[DBU‐H]+ and H2o as effective catalyst form for 2,3‐dihydropyrido[2,3‐d]pyrimidin‐4(1H)‐ones: A DFT Study

DFT investigations are carried out to explore the effective catalyst forms of DBU and H₂O and the mechanism for the formation of 2,3‐dihydropyrido[2,3‐d]‐pyrimidin‐4(1H)‐ones. Three main pathways are disclosed under unassisted, water‐catalyzed, DBU and water cocatalyzed conditions, which involves concerted nucleophilic addition and H‐transfer, concerted intramolecular cyclization and H‐transfer, and Dimroth rearrangement to form the product. The results indicated that the DBU and water cocatalyzed pathway is the most favored one as compared to the rest two pathways. The water donates one H to DBU and accepts H from 2‐amino‐nicotinonitrile ( 1 ), forming [DBU‐H]⁺‐H₂O as effective catalyst form in the proton migration transition state rather than [DBU‐H]⁺‐OH^?. The hydrogen bond between [DBU‐H]⁺···H₂O··· 1 ^? decreases the activation barrier of the rate‐determining step. Our calculated results open a new insight for the green catalyst model of DBU‐H₂O. © 2015 Wiley Periodicals, Inc.     

Tetrakis(μ‐2,3‐dimethoxybenzoato)bis[(2,2′‐bipyridine)(2,3‐dimethoxybenzoato)lanthanum(III)]

The title compound, tetrakis(μ‐2,3‐di­methoxy­benzoato)‐κ⁴O:O′;κ⁶O,O′:O′‐bis[(2,2′‐bi­pyridine‐N,N′)(2,3‐di­methoxy­benzoato‐O,O′)lanthanum(III)], [La₂(2,3‐DMOBA)₆(2,2′‐bpy)₂], where 2,3‐DMOBA is 2,3‐di­methoxy­benzoate (C₉H₉O₄) and 2,2′‐bpy is 2,2′‐bi­pyridine (C₁₀H₈N₂), is a dimer with a centre of inversion between the La atoms bridged by four carboxyl­ate ligands. The central La atom is ennea‐coordinated and has a distorted monocapped square‐antiprism geometry.     

Organic Thin Film Transistors Based on 2,3‐Dimethylpentacene and 2,3‐Dimethyltetracene

2,3‐Dimethylpentacene (DMP) and 2,3‐dimethyltetracene (DMT) were synthesized, characterized and employed as the channel material in the fabrication of thin‐film transistors. The two methyl groups increase the chemical stability of the compounds versus the pristine acene analogues. The crystals maintain herringbone‐like molecular packing, whereas the weak dipole associated with the unsymmetrical molecule induces an anti‐parallel alignment among the neighbors. This structural motif favors layered film growth on SiO₂/Si surface. Thin film transistors prepared on SiO₂/Si and n‐nonyltrichlorosilane‐modified SiO₂/Si at different substrate temperatures were compared. DMP‐based transistors prepared on rubbed n‐nonyltrichlorosilane‐modified SiO₂/Si substrate gave the highest field‐effect mobility of 0.46 cm²/Vs, whereas DMT‐based transistor gave a mobility of 0.028 cm²/Vs.     

Oxidative coupling polymerization of 2,3‐dihydroxynaphthalene with dinuclear‐type copper(II) catalyst

The oxidative coupling polymerization of 2,3‐dihydroxynaphthalene with the novel dinuclear‐type copper(II) catalysts successfully produced poly(2,3‐dihydroxy‐1,4‐naphthylene). For example, the MeOH‐insoluble polymer with a number average molecular weight of 4.4 × 10³ from the polymerization using the complex of CuCl₂ and N,N′‐bis(2‐morpholinoethyl)‐p‐xylylenediamine ( p ‐ 1 ) at room temperature under an O₂ atmosphere followed by acetylation of the hydroxyl groups was obtained in 63% yield. The structures of the tetraamine ligands and the counter anion of the copper(II) salts significantly influenced the catalyst activity. The polymerization of 2,2′‐dimethoxy‐1,1′‐binaphthalene‐3,3′‐diol with the 2CuCl₂‐ p ‐ 1 catalyst, however, resulted in a lower yield. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1635–1640, 2005     

