Desymmetrization of Achiral Heterobicyclic Alkenes through Catalytic Asymmetric Hydrophosphination.

Asymmetric addition of diarylphosphines to oxa- and azabicyclic alkenes proceeded in the presence of a chiral phosphapalladacycle catalyst and a mild acid at room temperature to give exclusively the enantioenriched addition products in excellent yields and good selectivities. Three new chiral carbon centers were generated stereoselectively by the catalytic hydrophosphination reaction.

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.