Reactions of endo-3-Diazotricyclo[3.2.1.02,4]oct-6-ene, a Potential Precursor for the Generation of a Neutral C8H8 Molecule with a Pyramidally Coordinated Carbon

Mieusset, Jean‐Luc; Brinker, Udo H.

doi:10.1021/jo061082y

Cited by 7 publications

(5 citation statements)

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“…This, in turn, often correlates with its nucleophilicitya kinetic term. Although the K b values for carbenes can be determined by comparison with those of known indicators, the PA values are usually calculated using theoretical methods, like ab initio B3LYP/6-31G(d) . Hence, the abilities of different carbenes to act as electron donors during an elementary step can be estimated and arranged.…”

Section: Resultsmentioning

confidence: 99%

Intra- and Intermolecular Reaction Selectivities of γ-Substituted Adamantanylidenes

et al. 2012

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A study of adamantanylidenes having a γ-substituent (R) was undertaken to gauge how inductive and steric effects of remotely positioned functional groups influence intra- and intermolecular product selectivity. 3H-Diazirines were thermolyzed or photolyzed to generate the corresponding carbenes. On rapid heating, the resulting carbenes isomerized to 2,4-didehydroadamantanes by intramolecular 1,3-CH insertions. When R was an electron donor (R(D)) mostly asymmetric 1-substituted derivatives were produced but when it was an electron acceptor (R(A)) the symmetric 7-substituted ones were formed. When solutions were exposed to UV-A light, intermolecular adducts from the carbenes and solvent predominated with lesser amounts of intramolecular product being formed. Valence isomerization of 3H-diazirines also afforded diazo compounds. In methanol, protonation of diazo compounds to give the corresponding 2-adamantyl cations exceeds their coupling. This diversion was controlled with fumaronitrile by trapping the diazo compounds. The adducts possessed mostly anti configurations with R = R(D) and syn arrangements with R = R(A). The connection between as- and anti-product formation and that of s- and syn-products was deemed to be the consequence of a rapid equilibrium between two distinct carbene conformations. This was qualified and quantified using ab initio calculations and NBO analyses.

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Section: Resultsmentioning

confidence: 99%

Intra- and Intermolecular Reaction Selectivities of γ-Substituted Adamantanylidenes

et al. 2012

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“…“Foiled reaction” carbenes were conceived as an approach toward stabilizing the closed-shell S 1 (n,p) state of a carbene to the point that it would supersede the T 0 (n,p) state, thus becoming the ground electronic state. − Computational chemistry is an indispensable method to study short-lived reaction intermediates . It has provided insight into the nature of foiled carbenes, − such as endo -tricyclo[3.2.1.0 2,4 ]oct-8-ylidene ( 1 ) (Figure a) − and bicyclo[2.2.1]hept-2-en-7-ylidene ( 2 ) (Figure b). , Intramolecular carbene cycloaddition is foiled because the product would be greatly strained by its inverted C atom . Instead, an in-between structure is adopted.…”

Section: Introductionmentioning

confidence: 93%

“…29,30 Intramolecular carbene cycloaddition is foiled because the product would be greatly strained by its inverted C atom. 31 Instead, an in-between structure 18 is adopted.…”

Section: Introductionmentioning

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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“…The computation of higher bicyclic homologues made the authors conclude that π ‐stabilization is only preferred over conventional hyperconjugation if the carbene features a cyclopentenylidene subunit. Apart from the norbornene system, Mieusset and Brinker86 also examined the related polycyclic carbene tricyclo[3.2.1.0 2,4 ]oct‐6‐ene‐3‐ylidene ( 3 ), which is able to undergo intramolecular cyclopropanation to yield a highly strained species featuring a pyramidally tetracoordinated carbon. The barrier for this process was determined to be less than 2 kcal mol −1 at B3LYP/6‐311+G( d,p ).…”

Section: Computational Characterization Of Carbenesmentioning

confidence: 99%

Computational methods for contemporary carbene chemistry

Gerbig

Ley

2012

WIREs Comput Mol Sci

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The use of computational methods in carbene chemistry has a long-standing tradition. Indeed, the field has come a long way since the first ab initio calculations on methylene. Computations now routinely accompany most experimental studies, either to validate the obtained results or to help design appropriate experiments. Advances in computational carbene chemistry within the last decade are covered in this text, encompassing a plethora of studies on alkyl-, aryl-, halo-, and heterocarbenes (N, P, O, S) as well as on persistent triplet carbenes. Moreover, the conceptual advancements in the fields of theoretical chemistry and computing technology have enabled researchers to conduct intricate ab initio studies. The application of leading-edge theory to multireference problems, high-accuracy thermochemical evaluations, atom tunneling, and the description of bonding is thoroughly reviewed. In addition, general recommendations for the choice of an appropriate method for a specific computational problem are given. Practitioners of the art are likely to discover new computational approaches in carbene chemistry applied to various examples from the current literature. C 2012 John Wiley & Sons, Ltd.

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Reactions of endo-3-Diazotricyclo[3.2.1.0^2,4]oct-6-ene, a Potential Precursor for the Generation of a Neutral C₈H₈ Molecule with a Pyramidally Coordinated Carbon

Cited by 7 publications

References 71 publications

Intra- and Intermolecular Reaction Selectivities of γ-Substituted Adamantanylidenes

Intra- and Intermolecular Reaction Selectivities of γ-Substituted Adamantanylidenes

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

Computational methods for contemporary carbene chemistry

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