Synthesis of 2,3-dihydrospiro[benzofuran-2,4′ -piperidines] and 2,3-dihydrospiro[benzofuran-2,3′-pyrrolidines]

The synthesis of 2,3-dihydrospiro[benzofuran-2,4′-piperidines] 3 and 2,3-dihydrospiro[benzofuran-2,3′]-pyrrolidine] 6 is described. The synthesis was achieved by a Grignard reaction of a 2-fluorobenzylhalide with an appropriate cycloazaalkyl ketone to yield the tertiary alcohols 1 and 4 . Subsequent intramolecular displacement of the aromatic fluoride by the derived alkoxides provided the novel system. Nitration of 1′-acetyl-2,3-dihydrospiro[benzofuran-2,4′-piperidine] 7 resulted in a 5-nitro derivative.     

Effective synthesis of 2,3-<Emphasis Type="Italic">seco</Emphasis>-2,3-dicarboxyplatanic acid

An effective method for preparing triterpene 2,3-seco-2,3-diacids by ozonolysis of 2-exomethylene-substituted derivatives of betulonic acid and 28-oxoallobetulone was proposed.     

Fragmentation pathways of 2,3‐dimethyl‐2,3‐dinitrobutane cations in the gas phase

2,3‐Dimethyl‐2,3‐dinitrobutane (DMNB) is an explosive taggant added to plastic explosives during manufacture making them more susceptible to vapour‐phase detection systems. In this study, the formation and detection of gas‐phase [M+H]⁺, [M+Li]⁺, [M+NH₄]⁺ and [M+Na]⁺ adducts of DMNB was achieved using electrospray ionisation on a triple quadrupole mass spectrometer. The [M+H]⁺ ion abundance was found to have a strong dependence on ion source temperature, decreasing markedly at source temperatures above 50°C. In contrast, the [M+Na]⁺ ion demonstrated increasing ion abundance at source temperatures up to 105°C. The relative susceptibility of DMNB adduct ions toward dissociation was investigated by collision‐induced dissociation. Probable structures of product ions and mechanisms for unimolecular dissociation have been inferred based on fragmentation patterns from tandem mass (MS/MS) spectra of source‐formed ions of normal and isotopically labelled DMNB, and quantum chemical calculations. Both thermal and collisional activation studies suggest that the [M+Na]⁺ adduct ions are significantly more stable toward dissociation than their protonated analogues and, as a consequence, the former provide attractive targets for detection by contemporary rapid screening methods such as desorption electrospray ionisation mass spectrometry. Copyright © 2009 Commonwealth of Australia. Published by John Wiley & Sons, Ltd.     

Pyrazine‐2,3‐dicarboxamide

In the crystal structure of the title di­amide, C₆H₆N₄O₂, linear tapes of carbox­amide N—H?O and pyrazine C—H?N hydrogen‐bond dimers are connected by N—H?O bonds to form a staircase‐like pattern.     

Nitration of 2,3′-bithienyl

The nitration of 2,3′-bithienyl ( 1 ) with fuming nitric acid in acetic anhydride at 0° gives a mixture of 3-nitro- ( 2 ), 2′ -nitro- ( 3 ) and 5-nitro-2,3′-bithienyl ( 4 ) with relative percentages of 38.7%, 34.8% and 26.5%. When the nitration of 1 was carried out with fuming nitric acid in acetic acid at 20°, the same compounds 2, 3 and 4 were obtained, but with different relative percentages: 20.4%, 36.5% and 43.1% respectively. The results of the mononitration of 1 are compared with those obtained in other electrophilic substitutions and with the theoretical predictions. The further nitrations of 2, 3 and 4 with nitric acid in acetic anhydride at room temperature lead to the formation of five dinitro-2,3′-bithienyl isomers. Compound 2 gives a mixture of 2′,3-dinitro- ( 5 ) and 3,5′-dinitro-2,3′-bithienyl ( 6 ); compound 3 gives a mixture of 5 , 2′,5-dinitro- ( 7 ) and 2′,4-dinitro-2,3′-bithienyl ( 8 ); compound 4 gives 7 and 5,5′-dinitro-2,3′-bithienyl ( 9 ). The possible reasons of the formation of the various dinitro-2,3′-bithienyl isomers are discussed.     

