Polar Effects. X. Polar Substituent Effects in the Solvolysis of 3‐Substituted 1‐Adamantyl Bromides and Toluenesulfonates

Grob, C. A.; Schaub, Bruno

doi:10.1002/hlca.19820650606

Cited by 28 publications

(24 citation statements)

References 27 publications

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“…This is ca. twice the p, of -1.26 reported for the mono-substituted tosylates 1 (X = OTs) [2] (Figure, upper line)12). Hence, the inductivity, i.e.…”

mentioning

confidence: 64%

“…), namely inductive, hyperconjugative, frangomeric, and homohyperconjugative effects [ 1] [2]. This follows from the reaction products and from the relationship between the rate constants k (in 80% EtOH) and the inductive constants o; [3] of the substituents.…”

Section: ~ ~~~~mentioning

confidence: 99%

“…The point for the electrofugal substituent R = CH,OH corresponds to an acceleration of 4 [2] and was omitted in Fig. 1.…”

mentioning

confidence: 99%

“…Finally, the rates of 3-substituted adamant-1-yl bromides and tosylates 1 were 4 to 26 times higher than predicted by their O: values for R = CH,OH, COOQ, or (CH,),Sn [ 1] [2]. ') According to the equation log k = pl.rri' + log k,.…”

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confidence: 99%

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Polar Effects. Part 15. Twin γ‐substituent effects in the formation of adamantyl‐1‐cations

Grob

Gründel

Sawlewicz

1988

Helvetica Chimica Acta

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~ ~~~~Solvolysis rates of several adamant-I-yl ( = tri~yclo[3.3.1.1~~~]dec-l-yl) p-toluenesulfonates and bromides 2 identically substituted at C(3) and C(5) (twin substitution) have been determined and compared with the rates of the corresponding 3-monosubstituted compounds 1. As expected, the rate factors for twin substitution are much larger, but less than the square of the rate factors for single substitution. Also the rate factors per substitutent in 2 are considerably smaller than those for one substituent in 1. This attenuation is attributed to electron repulsion which limits the convergence of electron density to the cationic center. On the other hand, the inductivity for twin substitution @I = -2.55) is ea. twice as high as for mono-substitution @I = -1.26).Four kinds of polar substituent effects are discernible in solvolysis reactions of 3-substituted adamant-1-yl ( = tricyclo[3.3.1.13~7]dec-l-yl) bromides and tosylates ( = ptoluenesuljonates) 1 (X = Br and OTs, resp.), namely inductive, hyperconjugative, frangomeric, and homohyperconjugative effects [ 1] [2]. This follows from the reaction products and from the relationship between the rate constants k (in 80% EtOH) and the inductive constants o; [3] of the substituents. Alkyl groups and common electron-attracting substituents like COOCH,, OAc, Br, CN, and NO, as well as H-C(3) control rates of forination of the adamant-1-yl cations 5 by their inductive ( I ) effects only, as shown by the linear correlation of log k with the corresponding 07 values '). The latter were derived from the pK, values of 4-substituted quinuclidinium perchlorates 4 [3] which are also controlled by 1 effects.On the other hand, rates were 3 to 44 times higher than calculated from the regression line for log k us. 07, when R was a + M substituent or n electron donor such as OH, OCH,, or SCH,. These exalted polar substituent effects were attributed to C,C hyperconjugative relay of positive charge from the cationic center C( 1) to the substituents in the incipient cations 6 (the dotted lines imply weak bonding interactions). However, if the + M effect of the substituents were stronger, as in 1 (R = NH,, 0-, or S-), C,C hyperconjugation merged with concerted fragmentation [4] and led to accelerated formation of the corresponding bicyclic compounds 8 (R = NH:, 0, or S, resp.). In these cases, formula 6 represents the transition state for fragmentation to 8.Finally, the rates of 3-substituted adamant-1-yl bromides and tosylates 1 were 4 to 26 times higher than predicted by their O: values for R = CH,OH, COOQ, or (CH,),Sn [ 1][2].') According to the equation log k = pl.rri' + log k,.

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“…This is ca. twice the p, of -1.26 reported for the mono-substituted tosylates 1 (X = OTs) [2] (Figure, upper line)12). Hence, the inductivity, i.e.…”

mentioning

confidence: 64%

Section: ~ ~~~~mentioning

confidence: 99%

“…The point for the electrofugal substituent R = CH,OH corresponds to an acceleration of 4 [2] and was omitted in Fig. 1.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Polar Effects. Part 15. Twin γ‐substituent effects in the formation of adamantyl‐1‐cations

Grob

Gründel

Sawlewicz

1988

Helvetica Chimica Acta

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“…Support for this hypothesis comes from the following study of the rates and products of the 7-anti-substituted 2-endo-and 2-exo-norbornyl tosylates 11 and 12 (a-h), respectively. While the number of intervening bonds and the direct distances between R and C(2) are the same in all four compounds 1, 2, 11 and 12 the strains which accompany bridging of C(2) with C(6) and C (7), respectively, 3,…”

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confidence: 94%

Carbon Participation in the Solvolysis of 6‐ and 7‐Substituted 2‐Norbornyl p‐Toluenesulfonates. Norbornanes, Part 11

Flury

Grob

1983

Helvetica Chimica Acta

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SummaryThe solvolysis rates and products of several 7-anti-substituted 2-endo-norbornyl p-toluenesulfonates 11 have been determined and compared with those of the previously reported 6-exo-substituted 2-exo-norbornyl p-toluenesulfonates 1. Although the number of bonds between the substituent and the reaction site is the same in the two series, the inductive effect of the substituents is transmitted far more strongly in the 6-exo-2-exo-series 1 than in the 7-anti-2-endo-series 11; i.e. their inductivities differ widely. It is concluded that through space induction involves graded bridging of the substituent-bearing C-atom to the incipient cationic center at C (2) and that this involves differential bridging strain. The different reactivities of unsubstituted 2-exo-and 2-endo-norbornyl derivatives can then be ascribed to a stereoelectronic effect.

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Ruthenium tetraoxide mediated reactions: The mechanisms of oxidations of hydrocarbons and ethers

Bakke

Frøhaug

1996

J. Phys. Org. Chem.

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The reaction mechanisms for the Ru0,-mediated oxidations of saturated hydrocarbons and of ethers were investigated. For both groups of compounds the kinetic influence of the reaction medium and of substituents near the reaction centre was determined together with deuterium isotope effects. The results do not support reaction mechanisms with carbocation intermediates. Reactions by radical pair intermediates are only possible if these collapse at rates faster than lO*s-'. For the oxidation of hydrocarbons the data fit a two step mechanism, a pre-equilibrium followed by a rate-determining concerted reaction. The results from the oxidation of ethers can be explained by a concerted, S,t-like type of reaction.

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Polar Effects. X. Polar Substituent Effects in the Solvolysis of 3‐Substituted 1‐Adamantyl Bromides and Toluenesulfonates

Cited by 28 publications

References 27 publications

Polar Effects. Part 15. Twin γ‐substituent effects in the formation of adamantyl‐1‐cations

Polar Effects. Part 15. Twin γ‐substituent effects in the formation of adamantyl‐1‐cations

Carbon Participation in the Solvolysis of 6‐ and 7‐Substituted 2‐Norbornyl p‐Toluenesulfonates. Norbornanes, Part 11

Ruthenium tetraoxide mediated reactions: The mechanisms of oxidations of hydrocarbons and ethers

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