Catalytic Asymmetric\nCycloaddition of Olefins with\nIn Situ Generated <i>N</i>‑Boc-Formaldimine

Chiral 1,3-amino alcohols are ubiquitous structural motifs\nin natural\nproducts and active pharmaceutical ingredients. We present a highly\nenantioselective, inverse-electron-demand hetero-Diels–Alder\nreaction of olefins with in situ generated <i>N</i>-Boc-formaldimine\ncatalyzed by strong and confined Bro̷nsted acids. This transformation\nprovides direct access to valuable 1,3-amino alcohols from styrenes\nand 1,1-disubtituted alkenes. Isotope labeling studies and kinetic\nanalysis reveal an unusual mechanism involving an oxazinium intermediate\nand a catalyst order greater than one.