Synthesis and Characterization of 11‐Amino‐3‐methoxy‐8‐substituted‐12‐aryl‐8,9‐dihydro‐7H‐chromeno[2,3‐b]quinolin‐10(12H)‐one Derivatives

A series of 2‐amino‐7‐methoxy‐4‐aryl‐4H‐chromene‐3‐carbonitrile compounds 2 were obtained by condensation of 3‐methoxyphenol with β‐dicyanostyrenes 1 in absolute ethanol containing piperidine. The intermediate enamines 3 were prepared by compounds 2 with 5‐substituted‐1,3‐cyclohexanedione using p‐toluenesuflonic acid (TsOH) as catalyst. The title compounds 11‐amino‐3‐methoxy‐8‐substituted‐12‐aryl‐8,9‐dihydro‐7H‐chromeno[2,3‐b]quinolin‐10(12H)‐one 4 were synthesized by cyclization of the intermediate enamines 3 in THF with K₂CO₃ /Cu₂Cl₂ as catalyst. The structures of all compounds were characterized by elemental analysis, IR, MS, and ¹H NMR spectra. The crystal structure of compound 4i was determined by single‐crystal X‐ray diffraction analysis.     

A Highly cis‐Selective and Enantioselective Metal‐Free Hydrogenation of 2,3‐Disubstituted Quinoxalines

A wide range of 2,3‐disubstituted quinoxalines have been successfully hydrogenated with H₂ using borane catalysts to produce the desired tetrahydroquinoxalines in 80–99 % yields with excellent cis selectivity. Significantly, the asymmetric reaction employing chiral borane catalysts generated by the in situ hydroboration of chiral dienes with HB(C₆F₅)₂ under mild reaction conditions has also been achieved with up to 96 % ee, and represents the first catalytic asymmetric system to furnish optically active cis‐2,3‐disubstituted 1,2,3,4‐tetrahydroquinoxalines.     

Highly Enantioselective Carbonyl–Ene Reactions of 2,3‐Diketoesters: Efficient and Atom‐Economical Process to Functionalized Chiral α‐Hydroxy‐β‐Ketoesters

Carbonyl–ene reactions of 2,3‐diketoesters catalyzed by [Cu{(S,S)‐tBu‐box}](SbF₆)₂ [box=bis(oxazoline)] generate chiral α‐functionalized α‐hydroxy‐β‐ketoesters in up to 94 % yield and 97 % ee. The 2,3‐diketoesters are conveniently accessed from the corresponding α‐diazo‐β‐ketoester, and a catalyst loading as low as 1.0 mol % can be achieved.     

2,3‐Dihydro‐1,3‐benzothiazol‐2‐iminium monohydrogen sulfate and 2‐iminio‐2,3‐dihydro‐1,3‐benzothiazole‐6‐sulfonate: a combined structural and theoretical study

The 2‐aminobenzothiazole sulfonation intermediate 2,3‐dihydro‐1,3‐benzothiazol‐2‐iminium monohydrogen sulfate, C₇H₇N₂S⁺·HSO₄⁻, (I), and the final product 2‐iminio‐2,3‐dihydro‐1,3‐benzothiazole‐6‐sulfonate, C₇H₆N₂O₃S₂, (II), both have the endocyclic N atom protonated; compound (I) exists as an ion pair and (II) forms a zwitterion. Intermolecular N—H...O and O—H...O hydrogen bonds are seen in both structures, with bonding energy (calculated on the basis of density functional theory) ranging from 1.06 to 14.15 kcal mol⁻¹. Hydrogen bonding in (I) and (II) creates DDDD and C(8)C(9)C(9) first‐level graph sets, respectively. Face‐to‐face stacking interactions are observed in both (I) and (II), but they are extremely weak.     

