Synthesis of (R)‐ and (S)2‐tert‐Butyl‐6‐trifluoro‐methyl‐1,3‐dioxin‐4‐ones, Transformations into 3‐Hydroxy‐3‐(trifluoromethyl)alkanoates, and Surprising Differences in the Reactivity of CH₃‐ and CF₃‐Substituted Compounds

A surprising inversion of the stereo- and regioselectivity on changing from CH3 to CF3 derivatives is found in the bromination of the appropriate enolates as shown by the products 1 and 2. Furthermore, the conjugate addition of the benzyl group to the related dioxinones leads to 3 and 4. The mechanistic implications of these findings is not yet clear.