Access to 1,4‐Thiazepanes via Gold‐Catalyzed 7‐exo‐dig Thioallylation and their Cycloisomerization to Bicyclic [4.3.1] Bridgehead‐Olefinic Systems

A series of 1,4‐thiazepanes were synthesized using gold‐catalysis from 1,3‐aminothioethers having two or three carbon stereocenters. The process consists in a 7‐exo‐dig cyclization with C−S bond formation and concomitant allyl S‐to‐C migration, which occurs intramolecularly as demonstrated by a cross‐over experiment. X‐ray crystal‐structure analysis of one product confirmed the expected stereochemistry. Two examples of reactions, azide‐alkyne cycloaddition (CuAAC) and N‐alkylation, illustrate the potential post‐functionalization of the synthesized 1,4‐thiazepanes. Finally, the N‐propargyl 1,4‐thiazepanes underwent a sulfur‐assisted 1,6‐enyne cycloisomerization, which led through a 6‐exo‐dig cyclization to N,S‐heterobicyclo[4.3.1] systems with a bridgehead double bond.