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

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posted on 2016-12-05, 00:00 authored by Chang-Zhi Zhong, Po-Ting Tung, Tsung-Han Chao, Ming-Chang P. Yeh
Six-membered ring 3-enynamides underwent cycloisomerization in the presence of a catalytic amount of a gold­(I) complex delivering mainly 4-azatricyclo­[,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.