A decennary update on applications of metal nanoparticles (MNPs) in the synthesis of nitrogen- and oxygen-containing heterocyclic scaffolds

Abstract

Heterocycles have been found to be of much importance as several nitrogen- and oxygen-containing heterocycle compounds exist amongst the various USFDA-approved drugs. Because of the advancement of nanotechnology, nanocatalysis has found abundant applications in the synthesis of heterocyclic compounds. Numerous nanoparticles (NPs) have been utilized for several organic transformations, which led us to make dedicated efforts for the complete coverage of applications of metal nanoparticles (MNPs) in the synthesis of heterocyclic scaffolds reported from 2010 to 2019. Our emphasize during the coverage of catalyzed reactions of the various MNPs such as Ag, Au, Co, Cu, Fe, Ni, Pd, Pt, Rh, Ru, Si, Ti, and Zn has not only been on nanoparticles catalyzed synthetic transformations for the synthesis of heterocyclic scaffolds, but also provide an inherent framework for the reader to select a suitable catalytic system of interest for the synthesis of desired heterocyclic scaffold.

Fig. 1. Number of publications versus corresponding year of publication for the search string ‘synthesis of heterocyclic scaffolds’ accessed by Sci-Finder on Nov 28, 2019.

Fig. 2. Recent applications of nanotechnology.

Fig. 3. Basic techniques for the characterization of nano-materials. Chemical characterization includes optical spectroscopy such as optical absorption spectroscopy, which includes UV-Vis spectroscopy, photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy; and electron spectroscopy including energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), and ultraviolet photoelectron spectroscopy (UPS). Structural characterization involves X-ray diffraction (XRD); electron microscopic techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), environmental transmission electron microscopy (ETEM), and scanning probe microscopy (SPM); and dynamic light scattering (DLS) using a particle size analyzer.

Fig. 4. Metal nanoparticle (MNP)-catalyzed synthesis of nitrogen- and oxygen-containing heterocyclic scaffolds.

Scheme 1. Synthesis of pyrimido[1,2-b]indazole derivatives (4) using AgNPs under solvent-free conditions.

Scheme 2. AgNP-catalyzed synthesis of pyrrolo[2,3,4-kl]acridin-1-ones (8).

Scheme 3. Chemoselective “on-water” synthesis of pyrano[2,3-c:6,5-c′]dipyrazol]-2-ones (11) catalyzed by AgNPs on GO composite.

Scheme 4. AgNP-catalyzed synthesis of cycloadduct (14) for the total synthesis of natural product (15).

Scheme 5. AgNP-catalyzed chemoselective reduction of nitroarenes (16) and synthesis of 19.

Scheme 6. Synthesis of benzopyranopyrimidines (23) reported by Heravi et al.

Scheme 7. Silver–graphene nanocomposite-catalyzed synthesis of propargyl amines (26a).

Scheme 8. Click reaction catalyzed by silver–graphene nanocomposites.

Scheme 9. AHA coupling catalyzed by NHC-protected AgNPs.

Scheme 10. Synthesis of tetrahydro-4H-chromenes (30) catalyzed by AuNPs@RGO-SH.

Scheme 11. Aerobic oxidative cyclocondensation of arylamines (6b) with arylalkyl aldehydes (31) in the presence of silica-supported AuNPs.

Scheme 12. AuNP-catalyzed one-pot synthesis of benzimidazoylquinoxalines (34a/b) from o-phenylene diamine (33) and glycerol/glyceraldehyde.

Scheme 13. Chemoselective hydrogenation of quinolines (35a) catalyzed by Au NPs.

Scheme 14. AuNP-catalyzed synthesis of quinoxalines (38a) from substituted o-phenylene diamine (33c) and glycols (37).

Scheme 15. Hydrogenation of N-heterocyclic compounds (39a/35b/38b/42a) catalyzed by AuNPs supported on amino-functionalized silica.

Scheme 16. AHA coupling catalyzed by AuNPs for the synthesis of propargylamines (45).

Scheme 17. Synthesis of 3-alkylidene-1,2,5-oxadisilolanes (47) reported by Stratakis et al.

Scheme 18. Au/TiO₂-catalyzed synthesis of 2,5-dihydro-1,2,5-oxadisiloles (49) from alkynes (48a) and dihydrosilanes.

Scheme 19. AuNP-catalyzed post-Ugi cycloisomerization of terminal alkynes (50).

Scheme 20. Catalytic hydration of cyanides (55/57/59) mediated under microwaves by Au@PS NPs.

Scheme 21. AuNP-catalyzed lactonization of allene-carboxylic acids (60).

Scheme 22. Cu₂⁺@MSNs⁻(CO₂)₂-catalyzed synthesis of pyrazolopyranopyrimidine-5,7-diones (65).

Scheme 23. Synthesis of substituted triazoles (68a) using CuNPs.

