2H-Chromenes from Salicylaldehydes by a Catalytic Petasis Reaction

The Petasis condensation of vinylic or aromatic boronic acids, aromatic aldehydes, and amines is assisted by a hydroxy group adjacent to the aldehyde moiety. The products derived from salicylaldehydes and vinylboronic acids undergo cyclization to 2H-chromene compounds with ejection of amine upon heating. A catalytic preparation of 2H-chromenes using resin-bound amine is reported, allowing the convenient incorporation of a variety of components.