| Autor: |
Han, Kehui, Wang, Yanyan, Zhao, Pei, You, Xiaohui, Wang, Jun, Guo, Yanchun, Zhao, Yufen, Cao, Shuxia |
| Zdroj: |
The Journal of Organic Chemistry; March 2021, Vol. 86 Issue: 6 p4512-4531, 20p |
| Abstrakt: |
The stereochemical mechanism of the nucleophilic substitution reaction at pentacoordinate phosphorus (P–V) atom is rarely studied. Here, we report the Atherton-Todd-type reaction of pentacoordinate hydrospirophosphorane with phenolic compounds in detail. The stereochemical mechanism of nucleophilic substitution at P–V atom was proposed by 31P NMR tracing experiment, X-ray diffraction analysis, and density functional theory calculations. The first step of the Atherton-Todd-type reaction is the formation of halogenated spirophosphorane intermediate with retention of configuration at phosphorus definitely. The second step is a nucleophilic substitution reaction at P–V atom of halogenated spirophosphorane. When using CCl4as a halogenating agent, the reaction of chlorinated spirophosphorane proceeds via SN2(P–V) mechanism, and the backside attack of P–Cl bond is the main pathway. For chlorinated spirophosphorane with ΔPconfiguration, the completely P-inverted product is normally obtained. As for chlorinated spirophosphorane with ΛPconfiguration, which has larger steric hindrance behind P–Cl bond, the proportion of P-retained products apparently increases and a pair of diastereoisomers is acquired. Furthermore, if CBr4is used as a halogenating agent, the nucleophilic substitution reaction of brominated spirophosphorane may go through a SN1(P–V) mechanism to afford a pair of diastereoisomers. |
| Databáze: |
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