Efficient AgOTf or Ph3PAuCl–AgSbF6 catalyzed cyclization of 1-hydroxy-2-alkynylallylphosphonates/2-alkynylallyl alcohols to 2-furylphosphonates/2,3,5-trisubstituted furans

Transition Metal-Catalyzed Hydroalkoxylation of Alkynes: An Overview

Oxygen-bearing motifs, mainly the congener heterocycles are ubiquitous due to their presence in various natural products and bioactive scaffolds. Although in literature, several strategies have been developed for their synthesis, hydroalkoxylation of alkynes has come forward as a method of choice and has been used extensively. In particular, hydroalkoxylation of alkynes has gained enormous attention from the synthetic community due to the rapid access to a very useful and reactive synthetic intermediate like 'enol ether'. Furthermore, to manifold the utility of these methods, reports have been developed elaborating the generation of 'enol ether' using hydroalkoxylation and their usage in various reactions in cascade or tandem manner. This review focuses on recent development on the hydroalkoxylation of alkynes for the synthesis of oxygen-containing entities.

Silver & gold-catalyzed routes to furans and benzofurans

Silver and gold have become incredibly versatile and mild catalysts for numerous transformations, especially in heterocycle synthesis. For the most prominent of them, i.e. furans, silver and gold, with their unique reactivity and mildness, allow numerous possible routes to highly substituted and/or functionalized furans from a large variety of starting materials. Silver and gold catalysis provide thus the most flexible way to this important family of compounds. The present review describes these silver and gold-catalyzed routes, with some emphasis on mechanistic aspects, and proposes a comparison of both the silver and the gold-catalyzed syntheses of furans.

Exploring the gold mine: [Au]-catalysed transformations of enynals, enynones and enynols

This review highlights reactions of enynals, enynones and enynols using gold catalysis which often lead to cycloaddition or cyclisation products.

Silver-catalysed reactions of alkynes: recent advances

Silver is a less expensive noble metal. Superior alkynophilicity due to π-coordination with the carbon-carbon triple bond makes silver salts ideal catalysts for alkyne-based organic reactions. This review highlights the progress in alkyne chemistry via silver catalysis primarily over the past five years (ca. 2010-2014). The discussion is developed in terms of the bond type formed with the acetylenic carbon (i.e., C-C, C-N, C-O, C-Halo, C-P and C-B). Compared with other coinage metals such as Au and Cu, silver catalysis is frequently observed to be unique. This critical review clearly indicates that silver catalysis provides a significant impetus to the rapid evolution of alkyne-based organic reactions, such as alkynylation, hydrofunctionalization, cycloaddition, cycloisomerization, and cascade reactions.

Recent advances in Michael addition of H-phosphonates

The review discusses recent achievements in the development of more environmentally friendly and economically competitive processes for the synthesis of biologically and synthetically important phosphorus-bearing compounds by conjugate addition of hydrogen-phosphonates to different Michael acceptors.

NHC–gold(i) catalysed [4 + 2] cycloaddition–acyclic addition of dialkyl substituted propargylic esters with 1,3-diphenylisobenzofuran: synthesis of novel benzo[c]fluorenols and substituted dienes

A new class of benzofluorenols is generated via a novel gold carbene complex [IPrAuCl/AgSbF₆] catalysed cycloaddition of propargylic esters with 1,3-diphenylisobenzofuran.

Gold(I)-catalyzed formation of furans from γ-acyloxyalkynyl ketones

Various γ-acyloxyalkynyl ketones were efficiently converted into highly substituted furans with 2.5 mol % of triflimide (triphenylphosphine)gold(I) as a catalyst in dichloroethane at 70 °C.