2,3‐Di(2‐pyridyl)‐5‐phenylpyrazine: A NN‐CNN‐Type Bridging Ligand for Dinuclear Transition‐Metal Complexes

A new bridging ligand, 2,3‐di(2‐pyridyl)‐5‐phenylpyrazine (dpppzH), has been synthesized. This ligand was designed so that it could bind two metals through a NN‐CNN‐type coordination mode. The reaction of dpppzH with cis‐[(bpy)₂RuCl₂] (bpy=2,2′‐bipyridine) affords monoruthenium complex [(bpy)₂Ru(dpppzH)]²⁺ ( 12+ ) in 64 % yield, in which dpppzH behaves as a NN bidentate ligand. The asymmetric biruthenium complex [(bpy)₂Ru(dpppz)Ru(Mebip)]³⁺ ( 23+ ) was prepared from complex 12+ and [(Mebip)RuCl₃] (Mebip=bis(N‐methylbenzimidazolyl)pyridine), in which one hydrogen atom on the phenyl ring of dpppzH is lost and the bridging ligand binds to the second ruthenium atom in a CNN tridentate fashion. In addition, the RuPt heterobimetallic complex [(bpy)₂Ru(dpppz)Pt(C?CPh)]²⁺ ( 42+ ) has been prepared from complex 12+ , in which the bridging ligand binds to the platinum atom through a CNN binding mode. The electronic properties of these complexes have been probed by using electrochemical and spectroscopic techniques and studied by theoretical calculations. Complex 12+ is emissive at room temperature, with an emission λ_max=695 nm. No emission was detected for complex 23+ at room temperature in MeCN, whereas complex 42+ displayed an emission at about 750 nm. The emission properties of these complexes are compared to those of previously reported Ru and RuPt bimetallic complexes with a related ligand, 2,3‐di(2‐pyridyl)‐5,6‐diphenylpyrazine.     

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.     

A Convenient Synthesis of 2,3‐Dihydro‐4H‐thiopyrano[2,3‐b]‐, ‐[2,3‐c]‐, or ‐[3,2‐c]pyridin‐4‐ones by the Reaction of the Corresponding 1‐(Chloropyridinyl)alk‐2‐en‐1‐ones with NaSH

2,3‐Dihydro‐4H‐thiopyrano[2,3‐b]pyridin‐4‐ones 4 were prepared by a three‐step sequence from commercially available 2‐chloropyridine ( 1 ). Thus, successive treatment of 1 with ⁱPr₂NLi (LDA) and α,β‐unsaturated aldehydes gave 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ols 2 , which were oxidized with MnO₂ to 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ones 3 . The reactions of 3 with NaSH?n H₂O proceeded smoothly at 0° in DMF to provide the desired thiopyranopyridinones. Similarly, 2,3‐dihydro‐4H‐thiopyrano[2,3‐c]pyridin‐4‐ones 8 and 2,3‐dihydro‐4H‐thiopyrano[3,2‐c]pyridin‐4‐ones 12 were obtained starting from 3‐chloropyridine ( 5 ) and 4‐chloropyridine ( 9 ), respectively.     

A photochromic dinuclear compound: aquatetrakis(μ‐2,3‐diphenylprop‐2‐enoato)bis(2,3‐diphenylprop‐2‐enoato)ethanolbis(1,10‐phenanthroline)dilanthanum(III)

The title dinuclear complex, (aqua‐1κO)tetrakis(μ‐2,3‐diphenylprop‐2‐enoato‐1:2κ²O:O′)bis(2,3‐diphenylprop‐2‐enoato)‐1κO;2κO‐(ethanol‐2κO)bis(1,10‐phenanthroline)‐1κ²N,N′;2κ²N,N′‐dilanthanum(III), [La₂(C₁₅H₁₁O₂)₆(C₁₂H₈N₂)₂(C₂H₅OH)(H₂O)], contains two similar La^III centres with distorted [LaO₆N₂] bicapped triganol–prismatic coordination polyhedra formed by six phenylcinnamate (PCA⁻ or 2,3‐diphenylprop‐2‐enoate) ligands, two 1,10‐phenanthroline (phen) ligands, a coordinating ethanol molecule and a coordinating water molecule. The two metal centres are bridged by four μ‐PCA⁻ ligands, with the remaining two PCA⁻ ligands coordinated in a monodentate fashion. The noncoordinated carboxylate O atoms on the terminal PCA⁻ ligands form O—H...O hydrogen bonds with the coordinated solvent molecules. Each La centre is also coordinated by a bidentate phen ligand. The PCA⁻ ligands all adopt syn–syn orientations, with the two phenyl rings presenting dihedral angles of about 70°. The compound displays photochromic behaviour both in solution and in the solid state.     

