Gold(I)‐Catalysis for the Synthesis of Terpenoids: From Intramolecular Cascades to Intermolecular Cycloadditions

Abstract

Gold(I)‐catalyzed cycloisomerizations of 1,n‐enynes proceed through electrophilic intermediates that can be trapped intra‐ or intermolecularly by a variety of hetero‐ and carbon nucleophiles to form complex skeletons in a single step. This review covers the efforts of our group towards the development of new reactions that have been successfully applied in the total synthesis of several natural terpenoids and related carbocyclic structures, as well as for the ready access to challenging linear acenes.

Generation of Gold(I) Carbenes by Retro‐Buchner Reaction: From Cyclopropanes to Natural Products Synthesis

“…As a part of our program to apply new synthetic methodologies in the synthesis of natural or biologically relevant products ,. we designed the first approach for the assembly of the carbon skeleton of the cycloaurenones and the dysiherbols .…”

Buchwald‐Type Ligands on Gold(I) Catalysis

“…In the first decade of the current century, homogeneous gold(I) catalysis has experienced a "gold rush" during which numerous transformations were developed for the assembly of complex molecular settings, [15][16][17][18][19][20] that were also applied in the context of natural product total synthesis. [21,22] Gold(I) carbenes were invoked as key intermediates in many of these transformations whereby their reactivity is strongly determined by the ancillary ligand. [23] According to the binding model described by Toste and Goddard, [24] gold(I) binds linearly via backdonation of its electrons in the filled 5d orbitals into the empty π orbitals of the ligand and the carbene.…”

“…The groups of Toste, Fürstner and our own group identified cationic phosphine gold(I) catalysts [R 3 PAuX] (X=labile anionic ligand) formed in situ from [R 3 PAuCl] by chloride abstraction with AgX or by protolysis of [R 3 PAuCH 3 ], to be the most active and selective in the cyclization of 1, n ‐enynes and other C−C and carbon‐heteroatom bond‐forming reactions. In the first decade of the current century, homogeneous gold(I) catalysis has experienced a “gold rush” during which numerous transformations were developed for the assembly of complex molecular settings, that were also applied in the context of natural product total synthesis . Gold(I) carbenes were invoked as key intermediates in many of these transformations whereby their reactivity is strongly determined by the ancillary ligand .…”

Gold-Catalyzed Synthesis of Small Rings

“… 117 , 118 This comes as a consequence of the ability of gold(I) complexes to activate π bonds in a very selective manner. 119 − 135 Its potential, attributed partially to relativistic effects, 136 is illustrated by the wide molecular complexity 137 − 184 that can be built through the gold(I)-catalyzed cycloisomerization of enynes ( Scheme 3 ). 185 − 206 …”