79938-37-7Relevant articles and documents
Restricted Rotation Involving the Tetrahedral Carbon. XXXIX. 9-(2-Methoxy-1-methylethyl)triptycene Derivatives
Suzuki, Masahiko,Yamamoto, Gaku,Kikuchi, Hiromi,Oki, Michinori
, p. 2383 - 2386 (1981)
9-(2-Methoxy-1-methylethyl)triptycenes were prepared from 9-(2-methoxy-1-methylethyl)anthracene and corresponding benzynes to examine the feasibility of isolating rotational isomers of 9-isopropyltriptycene derivatives at room temperature.They afforded crystalline ap forms which underwent internal rotation with activation energies of ca. 23 kcal/mol. 9-(2-Acetoxy-1-methylethyl)-1,2,3,4-tetrachlorotriptycene gave similar results.Based on the results, the barrier to rotation of 9-isopropyl-1,2,3,4-tetrabromotriptycene was reexamined to show that it must be corrected as 23.5 kcal/mol at 175 deg C.
Tautomerism and isomerism in some antitrichinellosis active benzimidazoles: Morphological study in polarized light, quantum chemical computations
Anichina, Kameliya,Mavrova, Anelia,Yancheva, Denitsa,Tsenov, Jordan,Dimitrov, Rasho
, p. 179 - 187 (2017/09/05)
The morphology of the crystal structure of some antitrichinellosis active benzimidazole derivatives including (1H-benzimidazol-2-ylthio)acetic acids, [1,3]thiazolo[3,2-a]benzimidazol-3(2H)-ones, 1H-benzimidazol-2-ylthioacetylpiperazines and starting 2-mercapto benzimidazoles, was studied by the use of Polarized Light Microscopy (PLM). Characterization of the crystal phase was complimented by Differential scanning calorimetry analysis (DSC) and spectroscopic data. DFT computations were performed in order to investigate the prototropic tautomerism and the geometry of the molecule of the synthesized compounds. One distinct type of crystal structure for each one of 5 or 6-methyl-(1H-benzimidazol-2-ylthio)acetic acid 6 was observed by PLM – dendritic and needle-shaped formations. Compound 14, containing a methyl substituent in the benzimidazole ring crystallized also into two phases; while for the unsubstituted compound 13 a separation of phases does not take place. The influence of the both solvents - chloroform and ethanol on the phase separation and the formation of the crystalline structure of compound 14 was investigated. The morphological study showed that the cyclization of 6 in the presence of acetic anhydride in pyridine medium led to a mixture of 6-methyl-[1,3]tiazolo[3,2-a]benzimidazol-3(2H)-one (10a) and 7-methyl-[1,3]thiazolo[3,2-a]-benzimidazole-3(2H)-one (10b), which crystallized in the form of fibrils and spherulites respectively. It was found that a difference in the crystal structures of substituted and unsubstituted benzimidazol-2-thiones, respectively benzimidazol-2-thiol derivatives exists, which may be due not only to the thiol-thione tautomerism but to the prototropic properties of the hydrogen atom in first position of the ring. The calculation results indicated that the thione form is more stable than the thiol tautomer by 51–55 kJ mol?1. But at the same time ΔG for the two thiol tautomers is below 0.5 kJ mol?1. In solid phase the 5(6)-substituted-1H-benzimidazol-2-thiols crystallized in two different crystal structures while the unsubstituted 1H-benzimidazol-2-thiol possess one type of crystal structure.
Synthesis and antitrichinellosis activity of some 2-substituted-[1,3] thiazolo[3,2-a]benzimidazol-3(2H)-ones
Mavrova, Anelia Ts.,Anichina, Kamelya K.,Vuchev, Dimitar I.,Tsenov, Jordan A.,Kondeva, Magdalena S.,Micheva, Mitka K.
, p. 5550 - 5559 (2007/10/03)
Some new thiazolo[3,2-a]benzimidazolone derivatives were synthesized using two methods. The structures of the synthesized compounds were proved by means of IR, 1H NMR and mass spectral data. Ab initio computations were performed in order to determine the electronic structure and geometry of the investigated molecules and to compare it to the geometry of albendazole. Biologically, experiments in vitro and in vivo were accomplished in order to identify the efficacy of the obtained thiazolobenzimidazolones against Trichinella spiralis. The effectiveness of compounds 4a-c in the intestinal phase of trichinellosis was 100% and in the muscle phase were 88% and 80% at a concentration of 100 mg/kg mw for the compounds 4a and 4c. The results of the hepatotoxicity test showed that the compounds 4a and 4b possess hepatotoxicity comparable to that of albendazole.
Nucleophilic Addition of Silyl Enol Ethers to Aromatic Nitro Compounds: Scope and Mechanism of Reaction
RajanBabu, T. V.,Reddy, G. S.,Fukunaga, Tadamichi
, p. 5473 - 5483 (2007/10/02)
In sharp contrast to alkali-metal enolates, silyl enol ethers and ketene silyl acetals add to aromatic nitro compounds in the presence of a fluoride ion source to give the intermediate dihydroaromatic nitronates, which can be observed by NMR.In situ oxidation of the intermediate with bromine or DDQ yields α-nitroaryl carbonyl compounds in moderate-to-high yields.The reaction is applicable to alkyl-, alkoxy-, and halogen-substituted nitrobenzenes as well as to heterocyclic and condensed nitroaromatic compounds.While substitution ortho to the nitro group predominates with sterically undemanding silyl reagents, para-substitution products are exclusively obtained with bulky reagents.However, by blocking the para position with an appropriate group such as chlorine, the addition can be directed to the ortho position.Halogen atoms of halogenated nitroaromatics and p-nitrocumenyl chloride are not displaced in the reaction, suggesting the absence of radical ion intermediates.Dihydroaromatic nitro derivatives ca be isolated in some cases, such as anthracene and naphthalene systems which are less prone to rearomatize.
