Experimental and Theoretical Studies of Bromination of Diethyl 2,4,6‐Trimethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylate

A reaction of diethyl 2,4,6‐trimethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylate with 1, 2, and more equivalents of N‐bromosuccinimide (NBS) in methanol was investigated by NMR spectroscopy at a temperature interval ranging from 25 to 40°C. The reaction was found to proceed through several steps. The structures of the intermediates diethyl 3‐bromo‐2,4,6‐trimethyl‐3,4‐dihydropyridine‐3,5‐dicarboxylate, diethyl 3‐bromo‐2‐methoxy‐2,4,6‐trimethyl‐1,2,3,4‐tetrahydropyridine‐3,5‐dicarboxylate, and diethyl 3,5‐dibromo‐2‐methoxy‐2,4,6‐trimethyl‐2,3,4,5‐tetrahydropyridine‐3,5‐dicarboxylate were identified by multinuclear (¹H, ¹³C, and ¹⁵N) NMR spectral data. The optimal structures of all species participating in the reaction as well as changes in their relative energies along with the proposed pathway of the reaction were analyzed by quantum‐chemical calculations. The mechanism of bromination of diethyl 2,4,6‐trimethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylate with NBS in methanol was found to favor the bromination in the 2,6‐methyl side chains as the only products in full agreement with experimental observations.     

Preparation,structure, and optical properties of chiral sulfoxides and disulfoxide with a trithiole ring

Optically active 4,9‐diethyl[1,4]‐dithiino[5,6‐f]benzo[1,2,3]trithiole 5‐oxide ( 3 ) and 4,9‐diethyl[1,4]dithiino[5,6‐f]benzo[1,2,3]trithiole 5,8‐dioxide ( 4 ) were obtained by the asymmetric oxidation of 6,11‐diethyl[1,4]dithiino[5,6‐h]benzo[1,2,3,4,5]pentathiepin ( 1 ). The reaction was accompanied by desulfurization and ring‐contraction reactions of the pentathiepin ring. Similarly, optically active 4,8‐diethyl[1,3]dithiolo[4,5‐f]benzo[1,2,3]trithiole 5‐oxide ( 7 ) was produced by the analogous asymmetric oxidation of 6,10‐diethyl[1,3]dithiolo[4,5‐h]benzo[1,2,3,4,5]pentathiepin ( 2 ). The specific rotations of 3 , 4 , and 7 were measured in chloroform, and their optical purity was verified by ¹H NMR with a shift reagent [Eu(hfc)₃]. The structures of 4 and 7 were determined by X‐ray crystallography using Cu Kα radiation, and the absolute configuration of the sulfinyl group was examined based on the Flack parameter, which revealed that 4 has an RR configuration, while 7 has an S configuration. The circular dichroism spectra of 3 , 4 , and 7 were measured in chloroform. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:88–94, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10104     

Synthese und Reaktivität von 2‐Brom‐1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol Molekülstruktur von Bis(1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol‐2‐yl)

Synthesis and Reactivity of 2‐Bromo‐1,3‐diethyl‐2,3‐dihydro‐1 H ‐1,3,2‐benzodiazaborole Molecular Structure of Bis(1,3‐diethyl‐2,3‐dihydro‐1 H ‐1,3,2‐benzodiazaborol‐2‐yl The reaction of a slurry of calcium hydride in toluene with N,N′‐diethyl‐o‐phenylenediamine ( 1 ) and boron tribromide affords 2‐bromo‐1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol ( 2 ) as a colorless oil. Compound 2 is converted into 2‐cyano‐1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborole ( 3 ) by treatment with silver cyanide in acetonitrile. Reaction of 2 with an equimolar amount of methyllithium affords 1,3‐diethyl‐2‐methyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborole ( 4 ). 1,3,2‐Benzodiazaborole is smoothly reduced by a potassium‐sodium alloy to yield bis(1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol‐2‐yl] ( 7 ), which crystallizes from n‐pentane as colorless needles. Compound 7 is also obtained from the reaction of 2 and LiSnMe₃ instead of the expected 2‐trimethylstannyl‐1,3,2‐benzodiazaborole. N,N′‐Bis(1,3‐diethyl‐2,3‐dihydro‐1 H‐1,3,2‐benzodiazaborol‐2‐ yl)‐1,2‐diamino‐ethane ( 6 ) results from the reaction of 2 with Li(en)C≡CH as the only boron containing product. Compounds 2 – 4 , 6 and 7 are characterized by means of elemental analyses and spectroscopy (IR, ¹H‐, ¹¹B{¹H}‐, ¹³C{¹H}‐NMR, MS). The molecular structure of 7 was elucidated by X‐ray diffraction analysis.     

