Efficient and General One‐Pot Synthesis of Diaryliodonium Triflates: Optimization, Scope and Limitations

Abstract

Symmetrical and unsymmetrical diaryliodonium triflates have been synthesized from both electron-deficient and electron-rich arenes and aryl iodides with mCPBA and triflic acid. A thorough investigation of the optimization, scope and limitations has resulted in an improved one-pot protocol that is fast, high-yielding, and operationally simple. The reaction has been extended to the direct synthesis of symmetrical iodonium salts from iodine and arenes, conveniently circumventing the need for aryl iodides.

Metal-Free N-Arylation of Secondary Amides at Room Temperature

“…The reaction could easily be scaled up to 1 mmol; the base should then be added last to ensure a good yield (entry 14). 15 Finally the influence of the iodonium anion (X) was investigated, and triflate 2a, tetrafluoroborate 2b and tosylate 2c all resulted in similar yields, whereas hexafluorophosphate 2d was inferior (entries 10, [15][16][17]. Compatibility with the common anions (OTf, OTs, BF 4 ) is important in order to avoid tedious anion exchanges, since different synthetic routes to diaryliodonium salts are employed depending on the structure and electronic properties of the aryl substituents.…”

“…15 The reaction was subsequently investigated with a range of diaryliodonium salts, which are easily available via one-pot reactions. 16 Unsymmetric diaryliodonium salts are generally easier to synthesize and can also be more economic in transfer of precious aryl moieties, since only a "dummy" iodoarene is wasted if the arylation proceeds with high chemoselectivity. 10 Ortho-substituted aryl groups, such as mesityl or triisopropylphenyl (TRIP), are often used as dummies in metal-catalyzed reactions with diaryliodonium salts.…”

Design and asymmetric synthesis of chiral diaryliodonium salts

“…Symmetrical and unsymmetrical diaryliodonium triflates can be obtained in high yields and short reaction times employing mCPBA and trifluoromethanesulfonic acid (TfOH), as depicted in Scheme 4a. 24,25 The protocol can be extended to the direct formation of diaryliodonium triflates from iodine and arenes. [24][25][26] A variation of this synthesis, employing p-toluenesulfonic acid (TsOH), gives access to electron-rich diaryliodonium tosylates (Scheme 4b).…”

Synthesis of Diaryliodonium Triflates Using Environmentally Benign Oxidizing Agents

“…Whilst efficient and operationally simple methodology for the preparation of such compounds has recently been developed within our laboratory (Scheme 1, method A), 5,6 use of stoichiometric m-chloroperbenzoic acid (mCPBA) as oxidizing agent and the concomitant production of mchlorobenzoic acid as waste make these protocols less desirable on an industrial scale. Other methods for the preparation of diaryliodonium salts have been reported, but they suffer from drawbacks such as the need to preform an iodine(III) species, 7 extended reaction times, 8 excess reagents 9 or toxic chromium compounds.…”

“…Preliminary investigations on the reaction mechanism were initiated after the observation of the comparatively poor yield of symmetrical tert-butyl salt 1m (entry 15), since this product has been obtained in good yield with the previously developed mCPBA protocol. 6 We decided to examine whether a free-radical process could be involved, either in formation of the product or in competing pathways leading to byproducts. Such a mechanism would also explain the vital influence of TFE, which is known to stabilize radical cation intermediates.…”