A Method for the Synthesis of 2,3-Disubstituted 2,3-Dihydrobenzofurans

Summary.  The synthesis of 2,3-disubstituted 2,3-dihydrobenzofuran diastereomers is described. The key step in the reaction sequence is the chemoselective reduction of a tert. alcohole with tert.-butylamine-borane/AlCl₃. The relative configuration of the substituents on the dihydrofurane moiety was assigned via NMR spectroscopy. Received September 7, 1999. Accepted November 9, 1999     

Terahertz spectroscopy of the explosive taggant 2,3-dimethyl-2,3-dinitrobutane

The terahertz spectrum of the crystalline explosive taggant 2,3-dimethyl-2,3-dinitrobutane (C(6)H(12)N(2)O(4)) has been investigated as an alternative means of detecting solid-state explosives. The room-temperature spectrum exhibits two broad absorption features centered at 38.3 and 49.2 cm(-1). Once the sample is cooled to liquid-nitrogen temperatures, the resolution of three additional peaks occurs, with absorption maxima now appearing at 40.1, 47.5, 56.6, 63.9, and 73.6 cm(-1). Solid-state density functional theory simulations, both with and without London force dispersion corrections, have been used for the assignment of the experimental cryogenic THz spectrum to specific molecular motions in the crystalline solid. The B3LYP hybrid density functional paired with the 6-311G(2d,2p) basis set provides an excellent reproduction of the experimental data revealing that the THz spectrum arises from a mixture of intramolecular torsional vibrations localized primarily in the nitro groups and intermolecular lattice vibrations composed of rigid molecular rotations.     

Electrochemical Synthesis of 2,3-Dimethyl-2,3-Dinitrobutane

Anodic oxidation of 2-nitropropane in a methanol solution of sodium iodide and hydroxide is found to produce 2,3-dimethyl-2,3-dinitrobutane with a yield of 65-70% under optimum conditions. Deceased.     

Reactions of Acylpyruvic Acids and 2,3-Dihydrofuran-2,3-diones with 2,3-Diaminopyridine

Acylpyruvic acids readily react with 2,3-diaminopyridine to form (Z)-3-acylmethylene-1H-3,4-di- hydropyrido[2,3-b]pyrazin-2-ones. 5-Aryl-2,3-dihydrofuran-2,3-diones which can be regarded as lactones derived from -enolized aroylpyruvic acids react with 2,3-diaminopyridine under mild conditions, yielding regioisomeric (Z)-2-aroylmethylene-4H-1,2-dihydropyrido[2,3-b]pyrazin-3-ones. The structure of the products and reaction chemoselectivity are discussed.     

meso-四苯基-2,3-二氢卟啉-2,3-二醇的合成

研究了一种关于meso-四苯基-2,3-二氢卟啉-2,3-二醇的避免使用昂贵且剧毒的四氧化锇的合成方法,整个合成过程中所用试剂廉价易得,反应操作简单.该合成方法可同时得到顺、反两种目标产物异构体.     

Preparation of 2,3-alloepimino-2,3-dideoxy-β-cyclodextrin as a versatile scaffold candidate for the hetero-2,3-bifunctionalization

3^A-Azido-3^A-deoxy-altro-β-cyclodextrin, although having as many as 20 different hydroxyl groups, was selectively sulfonylated at the 2^A-OH of the altrose residue by 2-mesitylenesulfonyl chloride to give 3^A-azido-3^A-deoxy-2^A-O-mesitylenesulfonyl-altro-β-cyclodextrin. A one-pot reduction-intramolecular substitution of the latter afforded the title compound as a promising intermediate for the introduction of two different functional groups to two different positions of one sugar unit, which has not been succeeded hitherto.     

内消旋和外消旋2,3-二氰基-2,3-二苯基丁二酸二乙酯对苯乙烯聚合反应的影响

测定了题目化合物立体异构体在80℃和90℃引发苯乙烯的自由基聚合反应。在相同条件下, 较活泼的meso-体为引发剂时, 聚合速率大, 产物分子量小; 而较稳定的dl-体则聚合速率小, 产物分子量大。且在所有反应条件下分子量均随反应时间增长。研究结果认为它们不同的聚合性能主要与异构体热分解速率对聚合动力学的影响有关。     

Synthesis of 2,3-diaryl-1,4-diazolyl-2,3-epoxybutanes

2,3-Diaryl-1,4-diazolyl-2,3-epoxybutanes have been prepared from dimethylstilbenes. An efficient although neglected synthesis of the required olefins has been recovered from the literature. The target compounds show moderate antifungal activity.     

First direct detection of 2,3-dimethyl-2,3-diphenylcyclopropanone

3,5-dihydro-3,5-dialkyl-3,5-diaryl-4H-pyrazol-4-ones stimulate interest as potential precursors for 2,3-diarylcyclopropanones. Photoreactions of trans-3,5-dihydro-3,5-dimethyl-3,5-diphenyl-4H-pyrazol-4-one were studied by continuous-wave (CW) and pulsed laser UV photolysis revealing an intermediate that undergoes rearrangement to form cis- and trans-1,3-dimethyl-1-phenyl-2-indanones with the yield of ca. 60%. Steady-state photolysis (254 and 350 nm excitation) in different solvents produced an intermediate cyclohexadiene as evidenced by UV/vis, IR, and 1H NMR spectra. In contrast, the nanosecond laser pulsed photolysis at 355 nm produced 2,3-dimethyl-2,3-diphenylcyclopropanone along with two products of retro-1,3-dipolar addition phenylmethylketene and 1-phenyldiazoethane. These can be observed by time-resolved IR (TRIR) spectroscopy as characteristic absorption bands at 1814, 2101, and 2038 cm-1, respectively. Similar retro-1,3-dipolar addition showed 1-phenyldiazoethane formed following flash photolysis of 1-pyrazoline (trans-4,5-dihydro-3,5-dimethyl-3,5-diphenyl-3H-pyrazol-4-ol). The formation of the corresponding cyclopropanone as well the products of retro-1,3-dipolar addition during photoreaction of starting pyrazol-4-one is directly confirmed by the nanosecond TRIR spectroscopy for the first time. On the basis of the CW and pulsed laser UV photolysis, a dynamic equilibrium between cyclopropanone and intermediate 2,4-diphenyl-3-pentanone-2,4-diyl (dimethyldiphenyloxyallyl) was proposed.     

2,3-Benzodiazepine-1-thione in the synthesis of substituted and hetero-annelated 2,3-benzodiazepines

A series of S-substituted and 1,2-annelated derivatives of 2,3-benzodiazepine has been obtained on the basis of 2,3-benzodiazepine-1-thione. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, 594-601, April, 2009.