Organophosphorus compounds are an important class of bioactive compounds. They are also the backbones to numerous chiral ligands, and have extensive applications in biology, medicine and organic synthesis. Common methods for the preparation of enantioenriched organophosphorus substances include resolution, chiral auxiliary induction, asymmetric cross-coupling and asymmetric addition reactions. Most of these reactions require transition metal catalysis and rather strict reaction conditions. Till now, only two publications demonstrate the synthesis of enantioenriched organophosphorus compounds via organocatalysis. Thus, developing organocatalytic approaches for the synthesis of enantioenriched organophosphorus compounds pose considerable challenges.
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1
Lewis base catalyzed asymmmetric allylic alkylation (AAA) of MBH adducts is a simple and efficient methods for the synthesis of enantioenriched compounds, yet the application of this system is mainly on the construction of stereogenic centers on carbon. Based on their previous triumph on the synthesis of enantioenriched aniline derivatives via AAA of MBH adducts, Jinpei Cheng, Xin Li and co-workers further discovered the potential of the AAA reaction for the asymmetric construction of non-carbon steregenic centers and discloseed a synthesis of enantioenriched organophosphrus compounds via AAA. The reactions shows broad substrate scope and extraordinary stereoselectivity. Large scale conduction of the reaction does not lead to enrosion in enantioselectivity. The products obtained could be further utilized in the synthesis of novel catalysts.
Figure 2
Linear free energy relationship analysis was conducted to shine light on the possible mechanism. It was discovered that the reaction was influenced by the sterics and electronic effect of the R2 group. Further, the R1 group attached to phosphrus also play a significant role on the stereoselectivity. According to theoretical calculations, these researchers proposed a resonable transition state model matching the experimental enantioselectivities, and successfully rationalized the informations obtained from linear free energy relationship analysis.
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This work is recently published on Chemical Science (Chem.Sci.,2019,10, 4322-4327. DOI: 10.1039/c8sc05439h. Guohui Yang is the first author of this article. This work is supported by the National Natural Science Foundation of China, Nankai University and the SKLEOC.