Thioamidium salts

Tertiary A-allylthioamides have been converted into thioamidium salts by the formation of complexes with Lewis acid. Further treatment with lithium hexamethyldisilazide (LiHMDS) affords the corresponding 1,2-disubstituted pyrroles (Scheme 25).52... 

S-alkylation to thioamidium salts and chlorination to amide chlorides (ref. 8, Scheme 8). The thioamidium salts react with hydride or other nucleophiles to give many useful intermediates. 

For comparison, non-fluorinated thioamidium salts were also reacted with cyanide and both the phenyl- and the tm-butyl derivative were obtained, but instead of the dicyano thioaminal, mainly the (presumably radical) dimer was found (Scheme 11). 

The three thioamidium salts differ in reactivity because of steric, electronic and polar substituent-effects, the thioaminals isomerised normally only in the tm-butyl case, lost the S-substituent by H-reduction in the phenyl derivative and yielded dimerisation of N,N-dimethyl amino and dicyanomethyl residue. The reduction of the C-phenyl derivative is suppressed when S-phenyl replaced S-methyl. Now the dipolar isomerisation occurs again (Scheme 12). 

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