elemental analysis, density and differential scanning calorimetry (DSC), and elemental analysis. Additionally, the structures of the ammonium ( 1 ) and isopropylideneaminoguanidinium ( 9 ) 2‐(dinitromethyl)‐3‐nitro‐1, 3‐diazacyclopent‐l‐ene salts were confirmed by single‐crystal X‐ray diffraction. Solid‐state ¹⁵N NMR spectroscopy was used as an effective technique to further determine the structure of some of the products. The densities of the energetic salts paired with organic cations fell between 1.50 and 1.79 g · cm^–3 as measured by a gas pycnometer. Based on the measured densities and calculated heats of formation, detonation pressures and velocities were calculated using Explo 5.05 and found to to be 25.2–35.5 GPa and 7949–9004 m · s^–1, respectively, which make them competitive energetic materials.     

Attempt to Synthesize Hindered 2,4,6‐Tri‐Aryloxy‐s‐Triazines: Bis(2,4‐di‐tert‐Butylphenyl) Carbonate – Crystal Structure

Some less hindered 2,4,6‐tri‐aryloxy‐s‐triazines were synthesized through the reaction of the corresponding phenols as a starting materials with cyanogen bromide (BrCN) to obtain the corresponding arylcyanates and then trimerized. Unexpectedly, 2,4‐di‐tert‐butyl‐1‐cyanatobenzene derived from 2,4‐di‐tert‐butylphenol did not trimerize but, indeed, yielded bis(2,4‐di‐tert‐butylphenyl) carbonate. The structures of 2,4,6‐tri‐aryloxy‐s‐triazines and bis(2,4‐di‐tert‐butylphenyl) carbonate were characterized by means of IR, ¹H, and ¹³C NMR spectroscopies. Also the structure of the latter compound was studied by X‐ray crystallography.     

Synthesis of triblock copolymers based on two isomer acrylate monomers by atom transfer radical polymerization

The syntheses of triblock copolymers by the atom transfer radical polymerization of tert‐butyl and iso‐butyl acrylates as inner blocks with cyclohexyl methacrylate as outer blocks are reported. The living behavior and blocking efficiency of these polymerizations were investigated in each case. The use of difunctional macroinitiators led to ABA triblock copolymers with narrow polydispersities and controlled number‐average molecular weights. These copolymers were prepared from bromo‐terminated macroinitiators of poly(tert‐butyl acrylate) and poly(iso‐butyl acrylate), with copper chloride/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalytic system, at 40 °C in 50% (v/v) toluene solutions. The block copolymers were characterized with size exclusion chromatography and ¹H NMR spectroscopy. Differential scanning calorimetry measurements were performed to reveal the phase segregation. The glass transition of the inner block was not clearly detected, with the exception of the copolymer synthesized with the longest poly(iso‐butyl acrylate) macroinitiator length. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4828–4837, 2005     

New phosphoric triamides: Chlorine substituents effects and polymorphism

New phosphoric triamides 1–10 were synthesized by the reaction of N‐2,4‐dichlorobenzoyl phosphoramidic dichloride with various cyclic aliphatic amines, and the products were characterized by ¹H, ¹³C, ³¹P NMR, and IR spectroscopy and elemental analysis. Surprisingly, the ¹H NMR spectra of compounds 1–7 demonstrate long‐range ⁴J(H,H) coupling constant from 1.5 to 1.9 Hz. Comparison of the NMR and IR spectra of N‐benzoyl, N‐4‐chlorobenzoyl, and N‐2,4‐dichlorobenzoyl phosphoric triamide analogues indicates that N‐2,4‐dichlorobenzoyl derivatives have the most upfield δ(³¹P) and the highest ν(CO) values. The crystal structures of 3 , 4 , 6 , 6a , and 10 have been determined by X‐ray crystallography. Interestingly, the structures of 6 and 6a are polymorphic. All structures form dimers through strong, intermolecular  PO···H N hydrogen bonds. The dimers connect to each other via weak C H···Cl and C H···OH bonds to produce two‐dimensional polymeric chains for 4 and three‐dimensional networks for others. Among new synthesized N‐2,4‐dichlorobenzoyl phosphoric triamides, one indicated polymorphism. All structures were characterized by ¹H, ¹³C, ³¹P NMR, and infrared spectroscopy and elemental analysis. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:168–180, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20592     

Syntheses,Spectroscopic, Structural,Fluorescent and Thermal Properties of Bis(saccharinato)copper(II) Complexes with two Bis(pyridylamine) Ligands

