2-Acetoxy-2-methoxy-5,5-dimethyl-Δ<sup>3</sup>-1,3,4-oxadiazoline and acetoxy(methoxy)carbene

Czardybon, Wojciech; Kłys, Arkadiusz; Warkentin, John

doi:10.1139/v03-126

Cited by 9 publications

(6 citation statements)

References 10 publications

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“…Δ 3 -1,3,4-Oxadiazolines are popular and versatile sources of free carbenes that can be liberated by either photolysis or thermolysis. − ,− The diastereomeric precursors r - 10 and s - 10 were used separately herein to generate carbene 1 (Figure ). They were dissolved in either PhC(O)H or PhC(O)Me and heated to T = 165 °C until fully decomposed (Scheme ).…”

Section: Results and Discussionmentioning

confidence: 99%

“…A solution of oxadiazoline s-10 (0.150 g, 0.720 mmol) in PhC(O)Me (7 mL) was stirred in a pressure tube for 4 h at T = 165 °C, and the product was isolated by column chromatography using hexane/EtOAc (4:1) eluant to yield ketone r-12b (0.113 g, 69%) as a white solid. (5), 197 (7), 183 (15), 172 (25), 158 (41), 144 (100), 129 (37), 115 (33), 105 (9), 91 (36), 79 (24), 65 (6)…”

Section: ■ Conclusionmentioning

confidence: 99%

“…are popular and versatile sources of free carbenes that can be liberated by either photolysis or thermolysis [71][72][73][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114][115]. The diastereomeric precursors r-10 and s-10 were used separately herein to generate carbene 1(Figure 4).…”

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confidence: 99%

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Intermolecular Reactions of a Foiled Carbene with Carbonyl Compounds: The Effects of Trishomocyclopropyl Stabilization

et al. 2015

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endo-Tricyclo[3.2.1.0(2,4)]oct-8-ylidene is a foiled carbene reaction intermediate. It was generated by thermolyzing Δ(3)-1,3,4-oxadiazoline precursors dissolved in benzaldehyde and acetophenone. The products appear to stem from direct insertion of the carbene's divalent C atom into the α-bonds of the carbonyl compounds; however, this is only superficial. The strict stereochemistry observed is due to the topologies of the reaction intermediates of the proposed two-step mechanism. Bimolecular nucleophilic addition generates bent 1,3-zwitterions. The neutral reaction intermediates undergo pinacolic rearrangements to form the observed adducts. Product ratios reflect the migratory aptitudes of the carbonyl compounds' α-substituents. The carbene reaction was modeled using DFT. The singlet carbene's bicoordinate C atom bends 31° toward the endo-fused cyclopropane bond, elongating it to r = 1.69 Å. The resulting trishomocyclopropyl HOMO{-1} is a three-center two-electron bond responsible for the electron-deficient carbene's nucleophilicity. Its calculated properties are consistent with this assertion: (1) singlet-triplet (ΔE(S-T)) energy gap of -25 kcal/mol, (2) gas-phase proton affinity (PA) value of 272 kcal/mol, (3) hard and soft acid and base (HSAB) ΔN value of -0.2 in its initial reaction with the carbonyl compounds, and (4) negative frontier orbital interaction values ΔΔE(PhC(O)H) = -4.38 eV and ΔΔE(PhC(O)Me) = -3.97 eV.

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Section: Results and Discussionmentioning

confidence: 99%

Section: ■ Conclusionmentioning

confidence: 99%

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Intermolecular Reactions of a Foiled Carbene with Carbonyl Compounds: The Effects of Trishomocyclopropyl Stabilization

et al. 2015

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“…Very fast chomatography on "old" neutral alumina (hydrated in an open beaker for 3 days) in a 15 cm × 3 cm column with hexane-EtOAc (95:5), collection of the first fraction, evaporation of the solvent immediately, and recrystallization from pentane at -20°C gave 1.3 g (46%) of colorless crystalline 4. 1 …”

Section: -Acetoxy-55 Dimethyl-2-methylthio-⌬ 3 -134-oxadiazoline (4)mentioning

confidence: 99%

“…Yield: 10%. IR (cm -1 ): 1754 1. H NMR (200 MHz, CDCl 3 ) δ : 2.12 (s, 3H), 2.24 (s, 3H), 2.36 (s, 3H), 2.42 (s, 3H).…”

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Reactions of acetoxy(methylthio)carbene and S-methyl thiopyruvate

Kłys¹,

Czardybon²,

Warkentin³

2005

Can. J. Chem.