Synthesis of novel N1‐(2‐furanidyl)‐5‐fluorouracil derivatives of α‐hydroxy(thio)phosphonates

Several N¹‐(2‐furanidyl)‐5‐fluorouracil derivatives of α‐hydroxythiophosphonates were synthesized via oxidation by Moffatt's method of N¹‐(2‐furanidyl)‐N³‐(hydroxyalkyl)‐5‐fluorouracil, followed by the addition of diethyl thiophosphite. The phosphonate products were obtained by the oxidation of the corresponding thiophosphonates with m‐chloroperoxybenzoic acid. The crystal structure of compound 6a was determined by X‐ray diffraction. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:211–215, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10021     

A New Class of Heterobinuclear Complexes: Crystal Structure and Magnetism of Copper(II)‐Nickel(II) Complexes Incorporating Two Different Macrocyclic Ligands

Three novel oxamido‐bridged heterobinuclear copper(II)‐nickel(II) complexes incorporating two different tetraazamacrocyclic compounds were synthesized and characterized by IR, ESR, and electronic spectra. They are of the formulas [(CuL¹)Ni(rac‐cth)](ClO)₄₂⋅H₂O ( 1 ), [Cu(L²)Ni(rac‐cth)](ClO₄)₂⋅0.5 EtOH ( 2 ), and [(CuL³)Ni(rac‐cth)](ClO₄)₂⋅H₂O ( 3 ). L¹, L², and L³ are the dianions of diethyl 5,6,7,8,16,17‐hexahydro‐6,7‐dioxo‐15H‐dibenzo[e,n][1,4,8,12]tetraazacyclopentadecine‐13,19‐dicarboxylate, diethyl 5,6,7,8,15,16‐hexahydro‐6,7‐dioxodibenzo[1,4,8,11]tetraazacyclotetracine‐13,18‐dicarboxylate, and diethyl 5,6,7,8,15,16‐hexahydro‐15‐methyl‐6,7‐dioxodibenzo[1,4,8,11]tetraazacyclotetradecine‐13,18‐dicarboxylate, respectively, and rac‐cth is rac‐5,7,7,12,14,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane. The crystal structures of 1 and 2 were determined by single‐crystal X‐ray analysis. The Ni^II ion is pseudooctahedrally coordinated. The coordination geometry around the Cu^II ion in 2 is slightly distorted square planar, while that in 1 shows significant distortion towards a tetrahedral structure. The temperature dependence of the magnetic susceptibility for 1 and 2 was analyzed by means of the Hamiltonian Hˆ =−2J Sˆ ₁⋅ Sˆ ₂, leading to J=−63.9 and −67.4 cm⁻¹ for 1 and 2 , respectively.     

π‐Excess Aromatic σ2P Ligands: Formation of a Heterocyclic 1,2‐Diphosphine by the Addition of tBuLi and Subsequent Inverse Addition of the Product at the P=C Bonds of Two Molecules of 1‐Neopentyl‐1,3‐benzazaphosphole

The reactivity of tBuLi (pentane) toward the N‐neopentyl‐substituted π‐excess P=CH–N heterocycle 1 depends on the solvent (tetrahydrofuran, diethyl ether, hexane, and toluene) and reaction conditions. Trapping of the resulting organolithium compounds with CO₂/ClSiMe₃, ClSiMe₃, or EtI led to various products indicating CH lithiation ( 1a , b ), normal addition of tBuLi at the P=C bond (E/Z ‐2a , b ), inverse addition of the primary addition product 2_Li at the P=C bond of a second molecule 1 , affording 3‐tert‐butyl‐2,2’‐bis(1,3‐benzazaphospholines) 3 , or inverse addition of tBuLi ( 4b,c ). The formation of 3 demonstrates a novel route to asymmetric heterocyclic 1,2‐diphosphine ligands. The structure elucidation of the new compounds is based on their ³¹P and ¹³C NMR data with conclusive chemical shifts and P–C coupling constants, that of the isolated PH‐functionalized diphosphine 3 on crystal structure analysis.     