Two new copper(II) complexes of saccharinate (sac) with bis(2‐pyridylmethyl)amine (bpma) and N,N′‐bis[1‐(pyridin‐2‐yl)ethylidene]ethane‐1,2‐diamine (bapen), [Cu(bpma)(sac)₂] · H₂O ( 1 ) and [Cu(bapen)(sac)₂] ( 2 ), were synthesized and characterized by elemental analysis, TG‐DTA, X‐ray diffraction, and UV/Vis and IR spectroscopy, respectively. In 1 , the copper(II) ion is coordinated by two N‐bonded sac ligands, and three nitrogen atoms of bpma, in a distorted square‐pyramidal coordination arrangement, whereas the arrangement around the copper ion in 2 is a distorted octahedron with two N‐coordinated sac ligands and a tetradentate bapen ligand. In addition to hydrogen bonding involving the water molecule in 1 , the mononuclear species of 1 and 2 are further connected by weak intermolecular C–H ··· π and C–H ··· O interactions to form a three‐dimensional network. Both complexes are luminescent at room temperature and their emissions seem to be due to ligand‐based π–π* transitions.     

Synthesis,Spectroscopic Characterization,and Oxidative C–C Coupling in New Copper(II) Salicylaldiminates Containing Sterically Hindered Phenol

New bis[N‐(2,6‐di‐tert‐butyl‐1‐hydroxyphenyl)salicylideneminato]copper(II) complexes bearing HO and CH₃O substituents on the salicyaldehyde moiety were prepared, and have been characterized by elemental analyses, IR, UV/Vis, ESR spectroscopy, and magnetic moments. It has been found that in the synthesis of CH₃O substituted complexes unlike HO bearing, the oxidative C–C coupling of coordinated salicylaldimine ligands take place. It has been suggested that the intermolecular H‐bonding is a dominant factor in controlling of oxidative C–C coupling conversion. The powder ESR spectra of CH₃O substituted compounds unlike of HO are typical of a triplet state Cu^II dimers with a half‐field forbidden (δM = ± 2) and the allowed (δM = ± 1) transitions at 300 and 113 K.     

Identification of tert‐Butyl Cations in Zeolite H‐ZSM‐5: Evidence from NMR Spectroscopy and DFT Calculations

Experimental evidence for the presence of tert‐butyl cations, which are important intermediates in acid‐catalyzed heterogeneous reactions, on solid acids has still not been provided to date. By combining density functional theory (DFT) calculations with ¹H/¹³C magic‐angle‐spinning NMR spectroscopy, the tert‐butyl cation was successfully identified on zeolite H‐ZSM‐5 upon conversion of isobutene by capturing this intermediate with ammonia.     

High Tg and high organosolubility of novel unsymmetric polyimides

A series of new polyimides (PIs) containing di‐tert‐butyl side groups were synthesized via a polycondensation of 1‐(4‐aminophenoxy)‐4‐(4‐amino‐2‐methylphenyl)‐2,6‐di‐tert‐butylbenzene ( 3 ) with various aromatic tetracarboxylic dianhydrides. The novel unsymmetric PIs exhibited a low dielectric constants (2.78–3.02), low moisture absorption (0.53–1.35%), excellent solubility, and high glass transition temperature (308–450 °C). The PI derived from the new diamine and the very rigid naphthalene‐1,4,5,8‐tetracarboxylic dianhydride (NTDA) was soluble in N‐methyl‐2‐pyrrolidone, chloroform, m‐cresol, and cyclohexanone. The unsymmetric di‐tert‐butyl pendent groups significantly enhance the rotational barrier of the polymer chains; thus these PIs had high T_gs. The ¹H NMR spectrum of the diamine 3 revealed that the protons of 4‐aminophenoxy moiety are not chemical shift equivalent. This is because the steric hindrance of the bulky di‐tert‐butyl groups prevents the benzene ring of 4‐aminophenoxy moiety from rotating freely. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2443–2452, 2009     

Synthesis and evaluation of new dental monomers with both phosphonic and carboxylic acid functional groups

