Switching Diastereoselectivity in Catalytic Enantioselective (3+2) Cycloadditions of Azomethine Ylides Promoted by Metal Salts and Privileged Segphos-Derived Ligands

Catalytic
enantioselective 1,3-dipolar cycloaddition between imino
esters and electrophilic alkenes, employing chiral metal complexes
derived from copper­(I) and silver­(I) salts and (S)-DM- or (S)-DTBM-Segphos as ligands produces diastereodivergently
exo- or endo-cycloadducts, respectively. The effect of the functional
group of the dipolarophile and the fine tuning of the catalyst plays
an important role in promoting reverse diastereoselectivities. The
origins of experimentally observed enantioselectivity and diastereoselectivity
data, as well as the origin of the observed switched endo/exo ratios,
are also explained by means of density functional theory calculations.