The concept of dual roles design in clean organic preparation

Herein we summarized some clean preparation examples to emphasize the concept of dual roles design (or named as “two birds one stone strategy”) in green and sustainable chemistry. In those examples, the reactants and/or solvent play dual roles rendering a cleaner organic preparation process. Consequently, both the chemical waste and manufacturing cost could be reduced.     

The application of clean production in organic synthesis

Clean production,as an important part of green chemistry,has received great atte ntion and considerable development in recent years.In this perspective article,we summarized some examples of(nearly)quantitative synthesis,clean separation and purification to emphasize clean production.These reactions were carried out by using eco-friendly solvents and the pure products could be easily obtained through clean procedures.     

Ultrasound-assisted tandem synthesis of tri- and tetra-substituted pyrrole-2-carbonitriles from alkenes,TMSCN and N,N-disubstituted formamides

An energy-saving and eco-friendly method for the efficient construction of various tri- and tetra-substituted pyrrolecarbonitriles through ultrasound-assisted multicomponent tandem reaction of readily available alkenes, TMSCN and N,N-disubstituted formamides within 40 min under metal-, solvent-free and mild conditions was developed. The dual role of iodine (catalyst and oxidant) notably simplified the reaction conditions and reduced the chemical waste generated     

Ultrasound-assisted tandem synthesis of tri- and tetra-substituted pyrrole-2-carbonitriles from alkenes,TMSCN and N,N-disubstituted formamides

An energy-saving and eco-friendly method for the efficient construction of various tri- and tetra-substituted pyrrolecarbonitriles through ultrasound-assisted multicomponent tandem reaction of readily available alkenes, TMSCN and N,N-disubstituted formamides within 40 min under metal-, solvent-free and mild conditions was developed. The dual role of iodine (catalyst and oxidant) notably simplified the reaction conditions and reduced the chemical waste generated.     

Copper(II) chloride-catalyzed Glaser oxidative coupling reaction in polyethylene glycol

Polyethylene glycol was shown to be an environmentally benign reaction medium for the copper(II) salt -catalyzed Glaser coupling reaction of terminal alkynes. In particular, oxygen as the sole oxidant worked very well for arylacetylenes even in short reaction time. The product was easily separated by extraction and the catalytic system could be reused four times without significant loss of reactivity.     

Green analytical chemistry in sample preparation for determination of trace organic pollutants

The principles of green chemistry are applied to not only chemical engineering and synthesis, but also increasingly analytical chemistry. We describe environment-friendly analytical techniques applied to isolate and to enrich trace organic pollutants from solid and aqueous samples. Amounts of organic solvents used in analytical laboratories are reduced by applying solventless extraction, extraction using other types of solvent, assisted solvent extraction and miniaturized analytical systems.     

The use of organophotoacids for deprotection reactions in organic synthesis

o-Hydroxymethylphenol was found to be an effective and environmentally benign organophotoacid. An increased acidity in the excited state, induced by photoirradiation, was sufficient for the deprotection of several protecting groups which are widely used in organic synthesis.     

Electrocatalytic Hydrogenation and Oxidation in Aqueous Conditions†

Water molecule contains one oxygen and two hydrogen atoms, making it a potential oxygen and hydrogen source. Electrocatalytic organic reduction and oxidation using water as oxygen and/or hydrogen donors provide an environmentally friendly and sustainable strategy to replace traditional chemical‐driven stoichiometric reactions that use sacrificial reagents. Furthermore, the development of electrochemical synthesis provides a potential application for low tension photoelectricity, which is not cost‐effective during boosted voltage and application. In the last decade, electrocatalytic redox reactions of organic molecules in aqueous media had shown progress owing to the development of electrode materials and water‐splitting technology. This paper highlights several electrocatalytic systems and corresponding mechanisms for both hydrogenation and oxidative transformation of representative compounds. The activation process of protons and water on the working electrode surface has received special focus. Furthermore, paired electrolysis using water as the oxygen and hydrogen source has been demonstrated. This paired system combines hydrogenation and oxidation half‐reactions in one cell using water as the hydrogen and oxygen source, resulting in high atomic and electron utilization rates.     

p-TSA-catalyzed facile and efficient one-pot eco-friendly synthesis of novel isoxazolyl amino furo[3,2-c]quinolinone derivatives in aqueous medium

A green and operationally simple approach for the synthesis of novel isoxazolyl amino furo[3,2-c]quinolinone derivatives by a one-pot three-component reaction of 4-amino-3-methyl-5 styrylisoxazoles, aryl glyoxal monohydrates and 4-hydroxy-1-methyl-2-quinolinone using p-TSA as the catalyst in aqueous medium was developed. The protocol proves to be an efficient and an environmentally benign in terms of high yields, operational simplicity, clean reaction profile, compatibility with wide range of substrates, water as a solvent and easy purification.     

