Synthesis of Azepines by a Gold-Catalyzed Intermolecular [4 + 3]-Annulation

摘要

Gold catalysis has recently generated a variety of valuable methods for the synthesis of complex structures from simple starting materials. While the majority of efforts have focused on intramolecular rearrangement and addition reactions, a number transformations taking advantage of intermolecular reaction of the a gold-stabilized cationic intermediate generated from the 1,2-rearrangement of propargyl esters have been described. In these reactions, the cationic intermediate shows reactivity analogous to that reported for electrophilic metal-stabilized vinylcarbenoids. For example, we have shown that sulfoxides react with intermediate A to form carbonyl compounds (eq I). On the basis of this reactivity, we postulated that allylgold intermediate B, generated by reaction of A with a nucleophile, could be induced to react with electrophiles. Herein, we report the realization of this goal leading to a convenient method for the construction of azepines.