Expeditious synthesis of diverse spiro fused quinoxaline derivatives using magnetically separable core–shell CoFe₂O₄@SiO₂‐SO₃H nanocatalyst under ultrasonication

Abstract

A magnetically separable core–shell CoFe2O4@SiO2‐SO3H nanocatalyst has been successfully exploited as a heterogeneous acid catalyst in the synthesis of diversely substituted biologically important spiro fused pyrrolo/indolo[1,2‐a]quinoxaline derivatives through the condensation of N‐(2‐aminophenyl)pyrroles/indoles and various cyclic conjugated 1,2‐diones in ethanol under ultrasonic irradiation. Room temperature synthesis, short reaction time, wide substrate scope, good to excellent yield of products and use of a magnetically separable and recyclable nanocatalyst make this method attractive and practicable.

Zinc(II)‐poly(urea‐formaldehyde) supported on magnetic nanoparticles: A hybrid nanocatalyst for green synthesis of spiropyrans, spiroxanthenes, and spiropyrimidines

“…These results indicate that the obtained CoFe 2 O 4 has a spinel structure and according to the standard JCPDS no.22–1,086. [ 54 ] The same peaks were observed in both the CoFe 2 O 4 and MNPs@SiO 2 @PUF@Zn patterns, indicating retention of the crystalline spinel ferrite core structure during the coating process. These results confirm that the functionalization process does not change the nanoparticle phase.…”

Design, Synthesis and Cytotoxicity Evaluation of Tetrahydro β‐Carboline‐Attached Spiroindolones/ Spiroacenapthylene by Using Lemon Juice as a Green Biocatalyst System.

“…), [9][10][11][12][13][14] lewis acids (BF 3 .Et 2 O, SnCl 4 , MgBr 2 .Et 2 O, TiCl 4 , LiCl, Yb(OTf) 3 , Cu(OTf) 2 , Sc(OTf) 3 , AuCl 3 /AgOTf etc.) [15][16][17][18][19][20][21][22][23] and also several miscellaneous catalysts like silica gel, [24] phosphate buffer, [25] β-cyclodextrin-SO 3 H, [26] CoFe 2 O 4 @SiO 2 -SO 3 H, [27] molecular iodine, [28] Dowex 50W-X4 acidic ion exchange resin, [29] heterogeneous acid H 3 PW 12 O 40 and 9-Borabicyclo[3.3.l]non-9yl(9-BBN) triflate [14] etc. These conventional synthetic processes for different pharmaceuticals and other relevant molecules produce large amount of waste and toxic by-product.…”

Three-Component Synthesis of Pyrrolo/indolo[1,2-a]quinoxalines Substituted with o-Biphenylester/N-arylcarbamate/N-arylurea: A Domino Approach Involving Spirocyclic Ring Opening

“…26 However, involvement of cyclic conjugated 1,2-diones such as isatins and 9,10-phenanthraquinones as carbonyl imitators is still a challenging task as in these cases the spirofused quinoxalines are found to be the sole product. 27 Inspired by the above-mentioned acid catalyzed ring opening strategies, 25,26 herein we report an acid catalyzed one-pot three-component synthesis of pyrrolo/indolo[1,2-a]quinoxalines substituted with o-biphenylester/ N-arylcarbamate/ N-arylurea at C-4 position starting from N-(2aminophenyl)pyrroles/indoles and cyclic 1,2-diones such as isatins and 9,10-phenanthraquinone (Scheme 1d ingly, in this synthesis the water-miscible aliphatic alcohols and amines participate both as solvents as well as reactants.…”