An eco-friendly catalytic route for synthesis of 4-amino-pyrazolo[3,4-d]pyrimidine derivatives by Keggin heteropolyacids under classical heating and microwave irradiation

Recent green approaches for the synthesis of pyrazolo[3,4-d]pyrimidines: A mini review

Pyrazolo[3,4-d]pyrimidine as a bioisostere of purine has drawn considerable attention as a privileged scaffold for the design and discovery of novel drugs. Green synthesis is an emerging area in the field of chemistry that provides economic and environmental benefits as an alternative to traditional methods. The present mini review reflects recent advances in the green synthesis of pyrazolo[3,4-d]pyrimidines, published in the time frame from 2006 to 2019.

Silver nanoparticles-decorated Preyssler functionalized cellulose biocomposite as a novel and efficient catalyst for the synthesis of 2-amino-4H-pyrans and spirochromenes

Silver nanoparticles-decorated Preyssler functionalized cellulose biocomposite (PC/AgNPs) was prepared and fully characterized by FTIR, UV–vis, SEM, and TEM techniques. The preparation of PC/AgNPs was studied systematically to optimize the processing parameters by Taguchi method using the amount of PC, reaction temperature, concentration of silver nitrate and pH of medium. Taguchi’s L9 orthogonal (4 parameters, 4 level) was used for the experimental design. The SEM analysis confirmed the presence of the Preyssler as a white cloud as well as spherical AgNPs on the surface of cellulose. The formation of AgNPs on the surface was observed by changing of the color from yellow to deep brown and confirmed by UV–vis spectroscopy. The best yield of AgNPs forming was obtained in pH 12.5 at 80 ºC in 20 min. TEM analysis confirmed the formation of spherical AgNPs with a size of 50 nm, at the 1% wt. loading of Preyssler. This easily prepared PC/AgNPs was successfully employed as an efficient, green, and reusable catalyst in the synthesis of a wide range of 2-amino-4H-pyran and functionalized spirochromene derivatives via a one-pot, multicomponent reaction. The chief merits realized for this protocol were the utilization of commercially available or easily accessible starting materials, operational simplicity, facile work-up procedure, obtaining of high to excellent yields of the products and being done under green conditions. The catalyst could be easily separated from the reaction mixture and reused several times without observing any appreciable loss in its efficiency.

Recent Advances in the Hofmann Rearrangement and Its Application to Natural Product Synthesis

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C-N bond formation reactions are the most important transformations in (bio)organic chemistry because of the widespread occurrence of amines in pharmaceuticals, natural products, and biologically active compounds. The Hofmann rearrangement is a well-known method used for the preparation of primary amines from amides. But, the traditional version of the Hofmann rearrangement often gave relatively poor yields due to over-oxidation or due to the poor solubility of some amides in aqueous base, and created an enormous amount of waste products. Developments over the last two decades, in particular, have focused on refining both of these factors affecting the reaction. This review covers both the description of recent advances (2000-2019) in the Hofmann rearrangements and its applications in the synthesis of heterocycles, natural products and complex molecules of biological interest. It is revealed that organo-catalytic systems especially hypervalent iodine-based catalysts have been developed for the green and environmentally friendly conversion of carboxamides to primary amines and carbamates.

Acid-functionalized Mesoporous Silicate (KIT-5-Pr-SO3H) Synthesized as an Efficient and Nanocatalyst for Green Multicomponent

Materials and Methods:

All reagents were purchased from Aldrich and Merck with high-grade quality and used as received. The structural characteristics of the KIT-5 which was obtained, using three-dimensional large cage type face-centered cubic Fm3m mesoporous silica materials (KIT-5) nanocages were obtained according to the procedure described by Kleitz et al. </P><P> Results: The purpose of this study is developing a new acid-functionalized mesoporous catalyst. Initially, (KIT-5) nanocages were obtained according to the procedure described by Kleitz et al. Then, KIT-5-Pr-SH was prepared by Mercaptopropyltriethoxysilane as illustrated in Scheme 1. In the next step, the solid product was oxidized with H2O2. </P><P> The full characterization for proving the structure of the nano-size particles was achieved using FT-IR, TGA, TEM, SEM, and EDX analysis.

Conclusion:

Acid-functionalized mesoporous silica has been proved to act as an effective catalyst in various organic reactions. In this project, for the first time, KIT-5 was functionalized by propyl-sulfonic acid as a heterogeneous solid acid catalyst. Sulfonic acid functionalized KIT-5 (KIT-5-Pr-SO3H) performs as an organicinorganic hybrid catalyst, whereas Brønsted acid sites have been selectively generated. In this regard, the catalytic activities of this novel heterogeneous catalyst were successfully examined by the one-pot multicomponent reaction.

A survey of the different roles of polyoxometalates in their interaction with amino acids, peptides and proteins

This perspective provides a comprehensive description of the different roles of POMs in their interaction with relevant biological molecules.

Synthesis and properties of novel reusable nano-ordered KIT-5-N-sulfamic acid as a heterogeneous catalyst for solvent-free synthesis of 2,4,5-triaryl-1 H-imidazoles

A novel silica-bonded propyl-

Synthesis and characterization of two novel organic-inorganic compounds based on tetrahexyl and tetraheptyl ammonium ions and the Preyssler anion and their catalytic activities in the synthesis of 4-aminopyrazolo[3,4-d]- pyrimidines

Two novel organic–inorganic compounds based on tetrahexylammonium (THA) and tetraheptylammonium (THPA) ions and the Preyssler anion, [NaP₅W₃₀O₁₁₀]^14-, were synthesized and formulated as (THA)_7.7H_6.3 [NaP₅W₃₀O₁₁₀] (A) and (THPA)_7.5 H_6.5[N aP₅W₃₀O₁₁₀] (B). The synthesized compounds were characterized by IR, UV, and TGA and used for the catalytic synthesis of 4-aminopyrazolo[3,4,-d]pyrimidine derivatives 2a-2d. Our findings showed efficient catalytic activities for A and B.

Unexpected synthesis of N-methylbenzo[d]isoxazolium hydroxides under microwave irradiation conditions

Microwave-assisted condensation of salicylaldehydes and N-methyl hydroxylammonium hydrochloride in the presence of K(2)CO(3) under solvent-free conditions afforded, unexpected N-methylbenzo[d]isoxazolium hydroxides (2a-d).

Dodecatungstophosphoric acid (H3PW 12O40), samarium and ruthenium (III) chloride catalyzed synthesis of unsaturated 2-phenyl-5(4H)-oxazolone derivatives under solvent-free conditions

We have found that dodecatungstophosphoric acid (H₃PW₁₂O₄₀), samarium or ruthenium(ΙΙΙ) chloride act as efficient catalysts for the synthesis of unsaturated 2-phenyl-5(4H)oxazolone derivatives under solvent-free conditions. The key features of the reported protocols are short reaction times, high yields of products under ambient conditions and simple workups.

Heteropolyacids as green and reusable catalysts for the synthesis of 3,1,5-benzoxadiazepines

Synthesis of 3,1,5-benzoxadiazepines from the condensation of o-phenylenediamine (o-PDA) and acyl chlorides in the presence of a catalytic amount of various heteropolyacids (HPAs) is reported.