Togni reagent II

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]

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 Y
3D model (JSmol)	Interactive image
ChemSpider	24807962 Y
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

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]