A Convenient Synthetic Route of Diethyl (4‐Oxo‐chromeno[2,3‐d]pyrimidin‐2(5)‐yl)phosphonates

Novel diethyl (4‐oxo‐3,4‐dihydro‐2H‐chromeno[2,3‐d]pyrimidin‐2‐yl)phosphonate as two enantiomers and diethyl (4‐oxo‐1,5‐dihydro‐4H‐chromeno[2,3‐d]pyrimidin‐5‐yl) phosphonate were obtained in easy procedure via reaction of 2‐imino‐2H‐chromene‐3‐carboxamide, dimethylformamide dimethyl‐acetal, and diethyl phosphite in a simple one pot. Possible reaction mechanisms were proposed. The structures of the obtained products were confirmed by elemental analyses and spectral tools.     

A convenient synthesis of novel 7‐phosphonylbenzyl‐2‐substituted pyrazolo[4,3‐e]‐1,2,4‐triazolo[1,5‐c]‐pyrimidine derivatives

A series of pyrazolo[4,3‐e]‐1,2,4‐triazolo‐[1,5‐c]pyrimidine derivatives, bearing phosphonylbenzyl chain in position 7, were conveniently synthesized in an attempt to obtain potent and selective antagonists for the A_2A adenosine receptor or potent pesticide lead compounds. Diethyl[(5‐amino‐4‐cyano‐3‐methylsulfanyl‐pyrazol‐1‐yl)‐benzyl]phospho‐nate ( 3 ), which was prepared by the cyclization of diethyl 1‐hydrazinobenzylphosphonate ( 1 ) with 2‐[bis(methylthio)methylene]malononitrile ( 2 ), reacted with triethyl orthoformate to afford diethyl[(4‐cyano‐5‐ethoxymethyleneamino‐3‐methylsulfanyl‐pyrazol‐1‐yl)‐benzyl]phosphonate ( 4 ), which reacted with various acyl hydrazines in refluxing 2‐methoxyethanol to give the target compounds 5a–h in good yields. Their structures were confirmed by IR, ¹H NMR, ¹³C NMR, MS, and elemental analysis. The crystal structure of 5e was determined by single crystal X‐ray diffraction © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:634–638, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20478     

Sequential Intramolecular Diels–Alder Reaction of 3‐Heteroaryl‐2‐propenylamides of Ethenetricarboxylate

The reaction of 1,1,2‐ethenetricarboxylic acid 1,1‐diethyl ester with E‐3‐(2‐furyl)‐2‐propenylamines under the amide condensation conditions (EDCI/HOBt/Et₃N) on heating at 80–110°C afforded cis‐fused tricyclic compounds, furo[2,3‐f]isoindoles as major product. On the other hand, the reaction with E‐3‐(3‐furyl)‐2‐propenylamines afforded trans‐fused tricyclic compounds predominantly. The formation of amide/[4 + 2] cycloaddition/hydrogen‐shift reactions proceed sequentially. The observed stereoselectivity of the fused rings has been investigated by the density functional theory calculations. The reaction of 1,1,2‐ethenetricarboxylic acid 1,1‐diethyl ester with 3‐(3‐pyridinyl)‐2‐propen‐1‐amine under the amide condensation conditions afforded HOBt‐incorporated 3,4‐trans‐pyrrolidine selectively. The chemoselectivity and stereoselectivity of the reactions with (3‐heteroaryl)‐2‐propen‐1‐amines depend on the nature of heteroarenes.     

Synthesis and crystal structure of ethyl benzimidazole-2-yl phosphonate

When N-cyanoimido-( O,O-diethyl)phosphonyl/S-methyl thiocarbonate (1) was treated with o-phenylenediamine in the presence of Et3N in ethanol,diethyl benzimidazole-2-yl phos-phonate (2) was obtained and hydrolyzed during the recrys-tallization in MeOH/H2O,generating ethyl benzimidazole-2-yl phosphonate (3).Hie crystal structure of compound 3 was determined by X-ray diffraction method.The crystals belong to monoclinic,space group C2/c,a = 1.78408(18) ,6 = 0.83725(9),c= 1.67401(18) nm,β= 118.997(2),V = 2.1870(4) nm3,Z = 8,Dc=1.374 g/cm3,F(000)=944.The final R and wR are 0.0499 and 0.1436,respectively.The mechanism of the above reaction is also discussed.     

