Gold-Catalyzed Stereoselective Synthesis of Bicyclic Lactams and Ketones from N‑Tosylynamidomethyl-Tethered Cyclohexenes

Six-membered ring 3-enynamides underwent cycloisomerization in the presence of a catalytic amount of a gold­(I) complex delivering mainly 4-azatricyclo­[4.3.1.0^3,10]­dec-2-ene derivatives and dibenz­[cd,f]­indole derivatives as the minor products under mild reaction conditions. Upon exposure to air, most aryl-substituted azatricycles led to bicyclic γ-lactams, while the ortho-tolyl- or alkyl-substituted azatricycles provided the corresponding bicyclic γ-lactams after oxidation with osmium tetraoxide and N-methylmorpholine-N-oxide. Under acidic conditions, the ortho-tolyl- or alkyl-substituted azatricycles were further transformed into 5-N-tosylaminomethyl-tethered bicyclo­[4.2.0]­octan-7-ones. The gold­(I)-catalyzed tandem cycloisomerization/oxidation reaction also provided a new route for the synthesis of bridged bicyclic δ-lactams from six-membered ring 4-enynamides. The mild reaction conditions allowed the synthesis of a range of bicyclic γ- and δ-lactams and N-tosylaminomethyl-tethered bicyclo[4.2.0]­octan-7-ones with high diastereoselectivities.