Flexible and practical synthesis of 3-oxyindoles through gold-catalyzed intermolecular oxidation of o-ethynylanilines

Shu, Chao; Li, Long; Xiao, Xinyu; Yu, Yanlin; Ping, Yu; Zhou, Jin‐Mei; Ye, Long‐Wu

doi:10.1039/c4cc03565h

Cited by 65 publications

(36 citation statements)

References 81 publications

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“…In summary, by utilizing the steric strain in ring formation to achieve the control of regioselectivity, a variety of gold-catalyzed anti-Markovnikov cycloisomerization-initiated tandem reactions have been developed, providing a facile and efficient way for the construction of various synthetically useful heterocycles, especially the optically active N-heterocycles by combining the chiral tert-butylsulfinimine chemistry and gold catalysis [65][66][67][68][69][70][71][72][73][74][75]. In our opinion, this study will continue to be a very exciting area for the expedient synthesis of valuable heterocycles [76].…”

Section: Discussionmentioning

confidence: 99%

Ring strain strategy for the control of regioselectivity. Gold-catalyzed anti-Markovnikov cycloisomerization initiated tandem reactions of alkynes

Shu

Tan

et al. 2017

Science Bulletin

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Section: Discussionmentioning

confidence: 99%

Ring strain strategy for the control of regioselectivity. Gold-catalyzed anti-Markovnikov cycloisomerization initiated tandem reactions of alkynes

Shu

Tan

et al. 2017

Science Bulletin

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“…In 2010, we reported that highly electrophilic α‐oxo gold carbene intermediates could be generated by intermolecular oxidation of benign alkynes instead of from hazardous diazo ketones (Scheme B) . The safety benefit of this strategy and the new approach to α‐oxo gold carbenes and their novel chemistry spurred a diverse range of subsequent studies by us and others, and established that the gold carbene intermediates, or in some cases their precursors, can undergo insertions into O−H, N−H, B−H, and even unactivated C−H bonds,, and cyclopropanate alkenes,,, including electron‐deficient ones, as well as undergo electrophilic arene substitutions or Buchner reactions, and the formation of ylides . Despite these advances, no Wolff‐type rearrangement involving these oxidatively generated α‐oxo gold carbenes has been reported to date.…”

Section: Methodsmentioning

confidence: 99%

Wolff Rearrangement of Oxidatively Generated α‐Oxo Gold Carbenes: An Effective Approach to Silylketenes

et al. 2019

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Gold-catalyzed oxidationso fa lkynes by N-oxides offer direct access to reactive a-oxo gold carbene intermediates from benign and readily available alkynes instead of hazardous diazoc arbonyl compounds.D espite various versatile synthetic methods developed based on this strategy,one of the hallmarks of a-oxo carbene/carbenoid chemistry,t hat is,t he Wolff rearrangement, has not been realized in this context. This study discloses the first examples that show the Wolff rearrangement can be readily realized by a-oxo gold carbenes oxidatively generated from TBS-terminated alkynes (TBS = tert-butyldimethylsilyl). The thus-generated silylketenes can be either isolated pure or subsequently trapped by various internal or external nucleophiles in one pot to afford a-silylated carboxylic acids,t heir derivatives,o rT BS-substituted allenes.The Wolff rearrangement [1] is one of the classical transformations of a-diazo ketones [2] and has been extensively studied and widely employed in organic synthesis (Scheme 1A). [3] Thek etene generated in this powerful reaction is ar eactive intermediate of exceptional synthetic value.T he main drawback of the reaction, however, is the use of diazo ketone substrates,w hich are hazardous and potentially explosive,b ut necessary to access highly reactive a-oxo carbenes/carbenoids or undergo concerted conversion (Scheme 1A).In 2010, [4] we reported that highly electrophilic a-oxo gold carbene intermediates could be generated by intermolecular oxidation of benign alkynes instead of from hazardous diazo ketones (Scheme 1B). [5] Thesafety benefit of this strategy and the new approach to a-oxo gold carbenes and their novel chemistry spurred ad iverse range of subsequent studies by us [4][5][6] and others, [7] and established that the gold carbene intermediates,orinsome cases their precursors,can undergo insertions into O À H, [4,6a] N À H, [7c] B À H, [7j] and even unactivated CÀHb onds [6f,g, 7a,d, 8] and cyclopropanate alkenes, [6d,e, 7g,h] including electron-deficient ones, [6e, 7g] as well as undergo electrophilic arene substitutions [6c, 7e] or Buchner reactions, [6h] and the formation of ylides. [7f, 9] Despite these advances,n o Wolff-type rearrangement involving these oxidatively generated a-oxo gold carbenes has been reported to date.H erein, we disclose af irst example,w hich offers one-step access to stable yet versatile silyl ketenes from readily available TBSterminated alkynes (Scheme 1C).In 2015, we reported that acyl/acyl-substituted gold carbenes generated upon gold-catalyzed oxidation of enones undergo insertions into unactivated C À Hb onds. [6f] In our effort to expand the C À Hinsertion chemistry,weexamined as substrates silyl-terminated alkynes including silylated 3phenyl-1-propyne (1). As shown in Table 1, entry 1, with the silyl group of 1 as TBS,IPrAuNTf 2 (5 mol %) as the catalyst, and 8-isopropylquinoline N-oxide as the oxidant, the goldcatalyzed oxidation occurred smoothly overnight to deliver three identifiable products.A mong them, the silylated indano...

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“…Most importantly, this protocol circumvents the use of hazardous and potentially explosive diazo carbonyl compounds, and makes alkynes as equivalents of α‐diazo ketones. In our recent study toward such a gold‐catalyzed oxidative cyclization,10 we reported a gold‐catalyzed intermolecular oxidation of o ‐ethynylanilines for the synthesis of synthetically useful 3‐oxyindoles, which outcompetes the typical indole formation 10c. Inspired by these results, we envisioned that the synthesis of 3‐coumaranones might be accessed directly from the corresponding o ‐ethynylphenol substrates by using a similar strategy (Scheme ) 11.…”

Section: Methodsmentioning

confidence: 99%

Für die Energiewende studieren

2014

Chemie in nserer Zeit

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Flexible and practical synthesis of 3-oxyindoles through gold-catalyzed intermolecular oxidation of o-ethynylanilines

Abstract: A novel gold-catalyzed intermolecular oxidation of o-ethynylanilines has been developed. A range of functionalized 3-oxyindoles are readily accessed by utilizing this strategy. Importantly, this gold-catalyzed oxidative process outcompetes the typical indole formation.

Cited by 65 publications

References 81 publications

Ring strain strategy for the control of regioselectivity. Gold-catalyzed anti-Markovnikov cycloisomerization initiated tandem reactions of alkynes

Ring strain strategy for the control of regioselectivity. Gold-catalyzed anti-Markovnikov cycloisomerization initiated tandem reactions of alkynes

Wolff Rearrangement of Oxidatively Generated α‐Oxo Gold Carbenes: An Effective Approach to Silylketenes

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