Electrochemical oxidation of two silyl-substituted tetrahedranes

Bo, Hong; Fox, Marye Anne; Maier, Günther; Hermann, Christian

doi:10.1016/0040-4039(95)02155-8

Cited by 6 publications

(3 citation statements)

References 13 publications

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“…Ionization from the propellane HOMO, located on the central C−C bond of 3 and 4 , leads to elongation of this “half-broken” bond (adiabatic process) and is accompanied by strain decrease in the partially distonic radical cation, making fragmentation energetically favorable. Radical cations 3 +• and 4 +• , in fact, are formed irreversibly − under adiabatic ionization of the strained hydrocarbon, and oxidation proceeds efficiently. As shown in Scheme , the oxidative fragmentation is more favorable for cyclobutane containing 3 and 4 due to larger central C−C bond elongation and more effective strain decrease in the resulting radical cations 3 +• and 4 +• .…”

Section: Resultsmentioning

confidence: 99%

Oxidative Single-Electron Transfer Activation of σ-Bonds in Aliphatic Halogenation Reactions

et al. 2000

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The reactions of a series of structurally related large-ring propellanes with iodine monochloride were studied experimentally and computationally. In the case of 1,3-dehydroadamantane (1) and [3.3.1]propellane (2) free-radical addition was observed. [3.3.2]Propellane (3) and 3,6-dehydrohomoadamantane (4), which are less prone to radical attack, selectively form products of formal double nucleophilic (oxidative) addition, e.g., dichloro (in ICl/CH2Cl2), dimethoxy (in ICl/CH3OH), and diacetamino (in ICl/CH3CN) derivatives under otherwise identical conditions. Single-electron transfer pathways involving the alkane radical cations are proposed for the activation step for aliphatic hydrocarbons with relatively low oxidation potentials such as cage alkanes. Similar mechanisms are postulated for the activation of the tertiary C−H bonds of adamantane based on H/D-kinetic isotope effect data. The latter compare well to the k H/k D value for hydrogen atom loss from the adamantane radical cation (measured 2.78 ± 0.21 and computed 2.0) and differ considerably from the kinetic isotope effects for electrophilic C−H bond activations (i.e., hydride abstraction) or for loss of a proton from a hydrocarbon radical cation (k H/k D = 1.0−1.4; computed 1.4). Hence, the reactions of alkanes with elementary halogens and other weak electrophiles (but strong oxidizers) do not necessarily involve three-center two-electron species but rather occur via successive single-electron oxidation steps. Upon C−C or C−H fragmentation, the incipient alkane radical cations are trapped by nucleophiles.

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Section: Resultsmentioning

confidence: 99%

Oxidative Single-Electron Transfer Activation of σ-Bonds in Aliphatic Halogenation Reactions

et al. 2000

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“…The radical cation generated from 216 cannot even be detected, because it immediately rearranges to the corresponding cyclobutadienyl radical cation . Similarly, the electrochemical oxidation of tri- tert -butyl(trimethylsilyl)tetrahedrane ( 220c ) proceeds irreversibly by one-electron transfer at E pa = +0.40 V with immediate fast (on the cyclic voltammetry time scale) rearrangement of the radical cation of 220c to the radical cation of the corresponding cyclobutadiene …”

Section: 3 Fused Systemsmentioning

confidence: 99%

“…178 Similarly, the electrochemical oxidation of tri-tert-butyl(trimethylsilyl)tetrahedrane (220c) proceeds irreversibly by one-electron transfer at E pa ) +0.40 V with immediate fast (on the cyclic voltammetry time scale) rearrangement of the radical cation of 220c to the radical cation of the corresponding cyclobutadiene. 179 Tricyclo 32). 180 This synthesis was of principal importance, but it had more theoretical than practical significance, because the starting material 231 was and is not readily available.…”

Section: Fused Systemsmentioning

confidence: 99%