ppm Pd-catalyzed, Cu-free Sonogashira couplings in water using commercially available catalyst precursors.

A new catalyst that derives from commercially available precursors for copper-free, Pd-catalyzed Sonogashira reactions at the sustainable ppm level of precious metal palladium under mild aqueous micellar conditions has been developed. Both the palladium pre-catalyst and ligand are commercially available, bench stable, and highly cost-effective. The catalyst is applicable to both aryl- and heteroaryl-bromides as educts. A wide range of functional groups are tolerated and the aqueous reaction medium can be recycled. An application to a key intermediate associated with an active pharmaceutical ingredient (ponatinib) is discussed

A Streamlined Synthesis of Androstadiene C-17 Ester Derivatives

The development of a fully telescoped synthesis of a derivative of androstadiene C-17 esters made from epoxyparamethasone was demonstrated. This streamlining allowed for the elimination of isolation and solvent change after each synthetic step. Thus it not only drastically reduced the solvent waste, but also minimized the potential exposure to highly active intermediates thereby increasing the overall yield. The intuitively obvious advantage inherent to lowering the number of solvents was illustrated by applying standard green metrics

A General Protocol for Robust Sonogashira Reactions in Micellar Medium

A robust and general protocol for a sustainable copper‐free Sonogashira cross coupling under micellar aqueous reaction conditions with high turnover was developed. By using the commercially available catalyst CataCXium A Pd G3 and THF as co‐solvent, various alkyne substrates were efficiently cross‐coupled with a broad range of aryl halides, providing improved yields and low catalyst loadings. The reaction parameters were optimized to render the process operationally simple, robust and scalable. The method gives access to alkynylated arenes, heterocyclic compounds, and monofunctionalized products from dihalogenated substrates with an improved selectivity achieved by the micellar aqueous reaction conditions

Biocatalysis in Water or in Non-Conventional Media? Adding the CO2 Production for the Debate

Biocatalysis can be applied in aqueous media and in different non-aqueous solutions (non-conventional media). Water is a safe solvent, yet many synthesis-wise interesting substrates cannot be dissolved in aqueous solutions, and thus low concentrations are often applied. Conversely, non-conventional media may enable higher substrate loadings but at the cost of using (fossil-based) organic solvents. This paper determines the CO2 production—expressed as kg CO2·kg product−1—of generic biotransformations in water and non-conventional media, assessing both the upstream and the downstream. The key to reaching a diminished environmental footprint is the type of wastewater treatment to be implemented. If the used chemicals enable a conventional (mild) wastewater treatment, the production of CO2 is limited. If other (pre)treatments for the wastewater are needed to eliminate hazardous chemicals and solvents, higher environmental impacts can be expected (based on CO2 production). Water media for biocatalysis are more sustainable during the upstream unit—the biocatalytic step—than non-conventional systems. However, processes with aqueous media often need to incorporate extractive solvents during the downstream processing. Both strategies result in comparable CO2 production if extractive solvents are recycled at least 1–2 times. Under these conditions, a generic industrial biotransformation at 100 g L−1 loading would produce 15–25 kg CO2·kg product−1 regardless of the applied media

A new, substituted palladacycle for ppm level Pd-catalyzed Suzuki-Miyaura cross couplings in water.

A newly engineered palladacycle that contains substituents on the biphenyl rings along with the ligand HandaPhos is especially well-matched to an aqueous micellar medium, enabling valued Suzuki-Miyaura couplings to be run not only in water under mild conditions, but at 300 ppm of Pd catalyst. This general methodology has been applied to several targets in the pharmaceutical area. Multiple recyclings of the aqueous reaction mixture involving both the same as well as different coupling partners is demonstrated. Low temperature microscopy (cryo-TEM) indicates the nature and size of the particles acting as nanoreactors. Importantly, given the low loadings of Pd invested per reaction, ICP-MS analyses of residual palladium in the products shows levels to be expected that are well within FDA allowable limits

Interface-rich Aqueous Systems for Sustainable Chemical Synthesis

Mimicking an enzyme's exquisite activity and selectivity is a long-standing goal for sustainable chemical method development in aqueous media. The use of interface-rich aqueous systems, such as single-chain polymers, micelles and vesicle membranes recently emerged as strategy to emulate the compartmentalization of natural systems. In aqueous solution, aggregates such as micelles or microemulsion droplets are formed, providing reaction environments different from bulk solutions that frequently improve selectivity and accelerate reaction rates for a wide array of chemical transformations. We present here selected examples of interface-rich aqueous systems and discuss the advantages they offer for chemical synthesis. In particular metal-catalyzed cross-coupling reactions are highlighted and future challenges to perform reactions in interface-rich aqueous media are discussed

Enantioselective Syntheses of Authentic Sclerophytin A, Sclerophytin B, and Cladiell-11-ene-3,6,7-triol

Two distinctively different total syntheses of natural sclerophytin A in its revised structural formulation are reported. The first proceeds from (S)-carvone via a cladiellene triol and involves photoisomerization of the double bond. The second route makes use of (5S)-5-(d-menthyloxy)-2(5H)-furanone, which is subjected to cycloaddition, Claisen ring expansion, and regiocontrolled dihydroxylation tactics

How Can Academia Help Industry Reduce the Footprint of Chemicals Manufacture?

Industrial representatives from the Swiss chemistry ecosystem met to formulate unmet needs in the field of sustainability and share the content of the exchange. The aim is to spark inspiration and trigger ambitious and pre-competitive projects collectively at the interface of the academic and industrial worlds, with the hope to profoundly change the current practices and provide an answer to some of the most urgent environmental challenges.