Spurred on by these findings, we investigated the activation of diazirine 1 with 460 nm light. The reaction was carried out in the presence of cyclohexane, which we and others have used as a convenient benchmarking substrate to compare the efficacy of various diazirine reagents. The unactivated C-H bonds in cyclohexane present a challenging target for carbene insertion, and the yield of the C-H insertion adduct reports on the degree of singlet stabilization for the intermediate carbene. Diazirine molecules that lead to ground-state triplet carbenes (e.g. the unsubstituted trifluoromethyl phenyl diazirine) give low yields of the desired C-H insertion product (typically <20%) due to competing reaction with adventitious oxygen (also a ground-state triplet). By contrast, diazirine molecules that beget ground-state singlet carbenes can lead to very high yields of the corresponding cyclohexane C-H insertion product. The champion carbene precursors in this regard are palkoxyphenyl trifluoromethyl diazirines, which are able to add to cyclohexane in >90% isolated yield, regardless of whether thermal or photochemical activation conditions are used. In the event, irradiation of diazirine 1 in cyclohexane with 460 nm light (supplied by commercial LED strip lights with a narrow emission profile; refer to the ESI for details) led to rapid consumption of the diazirine group. We were pleased to observe the formation of the desired adduct 7 in 60% isolated yield (Scheme 2). The production of 7 was confirmed by high- resolution mass spectrometry, as well as a variety of NMR methods. 1 H-coupled F NMR spectroscopy was particularly diagnostic; the splitting of the signal corresponding to the trifluoromethyl group (see Figure in the ESI) confirmed the presence of the neighbouring proton in the target compound. The F NMR chemical shift (-63.26 ppm) was also consistent with previously reported cyclohexane adducts. To the best of our knowledge, the experiment described above represents the first time that any trifluoromethyl aryl diazirine reagent has been successfully activated with >450 nm light, without the use of a separate photosensitizer. The observation of C-H insertion product 7 under these conditions provides strong evidence for the effective conjugation of the diazirine group to the extended pi system. Moreover, the good yield obtained for 7 indicates that the electron-donating dimethylamino group on the opposite ring is helping to stabilize the singlet state of the carbene-although certainly the effect of this electron-donating substituent is tempered by the fact that it is two rings distal to the reactive centre.