Iodonium salts toxicity

Iodonium salts are at present receiving much attention because of their similar reactivity to those of heavy metal reagents. The results of the application of salt are close to electrochemical oxidation. Added advantages that render them synthetically more attractive are their low toxicity, ready availability, and easy handling. In contrast to the anodic version, the iodonium reactions are amendable to large-scale synthesis. 

Aryl and heteroaryl (furyl, thienyl) boronic acids are especially suitable for the preparation of their iodonium salts, having the added advantage of better yields and lack of toxicity [108]. Tetraarylborates (sodium or potassium) reacted with (diacetoxyiodo)arenes in acetic acid to afford diaryliodonium salts in excellent yield (Scheme 37). It appears that triarylboranes formed upon reaction of the borates with acetic acid serve actually as the real arylating agents [109]. 

Sodium thiophenoxide and bis phenyliodonium acetylene triflate afforded cleanly l,2-bis(phenylthio)acetylene [6]. Alkynyl iodonium salts have alkynylated several arene sulphonates which were converted into alkynyl aryl sulphones. The process is probably the best among other methods, as far as yield, availability of starting materials, non-toxicity and ease of handling are concerned. 

Shirai, Kubo and Takahashi have prepared and examined a series of new substituted diaryliodonium hexafluorophosphates aiming at improved solubility and lower toxicity of the photoinitiators [36]. The alkyl substituted iodonium salts 8-13 (Figure 7.1) in combination with 2-ethyl-9,10-dimethoxyanthracene as the photosensitizer showed especially high photocuring ability [36]. 

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