TsCl-promoted sulfonylation of quinoline N-oxides with sodium sulfinates in water

An eco-friendly protocol for the synthesis of various 2-sulfonyl quinolines/pyridines through sulfonylation of heteroaromatic N-oxides with sodium sulfinates in water under metal-and oxidant-free conditions has been developed. The high reaction efficiency, operational simplicity, short reaction time, air-and moisture-insensitive conditions and remarkable functional group compatibility make the developed protocol very attractive for the preparation of 2-sulfonyl N-heteroaromatic compounds.     

Sustainable routes for quantitative green selenocyanation of activated alkynes

By using cheap lactic acid as the recyclable catalyst and reaction media, a sustainable protocol for the synthesis of Z-3-selenocyanatoacrylates and analogues through green selenocyanation of activated alkynes has been achieved.     

Rapid four-component reactions in water: synthesis of pyranopyrazoles

An environmentally benign four-component reaction in aqueous medium at room temperature has been developed for the synthesis of 6-amino-5-cyano-3-methyl-4-aryl/heteroaryl-2H,4H-dihydropyrano[2,3-c]pyrazoles.     

Clean preparation of S-thiocarbamates with in situ generated hydroxide in 2-methyltetrahydrofuran

A simple and clean protocol for the synthesis of various alkyl and (hetero)aryl S-thiocarbamates was established. The usage of in situ generated hydroxide as both an oxygen source and hydrogen source as well as biomass-derived 2-methyltetrahydrofuran as a green reaction medium, the avoidance of phosphorus-containing reductant, and the generation of harmless water and nitrogen as the side-products have given the present method atom-economy and environmental friendliness.     

One-step preparation of 1-substituted tetrahydroisoquinolines via the Pictet-Spengler reaction using zeolite catalysts

A new, environmentally friendly variation of the Pictet-Spengler reaction has been elaborated using a small pore size zeolite. The easily separable and recyclable catalyst provided high conversions and a shorter reaction time than the classical acetic acid or trifluoroacetic acid.     

Ionic liquids-assisted greener preparation of silver nanoparticles

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A new,convenient and expeditious synthesis of 4-alkyl-5-methyl-1H-pyrazol-3-ols in water through a multicomponent reaction

A new, simple and efficient synthesis of 4-alkyl-5-methyl-1H-pyrazol-3-ols in water by a two-pot four component reaction of ethyl acetoacetate, hydrazine hydrate, aldehyde and ketone in presence K₂CO₃ as the catalyst is described. Use of water as the reaction medium, operational simplicity, mild reaction conditions, application of a cost-effective, nontoxic and easily available catalyst with auto-tandem catalysis, wide substrate scope, easy workup and purification process make the protocol highly attractive.     

Determination of the chemical oxygen demand (COD) using a copper electrode: a clean alternative method

A clean alternative method for the determination of chemical oxygen demand (COD) was developed using a copper electrode as an electrocatalytic sensor. The measuring principle is based on oxidation current of organic compounds in the wastewater. The effects of important experimental conditions, such as electrolytic solution concentration and potential scan rate, on analytical performance have been investigated. Analytical linear range of 53.0–2,801.4 mg l⁻¹ COD with detection limit of 20.3 mg l⁻¹ COD was achieved. The procedure was successfully applied to the COD determination in wastewater from soft industries. The results obtained using the proposed method were in good agreement with those obtained using the conventional (i.e., dichromate) COD method. In this fashion, the COD value of a sample can be determined in a simple, rapid, accurate manner, and the end products do not contain toxic metals.     

The multiple roles of computational chemistry in fragment-based drug design

Fragment-based drug discovery (FBDD) represents a change in strategy from the screening of molecules with higher molecular weights and physical properties more akin to fully drug-like compounds, to the screening of smaller, less complex molecules. This is because it has been recognised that fragment hit molecules can be efficiently grown and optimised into leads, particularly after the binding mode to the target protein has been first determined by 3D structural elucidation, e.g. by NMR or X-ray crystallography. Several studies have shown that medicinal chemistry optimisation of an already drug-like hit or lead compound can result in a final compound with too high molecular weight and lipophilicity. The evolution of a lower molecular weight fragment hit therefore represents an attractive alternative approach to optimisation as it allows better control of compound properties. Computational chemistry can play an important role both prior to a fragment screen, in producing a target focussed fragment library, and post-screening in the evolution of a drug-like molecule from a fragment hit, both with and without the available fragment-target co-complex structure. We will review many of the current developments in the area and illustrate with some recent examples from successful FBDD discovery projects that we have conducted.     

Fast oxidation of secondary alcohols by the bromate-bromide system using cyclic microwave heating in acidic water

We report an improved, gentle, cyclic microwave activation technique for the oxidation of secondary alcohols using nonhazardous hypobromous acid (BrOH) as the reagent in acidic water. Several aliphatic and aromatic secondary alcohols were successfully oxidized to the corresponding ketones using this technique in high yields and with only minor amounts of side products.