Room‐Temperature C‐H Bromination and Iodination with Sodium Bromide and Sodium Iodide Using N‐Fluorobenzenesulfonimide as an Oxidant

Abstract

A transition‐metal‐free electrophilic bromination and iodination of arene through C−H cleavage at room temperature has been developed in excellent to quantitative yields with broad arene scope and good regioselectivity, in which environment‐benign and readily available sodium halides, NaBr or NaI, were employed as halogen sources in accompany with N‐fluorobenzenesulfonimide (NFSI) as an oxidant. Studies have also demonstrated that, in this air‐ and moisture‐resistant scalable halogenation under mild conditions, the oxidant NFSI is reduced to dibenzenesulfonimide which usually serves as the starting material for the preparation of NFSI, rendering this facile and versatile protocol promising potentials for future applications in organic synthesis.

Metal-free site-selective C–H cyanoalkylation of 8-aminoquinoline and aniline-derived amides with azobisisobutyronitrile

“…To our surprise, N-methyl pivalanilide 1r as same as the material 1a led to the product 2a in a moderate 45% yield, which brought to light the possibility of N-CH 3 bond oxidative dissociation by strong oxidant K 2 S 2 O 8 . 20 On the basis of the above control experiments and previous studies, 3k,5,9,21 a plausible mechanism was proposed, as outlined in Scheme 6. First, the decomposition of S 2 O 8 2À generated a sulfate radical anion SO 4 À c D by homolysis upon heating.…”

“…Pleasingly, as shown in Scheme 7, under the K 2 S 2 O 8 /CH 3 CN/ H 2 O system, 8-aminoquinoline amide 3b was treated with NaBr as the bromine source to afford C5-Br 8b readily in a high yield of 93% (eqn (1)). 20 Moreover, the para-dimerization products 9a and 9b were found when the experiment was carried out only in K 2 S 2 O 8 /DMSO system at 100 C (eqn (2)). In comparison with the reported synthetic strategy in which transition metal catalysts [Rh(COD)Cl] 2 (ref.…”

“…To our surprise, N -methyl pivalanilide 1r as same as the material 1a led to the product 2a in a moderate 45% yield, which brought to light the possibility of N–CH 3 bond oxidative dissociation by strong oxidant K 2 S 2 O 8 . 20 …”

Recent Update on Transition Metal‐Free C(sp2)−H Bond Halogenation in (Hetero) Arenes

“…N ‐flurobenzenesulfonimide (NFSI) was used as an oxidant and sodium salts of halogens (bromine and iodine) acted as halogen source for the halogenation of quinolines ( 137 )and arenes. This protocol has been achieved by Li et al [92] . in 2019(Scheme 83).…”

One‐Pot Functionalization of 8‐Aminoquinolines through the Acylation and Regioselective C5‐H Halogenation under Transition‐Metal‐Free Conditions

“…In 2013, Stahl and coworkers first reported the remote CuCl‐catalyzed C5 chlorination of 8‐amidoquinoline amides through a single electron transfer (SET) process. Since then, regioselective C5 halogenation of quinolines has been widely investigated, and various halogen sources such as NXS (X=Cl, Br or I),– halide salts,– molecular idodine, and other halogen reagents have been used for the synthesis of halogenated quinolines. Despite the significant progress, most of these methods cannot avoid the use of transition‐metals, and/or excess of oxidants and halogen sources, thus not conforming to the requirements of atom economy and green chemistry.…”