Figure Reaction of interest and the structures of molecular catalysts and radical initiator, 2,2'-azobis(2-amidinopropane) (AAPH). excess amounts of thiols (Figure ); however, the reactions were less than stoichiometric with the thiol-based molecules being consumed during the reactions. Even the best reaction using N-acetyl L-cysteine methyl ester (4) gave almost stoichiometric conversion, with the formation of adducts between thiols and maleate as the main products (Figures ), and this accounted for the total balance of thiols (Figure ). This is in good agreement with the previous computational studies where the 1,2-adducts are thermodynamically the most stable among reactants, products, and intermediates generated via the ionic processes. The use of 2,2'-azobis(isobutyronitrile) (AIBN) in organic solvents led to a moderate acceleration in the conversion (Table , entry 3), but was not effective.