Photoredox-Catalyzed Cascade sp² C–H Bond Functionalization to Construct Substituted Acridine with Diarylamine and Hypervalent Iodine(III) Reagents

Abstract

A photocatalyzed cascade double C−C formation via sp 2 C−H bond activation of diarylamines with hypervalent iodine diazo reagents was developed. A variety of diarylamines and hypervalent iodine(III) reagents were tolerated well, and a range of substituted acridines with yields ranging from moderate to excellent was provided efficiently. The protocol introduces diazo groups onto diarylamines and enables subsequent late-stage assembly point functionalization with the diazonium structure, forming two new C−C bonds in a sequential fashion.

α-Diazo-λ3-iodanes and α-diazo sulfonium salts: the umpolung of diazo compounds

“…Oxidation of this intermediate produces the observed acridines 42 (Scheme 11). 30 Other unsaturated organic nucleophiles can serve as diazomethyl radical acceptors as well. For example, a visible lightinduced [3+2] cyclization reaction of hydrazones (43) with reagent 10, to form 1-amino-1,2,3-triazoles (44) was reported by the group of Li in 2021 (Scheme 12a).…”

C−N and C−C Bond Formation in Annulation and Aromatization through Metal‐Catalyzed Photoredox C−H Functionalization

“…The approach introduces diazo groups to diarylamines and then facilitates late-stage assembly point functionalization with diazonium structure, ]. [46] The aroylation/sulfonylation cascade radical reaction to synthesis fused Indolo-pyridone nucleus was disclosed by Yang and co-workers in 2021. The oxidative aromatization reaction was accomplished using aroyl chlorides and sulfonyl chlorides, as radical species which is generated by fac-Ir(ppy) 3 photocatalyst under blue light irradiation.…”

“…Following photochemical generation of carbene 164 via N 2 extrusion form 165 and intramolecular cyclization to acridine 160 would occur [Scheme 38]. [46] …”

Remote Radical 1,3-, 1,4-, 1,5-, 1,6- and 1,7-Difunctionalization Reactions

“…In addition to traditional homolytic bond cleavage-based radical reactions induced by radical initiators or photolysis [ 15 , 16 , 17 ], other methods such as single electron transfer reagents [ 18 , 19 , 20 , 21 , 22 ], catalytic photoredox [ 23 , 24 , 25 , 26 , 27 , 28 ], and electrochemical reactions [ 29 , 30 , 31 , 32 , 33 , 34 , 35 ] have been developed and are gaining increasing popularity. For the remote 1,3-, 1,4-, 1,5-, 1,6- and 1,7-difunctionalization reactions presented in this paper, the initial addition of the radical X is followed by radical rearrangement through resonance, hydrogen atom transfer (HAT), group transfer, or opening of strained-rings to relocate the position of the radical.…”