Over the last decades, hexahydropyrrolo[2,3-
b]indoles (HPIs)/tetrahydrofuroindolines (TFIs), as representative indoline alkaloids, possessing the fused pentacyclic skeleton have attracted significant attention from the synthetic community [
1–
11] due to their family of biologically active natural products displaying the remarkable structural diversity (
e.g., acetylardeemin, psychotriasine,
WIN 64821, WIN 64745, chimonanthine, physovenine, madindoline A,
etc.) [
12–
20] and encompassing clinically important pharmaceutical molecules (physostigmine is clinically utilized for the treatment of myasthenia gravis, glaucoma, and Alzheimer's disease) (Fig, 1) [
21,
22]. Furthermore, 3a-bromo-substituted pyrroloindolines/furoindolines are significant and versatile building blocks to readily access a library of HPI and TFI alkaloids, in which the C–Br bond can be facilely transformed to a new C–C, C–N or C–O bond
via a substitution process with retention of configuration [
23–
46]. The cyclization reaction is regarded as one of the most practical methods to produce structural diverse
N-heterocycle derivates [
47–
53], therefore bromocyclization is an attractive way to construct 3a-bromo substituted pyrroloindinolines/furolinolines. As a result, tremendous efforts have been devoted to the construction of these scaffolds in the past decades (
Scheme 1A). Among them, the classical approach has utilized excessive amount of the highly sensitive and active bromine to construct these frameworks [
27–
29]. Moreover, many remarkable methodologies have employed stoichiometric electrophilic bromo reagents (PyHBr
3 [
30], NBS [
31–
42], DBDMH [
43], NBAc [
44], and DABCO-derived bromine salts [
45]) to approach both chiral and achiral derivatives, while the organic waste would be produced (
Scheme 1A, Path Ⅰ). In addition, the
in-situ generated electrophilic bromide assisted by the combination of bromo salts and extra oxidants would be successfully involved to the efficient bromocyclization (
Scheme 1A, Path Ⅱ) [
54–
57]. In this matter, Tong and co-workers have developed an oxone-mediated procedure, in which the organic waste could be eliminated, while the formation of less environmentally polluting salt (K
2SO
4) is inevitable [
48]. Recently, the electrochemical bromocyclization has been well-off for the establishment of 3a-bromopyrroloindolines and 3a-bromofuranoindolines along with the production of stoichiometric inorganic residues [
58,
59]. Though numerous methods have been applied to fabricate these units in high-efficiency, the development of more concise and efficient, greener, and milder methodologies to achieve these exquisite entities remains highly desired and sought-after [
60,
61].