Electropolymerization of 2,3‐diaminophenol

The optima conditions to electrosynthesize poly(2,3‐diaminophenol) by electro‐oxidation of the monomer were determined, and the electrodeposits obtained characterized by electrochemical methods, UV‐vis, FTIR, conductivity and viscosity measurements. The influence of parameters such as electrolytical medium and electrochemical conditions on the electro‐oxidation of 2,3‐diaminophenol were also investigated. It has been established that appropriate deposits are obtained only when very anhydrous acetonitrile is used as solvent. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1698–1703, 2000     

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.     

Dramatic Solvent Effect in the Reduction of 2,3—Allenoic Acid Esters.A Simple Synthesis of 2,3—Allenols from 2,3—Allenoates

2，3－Allenols were prepared conveniently from the reduction reaction of 2,3-allenoates with DIBAL-H(Diisobutylaluminum hydride) in toluene.A dramatic solvent effect was observed for this reaction.     

2,3-O-Isopropyliden-L-Sorbofuranose (MIPSF) und 2,3; 4,6-Di-O-Isopropyliden-L-Sorbofuranose (DIPSF)

Ohne Zusammenfassung     

Sensitive Voltammetric Sensing of the 2,3‐Dimethyl‐2,3‐dinitrobutane (Dmnb) Explosive Taggant

The highly sensitive voltammetric detection of the 2,3‐dimethyl‐2,3‐dinitrobutane (DMNB), a required additive to commercial plastic explosives, is described. The protocol relies on a fast square‐wave voltammetric measurement of the DMNB explosive taggant at an unmodified carbon fiber electrode using a phosphate buffer (pH 7.0) solution. Different solutions and working electrodes were evaluated. Under the optimal conditions, a linear response is observed over the 300–3000 μg/L DMNB concentration range examined, with a detection limit of 60 μg/L. A highly stable response, with a relative standard deviation (RSD) of 2.6%, is observed for 30 repetitive measurements. Such electrochemical approach offers great promise for a simple, rapid, sensitive and inexpensive field screening of plastic explosives. Preliminary data illustrate the utility of electrochemical detection for electrophoretic microchips for the simultaneous measurements of DMNB, cyclotrimethylenetrinitramine (RDX) and pentaerythritoltetranitrate (PETN).     

Stereocontrolled Organocatalytic Strategy for the Synthesis of Optically Active 2,3‐Disubstituted cis‐2,3‐Dihydrobenzofurans

An intramolecular, organocatalyzed Michael addition has been developed to obtain biologically important 2,3‐disubstituted cis‐2,3‐dihydrobenzofurans. By using mandelic acid salts of primary aminocatalysts, derived from cinchona alkaloids, the intramolecular cyclization reaction has been developed to proceed in high yield, with moderate to good diastereoselectivity, and up to 99 % ee. Based on the absolute configuration of the formed 2,3‐disubstituted‐cis‐2,3‐dihydrobenzofurans and by considering the observed substrate scope restrictions, a mechanistic rationalization has been presented.     

Synthesis and reactivity of thieno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridine-2,3-diamines

It has been established that the interaction of N¹-(2-hydroxyphenylmethylthieno[2,3-b]pyrid-3-yl)arylamides with hydrazine hydrate leads to thieno[2,3-b]pyridine-2,3-diamines. It was shown that the reaction of the latter with acetylacetone and acetoacetic ester occurs regioselectively at the amino group in position 3 of the thiophene ring. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1400–1408, September, 2007.     

Synthesis of [1,4]benzodioxino[2,3‐c and 2,3‐d]pyridazinones

Reaction of chloropyridazin‐3‐one 1, 5 and 10 with catechol in the presence of potassium carbonate gave the corresponding [1,4]benzodioxino[2,3‐e and/or 2,3‐d]pyridazinones 2, 7, 8 and 11 .