Vilsmeier–Haack Complex Formation by Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>@CS@POCl<sub>2–<i>x</i></sub>/DMF: An Efficient Catalyst for Conversion of Epoxides to β-Bromoformates

The in situ generation of the Vilsmeier-Haack complex was studied by combining Fe₃O₄@SiO₂@CS@POCl_2-x with <i>N</i>,<i>N-</i>dimethylformamide (DMF), demonstrating remarkable efficiency and regioselectivity in transforming epoxides into β-bromoformates. The reported yields were notably high and were achieved under mild reaction conditions. Interestingly, the removal of DMF led to the synthesis of <i>vic</i>-dihalide compounds. The product of this transformation depended on the specific details of how the experiment was done, highlighting how sensitive the process is to different ways of conducting the experiment. The use of a magnetic core-shell catalyst, Fe₃O₄@SiO₂@CS@POCl_2-x, facilitates a straightforward work-up procedure, simplifying the isolation of the desired products. Furthermore, the reactions were conducted under clean and neutral conditions, contributing to their environmentally friendly nature.