Gold-Catalyzed Cascade Cyclizations of 1,6-Diynyl Carbonates to Benzo[b]fluorenes Involving Arylation of Oxocarbenium Ion Intermediates and Decarboxylative Etherification

摘要

In recent years, the gold-catalyzed rearrangement reactions of propargylic esters have received considerable attention owing to their synthetic utility in a wide variety of fascinating transformations. Two main competitive processes, namely, 1,2-acyloxy migration and 3,3-rearrangement are usually involved in most cases of these gold-catalyzed rearrangement reactions as an initial step, which depends on the substitution patterns on either end of the propargyl moiety. The gold-catalyzed 3,3-rearrangement of propargyl esters leads to the formation of carboxyallenes, which can be further converted into various acyloxocarbenium ion intermediates by activation of the allene moiety by the same gold catalyst. The oxocarbenium ions generated in these reactions show diverse reactivities for further functionalization reactions.