Sulfur Dioxide and Related Compounds

Cycloaddition reactions of 1,3-dienes with sulfur dioxide, unlike its mono and bis imino derivatives, usually produce iive-membered ring 2,5-dihydrothiophene dioxides rather than Diels-Alder adducts [Eq. (36)]. 

Durst has shown that a Diels-Alder adduct is in fact the kinetic product of reactions of sulfur dioxide with conjugated dienes, but is thermally unstable and readily undergoes a retro-Diels-Alder reaction to butadiene and sulfur dioxide. A thermodynamically more favorable addition then ensues, producing a stable live-membered ring adduct. Thus, the apparent inability of sulfur dioxide to form Diels-Alder adducts is not one of reactivity, but of product instability. 

In a recent experiment. Durst has shown that six-membered ring ox-athiins are, in fact, the primary kinetic products of sulfur dioxide-diene reactions. An o-quinodimethane, which was generated from a diazo compound [Eq. (37)]. 

Soviet workers recently discovered that under high pressures (3-5 kbar) isoprene reacts with phenylsulfinyl chloride to give (Z)-chioro-sulfoxide 82 [Eq. (39)].  

It was suggested that this product arises via an intermediate Diels-Alder adduct 81. 

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A variety of miscellaneous derivatives of gulonolactone has been reported. Linn treated D-glucofuranurono-6,3-lactone (7) with chlorobenzene and aluminum trichloride in order to obtain115 6-deoxy-6,6-diphenyl-L-gulonic acid (70). Various related compounds were also prepared. When 7 was treated with sulfur dioxide and 2-(isonicotin-oyl)hydrazine in water, 6-deoxy-6-(2-isonicotinoylhydrazino)-6-sulfo-D-gulono-1,4-lactone (71) was formed in 81% yield.116,117 Kawabata... 

A characteristic property of thiirane 1,1-dioxides is the ease with which such molecules fragment into sulfur dioxide and the related olefin on standing for several hours at room temperature. The title compound is no exception however, the rate of decomposition may be reduced substantially by storage under an inert atmosphere in a freezing compartment (ca. —5°). Under such conditions the product may be kept for many months. 

A selection of methods which have been used to convert thiopyrans and related compounds to their 1-oxides or 1,1-dioxides is presented in Table 28 and reagents used to oxidize various thiopyranone derivatives at sulfur are collated in Table 29. 

Surveyed in this section are known SOg insertion and desulfination reactions. Kinetic and stereochemical results already discussed in Sections III-V, as well as the cycloaddition processes treated in Section V, have been given a cursory mention for the sake of completeness. The insertion reactions involving bonds other than M—C are omitted. Also excluded are all aspects of the chemistry of metal sulhnate complexes except sulfur dioxide insertion and desulfination. Readers interested in alternative methods of synthesis and in the physical and chemical properties of these and related compounds are referred to a recent review 128). 

Cycloaddition Reactions of Thiocarbonyl S,5-Dioxides and Related Sulfur(VI) Compounds... 

Neutralizing inhibitors lessen the corrosivity of the environment by decreasing hydrogen ion (H+) concentration, which reduces the concentration of the corrosive reactant. Neutralizers function by controlling the corrosion caused by acidic materials such as hydrogen chloride, CO2, sulfur dioxide (SO2), carboxylic acids, and related compounds (Neville and Wang 2009). 

Apparently 9-phenylfluorenyl is not only a good anion but also a bad cation. The chloride probably shares in some of the resonance stabilization of the anion while the cation does not. Another example of a connection between the resonance of an anion and the properties of a related covalent compound is provided by the hydrocarbon triphenyl-methylcyclopentadiene, which has an unusually high dipole moment although it does not conduct in liquid sulfur dioxide.180... 

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