Nayeem Ahmed | Aligarh Muslim University (original) (raw)
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Papers by Nayeem Ahmed
A simple, efficient and environmentally benign on-water protocol for the synthesis of novel 1,4-d... more A simple, efficient and environmentally benign on-water protocol for the synthesis of novel 1,4-dihydropyridine derivatives via pseudo four component addition and cyclization sequence using mesoporous alumina sulphuric acid as a recyclable and heterogeneous catalyst, has been described. Thecatalyst showed excellent catalytic activity giving products in high yields and could be reused for sevensuccessive catalytic cycles. The catalyst was characterized by FT-IR, XRD, FE-SEM, EDX and TG analyses.The mesoporosity of alumina was determined by BET and TEM analyses.
For the first time sulphated silica tungstic acid (SSTA) has been synthesized and used as an acid... more For the first time sulphated silica tungstic acid (SSTA) has been synthesized and used as an acidic catalyst in organic synthesis. The catalyst was prepared by a simple method based on the reaction of silica with SOCl 2 followed by addition of sodium tungstate and then functionalization with chlorosulfonic acid. The three-component Biginelli-like condensation of different heteroaldehydes, urea and ethyl cyanoacetate or phenyl acetic acid catalyzed by SSTA under solvent-free conditions afforded novel tetrahydropyrimidines in high yields. The catalyst tolerated different heteroaldehydes and also catalyzed the synthesis of Biginelli compounds efficiently giving excellent yield of products. The catalyst was characterized by FT-IR, XRD and SEM-EDX analyses. The stability of the catalyst was evaluated by DSC and TG analyses. The major advantages of the present method are high yields, short reaction times, and solvent-free reaction conditions. The activity and simple recyclability without losing catalytic activity make this catalyst a good replacement to literature methods.
NH 2 SO 3 H-SiO 2 as a new water-compatible, recyclable heterogeneous catalyst for the synthesis ... more NH 2 SO 3 H-SiO 2 as a new water-compatible, recyclable heterogeneous catalyst for the synthesis of novel (α,β-unsaturated) β-amino ketones via aza-Michael reaction Zeba N. Siddiqui* and Nayeem Ahmed NH 2 SO 3 H-SiO 2 /water as a novel catalytic system was used for the synthesis of (α,β-unsaturated) β-amino ketones via aza-Michael reaction at reflux conditions. The methodology was of general applicability and the catalyst exhibited activity up to five cycles. The catalyst was characterized for the first time using FT-IR, X-ray diffraction and scanning electron microscopic-energy dispersion analytical X-ray. The stability of the catalyst was evaluated by differential scanning calorimetry and TGA/differential thermal analysis. High efficiency of the catalyst along with its recycling ability and the rather low loading demonstrated in reactions are the merits of the presented protocol.
Highly efficient ZnO nanoparticle catalyzed one-pot solvent-free synthesis of novel pyridine deri... more Highly efficient ZnO nanoparticle catalyzed one-pot solvent-free synthesis of novel pyridine derivatives by three-component reaction of b-enaminones, different active methylene compounds, and ammonium acetate via Michael addition, cyclodehydration, and elimination sequence is reported. The catalyst was recyclable up to six catalytic cycles without a significant loss in the catalytic activity. This new protocol has the advantages of environmental friendliness, higher yields, solvent-free, low loading of catalyst, shorter reaction times, and convenient operation procedure. ZnO nanoparticles were characterized by XRD, SEM, and TEM analyses.
A simple, efficient and environmentally benign on-water protocol for the synthesis of novel 1,4-d... more A simple, efficient and environmentally benign on-water protocol for the synthesis of novel 1,4-dihydropyridine derivatives via pseudo four component addition and cyclization sequence using mesoporous alumina sulphuric acid as a recyclable and heterogeneous catalyst, has been described. Thecatalyst showed excellent catalytic activity giving products in high yields and could be reused for sevensuccessive catalytic cycles. The catalyst was characterized by FT-IR, XRD, FE-SEM, EDX and TG analyses.The mesoporosity of alumina was determined by BET and TEM analyses.
For the first time sulphated silica tungstic acid (SSTA) has been synthesized and used as an acid... more For the first time sulphated silica tungstic acid (SSTA) has been synthesized and used as an acidic catalyst in organic synthesis. The catalyst was prepared by a simple method based on the reaction of silica with SOCl 2 followed by addition of sodium tungstate and then functionalization with chlorosulfonic acid. The three-component Biginelli-like condensation of different heteroaldehydes, urea and ethyl cyanoacetate or phenyl acetic acid catalyzed by SSTA under solvent-free conditions afforded novel tetrahydropyrimidines in high yields. The catalyst tolerated different heteroaldehydes and also catalyzed the synthesis of Biginelli compounds efficiently giving excellent yield of products. The catalyst was characterized by FT-IR, XRD and SEM-EDX analyses. The stability of the catalyst was evaluated by DSC and TG analyses. The major advantages of the present method are high yields, short reaction times, and solvent-free reaction conditions. The activity and simple recyclability without losing catalytic activity make this catalyst a good replacement to literature methods.
NH 2 SO 3 H-SiO 2 as a new water-compatible, recyclable heterogeneous catalyst for the synthesis ... more NH 2 SO 3 H-SiO 2 as a new water-compatible, recyclable heterogeneous catalyst for the synthesis of novel (α,β-unsaturated) β-amino ketones via aza-Michael reaction Zeba N. Siddiqui* and Nayeem Ahmed NH 2 SO 3 H-SiO 2 /water as a novel catalytic system was used for the synthesis of (α,β-unsaturated) β-amino ketones via aza-Michael reaction at reflux conditions. The methodology was of general applicability and the catalyst exhibited activity up to five cycles. The catalyst was characterized for the first time using FT-IR, X-ray diffraction and scanning electron microscopic-energy dispersion analytical X-ray. The stability of the catalyst was evaluated by differential scanning calorimetry and TGA/differential thermal analysis. High efficiency of the catalyst along with its recycling ability and the rather low loading demonstrated in reactions are the merits of the presented protocol.
Highly efficient ZnO nanoparticle catalyzed one-pot solvent-free synthesis of novel pyridine deri... more Highly efficient ZnO nanoparticle catalyzed one-pot solvent-free synthesis of novel pyridine derivatives by three-component reaction of b-enaminones, different active methylene compounds, and ammonium acetate via Michael addition, cyclodehydration, and elimination sequence is reported. The catalyst was recyclable up to six catalytic cycles without a significant loss in the catalytic activity. This new protocol has the advantages of environmental friendliness, higher yields, solvent-free, low loading of catalyst, shorter reaction times, and convenient operation procedure. ZnO nanoparticles were characterized by XRD, SEM, and TEM analyses.