Alkyl sulfinates

Alkyl halides or alkyl sulfates, treated with the salts of sulfinic acids, give sulfones. A palladium catalyzed reaction with a chiral complexing agent led to sulfones with modest asymmetric induction. Alkyl sulfinates (R SO—OR) may be side products. Sulfonic acids themselves can be used, if DBU (p. 1337) is... 

Bacteria selected for growth with bis-(3-pentflnorophenylpropy)-sulfide as sulfur source are able to use dimethyl sulfoxide, dibenzyl snlfide, and some long-chain disulfides as sources of sulfur (van Hamme et al. 2004). Degradation takes place by oxidation to the sulfone, scission of the C-S bond to an alkanol, and an alkyl sulfinate that is degraded with loss of the snlfnr, which is nsed for growth. 

The bisphosphane BPA was selected as a ligand for the Pd atom because of the high enantioselectivities which had been recorded in the allylation of sulfinate ions with racemic allylic carbonates (vide supra). Besides the variations of the carbon skeleton, the substituent on the S atom of the racemic allylic sulfinates was varied in order to see whether both aryl and alkyl sulfinates are amenable to a highly selective rearrangement. 

The facile cleavage of the S-N (7-bond in the 1,2-thiazetidine A-oxide 54 is part of the driving force in its rearrangement and this feature was exploited in reaction with nucleophiles. Thus, treatment with methanol affords the ring-opened alkyl sulfinate 56 in 86% yield while similar reaction using -butylamine leads to the sulfmamide 57... 

By the interaction of sulfur dioxide and trialkyl alanes, when the A1—C bond is added across the S—0 bond, alkyl sulfinates of aluminum are obtained (231, 313). The analogous reaction with 3 moles of sulfur trioxide leads to alkyl sulfonates (19) ... 

Alkyl sulfinates. Reductive esterification of ArS02Cl with Ph P, and in situ sulfinylation, is accomplished in one flask. By using a chiral alcohol in this process, two diastereomers are obtained. 

It can be concluded that strongly electrophilic character of SO2 having a vacant orbital on sulfur enables to undergo the Se2 backside attack on the a-carbon of the alkyl ligand prior to binding to the metal, which leads to formation of an alkyl sulfinate anion with inversion at the carbon. Formation of the kinetic product,... 

In principle, insertion reacticms are reversible, but just as we saw for oxidative addition and reductive elimination in Chapter 6, for many ligands only one of die two possible directions is observed in practice, probably because this direction is strongly favored thermodynamically. For example, SO commonly inserts into M-R bonds to give alkyl sulfinate complexes, but these rarely eliminate SO2. Conversely, diazoaiene complexes readily eliminate Nj, but N2 has not yet been observed to insert into a metal-aryl bond. 

Sulfur dioxide is a strongly electrophilic species with a vacant orbital on sulfur, which it can use to attack even 18e metal complexes. Wojcicki and co-workers have studied these reactions in detail and find that the SO2 can give electrophilic attack at the a carbon of the alkyl from the side opposite the metal, which leads to the formation of an alkyl sulfinate ion (RS02 ) with inversion at carbon. Since the anion has much of its negative charge on the oxygens, it is not surprising that the kinetic product of ion recombination is the 0-bound sulfinato complex. On... 

Ethyl /m s -2-butenyl sulfone (86) together with some ethyl vinyl sulfone are obtained by the reaction of ethylene and. SO2 in wet benzene using PdCl2. SO2 behaves mechanistically similarly to CO in this reaction[66]. Hydrosulfination of alkenes with SO2 and H2 is catalyzed by the Pd(dppp) complex. The sulfinic acid 87 is a primary product, which reacts further to give the. S-alkyl alkanethiosulfonates 88 as the major product, and 89 and the sulfonic acid 90 as minor products[67]. 

Carbon-sulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol (201) (700S(50)104). If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. 

Alkylation of fluonnated carboxylate [4J] and sulfinate anions [42] occurs readily (equations 37 and 38)... 

Arylsulfmic acids are perfluoroalkylated under the conditions, but the yield IS low [77 (equation 70) The isolated product is an aryl perfluoroalkyl sulfone. The possible formation of a perfluoroalkyl aryl sulfinate intermediate, arising from an 0-alkylation reachon, has not been discussed. 

Benzopentathiepin rapidly reacts with sodium sulfinates RS02Na (R = alkyl or aryl) in ehloro-form/methanol at 20 °C to afford high yields of thiosulfonates RS02SNa.406... 

Aryl- and alkyl-magnesium halides were the first reagents used to form sulfoxides from sulfinate ester 19 and related (— )-menthyl arenesulfinates (equations 564,665,758 and 866). Whereas optically pure esters produced the homochiral sulfoxides shown in equations (5), (6) and (7), the ester shown in equation (8) was an oily mixture of four diastereomers which led to formation of a meso sulfoxide and a d, l pair enriched in one enantiomer. A homochiral sulfoxide was obtained by fractional crystallization. 

Esters and amides may be sulfinylated. Addition of a mixture of t-butyl acetate and sulfinate ester 19 to a THF-ether solution of magnesium diisopropylamide led to the formation of (R)-(+)-f-butyl p-toluenesulfinylacetate (49) in 90% yield (equation 14)7. t-Butyl propanoate and butanoate also underwent this sulfinylation to give 50 and 51 in yields of 68 and 45%, respectively83. The diastereomeric ratio was 1 1 for 50 and 3 7 for 51. These esters may also be obtained by alkylation of 49. Similarly, treatment of a-lithio-A, A -dimethylacetamide with sulfinate ester 19 gave (R)-( + )-N, Ar-dimethyl-p-toluene-sulfinylacetamide (52) (equation 15)84. 

TABLE 3. Sulfones from sulfinates R1S02M and alkyl halides... 

Between sulfur dioxide radical anions, dithionite, and sulfoxylate/sulfite there exists a pH-dependent equilibrium465 (equation 86). Therefore, dithionite has been used as a source of sulfoxylate in order to prepare sulfinate and hence sulfones. Alkylation with triethyl oxonium fluoroborate leads to ethyl ethanesulfinate, alkyl iodides lead to symmetrical sulfones466 (equation 87). 

Similarly, the reaction of the parent thiirane dioxide, the 2-chloro- and 2,3-cis-dimethylthiirane dioxides with either Grignard or alkyl lithium reagents, has been studied extensively. The fair-to-good yields of the sulfinates (62) obtained (48-82%), accompanied by ethylene (or the corresponding alkenes for substituted thiirane dioxide), have been interpreted in terms of initial nucleophilic attack of the base on the sulfur atom as depicted in equation 17116. 

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