Togni reagent II

Togni reagent II
Names
	Preferred IUPAC name 1-(Trifluoromethyl)-1λ3,2-benziodoxol-3(1H)-one
	Other names Togni's reagent II; Togni reagent 2
Identifiers
CAS Number	887144-94-7 ;
3D model (JSmol)	Interactive image;
ChemSpider	24807962 ;
ECHA InfoCard	100.214.822
PubChem CID	24850981;
UNII	DHY074A7WG;
CompTox Dashboard (EPA)	DTXSID10647708;
	InChI InChI=1S/C8H4F3IO2/c9-8(10,11)12-6-4-2-1-3-5(6)7(13)14-12/h1-4H Key: XHEOXSQMBWJOKP-UHFFFAOYSA-N;
	SMILES C1=CC=C2C(=C1)C(=O)OI2C(F)(F)F;
Properties
Chemical formula	C8H4F3IO2
Molar mass	316.018 g·mol−1
Appearance	colorless crystalline solid
Melting point	122.4–123.4 °C (252.3–254.1 °F; 395.5–396.5 K)
Solubility in water	soluble in methylene chloride, chloroform, acetonitrile, methanol, ethanol, acetone
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Togni reagent II (1-trifluoromethyl-1,2-benziodoxol-3(1H)-one) is a chemical compound used in organic synthesis for direct electrophilic trifluoromethylation.^[1]^[2]

History

Synthesis, properties, and reactivity of the compound were first described in 2006 by Antonio Togni and his coworkers at ETH Zurich.^[3] The article also contains information on Togni reagent I (1,3-dihydro-3,3-dimethyl-1-(trifluoromethyl)-1,2-benziodoxole).

Preparation

The synthesis consists of three steps. In the first step, 2-iodobenzoic acid is oxidized by sodium periodate and cyclized to 1-hydroxy-1,2-benziodoxol-3(1H)-one. The target compound can then be obtained by acylation with acetic anhydride and subsequent substitution reaction with trifluoromethyltrimethylsilane.^[4]

Alternatively, trichloroisocyanuric acid can be used as oxidant in the place of sodium periodate for a newer one-pot synthesis method.^[5]

Properties

Physical properties

The compound crystallized in a monoclinic crystal structure. The space group is P2₁/n with four molecules in the unit cell.^[3] From the crystallographic data, a density of 2.365 g·cm⁻³ was deduced.^[3]

Chemical properties

Pure Togni reagent II is metastable at room temperature. Heating it above the melting point will lead to strong exothermic decomposition, in which trifluoroiodomethane (CF₃I) is released.^[4] The heat of composition at a temperature of 149 °C and higher has been determined to be 502 J·g⁻¹.^[6] From recrystallization in acetonitrile, small amounts of trifluoromethyl-2-iodobenzoate and 2-iodobenzyl fluoride were observed as decomposition products.^[4] Togni reagent II reacts violently with strong bases and acids, as well as reductants.^[4] In tetrahydrofuran, the compound polymerizes.^[4]

Uses

Togni reagent II is used for trifluoromethylation of organic compounds. For phenolates, the substitution takes place preferably in the ortho position. It is possible to obtain a second substitution by using an excess of Togni reagent II.^[7]

Reactions with alcohols yield the corresponding trifluoromethyl ethers.^[8]

Trifluoromethylation of alkenes is possible under copper catalysis.^[9]

