Chiral Brønsted Acid Catalyzed Enantioselective Dehydrative Nazarov-Type Electrocyclization of Aryl and 2‑Thienyl Vinyl Alcohols

An
efficient chiral Brønsted acid-catalyzed enantioselective
dehydrative Nazarov-type electrocyclization (DNE) of electron-rich
aryl- and 2-thienyl-β-amino-2-en-1-ols is described. The 4π
conrotatory electrocyclization reaction affords access to a wide variety
of the corresponding 1H-indenes and 4H-cyclopenta­[b]­thiophenes in excellent yields of
up to 99% and enantiomeric excess (ee) values of up to 99%. Experimental
and computational studies based on a proposed intimate contact ion-pair
species that is further assisted by hydrogen bonding between the amino
group of the substrate cation and chiral catalyst anion provide insight
into the observed product enantioselectivities.