Progress in Synthesis of Oxindoles by Radical Addition-Cyclization

Abstract

In recent years, there are many reports about the synthesis of oxindoles by radical addition-cyclization. Most of these approaches are catalyzed by different transition metals, or under metal-free and photoredox catalysis conditions using N-arylacrylamides as main substrates. These methods have been a powerful strategy to obtain oxindoles in organic synthesis. At present, the studies on the synthesis of oxindoles by radical addition-cyclization are mainly focused on the types of radicals and the reaction mechanisms. This review will summarize the recent progress of the synthesis of oxindoles by radical addition-cyclization according to the different catalyst systems.

Metal-free cascade cyclization of alkenes toward perfluorinated oxindoles

“…1 Oxindoles are common structural motifs in pharmaceutical agents and natural products, 2 and the incorporation of fluorinated groups into these scaffolds by using the Togni reagent, 3 TMSCF 3 , 4 or CF 3 SO 2 Na 5 has attracted increasing interest. 9 Consistent with these findings, we envisage that incorporation of perfluorinated groups into oxindole via cascade radical addition/C(sp 2 )-H cyclization initiated by AIBN is possible. Therefore, increasing the diversity of available methods for incorporation of other fluorinated groups (e.g., perfluorinated groups) into the oxindole scaffold is in high demand.…”

Desulfonylation via Radical Process: Recent Developments in Organic Synthesis

“…To date, easily accessible N -aryl amides bearing a suitable pendant olefin have been considered as an exceptional precursor to N-heterocycles through the addition of carbon- or heteroatom-centered radicals and subsequent alkene difunctionalization. − Recognizing the need in this area, a Brønsted-base-assisted and photoredox-catalyzed intramolecular 5- exo -trig cyclization/intermolecular radical addition/elimination was developed to assemble alkyne- and alkene-decorated γ-lactams (pyrrolidin-2-ones), cyclic carbamates, and urea derivatives (Scheme A) . As such, the formation of two new C–C/C–N bonds and a new five-membered heterocyclic ring was accomplished in this synthetic strategy aiming at scaffold diversity (Scheme B).…”

“…Difunctionalization of unsaturated alkenes is considered to be attractive, as it allows the introduction of two versatile handles in a one-step manipulation. − As a logical extension of the radical addition cascade, the group of Hu further disclosed a simple fluoroalkylation–hydroxylation of alkenes with fluorinated sulfone and H 2 O (Scheme A) . By using various fluorinated sulfones and styrenes, β-fluoroalkyl benzyl alcohols were synthesized through the regioselective formation of C­(sp 3 )–CF 2 X and C­(sp 3 )–O bonds regardless of terminal or internal alkenes (Scheme B).…”

Syntheses of 3,3-Disubstituted Dihydrobenzofurans, Indolines, Indolinones and Isochromanes by Palladium-Catalyzed Tandem Reaction Using Pd(PPh3)2Cl2/(±)-BINAP as a Catalytic System

“…Compound V exhibits selective 5-hydroxytryptamine7 (5-HT 7 ) antagonist activity (K i = 0.79 nm) [13] and alstonisine (VI) also reveals antiplasmodial activity against Plasmodium falciparum, with an IC50 (half maximal inhibitory concentration) of 7.6 µM [14] (Figure 1). Therefore, organic chemists around the world made extensive efforts to develop the highly efficient methods of constructing these heterocycles [15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Of these molecules, 3,3-disubsitituted five-membered chemists around the world made extensive efforts to develop the highly efficient methods of constructing these heterocycles [15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

“…The domino reactions of the synthesis of them were summarized mainly as follows: (i) the Pd or Ni-catalyzed cyclocarbopalladation/coupling fractions, in which the process was initiated by Heck cyclization of a starter (halide) and a relay (alkene), followed by intermolecular coupling reactions with a terminator (organometallic reagents, alkenes, alkynes, etc. ), including Suzuki, Stille, Heck, Sonogashira, C-H activation, carbonylation and amination and so forth [15][16][17]22,24,25,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]; (ii) the C-H oxidative radical coupling reactions, in which these transformations were based on tandem radical addition/cyclization in the presence of oxidants with/without metal catalysts [18][19][20][21]23,26,[45][46][47][48][49][50][51][52][53][54][55]; and (iii) the other reactions [24,[56][57][58][5...…”