Blue/green light‐emitting diode based on diethyl[N‐arylmethylenethiobenzahydrazonato]gallium complexes

Three diethylgallium complexes of type Et₂GaL [L = N‐(4‐methoxy) benzylidenethiobenzahydrazonato ( 1 ), N‐(4‐N,N‐dimethylamino)benzy lidenethiobenzahydrazonato ( 2 ) and N‐(9‐anthryl)methylenethio benzahydrazonato ( 3 )] were synthesized by the reaction of triethylgallium with appropriate N‐arylmethylenethiobenzahydrazones. The compounds obtained were characterized by elemental analysis, ¹H NMR, IR and mass spectroscopy, respectively. Monolayer light‐emitting diodes based on the diethyl[N‐arylmethylenethio benzahydrazonato]gallium doped poly(vinylcarbazole) were fabricated using a spin coating method. The photoluminescent and electroluminescent emission spectra of 1 and 3 were measured (429 and 479 nm for 1 and 3 , respectively). The electroluminescent properties of 1 and 3 were also studied. The electroluminscence bands are located in the blue/green region (465 and 510 nm for complexes 1 and 3 , respectively). Copyright © 2006 John Wiley & Sons, Ltd.     

The psuedo‐michael reaction of 2‐aminoimidazolines 2. Part 1. Synthesis and structure assignment of isomeric 5(1H)‐Oxo and 7(1H)‐Oxo‐2,3‐dihydroimidazo[1,2‐a]pyrimidine‐6‐carboxylates

The pseudo‐Michael reaction of 1‐aryl‐2‐aminoimidazolines‐2 with diethyl ethoxymethylenemalonate (DEEM) was investigated. Extensive structural studies were performed to confirm the reaction course. For derivatives with N1 aromatic substituents, it was found that the reaction course was temperature dependent. When the reaction temperature was held at ?10 °C only the formation of 1‐aryl‐7(1H)‐oxo‐2,3‐dihydroimi‐dazo[1,2‐a]pyrimidine‐6‐carboxylates ( 4 ) was observed in contrast to earlier suggestions. Under the room temperature conditions, the same reaction yielded mixtures, with varying ratio, of isomeric 1‐aryl‐7(1H)‐oxo‐ ( 4a‐4f ) and 1‐aryl‐5(1H)‐oxo‐2,3‐dihydroimidazo[1,2‐a]pyrimidine‐6‐carboxylates ( 5a‐5f ). The molecular structure of selected isomers, 4b and 5c , was confirmed by X‐ray crystallography. Frontal chro‐matography with delivery from the edge was applied for the separation of the isomeric esters. The isomer ratio of the reaction products depended on the character of the substituents on the phenyl ring. The 1‐aryl‐7(1H)‐oxo‐carboxylates ( 4a‐4f ) were preferably when the phenyl ring contained H, 4‐CH₃, 4‐OCH₃ and 3,4‐Cl₂ substituents. Chloro substitution at either position 3 or 4 in the phenyl ring favored the formation of isomers 5a‐5f . The isomer ratios were confirmed both by ¹H NMR and chromatography. The reaction of the respective hydrobromides of 1‐aryl‐2‐aminoimidazoline‐2 with DEEM, in the presence of triethylamine, gave selectively 5(1H)‐oxo‐esters ( 5a‐5f ).     

Synthesis and Properties of a New Two—Photon—absorbed Material DMAEAS

IntroductionSubstitutedstilbeneshavesignificantpotentialapplica tionssuchasfluorescencemicroscopy ,two photonphotody namictherapy ,opticalpowerlimiting ,three dimensionalstorage,andthree dimensionalmicrofabrication .1 4 Thesedyeshavestrongtendencyofintra molecularchargetransferundertheexcitedstate.Asaresult,theyusuallyexhibitlargetwo photonabsorption (TPA) ,inthemeanwhileemitstrongup convertedfluorescence .Ontheotherhand ,theirsolutionsgenerallydisplaylineartransmissionof >90 %atwavelengthof…     

Study of reaction between activated acetylenes and N,N′‐diethyl‐2‐thiobarbituric acid in the presence of isocyanides or triphenylphosphine