Scheme 24. Synthesis of N-substituted triazoles (68a) catalyzed by CuNPs entrapped in a silica matrix.

Scheme 25. Synthesis of 1,4-disubstituted triazoles (68a) from alkyne (48a) and azide (69) catalyzed by CuNPs.

Scheme 26. Synthesis of triazoles (70) catalyzed by CRGO-Ima-Cu^I NCs.

Scheme 27. Click reaction for the synthesis of triazoles (73/75) catalyzed by CuNPs.

Scheme 28. Frieldländer synthesis of quinolines (78) catalyzed by Cu-HMOP.

Scheme 29. Click reaction for the synthesis of triazoles (80a) catalyzed by Cu-HMOP.

Scheme 30. CuNP-catalyzed 1,3-dipolar cycloaddition for the synthesis of triazoles (80b).

Scheme 31. N-Arylation of N–H heterocycles reported by Dabiri et al.

Scheme 32. CuNP-catalyzed N-arylation of imidazoles (81a), benzimidazole (84a) and pyrazole (92a).

Scheme 33. N-Arylation of imidazoles/triazoles/benzimidazoles (82a) catalyzed by CuNPs.

Scheme 34. N-Arylation of N-containing heterocycles (94b) catalyzed by CuNPs.

Scheme 35. N-Arylation of azoles with haloarenes (81d) catalyzed by CuO NPs.

Scheme 36. N-Arylation of N-containing heterocycles reported by Chattopadhyay et al.

Scheme 37. CuO NP-catalyzed C–N coupling of imidazoles, benzimidazoles, indoles (81c) with aryl iodides.

Scheme 38. N-Arylation of heterocycles catalyzed by CuNPs.

Scheme 39. N-Arylation of heterocycles catalyzed by CuNPs.

Scheme 40. CuNPs catalyzed C–N coupling of p-chloro nitrobenzene (82f) with morpholine (108a).

Scheme 41. CuNP-catalyzed N-arylation of N–H heterocycles.

Scheme 42. CuNP-catalyzed Ullmann coupling for the synthesis 4-pyridyl phenyl ether (112).

Scheme 43. Ullmann coupling of β-aminoalcohols (113) with aryl bromides (114) catalyzed by DMAP-CuNPs.

Scheme 44. CuNP-supported activated charcoal-catalyzed synthesis of indolizines (118d).

Scheme 45. CuNP-supported activated charcoal-catalyzed synthesis of heterocyclic chalcones (119).

Scheme 46. Synthesis of 2,4-disubstituted quinazolines (42b) from 2-aminobenzoketones (119a) and aryl or heteroaryl alkyl amine (117b).

Scheme 47. CuO NP-catalyzed synthesis of quinazolines (41c/d).

Scheme 48. Synthesis of 2-phenylbenzazoles (124a) from benzazoles (123a) and aryl iodides (82g) catalyzed by CuO NPs.

Scheme 49. Synthesis of 2-arylbenzoxazoles (124b) from o-halobenzanilides (125) catalyzed by CuO NPs.

Scheme 50. Cyclocondensation of 2-aminobenzothiazoles catalyzed by Cu(i) NPs.

Scheme 51. Synthesis of 2-substituted benzazoles (123b) from o-substituted anilines (6d) and aldehydes (2) catalyzed by heterogeneous NCs.

Scheme 52. Intramolecular cyclization of o-haloarenes (131/132) catalyzed by CuO NPs for the synthesis of benzimidazoles (84b), benzothiazoles and benzoxazoles (123c).

Scheme 53. CuI NP-catalyzed synthesis of benzimidazoles (124b) and quinazolinones (134a).

Scheme 54. Synthesis of 3-(benzimidazol-2-yl)quinolines (135) catalyzed by Cu@QCSSi.

Scheme 55. Synthesis of 2-substituted indazoles (92c) catalyzed by Cu@QCSSi.

Scheme 56. Synthesis of xanthones (136a) catalyzed by Cu-based magnetically recyclable NPs.

Scheme 57. Synthesis of pyrano[3,2-c]pyridines (138) catalyzed by nano Cu₂O-CP.

Scheme 58. Synthesis of pyrano[3,2-b]pyranoes (140) catalyzed by nano Cu₂O-CP.

Scheme 59. Synthesis of phenyl-1H-pyrazolo[3,4-b]pyridines (142a) catalyzed by CuO NPs.

Scheme 60. Synthesis of benzo[e]benzo[4,5]imidazo[1,2-c][1,3]thiazin-6-imines (144) using CuI NPs as the catalyst.

Scheme 61. CuO NP-catalyzed synthesis of 2,3-dihydroquinazolin-4(1H)-ones (146) and quinazolin-4(3H)-ones (134b). Conditions A: reflux, 3 h; and conditions B: 60 °C, ultrasound, 10–30 min.

Scheme 62. Synthesis of 2,3-disubstituted quinazolinones (134c) from 2-halobenzamides (133c) and arylalkyl amines (117e).

