Electrophilic Cyanations. I. Synthesis of Thiocyanatoheteroarenes and Tosylheteroarenes from Mercaptoheteroarenes Using p-Toluenesulfonyl Cyanide

Mercaptoheteroarenes(1) underwent electrophilic cyanation with ptoluenesulfonyl cyanide (TsCN) in THF i n the presence o f N a H to give the corresponding thiocyanatoheteroarenes (2) i n moderate to good yields.In DMF, tosylheteroarenes ( I ) wcrc forrncd by substitution with p-toluenesulfinate ion through thiocyanatoheteroarenes (2).Cyanation is an important reaction in organic synthesis, because it is a carbon~hain-forming reaction, and because the cyano group can be easily converted into other functional groups, such as ketone and carboxylic acid.Nucleophilic cyanation methods employing cyanide ion (CN-) or protected hydrogen cyanide are generally used,'.2but electrophilic cyanation i s also feasible.Cyanogen chloride (CICN)3 andcyanogen (dicyane, ( c N ) ~) ~ are available for this pulpose, but these compounds are not stable and are difficult to handle.Cyanogen bromide (BrCN) can be used, but may generate cyanide ion (CN-) because of the electronegativity o f bromine.p-Toluenesulfonyl cyanide (TsCN) can also achieve electrophilic anat at ion.^However, despite its stability and easy handling, only a few examples o f electrophilic cyanation using TsCN have been reported.6We therefore decided to examine the usefulness of electrophilic cyanation with TsCN to obtain thiocyanatoheteroarenes (2), which are useful starting compounds for thesynthesis o f fused thiazoles having an amino group such as Reagents for Electrophilic Cyanation 0 CICN (CN)2 BrCN