Bridgehead adamantyl, diamantyl, and related cations and dications

Oláh, George A.; Prakash, G. K. Surya; Shih, Joseph G.; Krishnamurthy, V. V.; Mateescu, Gheorghe D.; Liang, Gao; Sipos, György; Buß, Volker; Gund, Tamara; Schleyer, Paul von Ragué

doi:10.1021/ja00295a032

Cited by 94 publications

(60 citation statements)

References 7 publications

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“…1 and 2, cation A is shown to be involved in three processes: (1) a degenerate rearrangement involving an exo-3,2-hydride shift, (2) an irreversible rearrangement to the 1-adakantyl cation, and (3) a reaction sequence shown as This maximum AGZ estimate is reasonably in line with measured barriers of ca. 11 kcal/mol for this same overall rearrangement mechanism involving a number of different polymethyl-2-norbomyl cations (6).…”

Section: Resultssupporting

confidence: 72%

“…However, when one prepares cations from logical precursors of both A and D, only a single ion appears to be formed. This cation (the stereochemistry undefined) was originally prepared by Olah and co-workers in 1964 (1) and shown to rearrange to the 1-adamantyl cation R. In 1985, a full paper appeared (2), in which the cation was assigned the A structure. Our laboratory also studied this cation briefly a number of years ago (13c NMR), but with recent advances in NMR spectroscopy we have now undertaken a more complete study.…”

Section: Resultsmentioning

confidence: 99%

“…T h e reactive intermediates in this process are carbocations, and the overall reaction is "driven" by the thermodynamic stability skeleton by converting all o f the starting skeleton 2 to an observable carbocation, and this has also been shown to rearrange to the 1-adamantyl cation (1,2). In this case, almost all of the organic material exists as cloHT5 carbocations, with negligible amounts of neutral hydrocarbons present at any given time.…”

Section: Introductionmentioning

confidence: 99%

“…An alternative to a direct shift could proceed by way of two separate steps, an exo-1,2-hydride shift from the other side of the cation, followed by a 1,3-hydride shift, as shown in eq. [2] (the number description of hydride shifts is generic and does not refer to the actual carbon-hydrogen skeletons involved): Can. J. Chem.…”

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confidence: 99%

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A mechanistic study of the carbocation route from tetrahydrodicyclopentadiene to the adamantane ring

Kirchen¹,

Sorensen²,

Whitworth³

1993

Can. J. Chem.

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. Can. J. Chem. 71, 2016Chem. 71, (1993. The energy profile for the transformation of the endo-tetrahydrodicyclopentadienyl cation A into the 1-adamantyl cation R has been probed by means of six separate experiments employing superacid techniques. Of the approximately 14 cations between A and R , required as intermediates for the above transformation, it can be shown that only one of these is capable of direct observation. This cation, the tricyclo[5.2.1.03~8]dec-3-yl (homobrendyl) cation J , is characterized in detail in one of the six experiments. The rate of the rearrangement of J into the 1-adamantyl cation has been measured. Cation J also undergoes a degenerate rearrangement, the dynamics of which can be probed using NMR line-broadening and selective inversion-recovery experiments. The relationship between the exo and endo tetrahydrodicyclopentadienyl cations D and A has been studied. Only A is directly observable, even though in some experiments direct precursors of D were used as cation sources. Several experimental probes were made in an attempt to detect the presence of a small equilibrium concentration of D, without success, and a rationale is provided for the much greater stability of A vs. D. The remaining four experiments involved the addition of neutral precursors to superacid solutions, but the initially formed (expected) cations could not be observed, only cations A, J, or R being observed instead. These "partitioning3'-type experiments prove whether the corresponding left-hand or right-hand transition-state barriers are the lower in energy. In the case of starting with transient cation intermediate E, only observable cation J is obtained, showing that the barrier between B and E is the high point on the overall carbocation reaction profile. sans succks plusieurs sondes expkrimentales; on presente une rationalisation de la stabilite beaucoup plus grande de A par rapport a D. Les quatre dernikres expkriences impliquent ['addition de precurseurs neutres a des solutions de superacides; lorsque les cations formes (attendus) initialement n'ont pu &tre observes, seuls les cations A, J ou R ont etC observes. Ces expkriences de <> ont permis de determiner si les bamkres <> ou <

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Section: Resultssupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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A mechanistic study of the carbocation route from tetrahydrodicyclopentadiene to the adamantane ring

Kirchen¹,

Sorensen²,

Whitworth³

1993

Can. J. Chem.

