Summary: Pyridines or N, N, N', N'-tetramethyl-pphenylenediamine will undergo a photostimulated free radical chain reaction with alkylmercury halides or carboxylates, yielding ring alkylated substitution products. Alkene mercuration products (R'CH (Y) CH (R2) HgX with Y= HO, RO, CH3CONH; X= C1, CH3C02, CF3C02) can be used without isolation for the alkylation reaction.