The "Green" Electrochemical Synthesis of Periodate

Abstract

High-grade periodate is relatively expensive, but is required for many sensitive applications such as the synthesis of active pharmaceutical ingredients. These high costs originate from using lead dioxide anodes in contemporary electrochemical methods and from expensive starting materials. A direct and cost-efficient electrochemical synthesis of periodate from iodide, which is less costly and relies on a readily available starting material, is reported. The oxidation is conducted at boron-doped diamond anodes, which are durable, metal-free, and nontoxic. The avoidance of lead dioxide ultimately lowers the cost of purification and quality assurance. The electrolytic process was optimized by statistical methods and was scaled up in an electrolysis flow cell that enhanced the space-time yields by a cyclization protocol. An LC-PDA analytical protocol was established enabling simple quantification of iodide, iodate, and periodate simultaneously with remarkable precision.

Keywords: boron-doped diamond; electrolysis; flow chemistry; oxidation; periodate.

Scheme 1

Electrochemical synthesis of periodate. (BDD=boron‐doped diamond; CE=current efficiency; conv.=conversion).

Figure 1

Calibration plot for the liquid chromatography photodiode array (LC‐PDA) analysis.

Figure 2

Reaction mixtures from flow electrolysis. a) Low hydroxide concentration caused iodine precipitation; b,c) mixtures with sufficient hydroxide concentration (C(NaOH)=3 m) in chronological order.

Scheme 2

Half‐cell reactions at the anode and cathode, and the double salt formation of meta‐periodate (IO₄ ⁻) to para‐periodate (H₂IO₆ ³⁻). Negative charges are balanced out by Na⁺ and are omitted for clarity.

Scheme 3

Synthetic confirmation of the electrochemically synthesized meta‐periodate. Yields were determined by ¹H NMR spectroscopy versus caffeine as an internal standard. All reactions showed full conversion of the starting material.