Novel dental monomers containing both phosphonic and carboxylic acid functional groups were prepared. The monomers were based on t‐butyl α‐bromomethacrylate (t‐BuBMA) and synthesized in three steps: The reaction of o‐hydroxyaryl phosphonates [diethyl (2‐hydroxyphenyl) phosphonate, tetraethyl (2,5‐dihydroxy‐1,4‐phenylene) diphosphonate and tetraethyl 5,5′‐(propane‐2,2‐diyl)bis(2‐hydroxy‐5,1‐ phenylene) diphosphonate] with t‐BuBMA, the hydrolysis of phosphonate groups to phosphonic acid using trimethyl silylbromide, and the hydrolysis of the t‐butyl groups to carboxylic acid with trifluoroacetic acid. The monomers were solids and soluble in water and ethanol. The structures of the monomers were determined by Fourier transform infrared (FTIR), ¹H, ¹³C, and ³¹P nuclear magnetic resonance (NMR) spectroscopy. The copolymerization behaviors of the synthesized monomers with glycerol dimethacrylate were first investigated in bulk using photodifferential scanning calorimetry at 40 °C with 2,2′‐dimethoxy‐2‐phenyl acetophenone as photoinitiator. Then, the solution copolymerization of the monomers with acrylamide in ethanol and water was studied, indicating that the synthesized monomers are incorporated into the copolymers. The acidic nature of the aqueous solutions of these monomers (pH values 1.72–1.87) is expected to give them etching properties important for dental applications. The interaction of the monomers with hydroxyapatite was investigated using ¹³C NMR and FTIR techniques. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1953–1965, 2009     

Novel Dinuclear Redox‐isomeric Complexes with a Tetrapodal Pyridine‐based Ligand

Tris‐o‐semiquinonato cobalt complexes react with a tetrapodal pyridine‐derived ligand to form dinuclear cobalt compounds of general formula (OMP)[CoQ₂]₂, where OMP = 2,2′‐(pyridine‐2,6‐diyl)bis(N¹,N¹,N³,N³‐tetramethylpropane‐1,3‐diamine), Q = mono‐ or dianion of 3,6‐di‐tert‐butyl‐o‐benzoquinone (complex 1 ) and it derivatives: 3,6‐di‐tert‐butyl‐4,5‐N,N′‐piperazino‐o‐benzoquinone (complex 2 ), and 3,6‐di‐tert‐butyl‐4‐Cl‐o‐benzoquinone (complex 3 ). Single crystal X‐ray crystallography of 1 and 3 indicates two bis‐quinonato cobalt units bound by an OMP ligand, which acts as a bridge. Each central cobalt atom is chelated by one N¹,N¹,N³,N³‐tetramethylpropane‐1,3‐diamine and two o‐quinonato fragments. The nitrogen atom of the pyridine ring is uncoordinated. All complexes were characterized by NIR‐IR and EPR spectroscopy, precise adiabatic vacuum calorimetry, and by variable‐temperature magnetic susceptibility measurements. All data indicate a reversible thermally driven redox‐isomeric (valence tautomeric) transformation in the solid state for all complexes.     

Synthesis and Characteristics of Bis(2, 2‐dinitroethyl‐N‐nitro)ethylenediamine‐Based Energetic Salts

New energetic bis(2, 2‐dinitroethyl‐N‐nitro)ethylenediamine‐based salts exhibiting moderate physical properties, good detonation properties, and relatively low impact sensitivities were synthesized in high yield by direct reactions of bis(2, 2‐dinitroethyl‐N‐nitro)ethylenediamine with organic bases. The resulting salts were fully characterized by multinuclear NMR spectroscopy (¹H and ¹³C), vibrational spectroscopy (IR), differential scanning calorimetry (DSC), and elemental analysis. Solid‐state ¹⁵N NMR spectroscopy was used as an effective technique to further determine the structure of some products. Thermal decomposition kinetics and several thermodynamic parameters of some salts were obtained under non‐isothermal conditions by DSC. The densities of the energetic salts paired with organic cations were in the range 1.60–1.89 g · cm^–3 as measured with a gas pycnometer. Based on the measured densities and calculated heats of formation, detonation pressures and velocities were calculated using Explo 5.05 and found to be 23.6–44.8 GPa and 7790–9583 m · s^–1, respectively, which make them potentially useful as energetic materials.     

Synthesis and Characterization of (–)‐Menthyl Containing N‐Alkyl Cycloimmonium Salts

The reaction of 4‐phenyl‐2‐aminothiazole or 2‐amino pyridine with α‐bromo acetic (–)‐menthyl ester ( 2c ) yields new N‐alkyl cycloimmonium bromides ( 1c , 3 ) with the chiral (–)‐menthyl substituent, which were isolated and fully characterized by ¹H and ¹³C NMR spectroscopy for the first time. In addition, starting from 4‐phenyl‐2‐aminothiazole, two further N‐alkyl cycloimmonium bromides ( 1a , 1b ) were prepared. The molecular and crystal structures of all three thiazole derived N‐alkyl cycloimmonium bromides ( 1a – c ) were determined by single‐crystal X‐ray diffraction. In all cases the crystal structures are dominated by N–H ··· Br hydrogen bonds, which results in the formation of an extensive hydrogen bonded network in the crystal. Interestingly, in all structures S ··· Br^– distances shorter than the sum of the van der Waals radii are observed.