Gold(I)-Catalyzed Cascade Cyclization of Anilines with Diynes: Controllable Formation of Eight-Membered Ring-Fused Indoles and Propellane-Type Indolines

Copper-Catalyzed [2 + 2] Cyclization/Ring Expansion of Ene-Ynamides: Construction of Medium- and Large-Sized Rings

Catalytic cyclization of enynes is an efficient approach for the preparation of cyclic compounds, and a large variety of four- to six-membered rings could be synthesized using this method. However, it has been rarely employed for the construction of medium- and large-sized rings. Herein, we describe a copper-catalyzed cycloisomerization of ene-ynamides through a [2 + 2] cyclization/electrocyclic ring opening cascade, leading to the atom-economical assembly of indole-fused medium- and large-sized rings in moderate to excellent yields under mild reaction conditions. Importantly, the synthetic utility of this reaction was demonstrated by the convenient synthesis of iprindole.

Advancements in Gold-Catalyzed Cascade Reactions to Access Carbocycles and Heterocycles: An Overview

This review summarizes recent developments (from 2006 to 2022) in numerous important and efficient carbo- and heterocycle generations using gold-catalyzed cascade protocols. Herein, methodologies involve selectivity, cost-effectiveness, and ease of product formation being controlled by the ligand as well as the counter anion, catalyst, substrate, and reaction conditions. Gold-catalyzed cascade reactions covered different strategies through the compilation of various approaches such as cyclization, hydroarylation, intermolecular and intramolecular cascade reactions, etc. This entitled reaction is also useful for the synthesis of spiro, fused, bridged carbo- and heterocycles.

Gold(i)-catalyzed cycloisomerization of alcohol or amine tethered-vinylidenecyclopropanes providing access to morpholine, piperazine or oxazepane derivatives: a carbene versus non-carbene process

A gold(i)-catalyzed adjustable intramolecular cyclization of alcohol or amine tethered-vinylidenecyclopropanes (VDCPs).

Hydroelementation of diynes

This review highlights the hydroelementation reactions of conjugated and separated diynes, which depending on the process conditions, catalytic system, as well as the type of reagents, leads to the formation of various products: enynes, dienes, allenes, polymers, or cyclic compounds. The presence of two triple bonds in the diyne structure makes these compounds important reagents but selective product formation is often difficult owing to problems associated with maintaining appropriate reaction regio- and stereoselectivity. Herein we review this topic to gain knowledge on the reactivity of diynes and to systematise the range of information relating to their use in hydroelementation reactions. The review is divided according to the addition of the E-H (E = Mg, B, Al, Si, Ge, Sn, N, P, O, S, Se, Te) bond to the triple bond(s) in the diyne, as well as to the type of the reagent used, and the product formed. Not only are the hydroelementation reactions comprehensively discussed, but the synthetic potential of the obtained products is also presented. The majority of published research is included within this review, illustrating the potential as well as limitations of these processes, with the intent to showcase the power of these transformations and the obtained products in synthesis and materials chemistry.

Photoredox-catalyzed hydroxymethylation of β-ketoesters: application to the synthesis of [3.3.3] propellane lactones

Photoredox-catalysed hydroxymethylation of β-ketoesters substituted by an allyl subunit on the α-position afforded directly the corresponding bicyclic lactones possessing both a hydroxy group and an unsaturation. A subsequent regioselective iodoetherification led to the formation of original [3.3.3] propellane structures. Substitution of the iodine atom by various nucleophiles afforded highly functionnalized structures including triazolomethyl derivatives.

Synthesis of Medium-Sized Heterocycles by Transition-Metal-Catalyzed Intramolecular Cyclization

Medium-sized heterocycles (with 8 to 11 atoms) constitute important structural components of several biologically active natural compounds and represent promising scaffolds in medicinal chemistry. However, they are under-represented in the screening of chemical libraries as a consequence of being difficult to access. In particular, methods involving intramolecular bond formation are challenging due to unfavorable enthalpic and entropic factors, such as transannular interactions and conformational constraints. The present review focuses on the synthesis of medium-sized heterocycles by transition-metal-catalyzed intramolecular cyclization, which despite its drawbacks remains a straightforward and attractive synthesis strategy. The obtained heterocycles differ in their nature, number of heteroatoms, and ring size. The methods are classified according to the metal used (palladium, copper, gold, silver), then subdivided according to the type of bond formed, namely carbon-carbon or carbon-heteroatom.