Gold‐Catalyzed Cascade Reactions of Alkynes for Construction of Polycyclic Compounds

Abstract

The development of cascade reactions is an area of considerable interest in modern organic chemistry. Efficient cascade reactions realize the economical synthesis of complex target molecules through multiple bond formations in a single operation. Elementary reactions that form fewer waste products are desirable in terms of atom economy and in order to suppress side product formation in sequential processes. Recent advances in homogeneous gold catalysis have opened up further possibilities for cascade reactions. In this review, recent advances in gold‐catalyzed cascade cyclizations of alkynes are summarized. In particular, cascade reactions based on nucleophilic/electrophilic addition, carbene cyclopropanation/insertion, ring expansion, and cycloaddition are highlighted. Notably, many of the cascade reactions shown in this mini‐review feature no theoretical waste products.

Double Gold Activation of 1‐Ethynyl‐2‐(Phenylethynyl)Benzene Toward 5‐exo‐dig and 6‐endo‐dig Cyclization Reactions

“…While an exponential growth of activity in the field of homogeneous gold catalysis of organic reactions has been observed in the last 16 years, [1][2][3][4][5] it is only recently that the concept of dual activation has been discovered. [6] In this reactionm ode, which has no precedence in organometallic chemistry,t he organic substrate in the reactive species is activated by two mononuclear gold complexes at the same time, one coordinating in a s-mode to at erminal alkyne, the other in a p-mode coordinated to asecond alkynyl unit (see 1 in Figure 1f or arepresentative example).…”

Direkter Zugang zu Azulenen über eine Gold‐katalysierte Dimerisierung von Diarylalkinen

“…ImGebiet der Gold-Katalyse [1] sind Alkine nach wie vor die dominierende Substratklasse. [2] Neben den weit verbreiteten Reaktionen, in denen Nukleophile mit einem Alkin reagieren, gewinnen intramolekulare Reaktionskaskaden von zwei oder mehr verknüpften Alkinen an Bedeutung. [2a] Substrate mit mindestens einem terminalen Alkin kçnnen mit der dualen Gold-Katalyse [3] zu energiereichen Zwischenstufen wie Gold-Vinylidenen [4] und diaurierten Phenyl-Kationen umgesetzt werden.…”

Gold‐Catalyzed Indole Ring Synthesis

“…A common feature is that gold salts have an enormous affinity for multiple bonds and they behave as soft carbophilic Lewis acids, thus triggering subsequent chemistry. For excellent discussions of these mechanisms, see references [42][43][44][45][46][47][48]. …”