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“…Of particular interest is the bridgehead 1-adamantyl cation, which has been prepared and characterized under long-lived stable ion conditions (2). The bridgehead 1-adamantyl cation is stabilized by COC hyperconjugation.…”

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confidence: 99%

Density functional theory study of adamantanediyl dications C₁₀H₁₄²⁺andprotio-adamantyl dications C₁₀H₁₆²⁺

Rasul

Oláh

Prakash

2004

Proc. Natl. Acad. Sci. U.S.A.

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Structures of the isomeric adamantanediyl dications C10H14 2؉ and protio-1-and protio-2-adamantyl dications C10H16 2؉ were investigated by using the density functional theory (DFT) method at the B3LYP͞6 -31G** level. Four structures, 1 b-e, were found to be minima on the potential energy surface of C10H14 2؉ . The 1,3-adamantanediyl dication 1b with two bridgehead tertiary carbocationic centers was found to be the most stable structure. On the potential energy surface of C10H16 2؉ (protonated adamantly cation), five structures, 2 b-f, were found to be minima. Each of the structure contains a two-electron, three-center bond. The COC protonated 1-adamantyl dication, 2f, was characterized as the most stable structure. 13 C NMR chemical shifts of the structures were also calculated by using gaugeincluding atomic orbital-density functional theory and gauge-including atomic orbital-self-consistent field methods.A damantane, C 10 H 16 i, has been used extensively as a model compound to investigate electrophilic reactions of saturated hydrocarbons. The unique structural features of adamantane are ideal for a systematic study of its cations, including both their structure and chemical reactivity. The tight interlocking of cyclohexane rings into the rigid, relatively strain free-chair conformation in adamantane makes it stable against deprotonation, prohibiting the easy formation of double bonds and back-side (nucleophilic or electrophilic) attack (1).Of particular interest is the bridgehead 1-adamantyl cation, which has been prepared and characterized under long-lived stable ion conditions (2). The bridgehead 1-adamantyl cation is stabilized by COC hyperconjugation. X-ray crystal structural studies of the 3,5,7-trimethyl-1-adamantyl cation demonstrates the COC hyperconjugative effect elegantly (3). A series of 2,6-disubstituted 2,6-adamantanediyl dications ii (Scheme 1) (R ϭ C 6 H 5 , c-C 3 H 5 ) were also prepared in superacid media by Prakash et al. (4). The dications were stable only with stabilizing groups such as phenyl and cyclopropyl. Attempts to generate the unsubstituted secondary dication ii (R ϭ H) were unsuccessful (4). The previously attempted preparation of the 1,3-adamantanediyl dication in superacid solutions were also unsuccessful (3).We now report density functional theory (DFT) studies (5) of the possible isomeric adamantanediyl dications C 10 H 14 2ϩ and protio-adamantyl dications C 10 H 16 2ϩ , hitherto not yet observed as persistent long-lived species. Superelectrophilic (6) COH or COC protonation of the adamantyl cation is also possible and can lead to extremely reactive protio-adamantyl dications. Previously, we have been able to show by hydrogen͞deuterium exchange experiments and theoretical calculations that the tertbutyl (7) as well as isopropyl (8) cations can undergo COH protonation in superacids to form the activated highly electrondeficient gitonic carbenium-carbonium dications protio-tertbutyl and protio-iso-propyl dications, respectively (Scheme 2). ‡

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Synthesis and characterization of tough polycyclic polyamides containing 4,9-Diamantyl moieties in the main chain

Chern¹,

Wang²

1996

J. Polym. Sci. A Polym. Chem.

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Bridgehead adamantyl, diamantyl, and related cations and dications

Cited by 94 publications

References 7 publications

A mechanistic study of the carbocation route from tetrahydrodicyclopentadiene to the adamantane ring

A mechanistic study of the carbocation route from tetrahydrodicyclopentadiene to the adamantane ring

Density functional theory study of adamantanediyl dications C₁₀H₁₄²⁺andprotio-adamantyl dications C₁₀H₁₆²⁺

Synthesis and characterization of tough polycyclic polyamides containing 4,9-Diamantyl moieties in the main chain

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Bridgehead adamantyl, diamantyl, and related cations and dications

Cited by 94 publications

References 7 publications

A mechanistic study of the carbocation route from tetrahydrodicyclopentadiene to the adamantane ring

A mechanistic study of the carbocation route from tetrahydrodicyclopentadiene to the adamantane ring

Density functional theory study of adamantanediyl dications C10H142+andprotio-adamantyl dications C10H162+

Synthesis and characterization of tough polycyclic polyamides containing 4,9-Diamantyl moieties in the main chain

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Density functional theory study of adamantanediyl dications C₁₀H₁₄²⁺andprotio-adamantyl dications C₁₀H₁₆²⁺