Scheme 63. Three-component reaction for the synthesis of N-sulfonylformamidines (149) catalyzed by CuNPs.

Scheme 64. Synthesis of imidazo[1,2-a]pyridines (151) catalyzed by CuNPs.

Scheme 65. Cu(0)NP-catalyzed ring opening and domino cyclisation of Δ²-isoxazoline-5-esters (152).

Scheme 66. Synthesis of chromeno[2,3-d]pyrimidin-8-amines (154) catalyzed by CuNP-PNF.

Scheme 67. Synthesis of 2H-indazoles (92d) catalyzed by CuNP-PNF.

Scheme 68. Synthesis of propargylamines (45b) catalyzed by CuNPs@MS.

Scheme 69. A³ coupling catalyzed by zero valent CuA.

Scheme 70. A³ coupling catalyzed by CuMCM-41.

Scheme 71. CuO NP-catalyzed synthesis of 2-triazolyl-imidazo[1,2-a]pyridines (157/159).

Scheme 72. Synthesis of 2-amino-4H-chromenes (160a/b/c) catalyzed by Cu@MNPs.

Scheme 73. CuO NP-catalyzed synthesis of 3,4-dihydropyrano[c]chromenes (160a).

Scheme 74. Dehydrogenation of indolines (161a) and 1,2,3,4-tetrahydroquinolines (36c).

Scheme 75. Aerobic dehydrogenation of 1,2,3,4-tetrahydroquinolines (36a) catalyzed by nitrogen-doped carbon-supported CoNPs.

Scheme 76. Dehydrogenation of aza-heterocycles catalyzed by Co-Phen@C.

Scheme 77. Hydrogenation of aza-heteroaromatic compounds catalyzed by Co-Phen@C.

Scheme 78. Oxidative dehydrogenation of heterocycles (36e/40b/161c) and their formylation catalyzed by Co@NCTs-800. % Conversion is summarized in parentheses.

Scheme 79. Oxidative dehydrogenation of N-heteroaromatics. % Conversion is summarized in parentheses.

Scheme 80. Dehydrogenative coupling of amines with aldehydes catalyzed by CoNCs.

Scheme 81. Dehydrogenation and hydrogenation catalyzed by Co@NPGS.

Scheme 82. Synthesis of propargylamines catalyzed by CoNPs.

Scheme 83. Synthesis of 1,8-dioxo-octahydroxanthenes (168a).

Scheme 84. Synthesis of methylamines (117g) from cyanides (169a) catalyzed by CoNPs.

Scheme 85. CoNP-catalyzed reduction of nitro-containing heterocycles (170) to aromatic amines (117d).

Scheme 86. Friedländer annulation catalyzed by CoNPs catalyzed by RFCo500 aerogel and CoO-carbon.

Scheme 87. Fe₃O₄ MNP-catalyzed synthesis of polyhydroquinolines (171a) and 1,4-dihydropyrimidines (172).

Scheme 88. “On water” chemistry for the synthesis of 1,4-dihydropyrimidines (172b/c).

Scheme 89. Iron oxide NP-catalyzed synthesis of imidazo or thiazolopyrimidines (173).

Scheme 90. Synthesis of tetrazolopyrimidines (175).

Scheme 91. Synthesis of benzoimidazo[1,2-a]pyrimidines (177) and tetrahydrobenzo[4,5]imidazo [1,2-d]quinazolin-1(2H)-ones (178).

Scheme 92. Knoevenagel–Michael-cyclization of barbituric acid (62), malononitrile (29) and substituted benzaldehydes (21a).

Scheme 93. Synthesis of pyrano[2,3-b]pyridines (181) catalyzed by γ-Fe₂O₃/Hap MNPs.

Scheme 94. Synthesis of pyrano[2,3-d]pyrimidines (179b), and pyrido[2,3-d]pyrimidines (182) catalyzed by iron nanoparticles.

Scheme 95. Nano-FDP-catalyzed synthesis of dihydropyrano[2,3-c]pyrazoles (184a).

Scheme 96. Nano-FGT catalyzed synthesis of spirooxindoles (187).

Scheme 97. One-pot synthesis of pyrazolophthalazinyl spirooxindoles (189c) catalyzed by Fe₃O₄@dipyridines.

Scheme 98. Synthesis of chromeno[2,3-d]pyrimidines (190) catalyzed by Fe₃O₄ NPs.

Scheme 99. Synthesis of benzo[g]chromenes (160d) using nano-Fe₃O₄/PEG.

Scheme 100. Synthesis of 1,8-dioxo-octahydroxanthene (168b) and dihydropyrano[2,3-c]pyrazole derivatives (184b) catalyzed by MNPs.

Scheme 101. Synthesis of 4H-benzo[b]pyran derivatives (160a/e/b) catalyzed by Fe₃O₄@SiO₂/DABCO.

