Sulfinic reactions with elimination

Os(II) complexes of tosylmethylisocyanide react with aldehydes and ketones in the presence of sodium methoxide, producing cyclic carbene complexes (66). Compound 32 undergoes a rapid reaction with benzal-dehyde and NaOMe, yielding the oxazol-2-ylidene complex 33 and eliminating p-toluene sulfinic acid (66) ... 

The reaction of arylsulfonyl-substituted sulfines (175) with diazomethane gives A3-l,3,4-thiadiazoline 1-oxides (176) which, however, are unstable and rearrange via an isomerization of the A3- to the A-thiadiazoline oxide. This is followed by an elimination and readdition of sulfinic acid and loss of water in a Pummerer-type aromatization to give the rearranged thiadiazole (177 Scheme 24) (73TL5009). 

Lactols and their acetals can be transformed easily into their 2-arylsulfonyl derivatives 337 by reaction with a sulfinic acid under Lewis acid activation. The corresponding organolithiums are prepared by deprotonation with n-BuLi or LDA and, after reaction with electrophiles, a /(-elimination of sulfinic acid afforded a cyclic a-substituted enol ether514,547,548. 2-Lithio-2-(arylsulfonyl)tetrahydropyrans equilibrated to give mainly the anomer with the lithium atom at the equatorial position549. 

The kinetics of chromium(III)-catalysed oxidation of formic acid by Ce(IV) in aqueous H2SO4 can be rationalized in terms of initial formation of an outer-sphere complex involving oxidant, catalyst, and substrate (S), Ce(IV)(S)Cr(III), followed by an inner-sphere complex Ce(III)(S)Cr(IV). It is proposed that electron transfer occurs within this complex from substrate to Cr(IV) (with elimination of H+) followed by fast reaction to give CO2 (again with elimination of H+). " In contrast, there was no kinetic evidence for the accumulation of a corresponding inner-sphere intermediate in the osmium(VIII)-catalysed Ce(IV) oxidation of DMSO to dimethyl sulfone here, the observed rate law was rationalized in terms of rate-determining bimolecular electron transfer from DMSO to Os(VIII) in an outer-sphere step. The kinetics of oxidation of 2-hydroxy-1-naphthalidene anil by cerium(IV) in aqueous sulfinic acid have been... 

Methanol-0-4 methyl nitrite, and dimethyl disulfide have been examined as potential chemical probes for distinguishing between alkoxides and enolates in the gas phase. Methanol-0-(/ proved to be unsuitable and methyl nitrite reacts too slowly in contrast, the reactive ambident behaviour of dimethyl disulfide results in elimination across the C—S bond on reaction with alkoxides ( hard bases ) and attack at sulfin by enolates ( soft bases ). This probe has been applied to investigation of the anionic oxy-Cope rearrangement. The dianionic oxy-Cope rearrangement is a key step in a squarate ester cascade involving stereoinduced introduction of two alkenyllithium reagents cis to each other. 

Selenoxides ° and sulfinate esters R2CH-CHR-SO-OMe also undergo elimination by the E mechanism, the selenoxide reaction taking place at room temperature. The reaction with selenoxides has been extended to the formation of triple bonds. 

In a similar way, pyridine phosphonium salts and phosphonates can be prepared by reaction of trivalent phosphorus compounds with the more accessible iV-trifluoromethanesulfonyl-pyridinium salts, when tri-fluoromethanesulfone is the leaving group from nitrogen (as sulfinate anion) attack is normally at C-4, as illustrated below. The A -trifluoromethanesulfonyl-pyridinium salts also react with ketones or with electron-rich aromatic compounds to give 1,4-dihydropyridine adducts. Subsequent treatment with potassium t-butoxide brings about elimination of trifluoromethanesulfinic acid, and thus aromatisation. It is also possible to utilise phosphonates in reaction with aldehydes, leading finally to 4-substimted pyridines. ... 

Vinyl sulfones can function as acetylene equivalents through the elimination of sulfinic acid. Reck and coworkers prepared a series of vinyl sulfones for cycloaddition reactions with azides to prepare 1,2,3-triazole derivatives to be incorporated into new oxazolidinone antibacterial agents. Included in the series was the cycloaddition of l-fluoro-l-(phenylsulfonyl)ethylene with the oxizolidinone 156 to give, after elimination of phenylsulfonic acid, a 28% yield of a 1 7 mixture of the regioisomeric 4-and 5-fluorotriazoles (157 and 158) (Fig. 3.91). 

Much more widely used carbene precursors are tosylhydrazones, which are readily prepared from aldehydes or ketones by reaction with 4-toluenesulfonyl hydrazide. Tosylhydrazones produce transient diazo compounds by base-catalyzed elimination of toluenesulfinate. The diazo compound is not normally isolated, and decomposes to the carbene on heating. The whole process is known as the Bamford-Stevens reaction. The leaving group is not the famihar tosylate (toluene-p-sulfonate, p.CH3-C, H4S03 , TsO ), but the less famihar toluene-p-sulfinate (Ts , P.CH3-C5H4S02 ) (Scheme 5.7). 

The Julia olefination allows the generation of a double bond by alkylation of a suUbne, followed by a base-induced elimination of ben-zenesulfinic add. The water-soluble sulfinate can be separated off, and recovered as the free sulfinic add. The sulfone is then obtained by reaction ofthe sulfinic acid with the appropriate alkyl halide. [73]... 

Our attempts to prepare useful materials by chemical modification of poly(vinylidene bromide) (Ref. 50) were not very successful, although, in reactions with the anions of methyl mercaptan or 2-mercaptoethanol under phase transfer conditions, degrees of substitution as high as 55% were obtained, while a reaction with the less nucleophilic sodium methyl sulfinate gave only 46% conversion. The reactions were accompanied by extensive elimination and the final modified polymers were always highly colored. 

The concept of the conjugation reaction with sulfone 75 is presented in Equation 3.44. The nucleophilic addition of the heterocyclic nitrogen of the aromatic ring to the double bond affords intermediate 76, which upon elimination of tolyl-sulfinic acid forms a, 3-unsaturated ester 77. A second Michael addition finally gives cyclic bis-alkylated product 78 (Equation 3.44). 

Peterson-type reaction of a-silyl carbanions with sulfur dioxide gives sulfines 268. In this case, a C=S double bond is formed with elimination of lithium silanolate (Scheme 2.160) [443, 444]. This method can be applied to the synthesis of phos-phorylated sulfines and a,/i-unsaturated sulfines [445, 446]. 

Zwanenburg and Wagenaar have reported the rather unusual rearrangement of sulfone 81 to 82, after standing overnight at 0°, and suggested an elimination-addition mechanism, via initial isomerization of A to the A -thiazoline-oxide with subsequent elimination and readdition of sulfinic acid, followed by spontaneous loss of water in a Pummerer-type aromatization reaction. 

The reaction of OH radicals with dimethyl sulfoxide in aqueous solution was studied already in 1964 by Norman and coworkers . They used the system Tj -HjOj to produce OH radicals and using ESR/rapid mixing techniques they were able to demonstrate elimination of a methyl radical during the OH induced oxidation. Further studies showed the formation of sulfinic radicals in this reaction either directly or by spin trapping experiments . ... 

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