Abstract
The efficient hydrohydrazidation of terminal (6a–r, 18 examples, 0.1–0.2 mol % [(NHC)Au(NTf2)], T = 60 °C) and internal alkynes (7a–j, 10 examples, 0.2–0.5 mol % [(NHC)Au(NTf2)], T = 60–80 °C) utilizing a complex with a sterically demanding bispentiptycenyl-substituted NHC ligand and the benign reaction solvent anisole, is reported.
Highlights
Cationic gold complexes with weakly coordinating counterions (which are often considered to be solvent-separated ions) [1,2,3], render powerful catalysts for the transformation of organic substrates [4,5,6], the reactions of alkynes with a variety of heteroatom nucleophiles (Scheme 1) [7] such as water or alcohol [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22], primary or secondary amines [23,24,25,26,27,28], or hydrazine [29,30,31]
The [LAu(NTf2)]-catalyzed reaction can be described by a general mechanism (Scheme 1), in which the coordination of LAu+ by the alkyne [37,38] leads to the activation of the triple bond for a nucleophilic attack, generating a vinylgold complex [39,40]
We recently reported the excellent activity of the very bulky bispentiptycenyl-substituted (NHC)Au complexes in the hydration of terminal and internal
Summary
Cationic gold complexes with weakly coordinating counterions (which are often considered to be solvent-separated ions) [1,2,3], render powerful catalysts for the transformation of organic substrates [4,5,6], the reactions of alkynes with a variety of heteroatom nucleophiles (Scheme 1) [7] such as water or alcohol [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22], primary or secondary amines [23,24,25,26,27,28], or hydrazine [29,30,31]. The efficient hydrohydrazidation of terminal (6a–r, 18 examples, 0.1–0.2 mol % [(NHC)Au(NTf2)], T = 60 °C) and internal alkynes (7a–j, 10 examples, 0.2–0.5 mol % [(NHC)Au(NTf2)], T = 60–80 °C) utilizing a complex with a sterically demanding bispentiptycenyl-substituted NHC ligand and the benign reaction solvent anisole, is reported. The activity of gold complexes in such reactions tends to be higher, when using sterically demanding ligands (NHC, phosphine) [41].
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