Scheme 102. Synthesis of N-alkylated imidazoles (81f) catalyzed by Im-TBD@MNPs.

Scheme 103. Synthesis of arylamine-substituted chromeno[4,3-b]pyrrol-4(1H)-ones (195).

Scheme 104. Fe₃O₄@SO₃H NP-catalyzed synthesis of diaza-cyclooctanoids (197).

Scheme 105. Reactions of 2-oxo-2-phenylacetic acid (197) with substituted benzene-1,2-diamines (33d) in the presence of superparamagnetic Fe₂O₃ NPs.

Scheme 106. Fe₃O₄@SiO₂@propyl–ANDSA-catalyzed one-pot synthesis of tetrahydrobenzo[h]tetrazolo[5,1-b]quinazolines (199) and tetrahydrotetrazolo[1,5-a]quinazolines (200).

Scheme 107. Synthesis of pyranopyrazole derivatives (184c) using Fe₃O₄@SiO₂-HMTA-SO₃H as the catalyst.

Scheme 108. Fe₃O₄/SiO₂/(CH₂)₃N⁺Me₃Br₃-catalyzed synthesis of 2-aryl imidazoles (83g)/benzothiazoles (204a)/benzimidazoles (83h)/spermidine (206) derivatives.

Scheme 109. Synthesis of 2-aryl benzimidazoles (83h) from o-phenylene diamine (33e) and aryl aldehydes (21a) catalyzed by Fe NPs.

Scheme 110. Green one-pot synthesis of triazolo[1,2-a]indazole-triones (208) catalyzed by FeNi₃/quinuclidine.

Scheme 111. Oxidation of tetrahydroquinoline, piperidine and piperazine catalyzed by FeO_x@NGr-C.

Scheme 112. Synthesis of polyhydroquinolines (171b) using Fe₃O₄@B-MCM-41 as a new catalyst.

Scheme 113. S-Arylation of heteroaromatic thiols using aryl iodides (82h) catalyzed by Fe₃O₄@Si(CH₂)₃NH₂ NPs.

Scheme 114. Synthesis of pyrrolo[3,4-c]quinoline-1,3-diones (215) using Fe₃O₄ NCs.

Scheme 115. Synthesis of 2,3-dihydroquinazolin-4(1H)-ones (216a) and polyhydroquinolines (171c).

Scheme 116. FeNi₃-ILs catalyzed synthesis of the tetrahydrodipyrazolo pyridines (217).

Scheme 117. Synthesis of diazepines (220) catalyzed by Fe₃O₄/SiO₂ NPs.

Scheme 118. Synthesis of pyrido[2′,1′:2,3]imidazo[4,5-c]isoquinolines (221) reported by Maleki et al.

Scheme 119. Fe₃O₄ NP-decorated calix[n]arene sulfonic acid-catalyzed nucleophilic substitution of alcohols.

Scheme 120. Synthesis of 6H-chromeno[4,3-b]quinolin-6-ones (226).

Scheme 121. Synthesis of 2-aryl-quinoline-4-carboxylic acids (227) catalyzed by Fe₃O₄@SiO₂-UTSAC.

Scheme 122. Fe₃O₄ MNP-catalyzed synthesis of 1H-pyrrolo-[1,3]-oxazoles (232).

Scheme 123. Synthesis of cyano-heterocycles (169a) from heterocyclic carbaldehydes (2) catalyzed by Fe₂O₃–N/C.

Scheme 124. Friedel–Crafts alkylation of pyrroles (106b) using α,β-enal compounds (233).

Scheme 125. One-pot synthesis of spiro[chromeno[2,3-d]pyrimidine-5,3′-indoline] (234) and spiro[acenaphthylene-1,5′-chromeno[2,3-d]pyrimidine] (236).

Scheme 126. Synthesis of 2,3-dihydroquinazoli-4(1H)-ones (216b) catalyzed by Fe₃O₄ MNPs.

Scheme 127. Fe₃O₄@HNTs-PEI-catalyzed synthesis of dihydropyrano[2,3-c]pyrazoles (237).

Scheme 128. Synthesis of 2,4-diphenylpyrido[4,3-d]-pyrimidines (239) catalyzed by nanocatalysts.

Scheme 129. Synthesis of 1,2,4-triazolopyrimidines (240) and quinazolinones (241).

Scheme 130. Carboxylation of 2-aminobenzonitriles (6g) catalyzed by TBD@Fe₃O₄.

Scheme 131. LCMNP-catalyzed synthesis of 243.

Scheme 132. Synthesis of α-aminophosphates (246) catalyzed by LCMNP.

Scheme 133. Synthesis of pyranocoumarins (247).

Scheme 134. “On-water” synthesis of 248a and 168a.

Scheme 135. NiNPs catalyzed synthesis of 2H-indazolo[2,1-b]phthalazine-triones (250a).

