Understanding the Reactivity of Acyl Anion Equivalents: The Epoxide Ring Opening Case

Abstract Acyl anion equivalents (umpolung) are the practitioner's first choice en route to 1,3‐hydroxy keto compounds from epoxides. Why? This investigation evaluates computationally and experimentally the reactivity of a near comprehensive range of acyl anion equivalents using epoxide ring opening as a test vehicle. Reactivity understanding, reactivity order, surprise failures in performance, along with unprecedented, but far from superior, reactivity of TosMIC is presented for the first time.