References

^ PubChem. "1-(Trifluoromethyl)-1,2-benziodoxol-3(1H)-one". pubchem.ncbi.nlm.nih.gov. National Center for Biotechnology Information. Retrieved 2020-07-07.
^ Kieltsch, Iris; Eisenberger, Patrick; Stanek, Kyrill; Togni, Antonio (2008-04-30). "Recent Advances in Electrophilic CF3-Transfer Using Hypervalent Iodine(III) Reagents". CHIMIA International Journal for Chemistry. 62 (4): 260–263. doi:10.2533/chimia.2008.260.
^ ^a ^b ^c Eisenberger, Patrick; Gischig, Sebastian; Togni, Antonio (2006-03-08). "Novel 10-I-3 Hypervalent Iodine-Based Compounds for Electrophilic Trifluoromethylation". Chemistry - A European Journal. 12 (9): 2579–2586. doi:10.1002/chem.200501052. ISSN 0947-6539. PMID 16402401.
^ ^a ^b ^c ^d ^e Stanek, Kyrill; Koller, Raffael; Kieltsch, Iris; Eisenberger, Patrick; Togni, Antonio (2009-09-15), "1-(Trifluoromethyl)-1,2-benziodoxol-3(1 H )-one", in John Wiley & Sons, Ltd (ed.), Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, Ltd, pp. rn01121, doi:10.1002/047084289x.rn01121, ISBN 978-0-471-93623-7
^ Matoušek, Václav; Pietrasiak, Ewa; Schwenk, Rino; Togni, Antonio (2013-07-05). "One-Pot Synthesis of Hypervalent Iodine Reagents for Electrophilic Trifluoromethylation". The Journal of Organic Chemistry. 78 (13): 6763–6768. doi:10.1021/jo400774u. ISSN 0022-3263. PMID 23734560.
^ Fiederling, Nikolaus; Haller, Jan; Schramm, Heiko (2013-03-15). "Notification about the Explosive Properties of Togni's Reagent II and One of Its Precursors". Organic Process Research & Development. 17 (3): 318–319. doi:10.1021/op400035b. ISSN 1083-6160.
^ Stanek, Kyrill; Koller, Raffael; Togni, Antonio (2008-10-03). "Reactivity of a 10-I-3 Hypervalent Iodine Trifluoromethylation Reagent With Phenols". The Journal of Organic Chemistry. 73 (19): 7678–7685. doi:10.1021/jo8014825. ISSN 0022-3263. PMID 18771328.
^ Koller, Raffael; Stanek, Kyrill; Stolz, Daniel; Aardoom, Raphael; Niedermann, Katrin; Togni, Antonio (2009-06-02). "Zinc-Mediated Formation of Trifluoromethyl Ethers from Alcohols and Hypervalent Iodine Trifluoromethylation Reagents". Angewandte Chemie. 121 (24): 4396–4400. Bibcode:2009AngCh.121.4396K. doi:10.1002/ange.200900974.
^ Parsons, Andrew T.; Buchwald, Stephen L. (2011-09-19). "Copper-Catalyzed Trifluoromethylation of Unactivated Olefins". Angewandte Chemie. 123 (39): 9286–9289. Bibcode:2011AngCh.123.9286P. doi:10.1002/ange.201104053. PMC 3390945. PMID 21919144.

[1] PubChem. "1-(Trifluoromethyl)-1,2-benziodoxol-3(1H)-one". pubchem.ncbi.nlm.nih.gov. National Center for Biotechnology Information. Retrieved 2020-07-07.

[2] Kieltsch, Iris; Eisenberger, Patrick; Stanek, Kyrill; Togni, Antonio (2008-04-30). "Recent Advances in Electrophilic CF3-Transfer Using Hypervalent Iodine(III) Reagents". CHIMIA International Journal for Chemistry. 62 (4): 260–263. doi:10.2533/chimia.2008.260.

[:1-3] Eisenberger, Patrick; Gischig, Sebastian; Togni, Antonio (2006-03-08). "Novel 10-I-3 Hypervalent Iodine-Based Compounds for Electrophilic Trifluoromethylation". Chemistry - A European Journal. 12 (9): 2579–2586. doi:10.1002/chem.200501052. ISSN 0947-6539. PMID 16402401.

[:0-4] Stanek, Kyrill; Koller, Raffael; Kieltsch, Iris; Eisenberger, Patrick; Togni, Antonio (2009-09-15), "1-(Trifluoromethyl)-1,2-benziodoxol-3(1 H )-one", in John Wiley & Sons, Ltd (ed.), Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, Ltd, pp. rn01121, doi:10.1002/047084289x.rn01121, ISBN 978-0-471-93623-7

[5] Matoušek, Václav; Pietrasiak, Ewa; Schwenk, Rino; Togni, Antonio (2013-07-05). "One-Pot Synthesis of Hypervalent Iodine Reagents for Electrophilic Trifluoromethylation". The Journal of Organic Chemistry. 78 (13): 6763–6768. doi:10.1021/jo400774u. ISSN 0022-3263. PMID 23734560.

[6] Fiederling, Nikolaus; Haller, Jan; Schramm, Heiko (2013-03-15). "Notification about the Explosive Properties of Togni's Reagent II and One of Its Precursors". Organic Process Research & Development. 17 (3): 318–319. doi:10.1021/op400035b. ISSN 1083-6160.

[7] Stanek, Kyrill; Koller, Raffael; Togni, Antonio (2008-10-03). "Reactivity of a 10-I-3 Hypervalent Iodine Trifluoromethylation Reagent With Phenols". The Journal of Organic Chemistry. 73 (19): 7678–7685. doi:10.1021/jo8014825. ISSN 0022-3263. PMID 18771328.

[8] Koller, Raffael; Stanek, Kyrill; Stolz, Daniel; Aardoom, Raphael; Niedermann, Katrin; Togni, Antonio (2009-06-02). "Zinc-Mediated Formation of Trifluoromethyl Ethers from Alcohols and Hypervalent Iodine Trifluoromethylation Reagents". Angewandte Chemie. 121 (24): 4396–4400. Bibcode:2009AngCh.121.4396K. doi:10.1002/ange.200900974.

[9] Parsons, Andrew T.; Buchwald, Stephen L. (2011-09-19). "Copper-Catalyzed Trifluoromethylation of Unactivated Olefins". Angewandte Chemie. 123 (39): 9286–9289. Bibcode:2011AngCh.123.9286P. doi:10.1002/ange.201104053. PMC 3390945. PMID 21919144.

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