Scheme 136. Synthesis of pyrazol-4-yl-methyl-pyrimidine-2,4,6(1H,3H,5H)-triones (251).

Scheme 137. Synthesis of bis(4-hydroxy-2H-chromen-2-one) (252) and bis(3-hydroxy-5,5-dimethylcyclohex-2-enone) (253) catalyzed by NiNPs.

Scheme 138. Synthesis of benzimidazoles (84d), quinazolines (32b) and quinazolinones (134c) catalyzed by NiNPs.

Scheme 139. Hydrogenation of quinoline catalyzed by Ni@PC.

Scheme 140. C–N cross-coupling of 106d and 88b with phenyl boronic acids catalyzed by NiO NPs.

Scheme 141. Reductive amination of aldehydes or ketones (256a) to primary amines (117h).

Scheme 142. Knoevenagel condensation of aldehydes (2) and barbituric acids (62c) catalyzed by NiNPs.

Scheme 143. Synthesis of 1,2,3,4-terahydroquinolines (36h) catalyzed by Ni–NiAl-LDO NPs.

Scheme 144. Pd-catalyzed carbonylative cyclization for the synthesis of N-substituted isoindol-1,3-diones (105b) and isoquinolin-1,3-diones (259).

Scheme 145. Synthesis of 5-methyl-13,13a-dihydro-8H-isoquinolino[1,2-b]quinazolin-8-one derivatives (261) from 3-allyl-2-(2-bromophenyl)-2,3-dihydroquinazolin-4(1H)-one (260).

Scheme 146. Synthesis of 9-phenylacridine (263) from 9-chloroacridine (262) using SMNP@NHC–Pd as the catalyst.

Scheme 147. Synthesis of 1,2,3,4-tetrahydroquinolines or 1,2,3,4-tetrahydroquinoxalines (36i) from quinolines and quinoxalines (35h) using PdNPs.

Scheme 148. Synthesis of quinolines or quinoxalines (35h) catalyzed by PdNPs.

Scheme 149. Hydrogenation of quinoline and quinoxalines (35h) catalyzed by PdNPs.

Scheme 150. Pd/MgO-catalyzed hydrogenation of quinolines (35a) using a Parr hydrogenator.

Scheme 151. Catalytic dehydrogenation of indolines (161b) catalyzed by PdNPs supported on CNHs.

Scheme 152. PdNP-catalyzed synthesis of 2-phenyl indoles (88i) via C–H activation.

Scheme 153. Direct C-2 arylation of benzoxazole (264a) catalyzed by PdNPs.

Scheme 154. C–H activation of thiophenes (58b) and indoles (88j) reported by Yamada et al.

Scheme 155. Direct C–H arylation of thiazoles (266a) with bromoarenes (67c) catalyzed by Pd-DI@GO.

Scheme 156. Aminocarbonylation of aryl halides (82d/82j) catalyzed by PdNPs.

Scheme 157. Synthesis of 2-aryl quinazolinones (134d) catalyzed by Pd@PS.

Scheme 158. Dehalogenation of aryl halides using PdNPs.

Scheme 159. One-pot synthesis of N-containing heterocyclic compounds (213c) catalyzed by PdNPs.

Scheme 160. One-pot synthesis of tetrahydro-β-carboline compounds (272) catalyzed by PdNPs.

Scheme 161. Acyl Sonogashira reaction catalyzed by SWNT-PdNPs.

Scheme 162. One-pot synthesis of 2,4-disubstituted pyrimidines (213c).

Scheme 163. Synthesis of pyrazoles (92i) and oxazoles (274) catalyzed by in situ-formed PdNPs.

Scheme 164. N-arylation of N-containing heterocycles catalyzed by Pd(0)NPs.

Scheme 165. C–N coupling of azoles with aryl halides catalyzed by Pd/ZnO NPs.

Scheme 166. C–N cross coupling of aza-heterocycles catalyzed by PdNPs-SSS.

Scheme 167. Green synthesis of bis(heterocyclyl)methanes in water catalyzed by PdNPs.

Scheme 168. Synthesis of xanthones catalyzed by PdNPs.

Scheme 169. Regioselective and stereoselective synthesis of (Z)-3-methyleneisoindoline-1-ones (278) and furo[3,2-h]quinolines (279).

Scheme 170. Pd@PS-catalyzed synthesis of 1,2-disubstituted indoles (88m) and 3-pyrolines (281).

Scheme 171. Larock indole synthesis catalyzed by Pd clusters.

Scheme 172. Synthesis of benzofurans catalyzed by PdNPs.

Scheme 173. PdNP-catalyzed cyanation of bromo derivatives.

Scheme 174. Sonogashira cross-coupling catalyzed by PdNPs-nSTDP.

Scheme 175. Phosphine-supported RuNP-catalyzed synthesis of substituted pyrazines (284a) and imidazoles (81i) from α-diketones.

