From 4,5,6,7-tetrahydroindole to functionalized furan-2-one-4,5,6,7-tetrahydroindole-cyclobutene sequence in two steps

Ethyl 3-(4,5,6,7-tetrahydroindol-2-yl)propynoate, readily available from 4,5,6,7-tetrahydroindole and ethyl bromopropynoate, when treated with dichlorodicyanobenzoquinone (DDQ) in methanol affords furan-2-one-4,5,6,7-tetrahydroindole-cyclobutene sequence in a 52% yield. As kinetic and minor products, a furan-2-one isomer along with bicycloheptadienone have been either isolated or identified. The reaction has been shown to proceed via the isolable intermediate the [2+2]-cycloadduct of ethyl 3-(4,5,6,7-tetrahydroindol-2-yl)propynoate with DDQ. Other alcohols react with the [2+2]-cycloadduct in a similar way. The effect of the alcohol structure on the products ratio has been analyzed. All the intermediates and products are formed as single diastereomer, thus indicating a concerted character of the rearrangement.     

C(2)-Functionalization of 1-substituted imidazoles with cyanoacetylenes and aromatic or heteroaromatic aldehydes

Substituted imidazoles (substituents are Me, Et, i-Bu, n-Hexyl, (CH₂)₂S-Bu-n, Ph, Bn) react smoothly (room temperature, without catalyst and solvent) with cyanoacetylenes (3-phenyl-2-propynenitrile and 4-(1-butoxyethoxy)-4-methyl-2-pentynenitrile) and aromatic or heteroaromatic aldehydes (benzaldehyde, 4-CN-benzaldehyde, pyridine-3-aldehyde) to give 3-(2-imidazolyl)-3-aryl-2-acylpropanenitriles, a hitherto unknown family of functionalized imidazole derivatives, in up to 62% yield. This three-component manifold represents a novel C(2)-functionalization of the imidazole nucleus involving zwitterionic, carbene and enol ether intermediates. Unlike the analogous reaction with aliphatic aldehydes, which gives enol ethers, in this case the latter undergo the further rearrangement to 3-(2-imidazolyl)-3-aryl-2-acylpropanenitriles.     

Crystal Structures of Rb- and Ag-Substituted Forms of Natural Zeolite Amicite

Crystallography Reports - The crystal structures of ion-exchange products of the zeolite-group mineral amicite from Khibiny Alkaline Massif with silver and rubidium salts have been studied. The...     

Electroconducting Radical-Cation Salts Based on Tetrathiafulvalene Derivatives and Transition Metals Bis(dicarbollides)

Russian Journal of General Chemistry - The radical-cationic salts based on tetrathiafulvalene derivatives and bis(dicarbollide) transition metal complexes [3,3′-M(1,2-C2B9H11)2]? (M =...     

Conformational study of 2-arylazo-1-vinylpyrroles

Conformational study of 2-phenylazo-1-vinylpyrrole and 2-(4-bromophenyl)azo-5-methyl-1-vinylpyrrole was performed on the basis of the experimental measurements and high-level ab initio calculations of their 13C--13C and 13C--1H spin-spin coupling constants, showing marked stereochemical behaviour upon the internal rotation of the vinyl group and the pyrrolyl moiety. In liquid phase, both compounds were found to adopt predominant s-trans-s-trans conformation with the noticeable population (ca. 30%) of the higher-energy s-cis-s-trans conformation in the latter compound. As follows from the X-ray data, 2-phenylazo-1-vinylpyrrole crystallizes in s-trans-s-trans conformation while the crystalline molecular structure of 2-(4-bromophenyl)azo-5-methyl-1-vinylpyrrole is s-cis-s-trans.     

Naphthalene proton sponges as hydride donors: diverse appearances of the tert-amino-effect

It has been shown that the 1-NMe(2) group in the 2-substituted 1,8-bis(dimethylamino)naphthalenes (proton sponges) can intramolecularly donate a hydride ion to an appropriate electron-accepting ortho-substituent such as diarylcarbenium ion, β,β'-dicyanovinyl or methyleneiminium group. This produces the 1-N(+)(Me)=CH(2) functionality and triggers a number of further transformations (tert-amino effect) including peri-cyclization, ortho-cyclization or hydrolytic demethylation. In each particular case, the course of the reaction is determined by the nature of the ortho-substituent and the most potent nucleophile presenting in the reaction mixture. For 2,7-disubstituted 1,8-bis(dimethylamino)naphthalenes, two types of tandem tert-amino effect with the involvement of both peri-NMe(2) groups have been registered. The conclusion was made that proton sponges are generally more active in the tert-amino reactions than the corresponding monodimethylaminoarenes. This is ascribed both to higher electron donor ability of proton sponges and markedly shortened distance between electrophilic C(α)-atom in the ortho-substituent and hydrogen atoms of the nearest NMe(2) group. Most conversions observed proceed in good to high yields and are useful for the preparation of derivatives of benzo[h]quinoline, quino[7,8:7',8']quinoline, 2,3-dihydroperimidine, N,N,N'-trimethyl-1,8-diaminonaphthalene and proton sponge itself.     

Synthesis and Structural Characterization of the First Europium(III) Pyridylphosphine Complex, [Eu(N,N’,N”-2-Py3P)(NO3)3]

The first europium(iii) pyridylphosphine complex, [Eu(N,N’,N”-2-Py₃P)(NO₃)₃] was prepared by the reaction between Eu(NO₃)₃.6H₂O and tris(2-pyridyl)phosphine; its structure was characterized by single-crystal X-ray diffraction.     

Heterometallic compounds with the binuclear complex anion [Cr<Subscript>2</Subscript>(OH)(Ac)(Nta)<Subscript>2</Subscript>]<Superscript>2−</Superscript>: Synthesis and structure

Heterometallic compounds BaCr₂(OH)(Ac)(Nta)₂ · 4H₂O (I) and [Fe(L)₃][Cr₂(OH)(Ac)(Nta)₂] · nH₂O (L is Bipy (II) and Phen (III); Bipy is, αα′-bipyridine, Phen is o,o′-phenanthroline, Ac⁻ is acetate ion, Nta is nitrilotriacetate ion; n = 8 (II) and 6.25 (III)) are synthesized. According to the X-ray diffraction data, compounds II and III have ionic structures built of the isolated complex cations [Fe(L)₃]²⁺, binuclear complex anions [Cr₂(OH)(Ac)(Nta)₂]²⁻, and crystallization water molecules. The magnetic properties of compounds II and III in the interval from 2 to 300 K confirm assumptions on the diamagnetic character of [Fe(L)₃]²⁺ and indicate the antiferromagnetic interaction between the chromium atoms in the dimeric fragment [Cr₂(OH)(Ac)(Nta)₂]²⁻.     

Crystal and Molecular Structures of N-Ethylquinolinium Triiodide

Complexation in the N-ethylquinolinium iodide–molecular iodine system in a chloroform solution is studied. The stability constant of N-ethylquinolinium triiodide (I) is determined by spectrophotometric methods of stoichiometric dilution using the average iodine number function. Compound I with the [C₉H₇NC₂H₅]I₃ composition is studied by X-ray diffraction analysis. The crystal structure is formed by alternating layers of cations arranged by the ladder type and triiodide anions with equalized interatomic distances. The triiodide anions are linked to form chains through strongly shortened intermolecular contacts.