Visible-light-initiated tandem synthesis of difluoromethylated oxindoles in 2-MeTHF under additive-, metal catalyst-, external photosensitizer-free and mild conditions

Regioselective synthesis of 6-nitroindole derivatives from enaminones and nitroaromatic compounds via transition metal-free C–C and C–N bond formation

“…However, the details regarding the nitro group elimination are not very clear. 10 e–g ,15 In addition, pathway II , which involves benzyne A , may be ruled out in our system because only one isomer was produced, which is in agreement with the results of normal benzyne-involved cycloaddition reactions (Scheme 3, pathway II). 17…”

“…We speculated that new C–C and C–N bonds could be formed by nucleophilic aromatic substitution (S N Ar). 10 e – g ,11–13,15 To our delight, the desired product 3aa could be obtained in 9% liquid chromatography (LC) yield in the presence of Cs 2 CO 3 in 1,2-dichloroethane (DCE) without the involvement of any transition-metal catalyst (Table 1, entry 1). The use of chlorobenzene (PhCl) was found to give the best result after the screening of different solvents and provided the indole 3aa in moderate LC yield (50%; Table 1, entries 1–5).…”

Direct C(sp3)–H difluoromethylation via radical–radical cross-coupling by visible-light photoredox catalysis

“…Consequently, for this purpose, continuous efforts on difluoromethylating reagents and thereby difluoromethylation protocols have been increasingly made in the past decade. 5 Notably, the C(sp 3 )–CF 2 H moiety is of great interest in pharmaceutical chemistry because it is a bioisosteric replacement for aliphatic alcohols and thiols, two prevalent functional groups in drug design and discovery. 6 As one of the most straightforward and general reactions for the rapid and efficient installation of CF 2 H to a C(sp 3 ) center, the direct C(sp 3 )–H activation difluoromethylation represents a greatly reliable and ideal method for the construction of C(sp 3 )–CF 2 H bonds in the late-stage modification of bioactive molecules.…”

Updates on hypervalent-iodine reagents: metal-free functionalisation of alkenes, alkynes and heterocycles

“…A wide variety of N -arylacrylamide substrates successfully underwent difluoromethylation in this protocol (Scheme 43). 101…”