Scheme 176. RuNP-catalyzed regioselective deuteration of N-containing heterocycles.

Scheme 177. Ru@PsIL-catalyzed synthesis of N-formamides (123f/40d) and benzazoles (123g).

Scheme 178. RuNPs in IL-catalyzed selective hydrogenation of N-containing aromatic heterocycles.

Scheme 179. MNP-Ru@SiO₂-catalyzed ring-closing metathesis of dienes (288).

Scheme 180. N-oxidation of tertiary aromatic azacyclic amines.

Scheme 181. [SiPrPy]AlCl₄@MNP-catalyzed one-pot synthesis of dihydropyrano[3,2-b]chromenediones (292/293) using three component of aromatic aldehydes (21a), 1,3-diones (7b) and Kojic acid (139).

Scheme 182. SiO₂ NP-catalyzed synthesis of quinoxalines (38f) under solvent-free conditions.

Scheme 183. SiO₂ NP-catalyzed synthesis of quinolines (116g/h/i).

Scheme 184. Silica NP-catalyzed synthesis of benzopyranopyrimidines (295) under mild reaction conditions.

Scheme 185. Synthesis of 2-amino-4H-chromen-4-yl phosphonates (297) by Fe₃O₄ NPs supported on sulfochitosan (Fe₃O₄@CS).

Scheme 186. Green synthesis of 1,4-dihydropyrimidines (172d) in aqueous conditions.

Scheme 187. Synthesis of 2-azapyrrolizidine under aqueous conditions.

Scheme 188. Synthesis of 2-oxazolidinones (300) catalyzed by SiNPs.

Scheme 189. Synthesis of quinazoline-2,4-diones (242b) catalyzed by KCC-1.

Scheme 190. Environmentally benign synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones (250b).

Scheme 191. Synthesis of substituted pyrazolo[1,2-b]phthalazine-5,10-diones (250c) from aromatic aldehyde (2), 1,3-diketone (7a or 63g) and 2,3-dihydrophthalazine-1,4-dione (249).

Scheme 192. Synthesis of tetrahydrobenzo[b]pyrans (160f/g) catalyzed by SiO₂ NPs.

Scheme 193. IL@ZnO NP-catalyzed synthesis of 1,2-disubstituted benzimidazoles (85j) reported by Singh et al.

Scheme 194. Co-doped ZnS NP-catalyzed synthesis of pyrazolones (302) and 1,3-oxathiolan-5-ones (304) under IR irradiation.

Scheme 195. ZnO NP-catalyzed synthesis of 1,2-dihydro-1-arylnaphtho[1,2-e][1,3]oxazine-3-ones (305).

Scheme 196. ZnO NP-catalyzed synthesis of 14-substituted-14H-dibenzo[a,j]xanthenes (306).

Scheme 197. Synthesis of the pyridines catalyzed by ZnO NPs (10 mol%) at 70 °C.

Scheme 198. ZnO NP-catalyzed synthesis of imidazo[1,2-a]pyridines (311).

Scheme 199. ZnO NP-catalyzed synthesis of densely functionalized 4H-chromenes (160h).

Scheme 200. Synthesis of benzo[g]pyrimido[4,5-b]-quinoline-2,4,6,11(1H,3H)-tetraone (172e).

Scheme 201. Catalytic applications of nanorod-ZnO in the synthesis of polysubstituted pyrroles (107c).

Scheme 202. Synthesis of flavanones (314) under green benign conditions.

Scheme 203. Synthesis of 14-phenyl-14H-dibenzo[a,j]xanthenes (306) and 1,8-dioxooctahydroxanthenes (168a).

Scheme 204. ZnO NP-catalyzed synthesis of 2-amino-4H-chromenes (160b).

Scheme 205. ZnO NP-mediated synthesis of multi-armed poly(tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones) (316).

Scheme 206. ZnS NPs as heterogeneous catalyst in [3 + 2] cycloaddition.

Scheme 207. Synthesis of cyclic thioureas (22c) catalyzed by MgO NPs.

Scheme 208. Synthesis of spirooxindole-furan derivatives (319).

Scheme 209. Synthesis of polyhydroquinolines (171d) under neat conditions catalyzed by MgO NPs.

Scheme 210. MNP-catalyzed dehydrogenation and hydrogenation.

Scheme 211. One-pot synthesis of 4-phenyl-substituted pyrano-fused coumarins (160a) catalyzed by MoO₃ NPs under green conditions.

Scheme 212. Synthesis of 2,3-dihydroquinazolin-4(1H)-one (216c).

Scheme 213. Synthesis of polyhydroquinolines (171c) using the MNP/DETA-SA catalyst.

Scheme 214. Scope of SMNOP-1 catalyzed oxyalkylation of vinylarenes (192b).

Scheme 215. Sulfur NP-catalyzed synthesis of substituted 4H-pyrido[1,2-a]pyrimidines (322) in SDS-water medium.

