Mapping the Electronic Structure and the Reactivity Trends for Stabilized α-Boryl Carbanions
| Autor: | Ricardo J. Maza, Jorge J. Carbó, Elena Fernández |
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| Rok vydání: | 2021 |
| Předmět: |
Steric effects
chemistry.chemical_classification Full Paper Chemistry Organic Chemistry Synthon Hot Paper General Chemistry Full Papers Catalysis Metal descriptors borata Transition metal Computational chemistry visual_art density functional calculations visual_art.visual_art_medium Moiety Reactivity (chemistry) alpha-borylcarbanion Alkyl Carbanion |
| Zdroj: | Chemistry (Weinheim an Der Bergstrasse, Germany) |
| ISSN: | 1521-3765 |
| Popis: | The chemistry of stabilized α‐boryl carbanions shows remarkable diversity, and can enable many different synthetic routes towards efficient C−C bond formation. The electron‐deficient, trivalent boron center stabilizes the carbanion facilitating its generation and tuning its reactivity. Here, the electronic structure and the reactivity trends of a large dataset of α‐boryl carbanions are described. DFT‐derived parameters were used to capture their electronic and steric properties, computational reactivity towards model substrates, and crystallographic analysis within the Cambridge Structural Dataset. This study maps the reactivity space by systematically varying the nature of the boryl moiety, the substituents of the carbanionic center, the number of α‐boryl motifs, and the metal counterion. In general, the free carbanionic intermediates are described as borata‐alkene species with C−B π interactions polarized towards the carbon. Furthermore, it was possible to classify the α‐boryl alkylidene metal precursors into three classes directly related to their reactivity: 1) nucleophilic borata‐alkene salts with alkali and alkaline earth metals, 2) nucleophilic η 2‐(C−B) borata‐alkene complexes with early transition metals, Cu and Ag, and 3) α‐boryl alkyl complexes with late transition metals. This trend map aids selection of the appropriate reactive synthon depending on the reactivity sought. Carbanion cartography: This study maps the stability/reactivity space for α‐boryl carbanions leading to the prediction of novel species. Free carbanionic intermediates can be described as borata‐alkene species with a C−B π‐interaction strongly polarized towards the carbon, whereas multi‐boryl species have very polar C−B bonds. Extensive analysis of α‐boryl alkylidene metal precursors identifies three structural patterns that can be related to reactivity. |
| Databáze: | OpenAIRE |
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