A Gold Carbene Manifold to Prepare Fused γ‐Lactams by Oxidative Cyclisation of Ynamides

Sánchez-Cantalejo, Fernando; Priest, Joshua; Davies, Paul W.

doi:10.1002/chem.201804378

“…146 By using a similar strategy, Davies and co-workers in 2018 reported a gold-catalyzed oxidative C−H insertion of N-aryl ynamides 311, providing an efficient method for the synthesis of various valuable fused γ-lactams 312 (Scheme 129). 147 The use of bulky XPhosAuNTf 2 as the catalyst and bulky methylpico-linate-derived N-oxide as the oxidant could significantly prevent the overoxidation reaction previously observed in Li's protocol. 144 The authors proposed that α-oxo gold carbene intermediates were most likely involved in this oxidative cyclization.…”

Section: Nitrones As An Oxidantmentioning

confidence: 98%

Nitrene Transfer and Carbene Transfer in Gold Catalysis

Ye

¹

,

Zhu

²

,

Sahani

³

et al. 2020

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Catalytic transformations involving metal carbenes are considered one of the most important aspects of homogeneous transition metal catalysis. Recently, gold-catalyzed generation of gold carbenes from readily available alkynes represents a significant advance in metal carbene chemistry. This Review summarizes the advances in the gold-catalyzed nitrene-transfer reactions of alkynes with nitrogen-transfer reagents, such as azides, nitrogen ylides, isoxazoles, and anthranils, and gold-catalyzed carbene-transfer reactions, involving oxygen atom-transfer reactions of alkynes with nitro compounds, nitrones, sulfoxides, and pyridine N-oxides, through the presumable α-imino gold carbene and α-oxo gold carbene intermediates, respectively. Gold-catalyzed processes are reviewed by highlighting their product diversity, selectivity, and applicability, and the mechanistic rationale is presented where possible.

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“…Synthetic modification of phosphorus‐containing ligands can result in significant differences in the outcomes of reactions catalysed by their corresponding cationic gold(I) complexes. [4c], [19a], The regioselectivity of hydration of unsymmetrical internal alkynes has been previously probed by Nolan and co‐workers who identified anti‐Markovnikov‐selective gold(I)‐carbene complex‐catalysed hydration . As such, a model reaction, namely the hydration of unsymmetrical internal alkyne 15 was selected to probe selectivity that might arise from the structural modifications across the series of gold(I) complexes of phosphino‐triazoles prepared in this study (Table ).…”

Section: Resultsmentioning

confidence: 99%

Balancing Bulkiness in Gold(I) Phosphino‐triazole Catalysis

Zhao

¹

,

Wakeling

²

,

Meloni

³

et al. 2019

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The syntheses of a series of 1‐phenyl‐5‐phosphino 1,2,3‐triazoles are disclosed, within which, the phosphorus atom (at the 5‐position of a triazole) is appended by one, two or three triazole motifs, and the valency of the phosphorus(III) atom is completed by two, one or zero ancillary (phenyl or cyclohexyl) groups respectively. This series of phosphines was compared with tricyclohexylphosphine and triphenylphosphine to study the effect of increasing the number of triazoles appended to the central phosphorus atom from zero to three triazoles. Gold(I) chloride complexes of the synthesised ligands were prepared and analysed by techniques including single‐crystal X‐ray diffraction structure determination. Gold(I) complexes were also prepared from 1‐(2,6‐dimethoxy)‐phenyl‐5‐dicyclohexyl‐phosphino 1,2,3‐triazole and 1‐(2,6‐dimethoxy)‐phenyl‐5‐diphenyl‐phosphino 1,2,3‐triazole ligands. The crystal structures thus obtained were examined using the SambVca (2.0) web tool and percentage buried volumes determined. The effectiveness of these gold(I) chloride complexes to serve as precatalysts for alkyne hydration were assessed. Furthermore, the regioselectivity of hydration of but‐1‐yne‐1,4‐diyldibenzene was probed.

