A Gold(I)‐Catalyzed Domino Coupling of Alcohols with Allenes Enables the Synthesis of Highly Substituted Indenes

The reaction of aryl‐substituted allenes with alcohols under gold catalysis led to highly substituted indenes in good yields, with low catalyst loading and under mild conditions. During this domino transformation, two C?C bonds are formed with water as the only byproduct.     

Gold(I)‐Catalyzed Cycloisomerizations and Alkoxycyclizations of ortho‐(Alkynyl)styrenes

Indenes and related polycyclic structures have been efficiently synthesized by gold(I)‐catalyzed cycloisomerizations of appropriate ortho‐(alkynyl)styrenes. Disubstitution at the terminal position of the olefin was demonstrated to be essential to obtain products originating from a formal 5‐endo‐dig cyclization. Interestingly, a complete switch in the selectivity of the cyclization of o‐(alkynyl)‐α‐methylstyrenes from 6‐endo to 5‐endo was observed by adding an alcohol to the reaction media. This allowed the synthesis of interesting indenes bearing an all‐carbon quaternary center at C1. Moreover, dihydrobenzo[a]fluorenes can be obtained from substrates bearing a secondary alkyl group at the β‐position of the styrene moiety by a tandem cycloisomerization/1,2‐hydride migration process. In addition, diverse polycyclic compounds were obtained by an intramolecular gold‐catalyzed alkoxycyclization of o‐(alkynyl)styrenes bearing a nucleophile in their structure. Finally, the use of a chiral gold complex allowed access to elusive chiral 1H‐indenes in good enantioselectivities.     

Meeting the Challenge of Intermolecular Gold(I)‐Catalyzed Cycloadditions of Alkynes and Allenes

The development of gold(I)‐catalyzed intermolecular carbo‐ and hetero‐cycloadditions of alkynes and allenes has been more challenging than their intramolecular counterparts. Here we review, with a mechanistic perspective, the most fundamental intermolecular cycloadditions of alkynes and allenes with alkenes.     

Gold(I)‐Catalyzed Enantioselective Desymmetrization of 1,3‐Diols through Intramolecular Hydroalkoxylation of Allenes

A gold(I)‐catalyzed enantioselective desymmetrization of 1,3‐diols was achieved by intramolecular hydroalkoxylation of allenes. The catalyst system 3‐F‐dppe(AuCl)₂ /(R)‐C₈‐TRIPAg proved to be specifically efficient to promote the desymmetrizing cyclization of 2‐aryl‐1,3‐diols, which have proven challenging substrates in previous reports. Multisubstituted tetrahydrofurans were prepared in good yield with good enantioselectivity and diastereoselectivity by this method.     

Convergent Synthesis of (−)‐Quinocarcin Based on the Combination of Sonogashira Coupling and Gold(I)‐Catalyzed 6‐endo‐dig Hydroamination

The total synthesis of the pentacyclic tetrahydroisoquinoline alkaloid quinocarcin, which possesses intriguing structural and biological features, has been achieved through a gold(I)‐catalyzed regioselective hydroamination reaction. It is noteworthy that the regioselectivity of the intramolecular hydroamination of an unsymmetrical alkyne could be completely switched through substrate control. Other key features of this synthesis include the highly stereoselective synthesis of 2,5‐cis‐pyrrolidine through the intramolecular amination of the bromoallene and the Lewis acid mediated ring opening of dihydrobenzofuran.