Photochemical Cyclopropenation of Alkynes with Diazirines as Carbene Precursors in Continuous Flow

An efficient synthesis of 3-trifluoromethyl-3-aryl-cyclopropenes via the cyclopropenation reaction of alkynes with photolytically generated carbenes from diazirine compounds is described. This reaction is performed in continuous flow using readily available LEDs under mild reaction conditions. This new and efficient method describes the synthesis of 25 examples of 3-trifluoromethyl-3-aryl-cyclopropenes with yields up to 97%, achieved in continuous flow with a S min residence time. Control experiments highlighted that diazirines are more efficient than diazo compounds for this transformation.

Automated summary

Efficient synthesis of 3-trifluoromethyl-3-aryl-cyclopropenes was achieved via the cyclopropenation reaction of alkynes with photolytically generated carbenes from diazirine compounds. The reaction was conducted in continuous flow using readily available LEDs under mild reaction conditions, resulting in yields up to 97% for 25 examples. Control experiments showed that diazirines are more efficient than diazo compounds for this transformation.