Triflic-Acid-Catalyzed Tandem Allylic Substitution–Cyclization Reaction of Alcohols with ThiophenolsFacile Access to Polysubstituted Thiochromans

Hitherto inaccessible multisubstituted
thiochroman derivatives
were constructed via the one-pot reaction of thiophenols with allylic
alcohols catalyzed by 0.2 equiv triflic acid under metal-free conditions.
A variety of thiochroman derivatives can be obtained by this straightforward
protocol that allows the introduction of up to four substituents at
various locations on the thiochroman skeleton. Relative conformations
of all isolated products were confirmed by NOESY NMR studies, and
a stepwise mechanism, proceeding via an allylic substitution-intramolecular
cyclization protocol, is proposed on the basis of NMR experiments.