Dual Gold/Silver Catalysis Involving Alkynylgold(III) Intermediates Formed by Oxidative Addition and Silver‐Catalyzed C−H Activation for the Direct Alkynylation of Cyclopropenes

Abstract

While gold‐mediated synergistic catalytic processes involving transmetalations with other metals are well understood, AuI/AuIII cycles in these reactions are rarely reported. Herein a gold‐catalyzed direct alkynylation of cyclopropenes is enabled by two operating catalytic cycles, an oxidative catalytic cycle involving an alkynyl AuIII complex formed by oxidative addition and one involving a silver‐mediated C−H activation.

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

“…Possible mechanisms for the heterocoupling of terminal alkynes and alkynyl hypervalent iodiner eagents triggered by Au-TA/AgOTs catalysts and phene ligands. [214] Similart ot he findings by Zhu et al, [102] the Ag I catalyst activatest he CÀHb ond of the cyclopropane, whereas the Au catalyst activates the alkyne coupling partner (Scheme 31). OxidativeAu-catalyzed1,2-difunctionalization of ethyleneand proposed mechanisms.…”

“…[204] of cyclopropenes. [214] Similart ot he findings by Zhu et al, [102] the Ag I catalyst activatest he CÀHb ond of the cyclopropane, whereas the Au catalyst activates the alkyne coupling partner (Scheme 31). TIPS-EBX is used both as an oxidant for Au I and as the precursor for the alkyne coupling partners.…”

Oxidative Addition of Alkenyl and Alkynyl Iodides to a AuI Complex

“…The formation of homocoupled products then ensued, and these increased over a week, suggesting that their formation is promoted by decomposition products of the Au complex. Hashmi and co‐workers have developed catalytic C−C bond formations where alkynyl‐Au III species were generated by C−I cleavage; these processes did not proceed via formal C−I oxidative addition and required highly reactive alkynyl‐iodine(III) reagents . The present study suggests that more available and atom economical alkynyl‐iodine(I) precursors can form the basis for future Au‐catalyzed alkynylations (Scheme )…”

Gold‐Catalyzed Stereoselective Domino Cyclization/Alkynylation of N‐Propargylcarboxamides with Benziodoxole Reagents for the Synthesis of Alkynyloxazolines

“…Initially, the carbonyl oxygen atom stereoselectively attacks alkyne, which is π‐coordinated to gold, from the backside in an 5‐ exo‐dig fashion to form vinyl‐gold intermediate B . After that, the oxidative addition of intermediate B (which due to the negatively charged chloride ligand on gold is a locally negatively charged ate‐complex of gold(I), and thus easier to oxidize) and compound 4 b affords intermediate C , which then undergoes ligand exchange and reductive elimination to give the active gold(I) catalyst and the final product 3 b , which is obtained in 100% trans ‐configuration, which is based on the trans ‐selective formation of the vinylgold intermediate. In addition, the increased yield of product 3 b upon the addition of 0.5 equiv.…”