Sulfinic esters, formation

Pedersen and coworkers investigated the El mass spectra of several 2-hydroxyphenyl alkyl sulfones (39) and sulfoxides (Section II.B). The methyl derivative seemed to fragment only via sulfinate ester formation giving the primary product ions m/z 157 and 109 (equation 14). Obviously hydrogen bonding between the ortho hydroxyl and the sulfone sulfur makes the loss of CH3SO2 difficult in contrast to the situation in methyl phenyl sulfone. The sulfinate ester rearrangement is not important when R>Et in 39. 

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. 

The other fragmentation pathways are typical for diaryl sulfoxides1-4-6,1. A corresponding ortho effect was found in chlorodiphenyl ethers and sulfides but not in sulfones12 (12) were the sulfinate ester rearrangements1-4,6,11 and the consequent formation of the m/z 125 and m/z 159 ions suppress the other possible fragmentations of the molecular ions (equation 4). It is also noteworthy that the ratio [m/z 125] [m/z 159] increases with increasing distance between the chlorine and the sulfur (equation 4). 

The formation of cyclic sulfinic esters (sultines) from vinyl sulfenes is known , and the trapping of the expected intermediate vinyl sulfene in the thermolysis of thiete dioxide (6fc and 194) has been convincingly achieved . Specifically, thermolysis of thiete dioxide 6b in the presence of norbornenes gave cycloadducts of the Diels-Alder type (i.e. 252b), resulting from the trapping of the vinyl sulfene formed. The accumulated evidence thus supports the proposed mechanism for these thermolytic reactions. 

It is also known (Mikolajczyk et al., 1976) that treatment of an optically active sulfinamide with an alcohol in the presence of two moles of strong acid as catalyst results in the formation of optically active sulfinate esters of inverted configuration (152), although the degree of stereoselectivity depends on the... 

The carbanion generated by ot-proton abstraction of a 2-alkyloxazoline is capable of typical enolate chemistry. Thus, the carbanion was found to react with nitriles to give an enamine, with formate esters to give an aldehyde that can be trapped,with chiral sulfinate esters to give chiral sulfoxides,and with alkylating agents. A carbamate-protected aminomethyl chiral oxazoline was deprotonated and alkylated with diastereoselectivities up to 92% de. ... 

This is the second important contribution of Kagan s group in the synthesis of chiral sulfoxides. The method was reported in 1989 for the synthesis of tert-butyl sulfoxides,90 and the full paper on the generalization of the method was published in 1991.86 The approach is based on the synthesis and use of an o.p. cyclic sulfite in the synthesis of various sulfoxides by two successive condensations of two organometallic reagents, RjM and R2M. Thus, the sulfoxides are produced in three separate steps the formation of cyclic sulfite, synthesis of sulfinate esters, and transformation of sulfinates to chiral sulfoxides. 

The first parameter to optimize was the nature of the base used. While there were precedents in the literature for the change in the starting chiral alcohol, to the best of our knowledge there was no report on the effect of the base on the stereocourse of the formation of sulfmate esters. In the literature on the asymmetric synthesis of sulfinate esters, statements such as asymmetric synthesis of sulfinate esters is achieved by the reaction of sulfmyl chloride with a chiral secondary alcohol in the... 

The reactions of the other sulfinyl chlorides (n-Pr, z -Pr, p-Tol) with DAG using z -Pr2NEt as base led to the formation of (S)-sulfinate esters as the major isomers with high selectivity (89 to >95%) instead of (/ -)sulfinate esters predominantly obtained when pyridine was used as base (70 to > 95% de, Table 20). 

The intriguing and useful base effect on the stereocourse formation of sulfinate esters of DAG raises several questions. The first and most important is the origin of such effect. In order to answer this question it is essential to know the stereoelec-tronic prerequisite of a base so as to direct the main formation of R- or S-sulfinate. For this study, and taking into account the major sulfinate formed in this reaction,... 

Electrolysis of benzothiete sulfone 269 yields the phenylmethanesulfinate anion (major) and the o-toluenesulfinate anion (minor).Thermolysis 618,619 gj. photolysis of thiete 1,1-dioxides proceeds via ring-opening to vinyl sulfines, for example. 288, which have been trapped by reaction with water, phenol,methanol, or norbornenes. These intermediates may recyclize to unsaturated sultines (cyclic sulfinate esters) (e.g., 289) or lose sulfur monoxide to give mainly the trans isomers of a,j3-unsaturated carbonyl compounds (e.g., 290). Mass spectra also indicate the formation of unsaturated sultines. ... 

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. 

The reaction of tertiary propargyl sulfinate esters with (MeCuBr)MgCl or (MeCuBr)MgCl -LiBr in THF at 20 C gives rise to the formation of the allenic derivatives in 98% yield through a syn-process [81,82, Eq. (82)]. 

Type of reaction C-O bond formation Reaction condition solvent-free Keywords sulfinate ester, DCC, sulfinic acid... 

As indirect evidence for the formation of sulfuranes, the following reactions have been reported by Okuyama and co-workers [34]. They undertook the hydrolysis of sulfinic esters and sulfine amides 5 under acidic conditions using an 180-tracer. On the basis of 180 exchange and kinetic studies for the hydrolysis, they found that 180 exchange takes place in the reactions, and proposed that the mechanism for the hydrolysis involves the initial formation of sulfurane 6 as an intermediate as shown in Scheme 3. 

Other methods, among which thermolysis or photolysis of tetrazene [59], photolysis of nitrosoamines in acidic solution [60], photolysis of nitrosoamides in neutral medium [61], anodic oxidation of lithium amides [62], tributylstannane-mediated homolysis of O-benzoyl hydroxamic derivatives [63, 64], and spontaneous homolysis of a transient hydroxamic acid sulfinate ester [65] could have specific advantages. The redox reaction of hydroxylamine with titanium trichloride in aqueous acidic solution results in the formation of the simplest protonated aminyl radical [66] similarly, oxaziridines react with various metals, notably iron and copper, to generate a nitrogen-centered radical/oxygen-centered anion pair [67, 68]. The development of thiocarbazone derivatives by Zard [5, 69] has provided complementary useful method able to sustain, under favorable conditions, a chain reaction where stannyl radicals act simply as initiators and allow transfer of a sulfur-containing... 

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