Gold-Catalyzed Carbene Transfer Reactions

Gold catalyzed efficient preparation of dihydrobenzofuran from 1,3-enyne and phenol

A gold catalyzed formal intermolecular [2+3] cyclo-coupling of 1,3-enynes with phenols was developed to prepare dihydrobenzofuran derivatives with the addition of 2,6-dichloropyridine N-oxide, in which, a highly ortho-selective phenol S_EAr functionalization was achieved by using 1,3-enynes as α-oxo vinyl gold carbenoid surrogates.

Kinetics and Mechanism of the Gold-Catalyzed Hydroamination of 1,1-Dimethylallene with N-Methylaniline

The mechanism of the intermolecular hydroamination of 3-methylbuta-1,2-diene (1) with N-methylaniline (2) catalyzed by (IPr)AuOTf has been studied by employing a combination of kinetic analysis, deuterium labelling studies, and in situ spectral analysis of catalytically active mixtures. The results of these and additional experiments are consistent with a mechanism for hydroamination involving reversible, endergonic displacement of N-methylaniline from [(IPr)Au(NHMePh)]⁺ (4) by allene to form the cationic gold π-C1,C2-allene complex [(IPr)Au(η² -H₂ C=C=CMe₂ )]⁺ (I), which is in rapid, endergonic equilibrium with the regioisomeric π-C2,C3-allene complex [(IPr)Au(η² -Me₂ C=C=CH₂ )]⁺ (I'). Rapid and reversible outer-sphere addition of 2 to the terminal allene carbon atom of I' to form gold vinyl complex (IPr)Au[C(=CH₂ )CMe₂ NMePh] (II) is superimposed on the slower addition of 2 to the terminal allene carbon atom of I to form gold vinyl complex (IPr)Au[C(=CMe₂ )CH₂ NMePh] (III). Selective protodeauration of III releases N-methyl-N-(3-methylbut-2-en-1-yl)aniline (3 a) with regeneration of 4. At high conversion, gold vinyl complex II is competitively trapped by an (IPr)Au⁺ fragment to form the cationic bis(gold) vinyl complex {[(IPr)Au]₂ [C(=CH₂ )CMe₂ NMePh]}⁺ (6).

Gold-catalyzed cascade reactions of 4H-furo[3,2-b]indoles with propargyl esters: synthesis of 2-alkenylidene-3-oxoindolines

2-Trienyliden-indolin-3-ones were synthesised in high yields via a gold catalysed cascade reaction between 4H-furo[3,2-b]indoles and propargyl esters.

Catalytic Dearomative Spirocyclization via Gold Carbene Species Derived from Ynamides: Efficient Synthesis of 2-Azaspiro[4.5]decan-3-ones

An intramolecular catalytic dearomatization of phenols via gold carbene species proceeded to provide 2-azaspiro[4.5]decan-3-ones. The use of NHC ligand and water as a co-solvent was critical for achieving high reactivity. This reaction did not require hazardous diazo compounds as carbene sources and proceeded even under air. The obtained spirocyclic product could be readily transformed into a gabapentin derivative by hydrogenation and deprotection.

Synthesis and Photocatalytic Reactivity of Vinylsulfonium Ylides

Although sulfur ylides are textbook reagents in organic synthesis, surprisingly little variation of substituents on sulfur is usually observed. In particular, vinylsulfonium ylides have been neglected so far. Herein, we present a study on their synthesis and reactivity, including interesting behavior under photocatalytic conditions.