Donor and donor–donor carbenes are two important kinds of carbenes, which have experienced tremendous growth in the past two decades. This review provides a comprehensive overview of the recent development of donor and donor–donor carbene chemistry. The development of this chemistry offers efficient protocols to construct a wide variety of C–C and C–X bonds in organic synthesis. This review is organized based on the different types of carbene precursors, including diazo compounds, hydrazones, enynones, cycloheptatrienes and cyclopropenes. The typical transformations, the reaction mechanisms, as well as their subsequent applications in the synthesis of complex natural products and bioactive molecules are discussed. Due to the rapidly increasing interest in this area, we believe that this review will provide a timely and comprehensive discussion of recent progress in donor and donor–donor carbene chemistry.

Recent progress on donor and donor-donor carbenes.

Perfluoroalkyl substances (PFAS) are drinking water contaminants of emerging concern due to their persistence in the environment and tendency to bio-accumulate. Although anionic ion exchange (IX) resins offer a cost-effective alternative for removing PFAS from natural waters, the studies on PFAS removal by IX under the influence of variable characteristics of the organic compounds present in the natural water sources, have been overlooked. This is critically important given that the organic matter (OM) characteristics are spatially variable and can change seasonally. In the present study, a strongly basic anion exchange resin was used to remove two of the most persistent PFAS, namely per-fluorooctanoic acid (PFOA) and per-fluorooctanesulfonic acid (PFOS). Factors influencing the uptake behavior included the PFOA and PFOS concentrations, resin dosage, and background OM characteristics, more specifically the charge density and molecular weight distribution of source water OM. The equivalent background concentration (EBC) was employed to evaluate the competitive uptake between OM and PFAS. Experimental data were fitted to different mathematical and physical models to evaluate the competitive interactions. Further, IX was able to achieve complete PFAS removal with simultaneous >60% dissolved organic carbon (DOC) removal. Evidence of size exclusion and pore blockage was also observed in the presence of humics and larger molecular weight organic fractions. Results of this study indicate that IX exhibits great potential for simultaneous OM and PFAS removal for drinking and potable water reuse applications.

PFOA and PFOS removal by ion exchange for water reuse and drinking applications: role of organic matter characteristics

Removal of COD, and several toxic heavy metals (Cu2+ and Ni2+) from CNC (metalworking fluid) wastewater was investigated using electrocoagulation method (EC) with Fe and Al electrodes. The ...

Treatment of CNC industry wastewater by electrocoagulation technology: an application through response surface methodology

Pd-catalyzed cross-coupling of terminal alkynes with ene-yne-ketones: access to conjugated enynes via metal carbene migratory insertion

Various heterocyclic systems based on natural and unnatural biologically active products were synthesized by Bronsted acid-promoted cyclization. We have made an attempt to summarize the progress made in this area during the period 2005 to 2015. This article describes the synthetic routes of these heterocycles that involve a Bronsted acid-promoted cyclization as a crucial step or Bronsted acids as co-catalysts with other transition metals.

Brønsted acid-promoted synthesis of common heterocycles and related bio-active and functional molecules

Chloroacetic acid promotes an efficient and diastereoselective intramolecular cascade reaction of electron-deficient ynenones to deliver products featuring a 2,3,5-trisubstituted furan bearing a fused cyclopropyl substituent at the 5-position. Synthetically relevant polycyclic building blocks featuring rings of various sizes and heteroatoms have been synthesized in high yield using this mild acid-catalyzed reaction.

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Synthesis of cyclopropyl-substituted furans by brønsted Acid promoted cascade reactions.

Understanding the potential for selective natural organic matter removal by ion exchange

A high-yielding, diastereoselective intramolecular reaction cascade reaction is developed creating three new bonds in a single step, thus providing 2,3,5-substituted furans bearing a ring fused cyclopropyl substituent.

Joanna C. Redman

Papers

Synthesis of cyclopropyl-substituted furans by brønsted Acid promoted cascade reactions.

Understanding the potential for selective natural organic matter removal by ion exchange

Synthesis of Cyclopropyl‐Substituted Furans by Broensted Acid Promoted Cascade Reactions.