Search results for "GREEN"
showing 10 items of 1660 documents
Examples of xylochemistry: colorants and polymers
2017
Against the backdrop of modern sustainable chemistry and valorization of biomass for chemical raw materials, the syntheses of indigo dyes and polyamides as representatives of two classes of everyday chemical products based on xylochemicals are described. Wood-derived starting materials were transformed into functional materials using the principles of green chemistry to expand the scope of products gained from renewable resources. The indigo dyes were synthesized in a short, straightforward sequence starting from vanillin. Two polyamides, representatives of an important class of polymers, were obtained from 4-propylcyclohexanol, which is one of the longest known (and most abundant) hydrogen…
Sustainable access to biobased biphenol epoxy resins by electrochemical dehydrogenative dimerization of eugenol
2019
Limited fossil resources require innovative monomers and polymers derived from renewable feedstocks such as plant biomass. Thermosetting epoxy resins largely rely on petrochemical bisphenol-type monomers, which give high performance materials but are controversial due to their effects on human health. Herein, we present two biobased epoxy resins by direct dehydrogenative dimerization of eugenol, the main component of clove oil. Taking the Principles of Green Chemistry into account, we developed electrochemical dehydrodimerization at reticulated vitreous carbon (RVC) electrodes using methanol as environmentally benign solvent. Thus, fluorinated solvents such as 1,1,1,3,3,3-hexafluoroisopropa…
Cyclic dipeptides: catalyst/promoter-free, rapid and environmentally benign cyclization of free amino acids
2011
“The best catalyst is no catalyst.” With growing public concern over global warming and the amount of greenhouse gases, it is important to reduce the amount of chemicals and eliminate waste, to obtain better results in a simple, selective, safe, and environmentally benign fashion compared to conventional tedious chemical synthesis. Herein, we disclose an environmentally benign, rapid, catalyst/promoter/coupling reagent-free cyclization procedure of free amino acids to furnish exclusively cyclic dipeptides (2,5-diketopiperazines, DKPs) in excellent or even quantitative yield, along with their solid state self-assembling properties. This process is extremely simple and highly efficient with l…
Uncommon perspectives in palladium- and copper-catalysed arylation and heteroarylation of terminal alkynes following Heck or Sonogashira protocols: I…
2013
Abstract Conjugated alkynes are recurring building blocks in natural products and in a wide range of important compounds, such as pharmaceuticals, agrochemicals, or molecular materials. The palladium-catalysed cross-coupling reaction between the sp 2 -hybridized carbon atoms of aryl, heteroaryl, and vinyl halides with the sp -hybridized carbon atoms of terminal alkynes is one of the most important developments in the field of alkyne chemistry over the past 50 years. Room for improvement still exists in these important reactions of direct arylation of terminal alkynes. In this prospect, the present authors have developed several strategies aiming at improving the reactivity, the selectivity,…
Sustainable and cost-efficient electro-synthesis of formamidine acetate from cyanamide in aqueous acidic electrolyte
2021
Formamidine represents a versatile building block in synthetic organic chemistry. We developed a new electrochemical synthesis of formamidine acetate by cathodic reduction of cyanamide in an aqueous electrolyte and in high yield. The crude product could be used for further conversions, such as to pyrimidines without purification. Compared to established synthetic routes neither prior processing of cyanamide was necessary, nor precious transition-metal catalyst were required, nor any reagent waste was produced, and only biocompatible and sustainable solvents were employed for this process, following the requirements of green chemistry.
Photocatalytic Partial Oxidation of 5‐Hydroxymethylfurfural (HMF) to 2,5‐Diformylfuran (DFF) Over a Covalent Triazine Framework in Water
2020
Dehydrogenative Anodic Cyanation Reaction of Phenols in Benzylic Positions
2019
Evaluation of Antiradical Activity and Reducing Capacity of Synthesised Bispyridinium Dibromides Obtained by Quaternisation of 4-Pyridyl-1,4-dihydrop…
2015
New bispyridinium dibromides based on the 1,4-dihydropyridine (1,4-DHP) cycle were synthesised in the reaction between 4-pyridyl-1,4-DHP derivatives and propargyl bromide. It has been shown that variation of the substituent position on the pyridine as well as small changes in the electronic nature of the 1,4-DHP cycle as a result of the substituent nature at the 3 and 5 positions do not affect the course of the reaction and in all cases the corresponding bispyridinium dibromides 4a–e were formed. The antiradical activity, using 1,1-diphenyl-2-picrylhydrazine as a free radical scavenger, and the reducing capacity using phosphomolybdenum complexes have been evaluated for the newly synthesise…
Frontispiece: A Novel Cathode Material for Cathodic Dehalogenation of 1,1‐Dibromo Cyclopropane Derivatives
2015
Metal‐Free Twofold Electrochemical C−H Amination of Activated Arenes: Application to Medicinally Relevant Precursor Synthesis
2020
Abstract The efficient production of many medicinally or synthetically important starting materials suffers from wasteful or toxic precursors for the synthesis. In particular, the aromatic non‐protected primary amine function represents a versatile synthetic precursor, but its synthesis typically requires toxic oxidizing agents and transition metal catalysts. The twofold electrochemical amination of activated benzene derivatives via Zincke intermediates provides an alternative sustainable strategy for the formation of new C−N bonds of high synthetic value. As a proof of concept, we use our approach to generate a benzoxazinone scaffold that gained attention as a starting structure against ca…