Syn-Insertion of Alkynes into Gold–Phosphito Bonds: Stereoselectivity and Reversible Protodeauration

Abstract

The susceptibility of gold phosphito compounds to undergo alkyne insertion into gold–phosphorus bonds has been investigated. An electron-deficient alkyne (DMAD) underwent syn-insertion into the gold–phosphorus bond to generate a Z-vinylgold species, whereas electron-rich internal alkynes were unreactive. When a P-chiral phosphinate was used as a probe, the protodeauration and insertion steps were found to be stereospecific. In contrast to the insertion chemistry observed with DMAD, electron-deficient terminal alkynes generated alkynylgold compounds and released secondary phosphites through a reversible protodeauration process.

Syn-Aminoauration versus Anti-Aminoauration of Alkynes in Au(I)/Au(III) Catalysis: Understanding the Origin of Selectivity

“…Homogeneous gold catalysis has emerged as an important topic for the efficient construction of complex molecular architecture. − In general, these reactions are triggered by the nucleophilic attack on the gold-coordinated C–C multiple bonds to form an organo-gold intermediate that upon protodemetalation delivers the product. − On the contrary, the development of Au­(I)-catalyzed cross-coupling reactions seems to be quite challenging because unlike its isoelectronic counterpart Pd(0), Au­(I) does not change its oxidation state during the catalytic cycle. − This apparent reluctance to engage in redox activity is commonly attributed to the comparatively high redox potential of the Au­(I)/Au­(III) couple ( E ° = +1.41 V) to the Pd(0)/Pd­(II) couple ( E ° = +0.92 V) . Therefore, the oxidative addition of organic halides or equivalents ubiquitous in palladium/nickel-catalyzed reactions rendered nontrivial for Au­(I) for many decades. − However, recent research articles have revealed the use of strong oxidizing or fluorinating agents like (diacetoxyiodo)­benzene, Selectfluor, N -fluorobenzenesulfonimide, ArN 2 X, P–N ligand, etc.…”