In a series of separate experiments reaction between N,N′‐diethyl‐2‐thiobarbituric acid and acetylenic diesters in the presence of isocyanides or triphenylphosphine led to highly functionalized 4H‐pyrano[2,3‐d]thiopyrimidine or 1,4‐di‐ionic organophosphorus derivatives. The ¹H NMR spectra of diethyl‐7‐(2,6‐dimethylphenylamino)‐4‐oxo‐2‐thio‐ 1,3‐diethyl‐4H‐pyrano[2,3‐d]pyrimidine‐5,6‐dicarboxylate showed dynamic NMR effect that was attributed to restricted rotation around the aryl‐nitrogen single bond. Activation free energy (ΔG^≠) for this process is about 54.85 ± 2 kJ mol⁻¹. Betaines as 1,4‐diionic organophosphorus compounds in this reaction are possessed of two vicinal stereogenic centers and exist in the solution as a mixture of two diastereoisomers. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:228–235, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20601     

A Green Protocol for Simple One‐pot Synthesis of New Pyrimidine Derivatives Both Microwave Irradiation and Conventional Heating: Reactions,Characterization, and Theoretical Calculations

In this research, 5‐benzoyl‐6‐phenyl‐4‐(4‐trifluoromethylphenyl)‐2‐{oxo and thioxo}‐3,4‐dihydro‐1H‐pyrimidines ( 1 , 2 ) were synthesized by using multicomponent cyclocondensation reaction under microwave irradiation and classical heating. Compounds 3 , 4 , 6 , 7 , and 8 obtained reactions of 5‐benzoyl‐6‐phenyl‐4‐(4‐trifluoromethylphenyl)‐2‐thioxo‐3,4‐dihydro‐1H‐pyrimidine ( 1 ) and acetic anhydride, diethyl 2‐bromomalonate, bromoacetic acid, 3‐bromopropionic acid, methyl iodide, respectively. Compound 4 was both acetylated and hydrolyzed in acetic acid to give compound 5 . The structures of all compounds were determined by using spectroscopic techniques like FT‐IR, ¹H/¹³C NMR, and elemental analyses, and the structures of compounds 1 and 3 were analyzed by X‐ray crystal analysis. In addition, the quantum chemical parameters and full geometry optimizations for all compounds were computed using density functional theory based on B3LYP and the 6‐31G (d, p) basis set.     

Synthesis,Structural Characterization,Photophysics, and Broadband Nonlinear Absorption of a Platinum(II) Complex with the 6‐(7‐Benzothiazol‐2′‐yl‐9,9‐diethyl‐9 H‐fluoren‐2‐yl)‐2,2′‐bipyridinyl Ligand

A platinum complex with the 6‐(7‐benzothiazol‐2′‐yl‐9,9‐diethyl‐9H‐fluoren‐2‐yl)‐2,2′‐bipyridinyl ligand ( 1 ) was synthesized and the crystal structure was determined. UV/Vis absorption, emission, and transient difference absorption of 1 were systematically investigated. DFT calculations were carried out on 1 to characterize the electronic ground state and aid in the understanding of the nature of low‐lying excited electronic states. Complex 1 exhibits intense structured ¹π–π* absorption at λ_abs<440 nm, and a broad, moderate ¹M LCT/¹LLCT transition at 440–520 nm in CH₂Cl₂ solution. A structured ³π–π*/³M LCT emission at about 590 nm was observed at room temperature and at 77 K. Complex 1 exhibits both singlet and triplet excited‐state absorption from 450 nm to 750 nm, which are tentatively attributed to the ¹π–π* and ³π–π* excited states of the 6‐(7‐benzothiazol‐2′‐yl‐9,9‐diethyl‐9H‐fluoren‐2‐yl)‐2,2′‐bipyridine ligand, respectively. Z‐scan experiments were conducted by using ns and ps pulses at 532 nm, and ps pulses at a variety of visible and near‐IR wavelengths. The experimental data were fitted by a five‐level model by using the excited‐state parameters obtained from the photophysical study to deduce the effective singlet and triplet excited‐state absorption cross sections in the visible spectral region and the effective two‐photon absorption cross sections in the near‐IR region. Our results demonstrate that 1 possesses large ratios of excited‐state absorption cross sections relative to that of the ground‐state in the visible spectral region; this results in a remarkable degree of reverse saturable absorption from 1 in CH₂Cl₂ solution illuminated by ns laser pulses at 532 nm. The two‐photon absorption cross sections in the near‐IR region for 1 are among the largest values reported for platinum complexes. Therefore, 1 is an excellent, broadband, nonlinear absorbing material that exhibits strong reverse saturable absorption in the visible spectral region and large two‐photon‐assisted excited‐state absorption in the near‐IR region.     

