Carbon Participation in the Solvolysis of Tertiary Norbornyl Derivatives Norbornanes. Part 15. 6‐substituted 2‐methylnorbornyl 2‐<i>exo</i>‐ and 2‐<i>endo</i>‐2,4‐dinitrophenyl ethers

Mechanism of the Reaction of Trifluoromethanesulfonic Anhydride with Ketones:Reaction with Camphor Reaction of camphor (1) with trifluoromethanesulfonic anhydride (Tf20) in the absence of base yields a mixture of 2,2-bis(trifluoromethylsulfonyloxy)camphane (9), 1,2-bis(trifluoromethylsulfony1oxy)-endo-isocamphane (lo), and 2,4-bis(trifluoromethylsulfonyloxy)-endo-isocamphane (11). The ratio of these compounds depends on the reaction temperature. 9,10, and 11 could not be isolated because, during the final aqueous treatment, they undergo hydrolysis leading to 1, 1-camphenyl triflate (Z), and 4-camphenyl triflate (3). In the presence of 2,6-di-terf-butyl-4-methylpyridine (DTBMP) 2 is the main reaction product. The reaction rate is independent of the base concentration. It can be inferred that the base only neutralized the trifluoromethanesuffonic acid (TfOH), without reaction with Tf20. -Reaction of Z with TfOH in dichloromethane takes place with addition and Namefkin rearrangement. The ratio of these reactions depends on the reaction temperature. No rearrangement products are obtained in the reaction of 1 with TfOH. The reaction paths for the reaction of 1 with Tf20 are compared with those for other ketones, and some conclusions on the electronic requirements of the Namefkin rearrangement are inferred.Die Umsetzung von Trifluormethansulfonsaureanhydrid (Tf20) mit acyclischen und monocyclischen Ketonen oder Aldehyden ist die beste Methode zur Herstellung yon Vinyltriflaten, einer synthetischl) und theoretisch9 interessanten Verbindungsklasse. Die Umsetzung mit gespannten bicyclischen Ketonen fiihrt dagegen je nach Substratstruktur und Reaktionsbedingungen zu gemBistriflaten3), uic-Bistriflaten4), Briickenkopftriflatens) oder monocyclischen (seco-) Triflaten-3.Diese Umsetzungen sind vom mechanistischen Gesichtspunkt aus verhaltnismaliig wenig untersucht worden; sicher scheint die Bildung von Trifluormethylsulfonyloxy-Kationen als Zwischenstufen zu sein5.6.7). Die stereoelektronischen Bedingungen der Wagner-Meerwein-Umlagerungen bei der Umsetzung von gespannten bicyclischen Ketonen mit Tf,08) sowie deren Abhangigkeit vom Losungsmittel9) wurden schon von uns untersucht. Im folgenden erortern wir die Kinetik der Umsetzung von Campher (1) rnit Tf20, urn Ruckschliisse auf den Mechanismus zu ziehen.

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Mechanismus der Reaktion von Trifluormethansulfonsäureanhydrid mit Ketonen: Umsetzung mit Campher

Martı́nez

Vilar

Marín

et al. 1985

Chem. Ber.

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ChemInform Abstract: NORBORNANES. PART 15. CARBON PARTICIPATION IN THE SOLVOLYSIS OF TERTIARY NORBORNYL DERIVATIVES. 6‐SUBSTITUTED 2‐METHYLNORBORNYL 2‐EXO‐ AND 2‐ENDO‐2,4‐DINITROPHENYL ETHERS

Grob¹,

Waldner²

1984

Chemischer Informationsdienst

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Inductivity and Bridging in 2‐Bicyclo[2.2.2]octyl Cations. Polar Effects, Part 11

Grob

Sawlewicz

1984

Helvetica Chimica Acta

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The solvolysis rates and products of several 6-substituted 2-exo-and 2-endo-bicyclo[2.2.2]octyl p-toluenesulfonates, 12 and 13, respectively, are reported. Inductivity, as measured by the reaction constants p,, is considerably less in the exo-series 12 (p, = -1 S O ) than in the corresponding 2-exo-norbornyl p-toluenesulfonates 1 (pl = -2.0). It is proposed that, for geometrical reasons, bridging of the cationic center C(2) by C(6) is not as strong in the bicyclooctane series 12 as it is in the norbornane series 1. On the other hand, inductivity is higher in the 2-endo-bicyclooctane series 13 @, = -1.0) than in the corresponding 2-endo-norbornane series 3 @I = 0.78), probably, because in the former case bridging of C(6) is less hindered by the departing anion. The relative yields of exo-and endo-substitution products from the series 12 and 13, are in accord with graded bridging of C(6) in the incipient bicyclooctyl cations. But almost constant bridging of C(2) by C (7) is indicated in the ionization of the 2-endo-hicyclooctane series 13. Consequently, in the free unsubstituted bicyclooctane cation C(2) is bridged symmetrically by C(6) and C(7), in contrast to the current concept of 'nonclassical' two-electron-three-center bonding.According to studies of substituent effects in the solvolysis of the 2-exo-and 2endo-norbornyl p-toluenesulfonates (tosylates) 1 4 , the norbornane structure is anisotropic to the inductive ( I ) effect of substituents [l] [2a]. In fact, an evaluation of the sensitivity of the reaction rates of these tosylates to substituents at C(6) and C(7), i.e. their inductivity p,'), has led to an alternative explanation for the disparate reactivity of 2-ex0 -and 2-endo-norbornyl (NB) derivatives').Inductivity was much larger in the 6-exo-R-2-exo-NB series 1 (pl = -2.0 [la]) than in the 7-anti-R-2-endo series 2 (p, = -0.72 [le]) although the conformations and direct distances are practically the same'). It was, therefore, concluded that through-space ') Inductivity was defined as thc reaction constant p, in the equation log (klk,) = pluq, where k and k, are fmt-order rate consmiits for the substitutcd and unsubstituted tosylates, respectively, in 80% EtOH and u? i s the corresponding inductive substituent constant [3]. For recent reviews, see [2].X-ray data [&I] show that the C(2)-C(7) distance (2.40 A) in 2 is actually shorter than the C(2)-C(6) distancc (2.50 A) in 1. *) ')

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Carbon Participation in the Solvolysis of Tertiary Norbornyl Derivatives Norbornanes. Part 15. 6‐substituted 2‐methylnorbornyl 2‐exo‐ and 2‐endo‐2,4‐dinitrophenyl ethers

Cited by 7 publications

References 26 publications

Mechanismus der Reaktion von Trifluormethansulfonsäureanhydrid mit Ketonen: Umsetzung mit Campher

Mechanismus der Reaktion von Trifluormethansulfonsäureanhydrid mit Ketonen: Umsetzung mit Campher

ChemInform Abstract: NORBORNANES. PART 15. CARBON PARTICIPATION IN THE SOLVOLYSIS OF TERTIARY NORBORNYL DERIVATIVES. 6‐SUBSTITUTED 2‐METHYLNORBORNYL 2‐EXO‐ AND 2‐ENDO‐2,4‐DINITROPHENYL ETHERS

Inductivity and Bridging in 2‐Bicyclo[2.2.2]octyl Cations. Polar Effects, Part 11

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