A Multifaceted Directing Group Switching Ynones as Michael Donors in Chemo-, Enantio-, and γ-Selective 1,4-Conjugate Additions with Nitroolefins.

ABSTRACT

α,ß-Unsaturated ynones have historically been used as Michael acceptors in conjugate addition reactions. Herein, we have demonstrated for the first time that ynones can be harnessed as Michael donors for use in catalytic asymmetric conjugate addition reactions by strategically introducing a CO2t-Bu group as a multitasking directing group. Furthermore, this concept has enabled designer ynones as versatile synthetic equivalents of both α' anions of ynones and γ monoanions of 1,3-diketones, which are synthetically valued but difficult to generate. The first catalytic enantioselective conjugate addition of ynones as Michael donors has been realized in good yields with high enantioselectivities. A unified approach to regiospecifically and chemo- and enantioselectively access hitherto elusive γ-Michael adducts of 1,3-diketones has been achieved in a divergent manner. The strategy described here by exploring new reactivity and creating new reagents holds great potential applications in other still unsolved transformations.