Chirale 1,3,2‐Oxazaborolidine aus chiralen 2,3‐Dihydro‐1H‐1,3,2‐diazaborolen und Diphenylketen

Chiral 1,3,2‐Oxazaborolidines from the Reaction of Chiral 2,3‐Dihydro‐1H‐1,3,2‐diazaboroles and Diphenylketene Reaction of equimolar amounts of diphenylketene with 1,3‐di‐tert‐butyl‐2‐isobutyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborole ( 1 ) regioselectively afforded 1,3,2‐oxazaborolidine ( 2 ). The employment of a series of chiral diazaboroles ( 3a : X = nBu; b: iBu; c: CH₂SiMe₃; d: NHtBu) led to the formation of the diastereoisomeric oxazaborolidines ( 4a – d ) with diastereomeric excesses de, which increase with the steric demand of X from de = 55 % (X = nBu) to de ≥ 95 % (X = NHtBu). Under comparable conditions the treatment of the enantiomerically pure diazaborole ( 6 ) with the ketene yielded oxazaborolidine ( 7 ) with a de‐value of only 52 %. The new compounds, with exception of 2 and 4d , are thermolabile solids, which were characterized mainly by spectroscopy (¹H‐, ¹¹B{¹H}‐, ¹³C{¹H}‐NMR, MS). The X‐ray structure analysis of 2 revealed a slightly puckered five‐membered heterocycle with a long B–O bond.     

Synthesis of Thieno[2,3‐b]quinolinone Derivatives

The Knoevenagel reactions of malononitrile with acetophenone or 4‐substituted acetophenons were carried to give the corresponding 2‐(1‐aryle thylidene)malononitriles, which was further cyclized with sulfur using NaHCO₃ as catalysts to generate 2‐amino‐5‐arylthiophene‐3‐carbonitrile 2 . The intermediate enamines 3 were prepared by refluxing of 2 with 5‐substituted‐1,3‐cyclohexanedione using p‐toluenesulfonic acid as catalyst. The title compounds 4‐amino‐3‐aryl ‐7‐substituted‐7,8‐dihydrothieno[2,3‐b]quinolin‐5(6H)‐one were synthesized by cyclization of 3 in the presence of K₂CO₃ and Cu₂Cl₂. The structures of all compounds were characterized by elemental analysis, IR, MS, and ¹H‐NMR spectra.     

Three‐Step Synthesis of 3‐Aryl‐2‐sulfanylthieno[2,3‐b]‐, ‐[2,3‐c]‐, or ‐[3,2‐c]pyridines from the Corresponding Aryl(halopyridinyl)methanones

A convenient three‐step procedure for the synthesis of three types of 3‐aryl‐2‐sulfanylthienopyridines 4, 8 , and 12 has been developed. The first step of the synthesis of thieno[2,3‐b]pyridine derivatives 4 is the replacement of the halo with a (sulfanylmethyl)sulfanyl group in aryl(2‐halopyridin‐3‐yl)methanones 1 by successive treatment with Na₂S?9 H₂O and chloromethyl sulfides to give aryl{2‐[(sulfanylmethyl)sulfanyl]pyridin‐3‐yl}methanones 2 . In the second step, these were treated with LDA (LiNⁱPr₂) to give 3‐aryl‐2,3‐dihydro‐2‐sulfanylthieno[2,3‐b]pyridin‐3‐ols 3 , which were dehydrated in the last step with SOCl₂ in the presence of pyridine to give the desired products. Similarly, thieno[2,3‐c]pyridine and thieno[3,2‐c]pyridine derivatives, 8 and 12 , respectively, can be prepared from aryl(3‐chloropyridin‐4‐yl)methanones 5 and aryl(4‐chloropyridin‐3‐yl)methanones 9 , respectively.     

