Preparation and Reactions of Ethyl (R,R)‐ and (S,S)‐3‐Trifluoromethyloxirane‐2‐carboxylate, a Versatile, Easily Accessible CF3‐Containing Building Block for SynthesisA facile three‐step route has been elaborated leading from 4,4,4‐trifluoro‐3‐oxobutanoate to the trifluoro glycidic ester 1 mentioned in the title (0.1‐mole scale). Reactions with azide (→ 4, 5) and with organometallic compounds such as cuprates (→ 3, 6), lithium (→ 7, 8), and magnesium derivatives (→ 9–11) furnish novel enantiomerically pure trifluoromethyl‐substituted carboxylic esters, ketones, diols, and epoxy alcohols. The latter ones undergo selective isomerizations by Payne rearrangement (11 → 12) in aqueous NaOH/acetone or tert‐butyl alcohol.