A practical and reusable catalyst for the synthesis of donor-acceptor cyclopropane

Herein, a convenient, recyclable and inexpensive Cu-based catalytic system is developed for the synthesis of donor-acceptor (D-A) cyclopropane via the cycloaddition of styrene derivatives with diethyl bromomalonate. A core-shell catalyst of Fe3O4@Cu2O is used to promote the construction of D-A cyclopropane with different functional groups in good yields. In our experiments, many harsh conditions, such as strict anhydrous and anaerobic, are avoided. The Fe3O4@Cu2O particles are easily made, air-stable and of low cost. What's more, the magnetic property makes the catalyst easy to be separated and catalytical activity has no significant change even after being recycled for five times.