Silica-bonded N-propyl sulfamic acid as an efficient recyclable catalyst for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones under heterogeneous conditions

One-pot, solvent-free and efficient synthesis of 2,4,6-triarylpyridines catalyzed by nano-titania-supported sulfonic acid as a novel heterogeneous nanocatalyst

“…In all cases, aromatic aldehydes with substituents carrying either electron-donating or electron-withdrawing groups reacted successfully and gave the products in good yields (Table 3). It was found that aromatic aldehydes with electron-withdrawing groups (Table 3, entries 2, 3,5,8,11,13,15) reacted faster than those with electron-donating groups (Table 3, entries 4, 6, 7, 9, 12, 16-18, 20, 21), as would be expected [24,25]. These results justified one more time the efficiency of n-TSA.…”

“…Recently, solid-supported heterogeneous catalysts have gained considerable interest in organic synthesis because of their unique properties such as high efficiency due to more surface area, more stability, reusability, low toxicity and ease of handling [3][4][5][6][7][8]. We have recently reported nano titania-supported sulfonic acid (n-TSA) [9], as an effective heterogeneous acidic nanocatalyst for the promotion of a wide range of organic reactions as for its Lewis and Bronsted acidity features.…”

Nano silica-bonded N-propylsulfamic acid as an efficient and environmentally benign catalyst for the synthesis of 1,5-benzodiazepines

“…The peak at 1399 cm -1 represented Si-CH 2 stretching. Si-O-Si stretching and bending modes of SiO 2 appeared near 796 and 468 cm -1 in the catalyst [5,6]. These characteristic vibrations clearly indicate the formation of desired catalytic system.…”

“…Various chemical transformations reported with this catalyst include synthesis of aryl-14H-dibenzo[a,i]xanthenes, formylation and acetylation of alcohols and amines, synthesis of 1,8-dioxodecahydroacridines/1,8-dioxo-octahydroxanthenes/quinoxalines, chemoselective synthesis of 1,1-diacetates, transesterification of soybean oil/esterification of oleic acid with methanol, synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones [1][2][3][4][5][6], and so on. In recent years, growing attention has been devoted toward developing novel nanocatalysts [7,8].…”

1,3-Disulfonic acid benzimidazolium chloride as an efficient and recyclable ionic liquid catalyst for the synthesis of 3,4-dihydropyrimidine-2-(1H)-ones/thiones

“…DHPMs have received special attention given their wide range of biological and pharmaceutical activities, including antibacterial, antiviral, anticancer, antitumor, antifungal, antioxidant, anti-inflammatory, and antihypertensive properties, their use as calcium channel modulators, a 1A -antagonists, neuropeptide Y(NPY) antagonists, and other related properties [12][13][14][15][16]. Over the past decade, several methods have been reported for the synthesis of DHPMs using LaCl 3 -graphite [15], CuCl 2 Á2H 2 O [16], Yb(OTf) 3 [17], phytic acid [18], triphenylphosphine (PPh 3 ) [19], silica-bonded N-propyl sulfamic acid [20], Fe(OTs) 3 Á6H 2 O [21], bioglycerol-based sulfonic acid functionalized carbon [22], sulfonated carbon materials (SCM) [ [33] and silica-bonded S-sulfonic acid (SBSSA) [34]. While existing synthetic methods are effective for the preparation of target compounds, some suffer shortcomings such as long reaction time (2.5-43 h), elevated temperature (refluxing EtOH or MeCN and solvent-free 140°C), low yields, the use of hazardous organic solvents (e.g., EtOH, MeCN, AcOH, THF, isopropanol) or unrecyclable catalysts (e.g., CuCl 2 Á2H 2 O, InCl 3 , Yb(OTf) 3 , Fe(OTs) 3 Á6H 2 O), and poor compliance with the green chemistry protocols.…”