Cyclopropanation of Alkenes with Halodiazirines as Halocarbene Precursors in Continuous Flow

The cyclopropanation reaction of alkenes with photolytically‐generated chlorocarbenes from chlorodiazirines is reported as an effective way to prepare substituted 3‐chloro‐3‐aryl‐cyclopropanes. This practical and efficient approach allows the synthesis of various 3‐chloro‐3‐aryl‐cyclopropanes (32 examples) in continuous flow in 5‐minute residence time under light‐emitting diode (LED) irradiation. The conditions using 380 nm LED irradiation were successfully extended to the synthesis of substituted 3‐bromo‐3‐aryl‐cyclopropanes (3 examples).