Table summarizes the structural and energetic characteristics of the transition states found, which are visualized in Figure . As can be seen by the ∆G ‡ values in Table , the energetic barriers for antiperiplanar addition are much higher than synclinal addition (we were unable to obtain the correct transition state for the synclinal addition of methanethiolate to azetidinyl vinyl ketone). This shows that the reaction pathway for synclinal addition is much more energetically favorable than antiperiplanar additions, which has been reported in literature. Table . Structural and energetic characteristics of transition states during the synclinal and antiperiplanar nucleophilic additions of methanethiolate to various Michael acceptor warheads. Included are the: C α -C β -S-C dihedral angle (Θ ‡ ) ('syn' for synclinal and 'anti' for antiperiplanar), S-C β bond lengths (r ‡ ), magnitude of the frequencies of the sole imaginary mode (ν I ), and relative Gibbs free energies (∆G ‡ ) of the transition states during the nucleophilic addition of methanethiolate to various warheads. Data we were unable to acquire are denoted as '-'.