New Pathways for the Dual Gold‐Catalyzed Cyclization of Diynes

Abstract

The reaction of thiophene-based diynes with dual-activation gold catalysts can provide cyclobutene derivatives or different polycycles by selective C-H insertion reactions. Also, the first σ,π-digold diyne complex was obtained in a stoichiometric reaction, providing insight into the dual activation mechanism. The new products were unambiguously identified by X-ray single-crystal structure analysis.

Catalytic Gold Chemistry: From Simple Salts to Complexes for Regioselective C−H Bond Functionalization

“…It is noteworthy that these substrates generate strained cyclobutyl derivatives as a consequence of domino 6-endo-dig cyclization/ β-Csp 3 À H insertion. [293] Likewise, thienyl-2,3-diynes devoid of any γ-CÀ H bond did not undergo late-stage CÀ H annulation under dual-gold catalysis and exhibited only a formal cycliza-tion/dimerization cascade. [294] This reactivity pattern was in sharp contrast to the related 1,2-dialkynylbenzenes having no γ-CÀ H bonds (as shown in Scheme 59, Eq.…”

“…As opposed to the above‐mentioned examples which generally possess a γ‐Csp 3 −H bond on the alkyl side chain, substrates lacking γ‐Csp 3 hydrogen atoms were also shown to undergo cyclizations by gold‐catalyzed dual activation. It is noteworthy that these substrates generate strained cyclobutyl derivatives as a consequence of domino 6‐ endo ‐ dig cyclization/β‐Csp 3 −H insertion [293] . Likewise, thienyl‐2,3‐diynes devoid of any γ‐C−H bond did not undergo late‐stage C−H annulation under dual‐gold catalysis and exhibited only a formal cyclization/dimerization cascade [294] .…”

Dual Gold Catalysis: Bidirectional Processes and Tandem sp3‐C−H Insertion Reactions

“…However, an aromatic C−H group can also participate in the reaction, and 7 c is formed this way. Alternatively, as was shown earlier, dual gold activation can result in 5‐ endo cyclization, even in the case of thiophenes, and vinylidene intermediate B is formed that way. After that, activation of tertiary C−H bonds takes place, and 7 b is formed as a product.…”

Advances and Prospects in Gold‐Catalyzed C−H Activation

“…Hashmi and coworkers strategically studied the cyclization of diynes through dual activated gold catalyst (DAC) (Scheme ) . Their studies mainly concentrated on thiophene‐based diynes 191 , which underwent cyclization through selective C−H insertion leading to cyclobutene derivatives or different polycycles depending on the substrate.…”