Start-up funding from Sichuan University (YJ201965), National Natural Science Foundation of China (22001180), Thousand Young Talents Program of China (15-YINGXIA).
Gem-difluorinated cyclopropanes have become an important type of allyl surrogate in transition-metal-catalyzed ring-opening processes, as demonstrated recently through various important advances, especially with palladium catalysis. The versatile fluorinated allyl species generated in this way from gem-difluorinated cyclopropanes exhibit unique advantages compared with conventional allyl sources. By using gem-difluorinated cyclopropanes as allyl surrogates, we achieved a direct allylation of simple arenes through rhodium catalysis under mild conditions. This transformation permits directing-group-free allylation of simple arenes, including electron-neutral, electron-rich, and electron-deficient ones. Here, we give a brief introduction to this area and we discuss our thoughts regarding our recent work and its design.
1 Introduction
2 Our Design
3 Condition Optimization and Substrate Scope
4 Applications in Synthesis
5 Mechanistic Discussions
6 Conclusion and Outlook
Key words
difluorocyclopropanes -
transition-metal catalysis -
allylation -
C–C bond activation -
rhodium catalysis -
arenes
9
Suliman AM. Y,
Ahmed E.-AM. A,
Gong T.-J,
Fu Y.
Org. Lett. 2021; 23: 3259 . Very recently, the same group reported a similar three-component reaction using alkenes instead of alkynes, see: Suliman, A. M. Y.; Ahmed, E.-A. M. A.; Gong, T.-J.; Fu, Y. Chem. Commun. 2021, 57, 6400
22 A Pd-catalyzed C–H allylation of polyfluoroarenes with gem-difluorinated cyclopropanes as the allyl sources was recently developed, see:
Zhou P.-X,
Yang X,
Wang J,
Ge C,
Feng W,
Liang Y.-M,
Zhang Y.
Org. Lett. 2021; 23: 4920
26 This conclusion is also supported by the following two facts. (1) Our reaction is base-free and a release of HF is observed in the reaction, demonstrating that the reaction proceeds under acidic conditions. In comparison, CMD-type C–H activation processes usually occur under basic conditions. (2) Electron-rich arenes are more active, giving the allylated products at ambient temperatures, whereas electron-deficient arenes require elevated temperatures.