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.

Synthesis of 3-Sulfonylamino Quinolines from 1-(2-Aminophenyl) Propargyl Alcohols through a Ag(I)-Catalyzed Hydroamination, (2 + 3) Cycloaddition, and an Unusual Strain-Driven Ring Expansion

We describe herein a silver-catalyzed conversion of 1-(2-aminophenyl)-propargyl alcohols to 4-substituted 3-tosylaminoquinolines using TsN3 as an amino surrogate. Controlled reactions reveal the pathway consisting of Ag(I)-catalyzed 5-exo-dig cyclization, catalyst-free (2 + 3) cycloaddition, and ring-expansive rearrangement via nitrogen expulsion. As a support study, we show that the cyclic enamines in similar conditions produce amidines via a C-C bond migration.

Enantioselective construction of a 2,2′-bisindolylmethane scaffold via catalytic asymmetric reactions of 2-indolylmethanols with 3-alkylindoles

A chiral phosphoric acid-catalyzed asymmetric reaction of 2-indolylmethanols with 3-alkylindoles has been established to construct 2,2′-bisindolylmethane scaffold in good enantioselectivities.