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Names | |
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Preferred IUPAC name 1-(Trifluoromethyl)-1λ3,2-benziodoxol-3(1H)-one | |
Other names Togni's reagent II; Togni reagent 2 | |
Identifiers | |
3D model (JSmol) | |
ChemSpider | |
ECHA InfoCard | 100.214.822 |
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
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Properties | |
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) |
soluble in methylene chloride, chloroform, acetonitrile, methanol, ethanol, acetone | |
Hazards | |
GHS labelling: | |
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Warning | |
H315, H319, H335 | |
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). |
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]
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).
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]
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]
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]
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]