Einfluss der γ‐Verzweigung auf Solvolysegeschwindigkeit und Fragmentierung von Alkyl‐ und Cycloalkyl‐Halogeniden und ‐Arylsulfonaten. Fragmentierungsreaktionen, 8. Mitteilung

Grob, C. A.; Schwarz, W.; Fischer, H. P.

doi:10.1002/hlca.19640470602

Cited by 37 publications

(7 citation statements)

References 44 publications

(5 reference statements)

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“…alcohols VIIa and ethyl ethers VIIb, were obtained from reaction in 80% ethanol. Other unstrained y-branched alkyl and cycloalkyl derivatives behaved likewise [6], and when a rate increase was observable it was traced to a steric effect. On the other hand when strong electron donors R, such as NH2, N (CH,)2 [8], 0- [9] and S- [ 10a] were present at C (1) of (VI) 3-br~moadamantane~), concerted fragmentation to 7-methylidenebicyclo-[3.3.…”

Section: Ch3mentioning

confidence: 88%

“…While the mechanisms of olefin-forming fragmentation reactions have been studied in detail [I] [5], no systematic investigation of inductive and CC-hyperconjugative effects in solvolysis reactions has been recorded to our knowledge. Earlier studies of the solvolysis rates and products of bromoadamantane (VI, R = H) and its alkyl derivatives VI (R= CH,, C2H5, iso-C3H7 and t-C,H9) in our laboratory [6] and by Schleyer et al [7] failed to produce evidence for CC-hyperconjugation or for fragmentation. In fact only substitution products, i.e.…”

Section: Ch3mentioning

confidence: 93%

See 1 more Smart Citation

Inductive, Hyperconjugative and Frangomeric Effects in the Solvolysis of 1‐Substituted 3‐Bromoadamantanes. Polar effects IV

Fischer¹,

Grob²

1978

Helvetica Chimica Acta

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SummaryThree kinds of polar substituent effects are observable in the solvolyses of 1-Rsubstituted 3-bromoadamantanes P I ) . This follows from the relationship between products, rate constants k in 80% ethanol, and the inductive substituent constants OF of the substituent R. Alkyl groups and electron-attracting substituents at C (1) control the rate by their inductive effects alone, since logk correlates closely with OF. However, rates are higher than predicted on the basis of the respective of values when conjugating (+ M)-substituents or electrofugal groups are attached to C(1). These exalted substituent effects are attributed to CC-hyperconjugative relay of positive charge from the cationic center at C(3) to the substituent at C(1). When the substituent is a strong electron donor ( e g 0-and s-), accelerated substitution gives way to heterolytic fragmentation, rates and products then being controlled by the frangomeric effect.Introduction. -In theory a y-substituent R can affect the rate of ionization of a tertiary alkyl halide I in three conceptually distinctive ways (Scheme 1): a) by its inductive effect which acts on the cationic center in the incipient ion pair 11; b) by a hyperconjugative effect which transfers positive charge from C ( a ) to C (7) (CC-hyperconjugation) and is superposed on the inductive effect as in 111, and c) by a frangomeric effect [l] which operates as in b) except that the positive charge generated at C(a) is completely transfered to an electrofugal fragment IV [2] with concomitant cleavage of the C@)-C(y) bond2). While reactions a) and b) lead to the substitution and elimination products typical of SN1 and E l mechanisms [4], process c) leads to olefin-forming fragmentation [ 2 ] [5].As in concerted fragmentation c), CC-hyperconjugation b) should become observable when R represents an electron donor. In fact the transition states are

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Section: Ch3mentioning

confidence: 88%

Section: Ch3mentioning

confidence: 93%

Inductive, Hyperconjugative and Frangomeric Effects in the Solvolysis of 1‐Substituted 3‐Bromoadamantanes. Polar effects IV

Fischer¹,

Grob²

1978

Helvetica Chimica Acta

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“…306°C (ref. [11] 307-308°C [54] It was then converted into 3-isopropyladamantane-1-carboxylic acid according to the procedure described above. [11] 3.7 g (16.64 mmol) of 3-isopropyladamantane-1-carboxylic acid (13) was suspended in 10 mL nitric acid and cooled to 0°C with an ice bath.…”

Section: Methodsmentioning

confidence: 99%

γ‐Aminoadamantanecarboxylic Acids Through Direct C–H Bond Amidations

et al. 2007

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Utilizing bromine‐free, direct C–H bond amidations we have synthesized a large variety of adamantane amides. Depending on the precursors used these amides directly yield pharmaceutically active aminoadamantanes or γ‐aminoadamantanecarboxylic acids after hydrolytic cleavage. Theserigid analogues of γ‐aminobutyric acid (GABA) were protected at the C‐ and N‐termini and we synthesized a number of peptides incorporating γ‐aminoadamantanecarboxylicacids in solution as well as via solid phase peptide synthesis. These peptides are promising scaffolds for applications in medicinal chemistry as well as in organocatalysis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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mentioning

confidence: 99%

“…In fact this was practically ruled out in earlier work [21] [22] which showed that the solvolysis of 1-bromoadamantane (2a) is retarded when the H-atom in 3-position is replaced by methyl groups4). When branching in 3-position did produce a rate increase, as in 14, it was traced to a steric effect [21]. On the other hand the failure of a methyl group at C(3) in 2b and 3b, or at all three 3-positions of 2 [21], to increase the rate of ionization indicates that 1,3-bridging is favored in unsubstituted 1 -adamantyl cations, for alkyl groups are not as electrofugal and hence as effective o-electron donors5) as H-atoms.…”

mentioning

confidence: 99%

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

Grob

Schaub

1982

Helvetica Chimica Acta

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SummaryThe rate constants for 3-substituted adamantyl p-toluenesulfonates 3a-3k in ethanol/water 80 : 20 correlate well with the respective inductive substituent constants up. The reaction constant p for the toluenesulfonates 3 is 10% larger than for the corresponding bromides 2, indicating somewhat more charge separation in the activation of the toluenesulfonates. Evidence is presented that stabilization of the resultant 1-adamantyl cations by induction involves graded 1,3 -bridging, which is favored when the substituent is an electrofugal group, and that stabilization by n-electron donors involves C, C-hyperconjugation. Rate ratios for the toluenesulfonates 3 and the bromides 1 exceed lo3 and are almost independent of the 3-substituents. The implications of this are discussed in the light of current hypotheses.Introduction. -As shown in recent studies [ 1-51 reaction constants p, as derived

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Einfluss der γ‐Verzweigung auf Solvolysegeschwindigkeit und Fragmentierung von Alkyl‐ und Cycloalkyl‐Halogeniden und ‐Arylsulfonaten. Fragmentierungsreaktionen, 8. Mitteilung

Cited by 37 publications

References 44 publications

Inductive, Hyperconjugative and Frangomeric Effects in the Solvolysis of 1‐Substituted 3‐Bromoadamantanes. Polar effects IV

Inductive, Hyperconjugative and Frangomeric Effects in the Solvolysis of 1‐Substituted 3‐Bromoadamantanes. Polar effects IV

γ‐Aminoadamantanecarboxylic Acids Through Direct C–H Bond Amidations

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

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