Dynamic stereochemistry atsp2sp3 bonds part 1—the use of heterocyclic models for quantitative studies of steric effects of alkyl groups
摘要:
AbstractThe barriers to rotation of the 3‐substituent in six 3‐RCH2‐4‐Me‐δ4‐thiazoline‐2‐thiones (R Me, Et, Pr, Isobu, Isopr,t‐Bu) and in two analogous methiodides have been measured by the 1H DNMR technique. The barriers are discussed in relation to the possible conformations of the transition states, and comparisons are made with barriers to rotation of the same substituents in other frameworks. It is concluded that the relative steric effects are strongly dependent on the framework and that, in general, a conformational analysis of the individual cases is necessary to understand the steric effects of alkyl groups.