Rice husk: A mild, efficient, green and recyclable catalyst for the synthesis of 12-Aryl-8, 9, 10, 12-tetrahydro [a] xanthene-11-ones and quinoxaline derivatives

Abstract

Rice husk, as a green and cheap reagent, can be used for the promotion of the synthesis of 12-aryl -8, 9,10,12-tetrahydrobenzo[a] xanthen-11-one derivatives (ATXOs) via threecomponent reaction of aldehydes, 2-naphthol and 5,5-dimethyl-1,3-cyclohexadione (dimedone) under solvent-free conditions. This catalyst can also be used for the preparation of quinoxaline derivatives in a mixture of H 2 O and CH 3 CN at 50 8C. The present methodology offers several advantages such as high yields, simple procedure, low cost, short reaction times, mild reaction conditions and use of a green, cheap and reusable catalyst.

Synthesis and Applications of Silyl 2‐Methylprop‐2‐ene‐1‐sulfinates in Preparative Silylation and GC‐Derivatization Reactions of Polyols and Carbohydrates

“…Next, we employeds ilyl sulfinates 1a-d for the regioselective protection of the primary alcohol moieties of diol 7, methyl hexopyranosides 8-10, 12 and glucal (11)i nD MF at 20 8C. All reactions led to high yields ( Table 3, entries 1-9).…”

“…[8] Approaches that deal with GC derivatization frequently use N,O-bis(trimethylsilyl)acetamide (BSA), N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), N-trimethylsilylimidazole (TMSIM), N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA), and others. [9] Other methods are based on the S N 2 substitution of SiÀO, [10] SiÀN, [11] SiÀS, [12] or SiÀC [13] compounds or on catalyzed dehydrogenative silanolysis with R 3 SiH reagents. [14] Although these methods offer good reliability,t hey may fail because of low reactivity,d ifficult removal of excessb ase and byproducts, and/ort heir ability to epimerizeo rd estroy basesensitivec ompounds.…”

Synthesis, Characterization, and Catalytic Behavior of Bamboo Rice Husk Ash

“…BRiHA‐SiO 2 was synthesized using an already reported protocol . The formation of BRiHA‐SiO 2 was confirmed by FT‐IR, powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), and Brunauer–Emmett–Teller (BET) adsorption analysis.…”

“…There are a variety of heterogeneous catalysts such as alumina, titania, zirconia, zeolite, clay, and silica that have been successfully employed in several organic transformations to minimize wastage, which is a cause of environmental pollutions . Among them, silica has been successfully used to catalyze various organic transformations with excellent yields of the products . In this connection, here we report the development of an efficient protocol for the synthesis of tetrahydro‐4 H ‐chromene‐3‐carbonitrile using silica derived from bamboo rice husk ash (BRiHA‐SiO 2 ) as catalyst.…”

Synthesis of benzimidazole and quinoxaline derivatives using reusable sulfonated rice husk ash (RHA-SO3H) as a green and efficient solid acid catalyst

“…This attention can be attributed to the reduction of environmental pollution and the low cost of the applied methods. Rice husk ash is one of these types of reagents recently used as a solid acid catalyst in some of the important organic reactions [26][27][28][29].…”