Photochemical intramolecular cyclization of o-alkynylaryl isocyanides with organic dichalcogenides leading to 2,4-bischalcogenated quinolines

When a mixture of o-alkynylaryl isocyanides and organic dichalcogenides such as diselenides or ditellurides was irradiated with light of wavelength over 300 or 400 nm, the intramolecular cyclization of the isocyanides took place to afford the corresponding 2,4-bischalcogenated quinolines selectively. The photochemical cyclization of 2-(phenylethynyl)phenyl isocyanide could also proceed in the presence of hydrogen transfer reagents such as tris(trimethylsilyl)silane, tributylgermyl hydride, alkanethiols, and benzeneselenol, providing the corresponding 3-phenylquinoline as the result of 2,4-dihydrogenation.     

Indium trichloride mediated intramolecular Prins-type cyclization

[reaction: see text] Intramolecular Prins-type reactions of compounds having both functionalities of homoallyl alcohol and acetal moiety are described. The intramolecular Prins cyclizations were performed using indium trichloride in chloroform or 25% aqueous THF. Both 9-oxabicyclo[3.3.1]nonane and 3,9-dioxabicyclo[3.3.1]nonane compounds were successfully obtained in moderate yields.     

Consecutive cyclization of allylaminoalkene by intramolecular aminolithiation-carbolithiation

Consecutive cyclization of allylaminoalkenes by tandem aminolithiation-carbolithiation proceeded smoothly by using a lithium amide as a lithiating agent as well as protonating agent to give bicyclic amines, octahydroindolizine and hexahydro-1 H-pyrrolizine, in reasonably high yield and diastereoselectivity.     

Interaction of acetylene with organic disulfides

Conclusions Dialkyl disulfides are added to acetylene, forming 1,2-bis(alkyithio)ethenes and vinylalkyl sulfides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 454–456, February, 1967.     

Photoinduced intramolecular charge transfer in 9-aminoacridinium derivatives assisted by intramolecular H-bond

Fluorochromic dyes derived from 9-aminoacridinium containing a vinylene function with electron withdrawing groups such as diethyl [(acridinium-9-ylamino)methylene]malonate (I), ethyl [(acridinium-9-ylamino)methylene]cyanoacetate (II), [(acridinium-9-ylamino)methylene]malononitrile (III), are prepared and studied in their monoprotonated form. Absorption spectra of the new dyes are red shifted compared to that of the precursor dye. The observed dual fluorescence and multiexponential decay are ascribed to normal emission from the acridinium chromophore in addition to excited-state intramolecular charge transfer (ESICT) process. However, biexponential decay character is observed only for the dicyano derivative (compound III), whereas for the two other systems, more complex kinetics and a three-component decay is recovered. The analysis of the fluorescence decays in different solvents for the first two compounds reveals two short-lived components in the range of 160-350 ps and 1.1-3.0 ns, related to formation and decay of the ESICT state, plus a third one with decay time of about 9 ns, which is ascribed to the normal emission from the acridinium chromophore as an enol tautomer or as an intramolecular H-bond conformer (closed form tautomer). For the dicyano derivative, in which the absence of carbonyl group precludes the H-bond interaction, the biexponential fitting reveals a slightly fast formation rate of the ESICT state with values on the order of 10(10) s(-1), whereas its decay time is between 0.6 and 3.2 ns, depending on the solvent used.     

Synthesis of riccardin B by nickel-catalyzed intramolecular cyclization

Riccardin B, a macrocyclic bis(bibenzyl) possessing cytotoxic activity, and its dehydroxy derivative were synthesized in high yields using the nickel-catalyzed intramolecular coupling of the acyclic precursors.     

Photoinduced bimolecular cyclization of diarylamines with polyhalomethanes into acridines

It is shown on the basis of measurements of the activation parameters for the reaction of nucleophilic substitution, an intermediate stage of photochemical reactions, that the entropy factor makes the main contribution to the decrease in the reactivities of the intermediates that occurs on going from CHBr₃ to CBr₄ The low efficiency ofN-alkyl-substituted diarylamines in these photochemical transformations is explained by taking into consideration another intermediate stage (cyclization) and by quantum chemical modeling of the preceding isomerization.For Part 3, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 663–667, April, 1995.     

Unexpected intramolecular cyclization of some 2′-aminochalcones to indolin-3-ones mediated by Amberlyst-15

The intramolecular cyclization of 2′-aminochalcones derived from 2- and 4-pyridinecarboxaldehydes was carried out in the presence of Amberlyst^®-15/AcOH media. Unexpectedly, the reaction proceeded through a 5-exo process turning into an alternative approach for the synthesis of 2-(pyridinylmethylene)indolin-3-ones.     

Gold-catalyzed intramolecular cyclization of alkynones with pyridine anhydrobases

4-Alkylpyridines functionalized with alkynyl amide substituents can be converted to pyridyl-substituted lactams via Au-catalyzed cyclization at the pyridine benzylic carbon. These transformations proceed through alkylidene dihydropyridine (anhydrobase) intermediates and demonstrate the ability to utilize these species in metal-catalyzed C–C bond forming reactions.     

