Zinc Chloride Doped Natural Phosphate as 1,3-Dipolar Cycloaddition Catalyst

1,5-disubstituted 1,2,3-triazolylated carbohydrates and nucleosides

In general, 1,5-disubstituted 1,2,3-triazolyl moiety is much less common in the synthesis and applications in comparison to its regioisomeric counterpart. Moreover, the synthesis of 1,5-disubstituted 1,2,3-triazoles are not so straightforward as is the case for copper catalyzed strategy of 1,4-disubstituted 1,2,3-triazoles. The preparation of 1,5-triazolylated carbohydrates and nucleosides are even more complex because of the difficulties in accessing the appropriate starting materials as well as the compatibility of reaction conditions with the various protecting groups. 1,5-Disubstitution regioisomeric triazoles of carbohydrates and nucleosides were traditionally obtained as minor products through straightforward heating of the mixture of azides and terminal alkynes. However, the separation of isomers was tedious or in some cases futile. On the other hand, regioselective synthesis using ruthenium catalysis triggered serious concern of residual metal content in therapeutically important ingredients. Therefore, serious efforts are being made by several groups to develop non-toxic metal based or completely metal-free synthesis of 1,5-disubstituted 1,2,3-triazoles. This article strives to summarize the pre-Click era as well as the post-2001 reports on the synthesis and potential applications of 1,5-disubstituted 1,2,3-triazoles in biological systems.

Natural Phosphate and Potassium Fluoride Doped Natural Phosphate as New Catalysts for the Vilsmeir–Haack type Reaction

The catalytic activity of the inexpensive natural- or potassium fluoride doped phosphates as bases was evaluated in a Vilsmeier–Haack type reaction. High efficiency, in term of chemical yields and reaction rates was found in the preparation of 2-chlor-3-cyanopyridines starting from 2-propylidene-malonitriles.

p-Toluenesulfonic Acid Coated Natural Phosphate as an Efficient Catalyst for the Synthesis of 2-Substituted Benzimidazole

2-Substituted benzimidazoles are selectively synthesised in high yields via the condensation of o-phenylenediamine derivatives with aldehyde derivatives using catalytic amount of p-toluenesulfonic acid coated natural phosphate (NP/PTSA) under mild conditions. The use of NP/PTSA as a reusable catalyst makes this process simple, convenient, and environmentally friendly.

Ca10(PO4)6(OH)2-modified carbon-paste electrode for the determination of trace lead(II) by square-wave voltammetry

The analytical performance of hydroxyapatite Ca10(PO4)6(OH)2(HAp) screen-printed sensors designed for the detection of metals was evaluated. The hydroxyapatite plays an important role in modern analytical electrochemistry due to their usefulness for the preparation of sensors giving rise to improved responses from metals. The suitable HAp-modified carbon-paste electrode (HAp-CPE) for the electrochemical determination of lead is illustrated in this work using cyclic and square-wave voltammetry in the potential range between -0.3 and -0.8V. Perchlorate acid solution (1.0molL(-1)) was employed as the supporting electrolyte. The voltammetric measurements were carried out using as working electrode HAp-CPE, and a platinum electrode and an SCE electrode as auxiliary and reference electrodes, respectively. Under the optimized working conditions, calibration graph is linear for 5min of preconcentration time with the detection limit 7.68x10(-10)molL(-1). This detection limit is remarkably lower than those reported previously using other modified electrodes or amperometric detection. The results indicate that this electrode is sensitive and effective for the determination of Pb2+.

Electrochemical studies and square wave voltammetry of paraquat at natural phosphate modified carbon paste electrode

A square wave voltammetry (SWV) method for the determination of trace amounts of paraquat at carbon paste electrode modified with natural phosphate (NP-CPE) is proposed. Paraquat was accumulated onto natural phosphate at open circuit potential from aqueous solution. The reduction peaks of paraquat were observed around -0.7V and -1.0V (versus SCE). The response of paraquat at NP-CPE related to: the concentration of this herbicide, preconcentration time, natural phosphate loading and measuring solution pH, was investigated. It was observed that the increase of the cathodic peak currents using SWV, under the optimized condition, is linear with the increase of paraquat concentration in the range from 2.3x10(-8)molL(-1) to 300x10(-8)molL(-1). The detection limit (DL, 3S.D.) and quantification limit (QL, 10S.D.) for peak 1 were about 7.8x10(-10)molL(-1) and 2.59x10(-9)molL(-1), respectively, in pure electrolyte water with the relative standard deviation of 1.8% (n=7). The proposed method was successfully applied to the determination of paraquat in real water samples with satisfactory results.

Doped natural phosphate: a new and environmentally friendly catalyst in nucleoside synthesis

Doped natural phosphate is used as acidic or basic catalyst in nucleoside and acyclonucleoside synthesis. Some examples are given.

Building blocks for polyamide nucleic acids: facile synthesis using potassium fluoride doped natural phosphate as basic catalyst

Potassium fluoride doped natural phosphate, inexpensive and environmentally friendly catalyst, is shown to be an efficient basic catalyst for the N1/N9 alkylation of different nucleobases as synthons for PNAs.