Scheme 216. MnNP-catalyzed synthesis of flavones (323a).

Scheme 217. Selective reduction of 1-(pyridin-2-yl)ethan-1-one (110j) using RhNPs.

Scheme 218. RhNPs as a co-catalyst in the dehydrogenation of N-heteroaromatics.

Scheme 219. Hydrogenation of nitrogen- and oxygen-containing heterocyclic scaffolds.

Scheme 220. Hydrogenation of aza-heterocycles catalyzed by RhNPs supported on MgO. Complete product distribution (100%) was reported in each instance.

Scheme 221. RhNP-catalyzed synthesis of benzofurans and flemichapparin C.

Scheme 222. Pt@TiO₂-catalyzed one-pot synthesis of benzo[d]imidazoles (84e) from o-phenylene diamine (33a) and substituted alcohols (254c).

Scheme 223. One-pot synthesis of 1,4-dihydropyridines (172f) catalyzed by PtNPs@GO.

Scheme 224. Reductive amination of cyclohexanone (294b) with piperidine (285g) catalyzed by PtNPs supported on charcoal or metal oxides.

Scheme 225. TiO₂-nanoparticle-catalyzed synthesis of trifluoromethyl-4,5-dihydro-1,2,4-oxadiazoles (212c) and trifluoromethyl-1,2,4-oxadiazoles (212d).

Scheme 226. Nano-TiO₂ NP-catalyzed three-component reaction of o-amino benzoic acid (6q), ethyl acetate (329) and amine (117d).

Scheme 227. Synthesis of chromeno[b]pyridines (331) catalyzed by TiO₂ NPs.

Scheme 228. Synthesis of pyran-chromenes catalyzed by fluorescent t-ZrO₂ NPs.

Scheme 229. Synthesis of spirooxindoles (332a/332b) catalyzed by p-TSA@TiO₂ NPs.

Scheme 230. Synthesis of spiroannulated pyrimidophenazines (333a/b/c) catalyzed by Er-doped TiO₂ NPs.

Scheme 231. Ultrasound-mediated synthesis of benzo[d]imidazoles catalyzed by Zr-PCP-NH₂.

Scheme 232. Synthesis of quinoxalines (38g) catalyzed by nano-ZrO₂.

Scheme 233. Synthesis of Biginelli and Biginelli-like products catalyzed by ASA.

Scheme 234. MCM-41-HWO₄-catalyzed synthesis of pyrrolo[2,1-a]isoquinolines (337).

Scheme 235. Synthesis of quinolines (116j) catalyzed by tetraphenylcyclopentandienone@HgO NPs.

Scheme 236. Synthesis of benzoxazole Ni–Pd binary NCs for C–O bond activation for the Suzuki–Miyaura cross-coupling of o-heterocycle-tethered sterically hindered aryl ester (264c), silyl ether, sulfonates, carbamate, and carbonates with aryl boronic acids (255b).

Scheme 237. Reversible hydrogen uptake and release catalyzed by Pd₂Ru@SiCN bimetallic catalyst.

Scheme 238. Synthetic transformation from chalcone (2′-hydroxychalcone, 119b) into aurone (341), flavanone (323b), and flavones (323c) using Au and Pd metal catalysts.

Scheme 239. CuFeO₂ NP-catalyzed synthesis of imidazo[1,2-a]pyridines (151b).

Scheme 240. Synthesis of 1,8-dioxo-octahydroxanthenes (168c) using CuFe₂O₄@SiO₂-OP₂O₅H MNP catalyst.

Scheme 241. Synthesis of N-arylated heterocycles catalyzed by Cu₂FeO₄ MNPs.

Scheme 242. CuFe₂O₄ NP-catalyzed synthesis of aroylimidazo[1,2-a]pyrimidine/aroylimidazo[1,2-a]pyridines.

Scheme 243. Synthesis of pyrido[2,3-d:6,5-d′]dipyrimidines (172d) catalyzed by CuFe₂O₄ MNPs.

Scheme 244. Cu₂Fe₂O₄ NP-catalyzed Click reaction for the synthesis of 1,4-disubstituted 1,2,3-triazoles (68c).

Scheme 245. Synthesis of tetrahydro pyridines (342) and 1H-pyrrole derivatives (343) using microwave irradiation catalyzed by CoFe₂O₄.

Scheme 246. Synthesis of tetrahydrobenzo[h][1,3]thiazolo[4,5-b]quinolin-9-ones (345) reported by Hamad et al.

Scheme 247. One-pot synthesis of 2H-indazolo[2,1-b]phthalazine-triones (250d) using CoFe₂O₄@CS-SO₃H.

Scheme 248. Green synthesis of 3,6-di(pyridin-3-yl)-1H-pyrazolo[3,4-b]pyridine-5-carbonitriles (142b) reported by Zhang et al.