Kinetics and mechanism of gas‐phase pyrolysis of N‐aryl‐3‐oxobutanamide ketoanilides,their 2‐arylhydrazono derivatives,and related compounds

Rates and products of reaction and Arrhenius activation parameters were determined for the gas‐phase thermolysis of 14 substrates of the title compounds using sealed pyrex reactor tubes and HPLC/UV‐VIS to monitor substrate pyrolysis. The 14 compounds under study are N‐phenyl‐3‐oxo‐ ( 1 ), N‐(p‐chlorophenyl)‐3‐oxo‐ ( 2 ), N‐(p‐methylphenyl)‐3‐oxo‐ ( 3 ), and N‐(p‐methoxyphenyl)‐3‐oxobutanamide ( 4 ), in addition to (i) four substrates ( 5–8 ) obtained by the replacement of the pairs of methylene hydrogens at the 2‐position of compounds ( 1–4 ), each pair by a phenylhydrazono group; (ii) three arylhydrazono derivatives ( 9–11 ) in which Cl, CH₃, or OCH₃ groups are substituted at the para position of the phenylhydrazono moiety of compound 5 ; (iii) 3‐oxobutanamide (acetoacetamide, 12 ), N‐phenyl‐3‐oxo‐3‐phenylpropanamide ( 13 ), and N,N′‐diphenylpropanediamide ( 14 ). The reactions were conducted over 374–546 K temperature range, and the values of the Arrhenius log A(s^?1) and E_a(kJ mol^?1) of these reactions were, respectively, 12.0 ± 2.0 and 119.2 ± 17.0 for the ketoanilides ( 1–4, 12–14 ), and 13.0 ± 0.7 and 157.5 ± 8.6 for the arylhyrazono compounds ( 5–11 ). Kinetically, the arylhydrazono derivatives were found to be ca. 1.4 × 10³ to 5.7 × 10³ times less reactive than the parent ketoanilides. A mechanism is proposed to account for reaction products and to rationalize molecular reactivities. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 82–91, 2007     

β‐Ionone reactions with the nitrate radical: Rate constant and gas‐phase products

The bimolecular rate constant of k (9.4 ± 2.4 × 10^?12 cm³ molecule^?1 s^?1 was measured using the relative rate technique for the reaction of the nitrate radical (NO₃?) with 4‐(2,6,6‐trimethyl‐1‐cyclohexen‐1‐yl)‐3‐buten‐2‐one (β‐ionone) at (297 ± 3) K and 1 atmosphere total pressure. In addition, the products of β‐ionone + NO₃? reaction were also investigated. The identified reaction products were glyoxal (HC(?O)C(?O)H), and methylglyoxal (CH₃C(?O)C(?O)H). Derivatizing agents O‐(2,3,4,5,6‐pentafluorobenzyl)hydroxylamine and N,O‐bis(trimethylsilyl)trifluoroacetamide were used to propose the other major reaction products: 3‐oxobutane‐1,2‐diyl nitrate, 2,6,6‐trimethylcyclohex‐1‐ene‐carbaldehyde, 2‐oxo‐1‐(2,6,6‐trimethylcyclohex‐1‐en‐1‐yl)ethyl nitrate, pentane‐2,4‐dione, 3‐oxo‐1‐(2,6,6‐trimethylcyclohex‐1‐en‐1‐yl)butane‐1,2‐diyl dinitrate, 3,3‐dimethylcyclohexane‐1,2‐dione, and 4‐oxopent‐2‐enal. The elucidation of these products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible β‐ionone + NO₃? reaction mechanisms based on previously published volatile organic compound + NO₃? gas‐phase mechanisms. The additional gas‐phase products 5‐acetyl‐2‐ethylidene‐3‐methylcyclopentyl nitrate, 1‐(1‐hydroxy‐7,7‐dimethyl‐2,3,4,5,6,7‐hexahydro‐1 H‐inden‐2‐yl)ethanone, 1‐(1‐hydroxy‐3a,7‐dimethyl‐2,3,3a,4,5,6,‐hexahydro‐1 H‐inden‐2‐yl)ethanone, and 5‐acetyl‐2‐ethylidene‐3‐methylcyclopentanone are proposed to be the result of cyclization through a reaction intermediate. © 2009 Wiley Periodicals, Inc. *