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“…Benzene (C 6 D 6 ) was dried over sodium, while CDCl 3 and CD 2 Cl 2 were dried over molecular sieves (4 Å) and distilled under nitrogen. Compounds PMe 2 Ar′, 68 AuCl(THT) (THT = tetrahydrothiophene), 69 Au(PPh 3 )(NTf 2 ), 70 , 71 Au(PPh 3 )(NO 3 ), 72 , 73 AuCl(XPhos), 74 AuCl( t BuXPhos), 75 Au(XPhos)(NTf 2 ), 76 − 78 Au( t BuXPhos)(NTf 2 ), 78 AuCl(PMe 2 Ar Xyl2 ), 62 AuCl(PMe 2 Ar Dipp2 ), 46 AuCl(PMe 2 Ar Tripp2 ), 79 Au(PMe 2 Ar Xyl2 )(NTf 2 ), 62 Au(PMe 2 Ar Dipp2 )(NTf 2 ), 46 Au(PMe 2 Ar Tripp2 )(NTf 2 ), 79 Au(CH 3 )(PMe 2 Ar Dipp2 ) 46 ( 1c ), and [Au 2 (μ-CH 3 )(PMe 2 Ar Dipp2 ) 2 ][NTf 2 ] 46 ( 4c ) were prepared according to previously reported procedures. Compounds 1e and 1f were prepared according to the general method described below in yields of around 75%, exhibiting identical spectroscopic data to those previously reported.…”

Section: Experimental Sectionmentioning

confidence: 99%

Reductive C–C Coupling from Molecular Au(I) Hydrocarbyl Complexes: A Mechanistic Study

Miranda-Pizarro

¹

,

Luo

²

,

Moreno

³

et al. 2021

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Organometallic gold complexes are used in a range of catalytic reactions, and they often serve as catalyst precursors that mediate C–C bond formation. In this study, we investigate C–C coupling to form ethane from various phosphine-ligated gem-digold(I) methyl complexes including [Au 2 (μ-CH 3 )(PMe 2 Ar′) 2 ][NTf 2 ], [Au 2 (μ-CH 3 )(XPhos) 2 ][NTf 2 ], and [Au 2 (μ-CH 3 )( t BuXPhos) 2 ][NTf 2 ] {Ar′ = C 6 H 3 -2,6-(C 6 H 3 -2,6-Me) 2 , C 6 H 3 -2,6-(C 6 H 2 -2,4,6-Me) 2 , C 6 H 3 -2,6-(C 6 H 3 -2,6- i Pr) 2 , or C 6 H 3 -2,6-(C 6 H 2 -2,4,6- i Pr) 2 ; XPhos = 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl; t BuXPhos = 2-di- tert -butylphosphino-2′,4′,6′-triisopropylbiphenyl; NTf 2 = bis(trifluoromethyl sulfonylimide)}. The gem-digold methyl complexes are synthesized through reaction between Au(CH 3 )L and Au(L)(NTf 2 ) {L = phosphines listed above}. For [Au 2 (μ-CH 3 )(XPhos) 2 ][NTf 2 ] and [Au 2 (μ-CH 3 )( t BuXPhos) 2 ][NTf 2 ], solid-state X-ray structures have been elucidated. The rate of ethane formation from [Au 2 (μ-CH 3 )(PMe 2 Ar′) 2 ][NTf 2 ] increases as the steric bulk of the phosphine substituent Ar′ decreases. Monitoring the rate of ethane elimination reactions by multinuclear NMR spectroscopy provides evidence for a second-order dependence on the gem-digold methyl complexes. Using experimental and computational evidence, it is proposed that the mechanism of C–C coupling likely involves (1) cleavage of [Au 2 (μ-CH 3 )(PMe 2 Ar′) 2 ][NTf 2 ] to form Au(PR 2 Ar′)(NTf 2 ) and Au(CH 3 )(PMe 2 Ar′), (2) phosphine migratio...

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A Gold Carbene Manifold to Prepare Fused γ‐Lactams by Oxidative Cyclisation of Ynamides

Cited by 39 publications

References 59 publications

Nitrene Transfer and Carbene Transfer in Gold Catalysis

Nitrene Transfer and Carbene Transfer in Gold Catalysis

Balancing Bulkiness in Gold(I) Phosphino‐triazole Catalysis

Reductive C–C Coupling from Molecular Au(I) Hydrocarbyl Complexes: A Mechanistic Study

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