Recent Progress on Coupling Reaction of Potassium Hexacyanoferrate(II) as an Environmentally Friendly Cyanide Source

Cyanidation reactions are an essential method for creating C─CN bonds. Traditional cyanidation reactions usually require the use of highly toxic and unstable cyanide sources, such as NaCN, KCN, CuCN, and TMSCN. K₄[Fe(CN)₆], a product of the coal chemical industry, has the advantages of high yield and low toxicity. It is a very environmentally friendly, safe, and stable cyanide source. Since 2004, K₄[Fe(CN)₆] has emerged as a viable alternative to conventional, highly toxic, and hazardous cyanide sources like NaCN and KCN in cyanidation reactions. Over the past two decades, significant progress has been made in studying green cyanidation reactions involving K₄[Fe(CN)₆]. This paper reviews the advancements in the study of cyanidation coupling reactions between substrates such as aryl halides, sulfonates, aryl carboxylic acids, aromatic aldehydes, acyl chlorides, phenols, benzyl alcohols, and aryl sulfonium salts with K₄[Fe(CN)₆].