Gold‐Catalyzed Cyclizations of Alkynes with Alkenes and Arenes

Abstract

This chapter reviews the gold‐catalyzed cyclization reactions of alkynes with alkenes that proceed via selective activation of the alkyne by π‐coordination of the transition metal. Mechanistically related intermolecular reactions between alkynes and alkenes are also discussed, as are reactions of alkynes with arenes, heteroarenes, and related nucleophiles.

Role of σ,π-Digold(I) Alkyne Complexes in Reactions of Enynes

“…The gold(I)-catalyzed cycloisomerization of 1,6-enynes can proceed by two pathways, leading to five- or six-membered rings. 14 , 40 , 41 The 5- exo -dig cyclization of Ia – c leads to intermediates IIa – c , whereas IIIa – c are formed in a 6- endo -dig process that is less favorable kinetically ( Scheme 4 ). In most cases slightly higher energy barriers were observed for the cyclization with the more electron donating carbene ligand L 3 , which reduces the electrophilicity of AuL + .…”

“…The vast majority of the gold(I)-catalyzed chemistry of alkynes under homogeneous conditions can be understood by the initial π coordination via ligand substitution to form π-alkyne gold(I) complexes 1 , which then react with carbo- or heteronucleophiles ( Scheme 1 ). 14 , 15 Complexes of this type with nonterminal alkynes have been structurally characterized. 16 − 18 Alternatively, deprotonation of the terminal alkyne by the counterion X – can generate σ-alkynyl gold(I) complexes 2 .…”

Broad-Scope Rh-Catalyzed Inverse-Sonogashira Reaction Directed by Weakly Coordinating Groups

“… 4 The chemistry of alkynes has gained particular momentum in recent years by the discovery of a wide variety of catalytic transformations triggered by gold(I), platinum(II), and other alkynophilic Lewis acids. 5 Therefore, the development of methods for the introduction of alkyne groups onto organic molecules is of high importance. To this end, the Sonogashira coupling reaction is the most general method for the formation of C(sp)–C(sp 2 ) bonds from aryl or alkenyl (pseudo)halides and terminal alkynes.…”

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

“…Gold(I) carbenes can be generated through different methods in catalytic transformations (Scheme ). Among these strategies, the cycloisomerization of 1, n ‐enynes has attracted special attention to the synthetic community, and has been extensively explored in many different contexts ,,,…”