Regioselective Cis Insertion of DMAD into Au–P Bonds: Effect of Auxiliary Ligands on the Reaction Mechanism

Abstract

The cis insertion of dimethyl acetylenedicarboxylate (DMAD, 2) into the Au−P bond of Au(SAr)(PAr′ 3 ) (1) occurs selectively at room temperature to give adduct 3, whose X-ray crystallographic analysis exhibits the predominant character of an alkenylphosphorus zwitterion complex. The first-order kinetics with respect to 1 and 2 and the large negative value of ΔS ⧧ indicate that the reaction proceeds through the coordination of 2 to 1 followed by a concerted inner-sphere nucleophilic attack of PPh 3 on the coordinated triple bond. In contrast, Au(Cl)(PPh 3 ) (4) does not react with 2 even at 60 °C. However, the tricoordinated 16-electron complex Au(Cl)(PPh 3 ) 2 (5) quite successfully reacts with 2 to produce insertion product 6, demonstrating that two PPh 3 ligands are required for the reaction.

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

“…The transformation of the metal phosphite into a phosphonate was easy to follow since there was a 94 ppm change in the chemical shift of the −P­(O)­(OEt) 2 fragment. In contrast with several previous reports describing the reactivity of (R 3 P)­AuX compounds with activated alkynes, DMAD exclusively inserted into the Au–phosphito bond. , No insertion of DMAD into the Au–carbene bond was observed.…”

“…Several studies found that phosphine ligands were not entirely innocent and generated zwitterionic vinylgold compounds resulting from insertion of the alkyne into the gold–ligand bond. Kuniyasu and Kambe reported reactions between gold thiolate complexes of the type (Ph 3 P)­AuSAr and dimethyl acetylenedicarboxylate (DMAD) . Vinylgold compounds were generated from the insertion of the alkyne into the Au–PR 3 bond.…”

“…Kuniyasu and Kambe reported reactions between gold thiolate complexes of the type (Ph 3 P)AuSAr and dimethyl acetylenedicarboxylate (DMAD). 34 Vinylgold compounds were generated from the insertion of the alkyne into the Au−PR 3 bond. The Au−S bond was retained in these reactions.…”

Intramolecular anti‐Phosphinoauration of Alkynes: An FLP‐Motivated Approach to Stable Aurated Phosphindolium Complexes

“…Oner eason might be the assumption that in the case of stoichiometrica mounts of phosphine, as trong coordination to the free binding site of the gold catalyst can inhibit the catalysts activity.S of ar,o nly one reportb yK uniyasu and Kambed eals with the gold-mediated cis-addition of phosphines from RSAuPPh 3 complexes. [6] But due to the special electronic nature of the applied electron-deficienta lkyne,d imethylacetylendicarboxylate( which itselfi s ap owerful electrophile knownt ob ea ttackedby phosphines), no general information can be obtained regarding the tolerance of phosphinesi ng old catalysis;f or example, cis-additions are generally extremely rare, whichi ndicates that, triggered by the nature of this specific alkyne, an unusual pathway takes place. [6] Therefore, ag eneral study of ap hosphinoauration reaction with electronically non-activated alkynes that are usually applied in gold-catalyzed reactions is still missing.…”

“…[6] But due to the special electronic nature of the applied electron-deficienta lkyne,d imethylacetylendicarboxylate( which itselfi s ap owerful electrophile knownt ob ea ttackedby phosphines), no general information can be obtained regarding the tolerance of phosphinesi ng old catalysis;f or example, cis-additions are generally extremely rare, whichi ndicates that, triggered by the nature of this specific alkyne, an unusual pathway takes place. [6] Therefore, ag eneral study of ap hosphinoauration reaction with electronically non-activated alkynes that are usually applied in gold-catalyzed reactions is still missing. Other reports on the connection of aC ÀPb ond by means of homogeneousg old catalysts are restricted to the addition of ap hosphite onto an imine [7] or by reductivee limination from an intermediate gold(III) species.…”