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Thermolysis of 2-acetoxy-5,5-dimethyl-2-methylthio-∆ 3 -1,3,4-oxadiazoline in benzene at 110°C afforded Smethyl 2-oxopropanethioate (S-methyl thiopyruvate) from 1,2-acyl migration in acetoxy(methylthio)carbene, as well as S,S-dimethyl 2-acetoxy-2-methylpropanebis(thioate) and S-methyl 2-acetoxy-2-(methylthio)butanethioate. The latter two, both composed of two carbene units, are derived from reaction of the first product with the carbene.Résumé : La thermolyse de la 2-acétoxy-5,5-diméthyl-2-méthylthio-∆ 3 -1,3,4-oxadiazoline, dans le benzène à 110°C, conduit à la formation du 2-oxopropanethioate de S-méthyle (thiopyruvate de S-méthyle) qui provient d'une migration 1,2 d'un groupe acyle dans l'acétoxy(méthylthio)carbène, ainsi que du 2-acétoxy-2-méthylpropanebis(thioate) de S,S-diméthyle et du 2-acétoxy-2-(méthylthio)butanethioate de S-méthyle. Ces deux derniers produits, qui sont formés de deux unités de carbène, dérivent de la réaction du premier produit avec le carbène.

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Cyclopentanes from N‐Aminoglyconolactams: Reaction Mechanism and Improved Access to Diazocyclopentanones

Vasella

2004

Helvetica Chimica Acta

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One of the two mechanisms to rationalize the Pb(OAc) 4 oxidation of 1 to 2 and 3 postulates the intermediate generation of a carbene 25 via the acetoxy-diazepinone 22 and the oxadiazoline 23 (Scheme 2). This mechanism was excluded on the basis of the oxidation of the diazepinone 32 that was synthesized in six steps from the ribonolactone 26. Oxidation of 32 with Pb(OAc) 4 provided the unstable acetoxy-diazepinone intermediate 22, its C(5) epimer, and the stable 5-O-acetyl-1,5-ribonolactone 33; the 1 H-NMR spectra of the products of the oxidation of 32 and the decomposition of 22 showed no evidence for the formation of the acetoxy epoxide 2 and the diazo ketone 3, excluding 22 as intermediate in the oxidation of 1. To increase the yield of the diazo-cyclopentanones, we oxidized the acetohydrazide 34, the 4-toluenesulfonohydrazide 44, and the N,O-diacetate 46 with Pb(OAc) 4 . Oxidation of the acetohydrazide 34 with Pb(OAc) 4 led to a higher yield of the diazo ketone 3 (40%) than oxidation of the N-amino-ribonolactam 1 without affecting the yield of 2. Oxidation of the 4-toluenesulfonohydrazide 44 gave mostly the product 45 of C-acetoxylation, while the analogous oxidation of 46 gave the acetoxy lactone 33; neither 2 nor 3 could be detected among the products, excluding 46 as intermediate of the oxidation of 34. Oxidation of the N-acetamido-lyxonolactam 47 with Pb(OAc) 4 provided the diazo ketone 8 (77 vs. 37% from 5); higher yields of diazo ketones resulted also from the oxidation of the acetohydrazides 48 and 49.

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2-Acetoxy-2-methoxy-5,5-dimethyl-Δ³-1,3,4-oxadiazoline and acetoxy(methoxy)carbene

Cited by 9 publications

References 10 publications

Intermolecular Reactions of a Foiled Carbene with Carbonyl Compounds: The Effects of Trishomocyclopropyl Stabilization

Intermolecular Reactions of a Foiled Carbene with Carbonyl Compounds: The Effects of Trishomocyclopropyl Stabilization

Reactions of acetoxy(methylthio)carbene and S-methyl thiopyruvate

Cyclopentanes from N‐Aminoglyconolactams: Reaction Mechanism and Improved Access to Diazocyclopentanones

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2-Acetoxy-2-methoxy-5,5-dimethyl-Δ3-1,3,4-oxadiazoline and acetoxy(methoxy)carbene

Cited by 9 publications

References 10 publications

Intermolecular Reactions of a Foiled Carbene with Carbonyl Compounds: The Effects of Trishomocyclopropyl Stabilization

Intermolecular Reactions of a Foiled Carbene with Carbonyl Compounds: The Effects of Trishomocyclopropyl Stabilization

Reactions of acetoxy(methylthio)carbene and S-methyl thiopyruvate

Cyclopentanes from N‐Aminoglyconolactams: Reaction Mechanism and Improved Access to Diazocyclopentanones

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2-Acetoxy-2-methoxy-5,5-dimethyl-Δ³-1,3,4-oxadiazoline and acetoxy(methoxy)carbene