Majority‐Rules‐Type Helical Poly(quinoxaline‐2,3‐diyl)s as Highly Efficient Chirality‐Amplification Systems for Asymmetric Catalysis

A highly efficient majority‐rules effect of poly(quinoxaline‐2,3‐diyl)s (PQXs) bearing 2‐butoxymethyl chiral side chains at the 6‐ and 7‐positions was established and attributed to large ΔG_h values (0.22–0.41 kJ mol^?1), which are defined as the energy difference between P‐ and M‐helical conformations per chiral unit. A PQX copolymer prepared from a monomer derived from (R)‐2‐octanol (23 % ee) and a monomer bearing a PPh₂ group adopted a single‐handed helical structure (>99 %) and could be used as a highly enantioselective chiral ligand in palladium‐catalyzed asymmetric reactions (products formed with up to 94 % ee), in which the enantioselectivity could be switched by solvent‐dependent inversion of the helical PQX backbone.     

Convenient and Efficient Synthesis of 11‐Amino‐2,8‐substituted‐2,3,8,9‐tetrahydrobenzo[4,5]thieno[2,3‐b]quinolinone Derivatives

The Gewald reactions of 5‐substituted‐1,3‐cyclohexanedione, malononitrile, and powdered sulfur were carried out to give the corresponding products 2‐amino‐5‐substituted‐7‐oxo‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carbonitrile derivatives 1 . The intermediate enamines 2 were prepared by reaction of compounds 1 and 5‐substituted‐1,3‐cyclohexanedione with hydrochloric acid as catalyst. The title compounds 11‐amino‐2,8‐substituted‐2,3,8,9‐tetrahydrobenzo[4,5]thieno[2,3‐b]quinolinone 3 were synthesized by cyclization of compounds 2 in the presence of K₂CO₃ and Cu₂Cl₂. The structures of all compounds were characterized by elemental analysis, IR, MS, and ¹H‐NMR spectra.     

A one‐dimensional zigzag coordination polymer of di­aqua­(pyridine‐2,3‐di­carboxyl­ato)­cobalt(II)

The asymmetric unit of the title one‐dimensional coordination polymer, catena‐poly­[[μ‐pyridine‐2,3‐di­carb­oxyl­ato‐1κO:2κ²N,O′‐bis­[di­aqua­cobalt(II)]]‐μ‐pyridine‐2,3‐di­carboxyl­ato‐1κ²N,O:2κO′:1′κO′], [Co(C₇H₃NO₄)(H₂O)₂]_n, is composed of a cobalt(II) ion, a pyridine‐2,3‐di­carboxyl­ate dianion and two water mol­ecules. The polymer has a zigzag structure consisting of a chain of edge‐fused rings, and the polymer chains are linked by O—H⃛O hydrogen bonds into a three‐dimensional framework.     

Green Synthesis of 1‐(1,2,4‐Triazol‐4‐yl)spiro[azetidine‐2,3′‐(3H)indole]‐2′,4′(1′H)‐diones as Potential Insecticidal Agents

One pot green synthesis of 1‐(1,2,4‐triazol‐4‐yl)spiro[azetidine‐2,3′‐(3H)‐indole]‐2′,4′(1′H)‐diones was carried out by the reaction of indole‐2,3‐diones,4‐amino‐4H‐1,2,4‐triazole and acetyl chloride/chloroacetyl chloride in ionic liquid [bmim]PF₆ with/without using a catalyst. It was also prepared by conventional method via Schiff's bases, 3‐[4H‐1,2,4‐triazol‐4‐yl]imino‐indol‐2‐one. Further, the corresponding phenoxy derivatives were obtained by the reaction of chloro group attached to azetidine ring with phenols. The synthesized compounds were characterized by analytical and spectral (IR, ¹H NMR, ¹³C NMR, and FAB mass) data. Evaluation for insecticidal activity against Periplaneta americana exhibited promising results.     

One‐pot synthesis of 2,3‐disubstituted‐2,3‐dihydroquinazolin‐4(1H)‐ones using [Hmim][NO3]: An eco‐friendly protocol

An efficient method for the synthesis of a series of 2,3‐disubstituted‐2,3‐dihydroquinazolin‐4(1H)‐ones is described via one‐pot condensation reaction of isatoic anhydride, aryl aldehydes, and primary amines using a Brønsted acidic ionic liquid, [Hmim][NO₃], as a catalyst and medium. The present protocol enjoys convenient reaction and simple work‐up, greenness, short reaction times, and reusable catalyst as well as mild reaction conditions. J. Heterocyclic Chem., (2011).