Togni reagent

Two hypervalent iodine, electrophilic trifluoromethylation (Togni) reagents, which have CF3-iodine bonds are also worth including in this section (Scheme 5.6). 

As an orthogonal approach to the direct trifluoromethylation of indole derivatives, 2-trifluoromethylated indole 93 was prepared by subjecting isonitrile 92 to the hypervalent iodide (Togni) reagent and catalytic amounts... 

This scheme can be used in general to describe three catalytic transformations reported by MacMillan the enantioselective a-trifluoromethylation of aldehydes using the Togni reagent, the enantioselective a-aiylation of aldehydes, and the enantioselective ot-vinylation of aldehydes. ... 

The Togni reagents, as these compounds have come to be known, trifluoromethylate a variety of functional groups, including alcohols, phenols, thiols, -ketoesters and a-nitroesters ... 

Note The last reaction, which involves an a-nitroester, warrants a couple of comments. Note that a copper catalyst has been added this is sometimes done for Togni reagents. Unfortunately, a discussion of the role of the copper is outside the scope of this book. Second, the a-nitro-a-trifluoromethyl product may be transformed to the corresponding a-amino acids, which in turn may be applied to the synthesis of fluorinated pharmaceuticals. 

Kieltsch, I., Eisenberger, P. and Togni, A. (2007) Mild electrophilic trifluoromethylation of carbon- and sulfur-centered nucleophiles by a hypervalent iodine(III)-CF3 reagent. Angew. Chem. Int. Ed., 46, 754-757. 

Togni and coworkers have found that 1-trifluoromethylbenziodoxole 770 is a useful reagent for electrophilic trifluoromethylation of nucleophilic substrates. This reagent, in particular, reacts with (3-ketoesters 769 under mild conditions in the presence of potassium carbonate to give a-trifluoromethylated product 771 in good yield (Scheme 3.303) [1026, 1027]. Likewise, this mild electrophilic trifluoromethylating... 

Silver carbonate catalyzes the carbon phosphonation of aryl propiolates with dialkyl H-phosphonates in order to prepare 3-phosphonated conma-rins (140L3356). Other propiolates undergo copper(II)-mediated direct trifluoromethylation with Togni s reagent 19 providing 3-trifluoromethyl-coumarins (Scheme 54) (14OL4240). 

The Ir complexes are capable of affording trifluoromethylation of the different anilines 96 with Togni s reagent 97 as a sonrce of the CF radical to afford 98 (Eq. 9.19) [71]. When the para position has no snbstitnent, a mixtnre of prodncts is obtained ... 

Charpentier J, Frilh N, Togni A (2015) Electrophilic trifluoromethylation by use of hypervalent iodine reagents. Chem Rev 115 650-682. doi 10.1021/ci500223h... 

Matousek V, Pietrasiak E, Schwenk R, Togni A (2013) One-pot synthesis of hypervalent iodine reagents for electrophilic tiifluonnnethylation. J Org Chem 78 6763-6768. doi 10. 

Niedermann K, Welch JM, Roller R, Cvengros J, Santschi N, Battaglia P, Togni A (2010) New hypervalent iodine reagents for electrophilic trifluoromethylation and their precursors synthesis, structure, and reactivity. Tetrahedron 66 5753-5761. doi 10.1016/j.tet.2010.04.125... 

Eisenberger P, Kieltsch I, Annanino N, Togni A (2008) Mild electrophilic trifluoromethylation of secondary and primary aryl- and alkylphosphines using hypervalent iodine(III)-CF3 reagents. Chem Commun 1575-1577. doi 10.1039/B801424H... 

Roller R, Stanek K, Stolz D, Aardoom R, Niedermann K, Togni A (2009) Zinc-mediated formation of trifluoromethyl ethers from alcohols and hypervalent iodine trifluoromethylation reagents. Angew Chem Int Ed 48 4332-4336. doi 10.1002/anie.200900974... 

Niedermann K, Friih N, Senn R, Czamiecki B, Verel R, Togni A (2012) Direct electrophilic N-trifluoromethylation of azoles by a hypervalent iodine reagent. Angew Chem Int Ed 51 6511-6515. doi 10.1002/anie.201201572... 

Santschi N, Geissbuhler P, Togni A (2012) Reactivity of an electrophilic hypervalent iodine trifluoromethylation reagent with hydrogen phosphates - a mechanistic study. J Fluor Chem 135 83-86. doi 10.1016/j.jfluchem.2011.08.014... 

Wiehn MS, Vinogradova EV, Togni A (2010) Electrophilic trifluoromethylation of arenes and V-heteroarenes using hypervalent iodine reagents. J Fluor Chem 131 951-957. doi 10.1016/j. jfluchem.2010.06.020... 

Mejia E, Togni A (2012) Rhcmium-catalyzed trifluoromethylation of arenes and heteroarenes by hypervalent iodine reagents. ACS Catal 2 521-527. doi 10.1021/cs300089y... 

Kieltsch I, Eisenberger P, Stanek K, Togni A (2008) Recent advances in electrophilic CF3-transfer using hypervalent iodine(III) reagents. Chimia 62 260-263. doi 10.2533/chimia.2008. 260... 

Matousek V, PietrasiakE, Sigrist L, Czamiecki B, Togni A (2014) O-Trifluoromethylahon of N,N-disubstituted hydroxylamines with hypervalent iodine reagents. Eur J Org Chem... 

A novel methyltrioxorhenium (MTO) catalyzed methodology for the direct trifluoromethylation of both activated and nonactivated arenes and heteroarenes using an easily accessible, shelf-stable hypervalent iodine trifluoromethylating reagent has been developed by Togni and coworkers (Scheme 9.21). This reagent system exhibited a broad substrate scope in direct aromatic trifluoromethylation. 

Recently, simple copper-catalyzed trifluoromethylation of aryl boronic acids under mild conditions was developed. Using (trifluoromethyl)trimethylsilane (McsSiCFs) [93], trifluoromethyldibenzothiophenium triflate [94], or Togni s reagent [95], 2-trifluoromethylbenzo[fc]thiophene 173 was prepared in 45-73 % yields. 

Togni [62] found that both aromatic and aliphatic thiols undergo selectively and smoothly 5-trifluoromethylation in the presence of 1.1 equivalent of hypervalent CF3-iodine(III) reagents to afford the products of trifluoromethylation in good to excellent yields (Scheme 29). 

---