Stable carbocations. 212. On the structure of cyclopropylcarbinyl and cyclobutyl cations. 8,9-Dehydro-2-adamantyl and 2,5-dehydro-4-protoadamantyl cations

Oláh, George A.; Liang, Gao; Babiak, Kevin A.; Ford, Thomas M.; Goff, David L.; Morgan, Thomas K.; Murray, Roger K.

doi:10.1021/ja00473a027

Cited by 10 publications

(5 citation statements)

References 7 publications

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“…For small molecules, an analogous system would be that of 8,9-dehydro-2-adamantyl with a stable carbocation at −120 °C, as confirmed via 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy. 61 However, tracking carbocations with solution or solid-state NMR techniques is not possible due to the lack of sensitivity of NMR spectroscopy to trace surface groups on HPHT ND surfaces. The lability of the C−Br bond, the unique properties of diamond, and the low concentration of water molecules under atmospheric conditions have aided this finding.…”

mentioning

confidence: 99%

“…Their DFT calculations showed a surface bond angle of 112.9° that was interpreted as having sp 2 character and described as a “radical carbon.” We interpret our findings as a possible conformation of this unique bonding environment found on brominated diamond. For small molecules, an analogous system would be that of 8,9-dehydro-2-adamantyl with a stable carbocation at −120 °C, as confirmed via 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy . However, tracking carbocations with solution or solid-state NMR techniques is not possible due to the lack of sensitivity of NMR spectroscopy to trace surface groups on HPHT ND surfaces.…”

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confidence: 99%

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Metastable Brominated Nanodiamond Surface Enables Room Temperature and Catalysis-Free Amine Chemistry

Melendrez

Lopez-Rosas

Stokes

et al. 2022

J. Phys. Chem. Lett.

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Bromination of high-pressure, high-temperature (HPHT) nanodiamond (ND) surfaces has not been explored and can open new avenues for increased chemical reactivity and diamond lattice covalent bond formation. The large bond dissociation energy of the diamond lattice–oxygen bond is a challenge that prevents new bonds from forming, and most researchers simply use oxygen-terminated NDs (alcohols and acids) as reactive species. In this work, we transformed a tertiary-alcohol-rich ND surface to an amine surface with ∼50% surface coverage and was limited by the initial rate of bromination. We observed that alkyl bromide moieties are highly labile on HPHT NDs and are metastable as previously found using density functional theory. The strong leaving group properties of the alkyl bromide intermediate were found to form diamond–nitrogen bonds at room temperature and without catalysts. This robust pathway to activate a chemically inert ND surface broadens the modalities for surface termination, and the unique surface properties of brominated and aminated NDs are impactful to researchers for chemically tuning diamond for quantum sensing or biolabeling applications.

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confidence: 99%

mentioning

confidence: 99%

Metastable Brominated Nanodiamond Surface Enables Room Temperature and Catalysis-Free Amine Chemistry

Melendrez

Lopez-Rosas

Stokes

et al. 2022

J. Phys. Chem. Lett.

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“…l-(2'-Methyl-2'-hydroxyethyl)-2a-hydroxy-3/S-methyl-3ahydroxymethylnorbornane Isopropylidene Acetal (28). The ester 27 (0.30 g) was added to a solution of lithium diisopropylamide (prepared from diisopropylamine (0.31 mL) and n-butyllithium (1 mL) in dry tetrahydrofuran (5 mL) under N2 at -78 °C). The solution was stirred for 20 min at -78 °C and methyl iodide (0.1 mL) was added.…”

Section: Methodsmentioning

confidence: 99%

Studies on terpenes. 5. Synthesis of (+)-hinesol and (+)-10-epihinesol

Chass¹,

Buddhasukh²,

Magnus³

1978

J. Org. Chem.

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“…For small molecules, an analogous system would be that of 8,9-dehydro-2-adamantyl with a stable carbocation at -120°C, as confirmed via 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy. 59 However, tracking carbocations with solution or solid-state NMR techniques is not possible due to the lack of sensitivity of NMR spectroscopy to trace surface groups on HPHT ND surfaces. The lability of the C-Br bond, the unique properties of diamond and the low concentration of water molecules under atmospheric conditions have aided this finding.…”

Section: Diamond-bromine Bond Dissociation Studies In Open Airmentioning

confidence: 99%

A metastable brominated nanodiamond surface enables room temperature and catalysis-free amine chemistry

Melendrez

Lopez-Rosas

Stokes

et al. 2022

Preprint

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Bromination of high-pressure high-temperature (HPHT) nanodiamond (ND) surfaces has not been explored and can open new avenues for increased chemical reactivity and diamond lattice covalent bond formation. The large bond dissociation energy of the diamond lattice-oxygen bond is a challenge that prevents new bonds from forming and most researchers simply use oxygen-terminated ND (alcohols and acids) as a reactive species. In this work, we transformed a tertiary alcohol-rich ND surface to an amine surface with 50% surface coverage and was limited by the initial rate of bromination. We observed that alkyl-bromide moieties are highly labile on NDs and are metastable as previously found using density functional theory. The instability of the bromine terminated ND is explained by steric hindrance and poor surface energy stabilization. The strong leaving group properties of the alkyl-bromide intermediate were found to form diamond-nitrogen bonds at room temperature and without catalysts. The chemical lability of the brominated ND surface led to efficient amination with NH3•THF at 298 K, and a catalyst-free Sonogashira-type reaction with an alkyne-amine produced an 11-fold increase in amination rate. Overlapping spectroscopies under inert, temperature-dependent and open-air conditions provided unambiguous chemical assignments. Amine-terminated NDs and folic acid were conjugated using sulfo-NHS/EDC coupling reagents to form amide bonds, confirming that standard amine chemistry remains viable. This work supports that a robust pathway exists to activate a chemically inert diamond surface at room temperature, which broadens the pathways of bond formation when a reactive alkyl-bromide surface is prepared. The unique surface properties of brominated and aminated nanodiamond reported here are impactful to researchers who wish to chemically tune diamond for quantum sensing applications or as an electron source for chemical transformations.

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Stable carbocations. 212. On the structure of cyclopropylcarbinyl and cyclobutyl cations. 8,9-Dehydro-2-adamantyl and 2,5-dehydro-4-protoadamantyl cations

Cited by 10 publications

References 7 publications

Metastable Brominated Nanodiamond Surface Enables Room Temperature and Catalysis-Free Amine Chemistry

Metastable Brominated Nanodiamond Surface Enables Room Temperature and Catalysis-Free Amine Chemistry

Studies on terpenes. 5. Synthesis of (+)-hinesol and (+)-10-epihinesol

A metastable brominated nanodiamond surface enables room temperature and catalysis-free amine chemistry

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