Organocatalytic Asymmetric Cascade Reaction of 2‑Hydroxyphenyl-Substituted Enones and Isocyanates To Construct 1,3-Benzoxazin-2-ones

The development of a new bisguanidinium salt as a multifunctional organocatalyst for asymmetric cascade esterification/aza-Michael reaction between 2-hydroxyphenyl-substituted enones and isocyanates is reported. A high level of enantioinduction and excellent isolated yields were achieved under mild reaction conditions. Enantiomerically enriched 1,3-benzoxazin-2-ones were constructed, and a possible catalytic model was suggested based on the mechanism-driven experiments.