Recently, Prof. Jun-An Ma’s team from Tianjin University’s School of Science reported on RhII-catalyzed enantioselective cyclopropenation reaction of internal alkynes with a masked difluorodiazoethane reagent (PhSO2CF2CHN2, Ps‐DFA). The related work was published on Angew. Chem. Int. Ed. (10.1002/anie.201911701) and selected as Hot Paper and Back Cover for key report.

This asymmetric transformation offers efficient access to a broad range of enantioenriched difluoromethylated cyclopropenes. The optimized reaction condition is 1.5 mol % Hashimoto catalyst [Rh2(S‐TCPTTL)4] in dichloromethane to react in only 40 min at −30 °C.

Chiral cyclopropene has been widely noted in the field of synthetic chemistry due to its versatile reactivity. The asymmetric cyclopropylation of alkynes with diazo compounds is an effective way to construct such tension ring molecules. Doyle, Corey, Davies and others took the lead in the [2 + 1] cycloaddition reaction of terminal alkynes, and achieved great success. Due to the increase of steric hindrance and the decrease of activity, the catalytic asymmetric cyclopropylation is an important challenge in synthetic chemistry. Thus far, the Davies team has reported the only successful example, but it needs Au-Ag catalysis, and a donor acceptor type diazo ester substrate. In addition, fluorine-containing diazo compounds have developed into an important part for the construction of many fluoride alkylation carbocyclic rings, heterocycles and open-chain molecules in recent years, but the asymmetric cyclopropylation reactions in which they participate have not been reported.

The paper’s first author is Zhang Zhiqi, a TJU postgraduate, and the responding authors are Prof. Ilan Marek, Prof. Zhang Faguang and Prof. Ma Jun-an.

By the School of Science

Editors: Eva Yin & Doris Harrington