Gold-Catalyzed Stereoselective Synthesis of Bicyclic Lactams and Ketones from <i>N</i>‑Tosylynamidomethyl-Tethered Cyclohexenes
2016-12-05T00:00:00Z (GMT) by
Six-membered ring 3-enynamides underwent cycloisomerization in the presence of a catalytic amount of a gold(I) complex delivering mainly 4-azatricyclo[18.104.22.168<sup>3,10</sup>]dec-2-ene derivatives and dibenz[<i>cd</i>,<i>f</i>]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 <i>ortho</i>-tolyl- or alkyl-substituted azatricycles provided the corresponding bicyclic γ-lactams after oxidation with osmium tetraoxide and <i>N</i>-methylmorpholine-<i>N</i>-oxide. Under acidic conditions, the <i>ortho</i>-tolyl- or alkyl-substituted azatricycles were further transformed into 5-<i>N</i>-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 <i>N</i>-tosylaminomethyl-tethered bicyclo[4.2.0]octan-7-ones with high diastereoselectivities.