Recent Advances in the Construction of Spiro Compounds via Radical Dearomatization

Abstract

The field in dearomatization of aromatic compounds for the construction of spirocycle compounds has been developed rapidly over the last two decades and it provides alternative synthetic method without using extra stoichiometric amounts of chemical oxidants or reductants. In addition, the radical cascade reactions of alkenes or alkynes that produce multiple chemical bonds in one-step are significant in the direct and efficient building of complex molecules. By combining these two concepts, dearomatization and radical cascade reactions of alkenes or alkynes opens a new and powerful avenue in accessing spirocycle molecules. These cascade reactions have been well explored in the past decade. As a result, we summarize recent eventful advances in this rapidly growing area as a review, in which the typical examples are listed and mechanism are also discussed.

Spirocyclizative Remote Arylcarboxylation of Non-Activated Arenes with CO2 via Visible-Light-Induced Reductive Dearomatization

“…Furthermore, the reaction was explored with 2-tethered naphthalenes and phenyl aromatics (Scheme 4). Pleasingly, after subjected to our reaction conditions, 2-tethered naphthalenes led to 1,2-arylcarboxylation dearomatized products (45)(46)(47)(48) whose structures were different from abovementioned remote 1,4arylcarboxylation of 1-tethered naphthalenes, albeit in moderate yields. Of note, some 1,2-hydroarylation side product (10-20%) was also generated with these substrates.…”

“…In recent years, visible-light photoredox catalysis [35][36][37][38][39][40][41][42][43][44] has emerged as a promising strategy for developing mild protocols for dearomatization, [45][46][47][48][49][50][51][52][53][54][55][56][57][58] including several significant protocols for the dearomatization of nonactivated arenes, [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73] such as dearomative cycloadditions mainly from the groups of Sarlah and Bach, [59][60][61][62] and oxidative dearomatization. [63][64][65] A distinct redox-neutral hydroalkylative dearomatization of naphthalene derivatives was also reported by the group of Zhang, Mei and You.…”

Spirocyclizative Remote Arylcarboxylation of Nonactivated Arenes with CO 2 via Visible-Light-Induced Reductive Dearomatization

“…Of note, substrates bearing a methyl at the C4 position of the naphthalenyl were tolerated, producing the 4-carboxylated products (41)(42)(43) Furthermore, the reaction was explored with 2-tethered naphthalenes and phenyl aromatics (Scheme 4). Pleasingly, after subjected to our reaction conditions, 2-tethered naphthalenes led to 1,2-arylcarboxylation dearomatized products (45)(46)(47)(48) whose structures were different from abovementioned remote 1,4arylcarboxylation of 1-tethered naphthalenes, albeit in moderate yields. Of note, some 1,2-hydroarylation side product (10-20%) was also generated with these substrates.…”

“…In recent years, visible-light photoredox catalysis [36][37][38][39][40][41][42][43][44][45] has emerged as a promising strategy for developing mild protocols for dearomatization, [46][47][48][49][50][51][52][53][54][55][56][57][58][59] including several significant protocols for the dearomatization of nonactivated arenes, [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74] such as dearomative cycloadditions that were mainly from the groups of Sarlah and Bach, [60][61][62][63] and oxidative dearomatization. [64][65][66] A distinct redox-neutral hydroalkylative dearomatization of naphthalene derivatives was also reported by the group of Zhang, Mei and You.…”

Nitrogen radical-triggered trifunctionalizing ipso-spirocyclization of unactivated alkenes with vinyl azides towards new spiroaminal frameworks

“…Furthermore, the inherent three-dimensional (3D) conformational constraint character of the spirocyclic skeletons enables them as one of the excellent ligand [7][8][9][10] and organocatalyst 11,12 frameworks in the field of asymmetric catalysis. In this context, an elegant radical-mediated spirocyclization for the construction of the spirocyclic compounds, including dearomative 13 and non-dearomative 14 strategies, has been developed rapidly in the past decade. To the best of our knowledge, the existing approaches for the radical-mediated spirocyclization are solely based upon the elaboration of aromatic or aliphatic monocyclic precursors on which the second ring is newly appended, and compared with the former dearomative strategies, the latter non-dearomative strategies could provide structurally distinct spirocyclic compounds with varied functionality (Fig.…”