Bis-phosphoryl-bridged stilbenes synthesized by an intramolecular cascade cyclization

Bis-phosphoryl-bridged stilbenes have been synthesized using an intramolecular cascade cyclization. They show intense blue fluorescences at longer wavelengths with higher quantum yields compared to those of the known element-bridged stilbenes. In addition, they have much lower reduction potentials due to the inductive effect of phosphoryl groups. The incorporation of the phosphoryl moiety is an effective way for the construction of highly electron-accepting pi-conjugated systems.     

Reaction of diphenyl ditelluride with 2,3-dichloroprop-1-ene in the system hydrazine hydrate-KOH

Diphenyl ditelluride reacts with 2,3-dichloroprop-1-ene in the system hydrazine hydrate-KOH along several parallel routes. Beside the nucleophilic chlorine substitution at the sp ³-hybridized carbon atom resulting in 2-chloro-3-phenyltellanylprop-1-ene the elimination of both chlorine atoms occurs affording a mixture of allene and methylacetylene. The reasons of the dual elimination reaction paths are considered.     

Hypervalent iodine mediated intramolecular cyclization of thioformanilides: expeditious approach to 2-substituted benzothiazoles

A new, mild, and efficient method has been developed for the synthesis of 2-substituted benzothiazoles via the intramolecular cyclization of thioformanilides by using hypervalent iodine reagents in CH2Cl2 at ambient temperature. The reaction proceeds via a thiyl radical in high yields to give the novel compound oxybis benzothiazole and is also amenable to generating combinatorial libraries of heterocyclic compounds by solid-phase synthesis.     

Synthesis of 2,4-diiodoquinolines via the photochemical cyclization of o-alkynylaryl isocyanides with iodine

Upon photoirradiation of o-alkynylaryl isocyanides in the presence of iodine, the intramolecular cyclization of o-alkynylaryl isocyanides proceeds to afford the corresponding 2,4-diiodoquinolines in good yields. 2,4-Diiodoquinolines can be employed in transition metal-catalyzed cross-coupling reactions.     

Ruthenium-catalyzed intramolecular cyclization of hetero-functionalized allylbenzenes

Intramolecular addition of heterofunctionalities to CC double bonds without β-hydride elimination was investigated and catalyzed by ruthenium complexes. The combination of RuCl₃ · nH₂O (10 mol%) and 3 equiv. of AgOTf acted as a catalyst for cyclization of 2-allylphenol (1a) to 2,3-dihydro-2-methylbenzofuran (2a) in good yield in the presence of Cu(OTf)₂ as a co-catalyst and PPh₃ as a ligand. This catalyst system also catalyzed the cyclization of 2-allylbenzoic acid to lactone in 91% yield. Then, a new catalyst system (RuCp¹Cl₂)₂ (1.0 mol%)/4AgOTf/4PPh₃, was found to be more active even in the absence of Cu(OTf)₂. Furthermore, this catalysis was applied to asymmetric reaction of 2-allylphenol (1a). When using TolBINAP as a ligand, over 60% e.e. was achieved.     

Synthesis of tricyclic and tetracyclic sultones by Pd-catalyzed intramolecular cyclization

A new efficient synthesis of aromatic six-membered ring sultones by the implementation of ligand-free Pd-catalyzed intramolecular cyclization of aromatic sulfonates derived from various bromo phenols and naphthols is described.     

Photoinduced charge transfer mediated by DNA-wrapped carbon nanotubes

We report our observation of solution photochemical reactions catalyzed by carbon nanotubes. Addition of sub-millimolar Ag+ ions into a solution of DNA-wrapped carbon nanotubes (DNA-CNT) leads to a strong charge-transfer band in the UV region of the optical absorption spectrum. Light irradiation of the Ag+/DNA-CNT mixture results in reduction of Ag+ to Ag nanoparticles and concomitant oxidation of water.     

New processable polyaromatic ether-keto-sulfones curable by intramolecular cyclization. XV

New processable polyaromatic ether-keto-sulfones were prepared from 2,2′-diiododiphenyl-4,4′-dicarbonyl dichloride (I), bis(p-phenoxybenzene)sulfone (II), isophthaloyl chloride (III), and diphenyl ether (IV) in Friedel–Crafts-type polymerizations. In the most promising of the iodine-containing polymers phenylacetylenyl groups were introduced in place of iodine. This polymer, with an initial monomer ratio of I:II:III:IV = 1:5:7:3, was further investigated. It is soluble in DMF, DMA, pyridine, and sulfuric acid. After curing it was insoluble in all solvents used and lost only 1.1% of its weight at 300°C when heated in air for three days. Hence in this cured state it has excellent chemical and thermal resistance. It can be cast into a film from solution in DMAc and a glass fiber laminate is readily prepared. The film is tough, transparent, and brown in color. The cured film is tougher than the uncured. The glass fiber laminate is also tough and fairly flexible. A distinct advantage of this type of polymer is its ready availability in relatively cheap raw materials. The phenylacetylenyl-group-containing polymer showed a transition temperature at 175°C and two exotherm peaks at 243 and 361°C which disappeared after curing in a DSC thermogram. Before and after curing this polymer displayed softening temperatures at 149 and 171°C, respectively, measured by a Vicat apparatus at a heating rate of 1°C/min. No melting temperatures up to 500°C were observed for any of the polymers in this study.