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

Int J Chem Kinet 41: 629–641, 2009     

Highly efficient blue organic light-emitting diodes based on 2-(diphenylamino)fluoren-7-ylvinylarene derivatives that bear a tert-butyl group

Blue fluorescent materials with a 2‐(diphenylamino)fluoren‐7‐ylvinylarene emitting unit and tert‐butyl‐based blocking units were synthesized. The photophysical properties of these materials, including UV/Vis absorption, photoluminescent properties, and HOMO–LUMO energy levels, were characterized and rationalized with quantum‐mechanical DFT calculations. The electroluminescent properties of these molecules were examined through the fabrication of multilayer devices with a structure of indium–tin oxide, 4,4′‐bis{N‐[4‐(N,N‐di‐m‐tolylamino)phenyl]‐N‐phenylamino}biphenyl, 4′‐bis[N‐(1‐naphthyl)‐N‐phenylamino]biphenyl, and blue materials doped in 2‐methyl‐9,10‐di(2‐naphthyl)anthracene/tris(8‐quinolinolato)aluminum/LiF/Al. All devices exhibit highly efficient blue electroluminescence with high external quantum efficiency (3.20–7.72 % at 20 mA cm^?2). A deep‐blue device with Commission Internationale de l’Eclairage (CIE) coordinates of (0.15, 0.11) that uses 7‐[2‐(3′,5′‐di‐tert‐butylbiphenyl‐4‐yl)vinyl]‐9,9‐diethyl‐2‐N‐(3,5‐di‐tert‐butylphenyl)‐2,4‐difluorobenzenamino‐9H‐fluorene as a dopant in the emitting layer showed a luminous efficiency and external quantum efficiency of 3.95 cd A^?1 and 4.23 % at 20 mA cm^?2, respectively. Furthermore, a highly efficient sky‐blue device that uses the dopant 7‐{2‐[2‐(3,5‐di‐tert‐butylphenyl)‐9,9′‐spirobifluorene‐7‐yl]vinyl}‐9,9‐diethyl‐2‐N,N‐diphenylamino‐9H‐fluorene exhibited a luminous efficiency and high quantum efficiency of 10.3 cd A^?1 and 7.7 % at 20 mA cm^?2, respectively, with CIE coordinates of (0.15, 0.20).     

Conformational dynamics of bis(BF2)‐2,2′‐bidipyrrins revealed by through‐space 13C?19F and 19F?19F couplings

The conformation of [bis‐(N,N′‐difluoroboryl)]‐3,3′‐diethyl‐4,4′,8,8′,9,9′,10,10′‐octamethyl‐2,2′‐bidipyrrin (1) in solution was studied by analyzing the ¹³C? ¹⁹F and ¹⁹F? ¹⁹F through‐space spin–spin couplings. The ¹H and ¹³C NMR spectra were assigned on the basis of nuclear Overhauser effect spectroscopy (NOESY), heteronuclear single‐quantum correlation (HSQC), and heteronuclear multiple‐bond correlation (HMBC) experiments. The ¹⁹F spectrum of 1 was compared with that of 2‐ethyl‐1,3,5,6,7‐pentamethyl‐4,4‐difluoro‐4‐bor‐3a,4a‐diaza‐s‐indacen (2). The ¹⁹F? ¹⁹F through‐space spin? spin coupling in 1 was thus assigned and the coupling constant was obtained by simulating the coupling patterns. The obtained conformation of 1 was compared with those of the known complexes [bis‐(N,N′‐difluoroboryl)]‐3,3′,8,8′,9,9′‐hexaethyl‐4,4′,10,10′‐tetramethyl‐6,6′‐(4‐methylphenyl)‐2,2′‐bidipyrrin (3)and [bis‐(N,N′‐difluoroboryl)]‐9,9′‐diethyl‐4,4′,8,8′,10,10′‐hexamethyl‐3,3′‐bis(methoxycarbonylethyl)‐2,2′‐bidipyrrin (4). The conformational dynamics of 1, 3, and 4 was surveyed by observing the temperature dependence of the through‐space coupling constants between 253 and 333 K. The ¹³C? ¹⁹F and ¹⁹F? ¹⁹F through‐space spin–spin couplings thus confirm similar conformations of different BisBODIPYs in solution in contrast to earlier findings in the solid state. Copyright © 2009 John Wiley & Sons, Ltd.