H5PW10V2O40@VOx/SBA-15-NH2 catalyst for the solventless synthesis of 3-substituted indoles

Abstract

Functionalization of mesoporous SBA-15 frameworks by transition metal oxides offers a flexible route to fabricate new heterogeneous catalysts. Here, an inorganic-organic hybrid nanoporous catalyst H 5 PW 10 V 2 O 40 @VO x /SBA-15-NH 2 , was prepared and utilized as an efficient, ecofriendly, and recyclable catalyst for the one-pot, multi-component synthesis of 3-substituted indoles by indole substitution with aldehydes and malononitrile under solvent-free conditions. Catalysts were prepared by the non-covalent attachment of H 5 PW 10 V 2 O 40 to a 3 wt%VO x /SBA-15 nanoporous support through a 3-(triethoxysilyl)propylamine linker. VO x /SBA-15 was prepared by a one-pot hydrothermal synthesis from TEOS and vanadium(V) oxytri-tert-butoxide [VO(O-t Bu) 3 ]. The resulting H 5 PW 10 V 2 O 40 @VO x /SBA-15-NH 2 material was characterized by bulk and surface analysis including N 2 porosimetry, FE-SEM, XRD, XPS, FT-IR, TGA-DTA, UV-Vis and ICP-OES, evidencing retention of the heteropolyacid Keggin structure. H 5 PW 10 V 2 O 40 @VO x /SBA-15-NH 2 exhibits high activity and excellent yields (70-95 %) of 3substituted indoles under mild conditions, with negligible deactivation.

Recent Applications of Heteropolyacids and Related Compounds in Heterocycle Synthesis. Contributions between 2010 and 2020

“…In these conditions, 10 spirooxindoles were obtained with yields between 70 and 98% (Scheme 17). Mahdizadeh Ghohe et al [77] synthesized vanadium-doped SBA-15 (VOx/SBA-15) materials by sol-gel synthesis; subsequently the surface of the resulting VOx/SBA-15 material was modified by adding 3-(triethoxysilyl) propylamine as a linker compound to finally non-covalently support the heteropolyacid H 5 PW 10 V 2 O 40 , thus obtaining a new inorganic-organic nanoporous material named PW 10 V 2 @VOx/SBA-15-NH 2 . The materials were extensively characterized, determining that the Keggin-type structure was preserved after immobilization of the HPA and that they presented a solid Lewis-Brønsted acid character.…”

H3PW12O40/SBA-15 for the Solventless Synthesis of 3-Substituted Indoles

“…Further purification of the desired products was achieved via re-crystallization in ethanol. Physical and spectroscopic properties of the pure products were compared with the corresponding known properties of 2-[(1H-indol-3-yl)(aryl)methyl]malononitriles [20,21].…”

One Pot Synthesis, Characterization of Benzothiazole/ Benzimidazole Tethered Imidazole Derivatives using Clay as Catalyst

“…The mesoporous catalyst Nb-Zr/KIT-6 successfully used for benzylpyrazolyl coumarins synthesis 5 . The synthesis of 3-substituted indoles were reported by using H 5 PW 10 V 2 O 40 @VO x / SBA-15-NH 2 as a catalyst 6 . Heterogeneous catalysts exhibit properties like low toxicity, recyclability, easy separation, great diversity at structural level and stability at high temperatures [7][8][9][10] .…”