Sulfenylation, Thiocyanation and Cyanation

2- Methylindole undergoes clean 3-sulfenylation with M-methylthiomorpholine in TFA. Indole itself gives mainly 3-methylthioindole (57%) with 1.5 equiv. of the reagent, but the 1,3- (61%) and 2,3- (22%) h s-sulfenyl derivatives are the main products with 2.5 equiv. [74]. 

Indole, 1- and 2-methyl and C-substituted derivatives give good yields of 

3- thiocyano indoles when treated with NH4SCN and I2 in methanol [75]. Ammonium thiocyanate and diiodine pentoxide also give 3-thiocyanation of indole and 

Oxidative cyanation of the indole ring at C-2 and C-3 has been observed for W-tosyl indoles on reaction with trimethylsilyl cyanide and phenyliodonium bis-trifluoroacetate in the presence of BF3 [78]. The reaction is distinctive in giving a preference for 2-substitution and is thought to proceed through radical cation intermediates. 

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