Chiral Supramolecular U-Shaped Catalysts Induce the Multiselective Diels-Alder Reaction of Propargyl Aldehyde.

The Diels-Alder reaction, which is a traditional [4 + 2] cycloaddition with two carbon-carbon bond formations, is one of the most powerful tools to synthesize versatile and unique six-membered rings. We show that chiral supramolecular U-shaped boron Lewis acid catalysts promote the unprecedented multiselective Diels-Alder reaction of propargyl aldehyde with cyclic dienes. Independent from the substrate control, enantio-, endo/exo-, π-facial-, regio-, site-, and substrate-selectivities could be controlled by the present U-shaped catalysts. The obtained reaction products could access the concise synthesis of chiral diene ligands and a key intermediate of (+)-sarkomycin. The results presented here might partially contribute to the development of artificial enzyme-like supramolecular catalysts for multiselective reactions, which will be able to target organic compounds that have thus far eluded synthesis.