Recent advances in Cu-catalyzed transformations of internal alkynes to alkenes and heterocycles

Abstract

Numerous metal-catalyzed reactions involving internal alkynes and aimed towards synthetically and pharmacologically important alkenes and heterocycles have appeared in the literature.

Mechanistic Study of Alkyne Insertion into Cu–Al and Au–Al Bonds: A Paradigm Shift for Coinage Metal Chemistry

“…28−32 Cu-catalyzed reactions of internal alkynes for the synthesis of different valuable alkenes and heterocycles have also appeared in the literature in the last decade and they follow analogous mechanisms, with the functionalization occurring via both an inner-and an outersphere mechanism. 33 However, the M−alkyne (M = Cu, Au) bond energies vary generally in the order Cu < Au, indicating a more efficient activation of the triple bond by gold complexes, due to their higher electrophilicity. In addition, dinuclear gold (and heterobimetallic Cu/Au) complexes and their use in catalysis have recently received significant attention and comparative studies of the controversial mono-vs dual-metal-catalyzed pathways have appeared in the literature.…”

“…Alternatively, the nucleophilic attack has been proposed to involve coordination of the nucleophile to gold and syn insertion of the substrate into the Au–Nu bond, leading to cis vinyl gold intermediates (inner-sphere mechanism, Scheme ). However, no direct unambiguous evidence for the inner-sphere mechanism has been reported to date. − Cu-catalyzed reactions of internal alkynes for the synthesis of different valuable alkenes and heterocycles have also appeared in the literature in the last decade and they follow analogous mechanisms, with the functionalization occurring via both an inner- and an outer-sphere mechanism …”

“… 28 − 32 Cu-catalyzed reactions of internal alkynes for the synthesis of different valuable alkenes and heterocycles have also appeared in the literature in the last decade and they follow analogous mechanisms, with the functionalization occurring via both an inner- and an outer-sphere mechanism. 33 …”

Unified Total Syntheses of Benzenoid Cephalotane-Type Norditerpenoids: Cephanolides and Ceforalides

“…However, these established conditions resulted in nonspecific decomposition of the substrate along with only a trace amount of the trimethylsilyl (TMS)-cleaved free alcohol. Changing the solvent to tetrahydrofuran (THF) (entry 3), which is often employed in the alkylboration of alkynes, 36 resulted in productive reactions of 27; however, the organocopper intermediate underwent competing protonation instead of methylation to afford 43 as a single isomer. Because 43 was unstable during purification using silica gel, NMR yields are provided for this reaction.…”

Base-promoted synthesis of tetrasubstituted alkenylboronates from propargyl amines and B2pin2via dual 1,4-metallate shift and B–N elimination

“…1A). 1,2 Among them, tetrasubstituted alkenylboronates are the most important ones, which could serve as the key precursors and provide the feasibility for selective construction of multiple C–C or C-heteroatom bonds to generate valuable compounds and new tetrasubstituted alkenes. 3,4…”