Acid-mediated formation of trifluoromethyl sulfonates from sulfonic acids and a hypervalent iodine trifluoromethylating agent

Koller, Raffael; Huchet, Quentin A.; Battaglia, Philip; Welch, Jan M.; Togni, Antonio

doi:10.1039/b913962a

Cited by 97 publications

(64 citation statements)

References 14 publications

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“…The Brønsted acid activation of 7 was further used by Togni for the trifluoromethylation of sulfonic acids (eqn 14). 41 Strong acids were required and the use of the toluenesulfonate 60 salts failed to give the product. Interestingly, the Hammett plot showed that the substituent on the sulfonic acid had only a minor effect on the reaction rate.…”

Section: Trifluoromethylationmentioning

confidence: 99%

Benziodoxole-based hypervalent iodine reagents for atom-transfer reactions

et al. 2011

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In the last decades, hypervalent iodine reagents have raised from chemical curiosities to mainstream reagents in organic synthesis. The use of benziodoxole-derived reagents has been especially successful in oxidation methods, whereas non-cyclic iodinanes have been used both for oxidation and atom-transfer reactions. On the other hand, the exceptional properties of 10 benziodoxole reagents for atom-transfer reactions have only started to attract the attention of the synthetic community more recently. In this review, progress in the use of these compounds for C-X and C-C bond formations will be presented. In particular, recent breakthroughs in trifluoromethylation and alkynylation reactions have been realized since 2006 bas ed on benziodoxole-derived reagents and these results are the main focus of this article.

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Section: Trifluoromethylationmentioning

confidence: 99%

Benziodoxole-based hypervalent iodine reagents for atom-transfer reactions

et al. 2011

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“…This is in line with our previous observations concerning the trifluoromethylation of THF [15] and toluenesulfonic acid. [11] On the basis of these rate studies and our previous experience with these systems, we propose the mechanism shown in Scheme 3. The protonated form of reagent 1 is the reactive species.…”

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confidence: 98%

“…Despite their purported soft nature, reagents 1 and 2 do trifluoromethylate alcohols and sulfonic acids upon activation with Lewis [10] and Brønsted acids, [11] respectively, thus significantly expanding their application range.…”

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confidence: 99%

A Ritter‐Type Reaction: Direct Electrophilic Trifluoromethylation at Nitrogen Atoms Using Hypervalent Iodine Reagents

et al. 2010

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The unique features the trifluoromethyl group imparts to pharmaceuticals, crop-protection agents, and functional materials emphasize the necessity to design and develop new reagents and methods for the direct trifluoromethylation of a wide range of organic substrates. Electrophilic trifluoromethylation, that is, the reaction of a suitable reagent capable of formally transferring an intact CF 3 + unit, has been shown to be one of these methods.[1] However, despite the availability of several such effective reagents, the electrophilic trifluoromethylation of hard nucleophiles, for example, oxygen-or nitrogen-centered ones, remains challenging. In particular, the formation of a N À CF 3 bond by such a reaction is still extremely rare. In fact, the NCF 3 unit is usually constructed by the interconversion of suitable functional groups. Thus, fluorination of N-formylamines, [2] thiuram sulfides, [3] isocyanates, [4] and trichloromethylamines, [5] the reaction of secondary amines with CBr 2 F 2 and tetrakis(dimethylamino)ethylene, [6] and the electrochemical fluorination of alkylamines [7] constitute the still relatively modest set of methods. Of these, the most frequently used approach is the oxidative desulfurization-fluorination of dithiocarbamates first described for the generation of NCF 3 groups by Hiyama and Kuroboshi.[8]The single, still very recent report of a direct trifluoromethylation at nitrogen is due to Umemoto and co-workers.[9] They describe the direct N-trifluoromethylation of amines, anilines, and pyridines under very mild conditions achieved with in situ generated and thermally unstable O-(trifluoromethyl)dibenzofuranium salts (corresponding reactions of alcohols and phenols are also known). However, this type of reagent suffers from several shortcomings. The active CF 3 source is obtained by photochemical decomposition of diazonium salts at very low temperature, and the synthesis requires several steps including the construction of a CF 3 O-aryl moiety. It is therefore likely that this methodology will not replace the corresponding functional-group interconversions in the near future.We have shown that a new generation of readily accessible trifluoromethylation reagents based on hypervalent iodine, such as compounds 1 and 2 (Scheme 1), display the desired reactivity towards a number of C-, S-, P-, and O-centered nucleophiles. Despite their purported soft nature, reagents 1 and 2 do trifluoromethylate alcohols and sulfonic acids upon activation with Lewis [10] and Brønsted acids, [11] respectively, thus significantly expanding their application range.During a recent investigation of the direct electrophilic trifluoromethylation of heteroarenes [12] using reagent 1 and catalytic amounts of bis(trifluoromethanesulfonyl)imide (HNTf 2 ) in acetonitrile, we surprisingly found that benzotriazole (3) is converted to the corresponding N-substituted N-trifluoroimidoyl derivative 4, as shown in Scheme 2. The generation of compound 4 corresponds to a novel Rittertype [13] reaction during which a new NÀCF 3 bond...

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“…Entgegen ihrer vermeintlich weichen Natur trifluormethylieren 1 und 2 Alkohole oder Sulfonsäu-ren nach Aktivierung mit Lewis- [10] bzw. Brønsted-Säuren, [11] womit ihr Einsatzbereich erheblich erweitert wird.…”

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