A Pd−H/Isothiourea Cooperative Catalysis Approach to Anti‐aldol Motifs: Enantioselective Α‐alkylation of Esters with Oxyallenes**

The biological and therapeutic significance of polyketides is a powerful impetus for the development of efficient methods to facilitate their construction. Emulating the efficiency of polyketide biosynthesis, a sophisticated arsenal of aldol-based strategies has evolved that is contingent on the generation of single enolate isomers. Since this has the potential to compromise efficiency in reagent-based paradigms, direct catalysis-based solutions would be enabling. To complement the array of substrate-based strategies, and regulate enolate geometry at the catalyst level, a direct catalytic alkylation of esters with oxyallenes has been developed. Synergizing metal hydride reactivity with Lewis base catalysis has resulted in a broad reaction scope with useful levels of stereocontrol (up to >99% ee). Facile derivatization of these ambiphilic linchpins is demonstrated, providing access to high-value vicinal stereocenter-containing motifs, including 1,2-amino alcohols.