Synthesis of functionalized carbo- and heterocycles via gold-catalyzed cycloisomerization reactions of enynes

The PPh3AuCl/AgSbF6 catalytic system promotes a tandem Friedel-Crafts' type addition of electron-rich aromatic and heteroaromatic derivatives to unactivated alkene followed by a C-C bond cyclization reaction. The efficiency of this system allowed room temperature reactions in a very short time. The scope and limitations of this reaction were investigated. The reaction conditions were compatible with various functional groups on the nucleophiles. Severe limitations were observed when the allylic position of the enyne is substituted by electron-withdrawing groups. The mechanism of the reaction was investigated via the synthesis of a deuterated aromatic ring: we showed that the source of proton involved in the protodemetallation step originates from the acidic activated C-H bond of the nucleophile.