Scheme 249. Ultrasonic wave-mediated synthesis of dihydropyrimido[4,5-b]quinolinetriones (172h).

Scheme 250. Synthesis of pyrano[3,2-c]quinolines (348) and spiro-oxindoles (349) catalyzed by cobalt-ferrite NPs.

Scheme 251. NiFe₂O₄ MNP-catalyzed Claisen–Schmidt condensation for the synthesis of the chalcones (350b).

Scheme 252. ZnFe₂O₄ NP-catalyzed synthesis of pyrano[2,3-d]pyrimidines (179c) reported by Khazaei et al.

Scheme 253. Aqueous pyrazole-fused chromenes (351) catalyzed by zinc ferrite NPs.

Scheme 254. Synthesis of 1-and 5-substituted tetrazoles (86c/87b) catalyzed by the salen complex of Cu(ii) supported on superparamagnetic Fe₃O₄@SiO₂ NPs.

Scheme 255. Synthesis of N-arylated heterocycles catalyzed by Fe₃O₄@SiO₂-TCT-PVA-Cu(ii).

Scheme 256. Synthesis of 5-aryl tetrazoles (87c) catalyzed by Fe₃O₄@SiO₂-TCT-PVA-Cu(ii).

Scheme 257. Synthesis of arylated N-containing heterocycles (124d/109f) using Fe₃O₄@SiO₂-dendrimer-encapsulated Cu(ii) catalyst.

Scheme 258. Fe₃O₄@SiO₂-dendrimer-encapsulated Cu(ii)-catalyzed synthesis of benzazoles (124e).

Scheme 259. Synthesis of arylated 1,2,3,4-tetrazoles (87c).

Scheme 260. Synthesis of 2,3-dihydroquinazolin-4(1H)-ones (216c) catalyzed by Cu(ii)/l-His@Fe₃O₄ NCs.

Scheme 261. Synthesis of polyhydroquinolines (171d) catalyzed by Cu(ii)/l-His@Fe₃O₄ NCs.

Scheme 262. Synthesis of 2-amino-3,5-dicarbonitrile-6-thio-pyridines (110p) catalyzed by Cu(ii)/l-His@Fe₃O₄ NCs.

Scheme 263. FMNP@TD–Cu(ii) catalyzed synthesis of regioselective 1,4-disubstituted 1,2,3-triazoles (68c).

Scheme 264. Aqueous synthesis of bis(indolyl)methanes (276b).

Scheme 265. Aqueous synthesis of N-arylalkyl 1,2,3-triazoles (71b).

Scheme 266. Synthesis of triazole via the click reaction among alkyl halides (67e), alkynes (48a) and 66 in the presence of a catalyst such as Cu(ii) complex on Fe₃O₄@SiO₂ NPs.

Scheme 267. Synthesis of quinazolinones (134f) catalyzed by Cu(i)Fe₃O₄@SiO₂.

Scheme 268. Synthesis of 2-alkynylpyrrolidines/piperidines (45e) reported by Rawat et al.

Scheme 269. N-substituted pyrroles (106b) synthesized in water using nano γ-Fe₂O₃@SiO₂–Sb-IL.

Scheme 270. Synthesis of 3,4-dihydro-2H-pyrans (353).

Scheme 271. Synthesis of 1H-pyrazolo[1,2-b]phthalazinediones (250e) reported by Arora et al.

Scheme 272. 1H-pyrazolo[1,2-b]phthalazinediones (250f) reported by Maleki et al.

Scheme 273. Ni(NO₃)₂-imine/thiophene-Fe₃O₄@SiO₂ NP-catalyzed synthesis of polyhydroquinolines (171e).

Scheme 274. Ni(NO₃)₂-imine/thiophene-Fe₃O₄@SiO₂ NP-catalyzed synthesis of 2,3-dihydroquinazolin-4(1H)-ones (216a).

Scheme 275. Synthesis of 3-benzoxazol-2-yl-chromen-2-ones (354) assisted by Co–Si NCs.

Scheme 276. CeO₂–Fe₃O₄ MNP-catalyzed C–H activation of benzoxazole and benzothiazoles (124a).

Scheme 277. Synthesis of acridinediones (172i) catalyzed by bifunctional nanocatalysts.

Scheme 278. LAIL@MNP- catalyzed three-component and one-pot synthesis of benzoxanthenes (355).

Scheme 279. Paal–Knorr reaction catalyzed by LAIL@MNP.

Scheme 280. Synthesis of 2-phenyl-8H-thieno[2,3-b]indoles (356) using DES@MNP.

Scheme 281. Synthesis of 3-phenyl-2-oxazolidinones from styrenes (192c), anilines (6f) and gaseous carbon dioxide.

Scheme 282. Cu-catalyzed A³ coupling for the synthesis of propargylamines (45f).

Scheme 283. CuAAC reactions of alkynes (48a) and azides (69).

Tejas M. Dhameliya