The semiempirical PM3 study of the catalytic activity of [(2S)-1-benzylpyrrolidinyl]methanethiol 1, S-([(2S)-1-(2,2-dimethylpropanoyl)pyrrolidinyl]methyl)ethanethioate 2 and [(2S)-1-neopentylpyrrolidinyl]methanethiol 3 is described here, also an alternative mechanism for thioacetates type ligands is proposed.