Trifluoromethanesulfinate from

Intramolecular iminoacetonitrile [4-1-2] cycloaddition has been exploited in the synthesis of quinolizidine alkaloids (Scheme 54). The intermediate 187 was generated by elimination of trifluoromethanesulfinate from 188 and underwent the desired aza Diels-Alder reaction to give 189. A series of steps which included reduetive decyanation, alkylation with (Z)-3-bromo-l-chloropropene, classical resolution, and Sonogashira coupling provided the alkaloid (-)-217A 190<050L3115>. 

Fig. 16. Formation of sodium trifluoromethanesulfinate from sodium dithionite...

Primary and secondary trifluoromethylsulfones (triflones) such as 12 are efficiently obtained from readily available sodium trifluoromethanesulfinate (10) and alkyl bromides (e. g., 11) in A, A -dimethylacetamide (DMAC). Simple primary alkyl bromides may also be employed. 

More useful from a synthetic point of view than any of these variations is the discovery by Hendrickson that trifluoromethanesulfinate ( triflinate ) is a very effective leaving group in Ramberg-BScklund reactions. The reaction succeeds only if the precursors, a-triflyl sulfones, are fully substituted at the a-position if they are not, simple deprotonation occurs under the basic reaction conditions because the triflyl group is so strongly electron withdrawing. Consequently, this approach is applicable only to the syndesis of 1,1-di-, tri- and tetra-substituted alkenes. 

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. ... 

The relatively stable trifluoromethanesulfinic acid azide,14 synthesized from trifluoromethane-sulfinyl chloride and sodium azide, begins to decompose at — 10 C to give the extremely reactive sulfur oxide nitrene 4. The intermediate 4 oligomerizes spontaneously, but in the presence of acetonitrile compound 4 forms the stable dithiatriazine 1,3-dioxide 5. cis- and ri-mw-Isomers of compound 5 can be detected by gas chromatography (ratio 8 10). 

No reaction between trimethy](trifluoroniethyl)silane and sulfur dioxide occurs in the absence of an anionic initiator when one molar equivalent of tetrabutylammonium fluoride is used, clean formation of tetrabutylammonium trifluoromethanesulfinate is observed.112 Although oxidation to the corresponding sulfonate occurred readily upon treatment with 30% hydrogen peroxide, attempts to liberate the free acid from the salt proved unsuccessful. When sodium trimethylsilanolate was used as the initiator, however, the reaction sequence was successful. The overall yield of trifluoromethanesulfonic acid (31) was about 30%. 

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