Dataset Information

Preparation of Primary and Secondary Dialkylmagnesiums by a Radical I/Mg-Exchange Reaction Using sBu₂ Mg in Toluene.

ABSTRACT: The treatment of primary or secondary alkyl iodides with sBu₂ Mg in toluene (25-40 °C, 2-4 h) provided dialkylmagnesiums that underwent various reactions with aldehydes, ketones, acid chlorides or allylic bromides. 3-Substituted secondary cyclohexyl iodides led to all-cis-3-cyclohexylmagnesium reagents under these exchange conditions in a highly stereoconvergent manner. Enantiomerically enriched 3-silyloxy-substituted secondary alkyl iodides gave after an exchange reaction with sBu₂ Mg stereodefined dialkylmagnesiums that after quenching with various electrophiles furnished various 1,3-stereodefined products including homo-aldol products (99 % dr and 98 % ee). Mechanistic studies confirmed a radical pathway for these new iodine/magnesium-exchange reactions.

SUBMITTER: Sunagatullina AS

PROVIDER: S-EPMC9302629 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature

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Preparation of Primary and Secondary Dialkylmagnesiums by a Radical I/Mg-Exchange Reaction Using sBu<sub>2</sub> Mg in Toluene.

Sunagatullina Alisa S AS Lutter Ferdinand H FH Knochel Paul P

Angewandte Chemie (International ed. in English) 20220209 13

The treatment of primary or secondary alkyl iodides with sBu<sub>2</sub> Mg in toluene (25-40 °C, 2-4 h) provided dialkylmagnesiums that underwent various reactions with aldehydes, ketones, acid chlorides or allylic bromides. 3-Substituted secondary cyclohexyl iodides led to all-cis-3-cyclohexylmagnesium reagents under these exchange conditions in a highly stereoconvergent manner. Enantiomerically enriched 3-silyloxy-substituted secondary alkyl iodides gave after an exchange reaction with sBu<su ...[more]

PMID: 35044040

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Project description:RationaleOxygen isotope exchange between O2 and CO2 in the presence of heated platinum (Pt) is an established technique for determining the δ17 O value of CO2 . However, there is not yet a consensus on the associated fractionation factors at the steady state.MethodsWe determined experimentally the steady-state α17 and α18 fractionation factors for Pt-catalyzed CO2 -O2 oxygen isotope exchange at temperatures ranging from 500 to 1200°C. For comparison, the theoretical α18 equilibrium exchange values reported by Richet et al. (1997) have been updated using the direct sum method for CO2 and the corresponding α17 values were determined. Finally, we examined whether the steady-state fractionation factors depend on the isotopic composition of the reactants, by using CO2 and O2 differing in δ18 O value from -66 ‰ to +4 ‰.ResultsThe experimentally determined steady-state fractionation factors α17 and α18 are lower than those obtained from the updated theoretical calculations (of CO2 -O2 isotope exchange under equilibrium conditions) by 0.0024 ± 0.0001 and 0.0048 ± 0.0002, respectively. The offset is not due to scale incompatibilities between isotope measurements of O2 and CO2 nor to the neglect of non-Born-Oppenheimer effects in the calculations. There is a crossover temperature at which enrichment in the minor isotopes switches from CO2 to O2 . The direct sum evaluation yields a θ value of ~0.54, i.e. higher than the canonical range maximum for a mass-dependent fractionation process.ConclusionsUpdated theoretical values of α18 for equilibrium isotope exchange are lower than those derived from previous work by Richet et al. (1997). The direct sum evaluation for CO2 yields θ values higher than the canonical range maximum for mass-dependent fractionation processes. This demonstrates the need to include anharmonic effects in the calculation and definition of mass-dependent fractionation processes for poly-atomic molecules. The discrepancy between the theory and the experimental α17 and α18 values may be due to thermal diffusion associated with the temperature gradient in the reactor.

Project description:Toluene, a prominent member of volatile organic compounds (VOCs), exerts a substantial adverse influence on both human life and the environment. In the context of advanced oxidation processes, the ·OH radical emerges as a highly efficient oxidant, pivotal in the elimination of VOCs. This study employs computational quantum chemistry methods (G4MP2//B3LYP/6-311++G(d,p)) to systematically investigate the degradation of toluene by ·OH radicals in an implicit solvent model, and validates the rationale of choosing a single-reference method using T1 diagnostics. Our results suggest three possible reaction mechanisms for the oxidation of toluene by ·OH: firstly, the phenyl ring undergoes a hydrogen abstraction reaction followed by direct combination with ·OH to form cresol; secondly, ·OH directly adds to the phenyl ring, leading to ring opening; thirdly, oxidation of sidechain to benzoic acid followed by further addition and ring opening. The last two oxidation pathways involve the ring opening of toluene via the addition of ·OH, significantly facilitating the process. Therefore, both pathways are considered feasible for the degradation of toluene. Subsequently, the UV-H2O2 system was designed to induce the formation of ·OH for toluene degradation and to identify the optimal reaction conditions. It was demonstrated that ·OH and 1O2 are the primary active species for degrading toluene, with their contribution ranking as ·OH > 1O2. The intermediates in the mixture solution after reactions were characterized using GC-MS, demonstrating the validity of theoretical predictions. A comparative study of the toluene consumption rate revealed an experimental comprehensive activation energy of 10.33 kJ/mol, which is consistent with the preliminary activation energies obtained via theoretical analysis of these three mechanisms (0.56 kJ/mol to 13.66 kJ/mol), indicating that this theoretical method can provide a theoretical basis for experimental studies on the oxidation of toluene by ·OH.

Dataset Information

Preparation of Primary and Secondary Dialkylmagnesiums by a Radical I/Mg-Exchange Reaction Using sBu₂ Mg in Toluene.

Publications

Preparation of Primary and Secondary Dialkylmagnesiums by a Radical I/Mg-Exchange Reaction Using sBu<sub>2</sub> Mg in Toluene.

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Preparation of Primary and Secondary Dialkylmagnesiums by a Radical I/Mg-Exchange Reaction Using sBu2 Mg in Toluene.

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Preparation of Primary and Secondary Dialkylmagnesiums by a Radical I/Mg-Exchange Reaction Using sBu<sub>2</sub> Mg in Toluene.

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Preparation of Primary and Secondary Dialkylmagnesiums by a Radical I/Mg-Exchange Reaction Using sBu₂ Mg in Toluene.