Synthesis of Five‑, Six‑, and Seven-Membered 1,3- and 1,4-Heterocyclic Compounds via Intramolecular Hydroalkoxylation/Hydrothioalkoxylation of Alkenols/Thioalkenols

Intramolecular hydroalkoxylation/hydrothioalkoxylation of nitrogen-tethered alkenes and alcohols/thiols mediated by boron trifluoride etherate leads to five-membered thiazolidine, six-membered 1,4-oxazines (morpholines) and tetrahydro-2H-1,4-thiazines (thiomorpholines), and seven-membered 1,4-oxazepanes in good yields.