Intramolecular ene reaction of 1,6-fullerenynes: a new synthesis of allenes

[Structure: see text] Thermal treatment of 1,6-fullerenynes bearing an alkyl group on the terminal carbon of the alkyne moiety leads quantitatively to new allenes through a reaction mechanism involving an intramolecular ene process. This reaction outcome is in contrast to that recently found for free terminal alkynes which form cyclobutene derivatives through a [2+2] cyclization mechanism.     

Photochemical reaction of magnesium tetraphenyl porphyrin with sulfur dioxide

<正>The photochemical reaction of magnesium tetraphenyl porphyrin(MgTPP) with sulfur dioxide(SO_2) was investigated in dichloromethane(CH_2Cl_2) by steady-state fluorescence,UV-vis absorption,MS,and XRD spectroscopic techniques.These spectra showed that under irradiation MgTPP reacted with SO_2 to form 1:1 molecular adduct at first step.During the process of keeping irradiation and maintaining the flow of SO_2,SO_2 was reduced into S~(2-) by MgTPP and the results were detected using MS and XRD techniques.Understanding the photochemical reaction of MgTPP with SO_2 is of key interest in elucidating fundamental photochemical reaction mechanisms associated with this class of chlorophyll in the presence of SO_2.     

Sulfur dioxide mediated one-pot, three- and four-component syntheses of polyfunctional sulfonamides and sulfonic esters: study of the stereoselectivity of the ene reaction of sulfur dioxide

The ene reaction of sulfur dioxide with enoxysilanes or with allylsilanes generates silyl sulfinates that can be brominated (Br(2) or NBS) or chlorinated (NCS or Cl(2)) to produce the corresponding sulfonyl halides. They react with primary and secondary amines or alcohols to give the corresponding sulfonamides and sulfonic esters, respectively. The hetero-Diels-Alder addition of sulfur dioxide to 1-oxy- or 1,3-dioxy-1,3-dienes generates zwitterions that add to enoxysilanes or allylsilanes giving silyl sulfinates that can be converted in situ into polyfunctional sulfonamides or sulfonic esters. This realizes quick access to libraries of complicated sulfonamides and sulfonic esters applying one-pot, three- and four-component methods.     

Diffusional study of the reaction of sulfur dioxide with reactive porous matrices

A single-pellet high-temperature diffusion cell reactor is used to study the sulfation of calcined Greer limestone pellets. The effective diffusivities of gases through the reactive pellets, during the calcination and sulfation are determined. The experimentally determined effective diffusivity of sulfur dioxide through the pores of the product shell is used in the modified expanding grain model to obtain the diffusivity of sulfur dioxide through the product shell of the grains as a function of the conversion and the reaction temperature. The activation energy for the initial diffusivity of sulfur dioxide through the product shell of grains, is found to be 34.13 kcal mol^?1; the diffusivity values decreased with increasing conversion. Additionally it is found that the ratio of the tortuosity of reacting shell of pellet to the initial pellet tortuosity before any sulfation was increased with increasing conversion.     

Chemoselective ligation of sulfinic acids with aryl-nitroso compounds

Making a comeback: The inefficient condensation of sulfinic acid and aryl nitroso compounds has been transformed into a chemoselective process that converts sulfinic acid into stable cyclic sulfonamide analogues (see scheme). This ligation proceeds rapidly under aqueous conditions in high yield, and lays the groundwork for the development of sulfinic acid detection methods in biological systems.     

The photochemically induced reaction of sulfur dioxide with alkanes and carbon monoxide

Abstract— The gas phase photochemical reactions of SO₂ induced by 3130 Å radiation have been studied in the presence of added alkanes or added CO. The quantum yields obtained in the reactions with the low molecular weight alkanes employed are lower than those obtained by previous workers. The quantum yields were found to be pressure dependent increasing slowly with increasing pressure. A stoichiometric ratio of one SO₂ removed per molecule of hydrocarbon consumed was observed only under experimental conditions of [SO₂] < [RH]. For reaction mixtures where [SO₂] < [RH] the ratio of [SO₂]/[RH] reacted always exceeded unity. The quantum yields decreased slightly with increasing temperature. In all the alkane reaction systems studied, the deposition of viscous, nonvolatile reaction products was observed. In the experiments with added CO, the quantum yields were computed with respect to the rate of CO₂ formation. At 25°C and equal pressures of SO₂ and CO, φco₂ was observed to be 0.005 and it decreased slightly with increasing temperature. The results obtained are interpreted in terms of the sulfoxidation of the alkanes and the oxidation of CO proceeding by way of a ³SO₂ reaction intermediate.     

The reaction of CO2 dimer ions with sulfur dioxide

The rate coefficient and the product distribution have been determined for the reaction CO₂-CO⁺₂ with sulfur dioxide.     

Palladium-catalyzed regioselective cascade reaction of carbon dioxide,amines and allenes for the synthesis of functionalized carbamates

A palladium-catalyzed regioselective three-component cascade reaction of carbon dioxide,amines and allenes has been developed,providing an expedient and practical method for the construction of a range of functionalized carbamates containing dihydrobenzofuran or indole moiety in moderate to excellent yields.The broad substrate scope,good functional group tolerance and excellent chemo-and regioselectivity are the features of the transformation.     

Stereochemistry at titanium in the sulfur dioxide insertion reaction of titanocene compounds

The insertion reaction of SO₂ has been studied for the two diastereoisomeric forms of η⁵-C₅H₅-η⁵-C₅H₄ CHMePhTi(C₆F₅)CH₃. The reaction is regioselective and stereospecific. Arguments that it involves a retention at the titanium atom are given.     

Stereochemistry of the glyoxylate N-sulfonylimine ene reaction

Ene reactions of sulfonylimine $\text{1b}$ with cyclohexane and $\text{trans}$-2-butene are highly stereoselective, affording products $\text{4}$ and $\text{10}$, respectively.     

High-efficiency process for production of sulfur from metallurgical sulfur dioxide gases

Process in which sulfur is produced from a gas containing 25–55% SO₂ was studied in order to evaluate the real efficiency of the catalytic post-reduction of sulfur dioxide in a pilot unit with gas flow rate of up to 1.2 nm³ h^–1 at the following temperatures (°C): thermal stage 850–1100, catalytic conversion 350–570, and Claus reactor 219–279. It was found that the conversion at 400–550°C and space velocity of 1600 h^–1 on AOK-78-57 promoted aluminum oxide catalyst provides full processing of organosulfur compounds (CS₂ and COS). The temperature dependence of the conversion/generation of hydrogen sulfide on AOK-78-57 catalyst corresponds to the equilibrium model. It was experimentally confirmed that the homogeneous reduction of sulfur dioxide gas with methane at T ≈ 1100°C, with catalytic post-reduction at 400–550°C and subsequent Claus-conversion of the reduced gas at 230–260°C, provide a sufficiently deep (by 92–95%) general processing of sulfur dioxide gas to sulfur.     

Selenium dioxide oxidation of alkylcoumarins and related methyl-substituted heteroaromatics

By the use of selenium dioxide as the specific oxidizing agent in the coumarin series, the 4-ethyl, 4-propyl and 4-benzyl substituents of coumarin were converted into α-alcohols 2 and/or ketones 3 , while 3-methyl- and 3-benzylcoumarins were converted into 3-acyl derivatives 7 . The methyl substituent of the analogous thiocoumarin 5 , chromones 10 or thiochromone 11 was also oxidized into the formyl functionality. Facile oxidative desulfurization into the ketone functionality, prior to methyl oxidation, was observed for the thione derivatives of 1a, 5, 6 and 10.