A full account of the Brønsted acidcatalyzed, enantioselective synthesis of 4H-chromenes and 1H-xanthen-1-ones from o-hydroxybenzyl alcohols and β-dicarbonylcompounds is provided. The central step of our strategy is the BINOL–phosphoric acidcatalyzed, enantioselective cycloaddition of β-diketones, β-keto nitriles, and β-keto esters to in situ generated, hydrogen-bonded o-quinone methides. Upon acid-promoted
Chiral Brønsted acid-catalyzed Friedel–Crafts alkylation of electron-rich arenes with in situ-generated ortho-quinone methides: highly enantioselective synthesis of diarylindolylmethanes and triarylmethanes
Hydrogen-bonded, in situ-generated ortho-quinone methides undergo highly enantioselective Friedel–Crafts reactions with indoles and naphthols under mild reaction conditions.
Brønsted Acid Catalyzed, Conjugate Addition of β-Dicarbonyls to In Situ Generated<i>ortho</i>-Quinone Methides-Enantioselective Synthesis of 4-Aryl-4<i>H</i>-Chromenes
and biologically active compounds. A sequence comprising a conjugate addition of β‐diketones to in situ generated ortho‐quinone methides followed by a cyclodehydration reaction furnished 4‐aryl‐4H‐chromenes in generally excellent yields and high optical purity. A BINOL‐based chiral phosphoric acid was employed as a Brønstedacid catalyst which converted ortho‐hydroxy benzhydryl alcohols into hydrogen‐bonded