Gold-Catalyzed Carbenoid Transfer Reactions of Diynes - Pinacol Rearrangement versus Retro-Buchner Reaction

Aromatic diyne systems bearing one terminal propargylic acetate moiety and one tertiary propargylic alcohol subunit were converted in the presence of a gold catalyst. After an initial 1,2-migration of the acetoxy group at the terminal alkyne, a gold carbenoid is formed which is then transferred onto the internal alkyne of the propargylic alcohol. This combination enables the use of propargylic acetates as precursors for a gold-catalyzed pinacol-type rearrangement. In the final pinacol-like step the shift of an alkyl or aryl moiety onto an electrophilic gold carbenoid/cation terminates the reaction and 1-naphthyl ketones are obtained as products. If electron-rich aromatic backbones are used, a mechanistically interesting alternative pathway including a retro-Buchner reaction is opened.