Reactions of ketenes with peracids and ozone

Crandall, Jack K.; Sojka, Stanley A.; Komin, Joyce B.

doi:10.1021/jo00929a007

Cited by 16 publications

(8 citation statements)

References 9 publications

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“…An even stronger acceleration was discovered with the homogeneous solution of KOCH 3 (18 equiv., in place of NaOCH 3 ), ketene 2 , and methanol (18 equiv.) in DMSO at 23 °C, which again produced only the methyl ester36 in less than 48 min 43. Thus, the addition of methanol to 2 is acid‐catalyzed in diglyme solution at 110 °C, but base‐catalyzed in DMSO at 23 °C.…”

Section: Resultsmentioning

confidence: 99%

“…at 110 °C for more than 2 h, whereas a parallel run with acid 3 (1.4 equiv.) in lieu of NaOCH 3 at 110 °C was complete within 125 min to produce the known36 methyl ester, t Bu 2 CHCO 2 CH 3 (yield 60 %), together with anhydride 5 (23 %) (this methyl ester could not be prepared through a direct esterification of 3 with methanol in diglyme at 110 °C over more than 10 h). These results are compatible with initial nucleophilic addition of methanol to C‐1 of 2 , followed by C‐2 protonation37–39 by acid 3 , in analogy with the addition of methanol to dimethylketene at 25 °C as catalyzed40 by weak carboxylic acids.…”

Section: Resultsmentioning

confidence: 99%

“…The higher reaction temperatures (110 °C or more) and the inability of ketene 2 to add methanol in diglyme without acid catalysis illustrate the mechanistic consequences of steric shielding in 2 . This inability disappeared upon replacement of diglyme by the more polar42 solvent DMSO: While ketene 2 still did not react with methanol (36 equiv., 7 vol.‐%) in DMSO at 23 °C within at least 2 h, the subsequent addition of solid NaOCH 3 (which is barely soluble) started the production of t Bu 2 CHCO 2 CH 3 ,36 presumably via the ester enolate t Bu 2 C=C(O – )OCH 3 and its subsequent protonation by methanol, so that the reaction appears to be catalyzed by methoxide. This clean conversion was complete after 5 h, which indicates a temperature reduction of much more than 87 °C in comparison with the total kinetic inactivity of NaOCH 3 in diglyme at 110 °C as described above.…”

Section: Resultsmentioning

confidence: 99%

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Acylation Mechanisms of DMSO/[D₆]DMSO with Di‐tert‐butylketene and Its Congeners

Knorr

2011

Eur J Org Chem

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Dimethyl sulfoxide (DMSO) and tBu 2 C=C=O in diglyme require heating to about 150°C to furnish the Pummerer-type product tBu 2 CHCO 2 CH 2 SCH 3 through a novel mechanistic variant. The "ester enolate" tBu 2 C=C(O -)-O-S + (CH 3 ) 2 arising through the reversible addition of DMSO (step 1) to C-1 of tBu 2 C=C=O must be trapped through protonation (step 2) at C-2 by a carboxylic acid catalyst to form tBu 2 CH-C(=O)-O-S + (CH 3 ) 2 so that the reaction can proceed. The ensuing cleavage (step 3) of the O-S bond and one of the C-H bonds in the -S(CH 3 ) 2 group (E2 elimination, no ylide intermediate) results in the formation of tBu 2 CHCO 2 -and H 3 CS-CH 2 + , whose combination (step 4) generates the final product. With a mixture of DMSO and [D 6 ]DMSO competing for tBu 2 C=C=O in diglyme, the small value of the kinetic H/D isotope effect (KIE) k H /k D = 1.26 at 150°C indicates that the cleavage of the C-H/C-D bonds (step 3) does not occur in the transition state with the highest free enthalpy. Therefore, the practically isotope-independent steps 1 and 2 determine

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Acylation Mechanisms of DMSO/[D₆]DMSO with Di‐tert‐butylketene and Its Congeners

Knorr

2011

Eur J Org Chem

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“…This reaction represents a unique synthesis of an acylsilane, a family of significant interest. 9 The formation of a-lactones in ketene oxidations with peracids has been observed, 10 and in some instances these react by decarbonylation, perhaps with assistance by nucleophilic attack on the a-lactone.…”

Section: Equation 13mentioning

confidence: 99%

“…(CH 3 ) 3 Si], 1.34 (t, 3 H, CH 3 , J = 7.1 Hz), 3.45 (m, 2 H, OCH 2 ), 6.48 (s, 1 H, C=CH). 13 C NMR (CDCl 3 ): d = 0.97, 2.06, 14.0, 47.1, 51.5, 62.4, 107.1, 107.6, 107.8, 109.2, 122.5, 139.9, 152.8, 163.3, 175.0, 177.4. EI-MS: m/z = 424 (M + , 2), 409 (M + -CH 3 , 13) 381 (11), 353 (12), 296 (10), 165 (10), 73 (Me 3 Si + , 100).…”

Section: Ethyl 34-bis(trimethylsilyl)benzoate (28)mentioning

confidence: 99%

Allenylketenes: Versatile Substrates in Nucleophilic, Electrophilic, and Cycloaddition Reactions

