Visible light induced cyclopropanation at 20 °C under magnetic stirring (1300 rpm).
Add 3.0 mmol 2,3-dihydrofuran in dichloromethan togehter with 1.0 mmol methyl 2 phenyl 2 diazoacetate in a 30 ml vial, degas by bubbling nitrogen and react with blue light (455 nm) for 4 h. Upscaling and reaction optimization by using different LED sources.