Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes

Marsden, Stephen P.; Ducept, Pascal

doi:10.1186/1860-5397-1-5

Cited by 9 publications

(6 citation statements)

References 30 publications

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“…[10] The silylation of diazomethyl ketones 1a-c with trimethylsilyl triflate or triethylsilyl triflate and diisopropylethylamine in ether or diethyl ether/pentane mixtures provided the corresponding α-silyl α-diazo ketones 2a-e (Scheme 1). The synthesis of 2b and 2d by this method has been described before, [4,8] but in the present study we prepared only concentrated solutions of 2a-e that were suitable for further transformations (see below). It should be recalled that no α-Scheme 1.…”

Section: Resultsmentioning

confidence: 99%

“…(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) practical method to prepare α-silyl α-diazo ketones. [4,8,9] Typically, diethyl ethyl ether is used as the reaction medium, from which most (but not all) of the formed trialkylammonium triflate precipitates as the reaction proceeds. In order to avoid protonation/desilylation of the product by the acidic ammonium salt, Danheiser et al have used the less polar reaction medium diethyl ether/hexane (1:1), in which the ammonium salt is less soluble, and in fact obtained the silyldiazo ketones in higher yields.…”

Section: Resultsmentioning

confidence: 99%

“…Usually, silyl ketenes are prepared from silyldiazo ketones such as 2 in an additional step by a photochemical [10,14,15] or transition-metal (copper [14] or rhodium [4] ) catalyzed Wolff rearrangement. Attempts to isolate silyldiazo ketone 2c met with another surprise (Scheme 4): diazo ketone 1b was trimethylsilylated in ether in the presence of NEtiPr 2 as usual, the precipitated ammonium salt was filtered off, and the solvent was removed completely.…”

Section: Resultsmentioning

confidence: 99%

“…[1,2] For example, trialkylsilyl ketenes can be transformed into allenylsilanes with phosphonium ylides by Wittig olefination [3,4] and also with organometallic methylenation reagents. [4] The long-known [5] reactivity of ketenes towards diazoalkanes has also been extended to silyl ketenes. [1,2] Of particular interest to the present study are reactions between (diazomethyl)trialkylsilanes and trimethylsilyl ketene, which afford 1-trimethylsilyl-2-trialkylsilylcyclopropanones.…”

Section: Introductionmentioning

confidence: 99%

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Aryl Trialkylsilyl Ketenes: Acid‐Catalyzed Synthesis from 1‐Aryl‐2‐diazo‐2‐trialkylsilylethanones and Their Conversion into 3‐Silyl‐1‐silyloxyallenes

2008

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Aryl‐substituted α‐silyl α‐diazo ketones are readily transformed into aryl silyl ketenes in the presence of a catalytic amount of triflic acid. Thus, a convenient method to prepare these silyl ketenes becomes available, which combines two steps, silylation of an aryl diazomethyl ketone and acid‐induced Wolff rearrangement of the formed α‐silyl α‐diazo ketone, in a one‐pot procedure. It appears that the trialkylammonium salt, which is formed in the silylation step, can also catalyze the Wolff rearrangement, but distinctly more slowly than the proton acid. The silyl ketenes react smoothly with α‐silyl α‐diazo ketones to form 3‐silyl‐1‐silyloxyallenes in fairly good yields. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Aryl Trialkylsilyl Ketenes: Acid‐Catalyzed Synthesis from 1‐Aryl‐2‐diazo‐2‐trialkylsilylethanones and Their Conversion into 3‐Silyl‐1‐silyloxyallenes

2008

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“…For trapping by other external nucleophiles, the silylketene 4 a was prepared on a 3 mmol scale without incident (Scheme ). The crude reaction mixture was treated with several heteronucleophiles, including water, benzylamine, and ethanol . All the reactions proceeded smoothly to afford the carboxylic acid 13 , the carboxamide 14 and the ester 15 , respectively, in good yields.…”

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

et al. 2019

View full text Add to dashboard Cite

Gold-catalyzed oxidations of alkynes by N-oxides offer a direct access to reactive α-oxo gold carbene intermediates from benign and readily available alkynes instead of hazardous diazo carbonyl compounds. Despite various versatile synthetic methods developed based on this strategy, one of the hallmarks of α-oxo carbene/carbenoid chemistry, i.e., the Wolff rearrangement, has not been realized in this context. This study discloses the first examples that the Wolff rearrangement can be readily realized by α-oxo gold carbenes oxidatively generated from TBS-terminated alkynes. The thus-generated silylketenes can be isolated pure or subsequently trapped by various internal or external nucleophiles in one pot to afford α-silylated carboxylic acids, their derivatives or TBS-substituted allenes.

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Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes

Abstract: Background

Cited by 9 publications

References 30 publications

Aryl Trialkylsilyl Ketenes: Acid‐Catalyzed Synthesis from 1‐Aryl‐2‐diazo‐2‐trialkylsilylethanones and Their Conversion into 3‐Silyl‐1‐silyloxyallenes

Aryl Trialkylsilyl Ketenes: Acid‐Catalyzed Synthesis from 1‐Aryl‐2‐diazo‐2‐trialkylsilylethanones and Their Conversion into 3‐Silyl‐1‐silyloxyallenes

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

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

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