Huang¹,

Tidwell²

2000

Synthesis

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4-Methylene-2-trimethylsilyl-3-phenylcyclobutenones 3 are obtained from the corresponding cyclobutenedione 7 by Tebbe and Peterson methylenation reactions, and upon photolysis give 3-phenyl substituted allenylketenes R 1 CH=C=C(Ph)C(SiMe 3 )=C=O 4. These are more reactive in ring closure back to 3 than are the 3-trimethylsilyl analogs 1, as predicted on the basis of molecular orbital calculations. Reactions of allenylketenes 1 and 4 include addition of H 2 O followed by cyclization to form butenolides 13, addition of aniline to give allenyl carboxamide 14 and lactam 15, addition of CF 3 CO 2 H to form allenyl carboxylic acid 17, addition of Br 2 in a 1,4-fashion to give penta-2,4-dienoic acid derivatives 18, and reaction with m-chloroperbenzoic acid to give the unique allenyl acylsilane 23.[4+1]-Cycloaddition reactions of 1 and 4 with Me 3 SiCHN 2 give methylenecyclopentenones 24 and 25 while acetaldehyde undergoes BF 3 ∑OEt 2 catalyzed [2+2] cycloadditions forming b-lactones.[4+2] Cycloadditions occur with benzaldehyde to form the highly crowded exomethylene pentenolactone 29, and with TCNE forming methylenecyclohexenones 31. IntroductionWe have reported the formation of stabilized and persistent allenylketenes 1 from photolysis of 2,3-bis(trimethylsilyl)-substituted methylenecyclobutenones 2 (Eq. 1). 1a The allenylketenes were isolated as long-lived species at room temperature, but at thermal equilibrium both 1 and 2 were present in significant amounts. The stabilization of these ketenes by silyl substituents is a manifestation of the b-silicon effect, and arises from s-p hyperconjugative electron donation of the Si-C bond to the electron-deficient p-orbital of the ketene carbonyl. This stabilization has been quantified using ab initio molecular orbital calculations, and for different substituents is correlated with group electronegativities, so that the less electronegative groups are the more stabilizing. 1b,c Stabilization parameters SE for substituents on ketenes 1b,c and allenes 1c relative to hydrogen were derived from ab initio molecular orbital calculations and isodesmic reactions (Eq 2) and together with the calculated relative energies of the parent compounds give accurate predictions of the relative amounts of 1 and 2 present at thermal equilibrium. 1a The predicted preference for the depicted anti-planar geometry of 1a (R 1 = Ph) has been confirmed by X-ray crystallography. 1aAllenylketenes 1 were shown to react with nucleophilic water to form lactones (Eq. 3) 1a and with nitroxyl radicals with oxygen atom transfer, to give butenolides (Eq. 4), 1dand have considerable promise as synthetic reagents. The related 1,2-bis(ketenes), 2 vinylallenes, 3 and 1,2-bis(allenes) 4 have also attracted a great deal of recent attention in synthetic and mechanistic study. Equation 3Equation 4 Danheiser and co-workers 5 have prepared a-silylalkenylketenes 5 by Wolff rearrangements, by dehydrochlorinations, and by cyclobutenone ring opening (Eq. 5). Unsubstituted vinylketene is calculated to be of approximately equa...

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Heterocyclische Analoga von Methylencyclopropanen

L'abbé

1980

Angew. Chem.

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Dreigliedrige Heterocyclen rnit exocyclischer Doppelbindung verdienen wegen ihrer Ringspannung und ihrer faszinierenden chemischen Eigenschaften spezielles Interesse. In diesem Beitrag werden Synthesen, thermische Zersetzung, Ringoffnung und Cycloadditionen behandelt. &-Lactame, Alkylidenaziridine, Diaziridinone und Diaziridinimine gehoren zu den am besten bekannten Verbindungen dieser Art, aber auch Alkylidenoxirane und -thiirane sowie aLactone, a-Thiolactone, Thiiranimine und Aziridinimine sind in gewissem AusmaR untersucht worden. Noch nicht isoliert werden konnten Oxiranimine und Thiaziridinimine; die ersteren wurden als reaktive Zwischenstufen der thermischen Zersetzung von a-lactamen postuliert, die letzteren lieBen sich bei der Thermolyse von N-Sulfonyliminothiatriazolinen mit Doppelund Dreifachbindungssystemen abfangen. Trotz vieler Versuche konnten noch keine ThionDerivate der Titelverbindungen erzeugt werden. -Der Beitrag schlieRt rnit der Besprechung einiger offenkettiger dipolarer Spezies, die mit den dreigliedrigen Heterocyclen isomer sind.

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Reactions of ketenes with peracids and ozone

Cited by 16 publications

References 9 publications

Acylation Mechanisms of DMSO/[D₆]DMSO with Di‐tert‐butylketene and Its Congeners

Acylation Mechanisms of DMSO/[D₆]DMSO with Di‐tert‐butylketene and Its Congeners

Allenylketenes: Versatile Substrates in Nucleophilic, Electrophilic, and Cycloaddition Reactions

Heterocyclische Analoga von Methylencyclopropanen

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Reactions of ketenes with peracids and ozone

Cited by 16 publications

References 9 publications

Acylation Mechanisms of DMSO/[D6]DMSO with Di‐tert‐butylketene and Its Congeners

Acylation Mechanisms of DMSO/[D6]DMSO with Di‐tert‐butylketene and Its Congeners

Allenylketenes: Versatile Substrates in Nucleophilic, Electrophilic, and Cycloaddition Reactions

Heterocyclische Analoga von Methylencyclopropanen

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Acylation Mechanisms of DMSO/[D₆]DMSO with Di‐tert‐butylketene and Its Congeners

Acylation Mechanisms of DMSO/[D₆]DMSO with Di‐tert‐butylketene and Its Congeners