Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• photoredox catalyst mediated by light to overcome the challenge of metal contamination in the precipitated polymers [58]. After the ATRP reaction, a reactive chain end retains as a stable alkyl halide moiety. Therefore, ATRP is particularly suitable for the synthesis of polymers with complex architectures

Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• successfully coupled to a Suzuki–Miyaura reaction [119]. Crystallization was identified as a suitable purification technique to separate products from unreacted starting materials while avoiding metal contamination. Water was used as antisolvent and two mixing units were needed in the crystallization process

B–N/B–H Transborylation: borane-catalysed nitrile hydroboration

• Filip Meger,
• Alexander C. W. Kwok,
• Franziska Gilch,
• Dominic R. Willcox,
• Alex J. Hendy,
• Kieran Nicholson,
• Andrew D. Bage,
• Thomas Langer,
• Thomas A. Hunt and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2022, 18, 1332–1337, doi:10.3762/bjoc.18.138

• traditional metal catalysis, including trace metal contamination [11][12] and volatility of supply. Whilst there are several examples of main-group catalysed nitrile hydroboration reactions [13][14][15][16][17][18][19][20][21][22][23][24][25][26], currently, there are only two reported metal-free catalytic

Heterogeneous metallaphotoredox catalysis in a continuous-flow packed-bed reactor

• Wei-Hsin Hsu,
• Susanne Reischauer,
• Peter H. Seeberger,
• Bartholomäus Pieber and
• Dario Cambié

Beilstein J. Org. Chem. 2022, 18, 1123–1130, doi:10.3762/bjoc.18.115

• packed bed. Together with the catalyst deactivation observed in the temperature study, this result points at a temperature-dependent ligand photodegradation as a likely deactivation mechanism. The amount of nickel leaching observed is significant and, depending on the substrate, the metal contamination

Inductive heating and flow chemistry – a perfect synergy of emerging enabling technologies

• Conrad Kuhwald,
• Sibel Türkhan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2022, 18, 688–706, doi:10.3762/bjoc.18.70

• reaction. Reactions with soluble metal complexes or metal nanoparticles, utilized in transition-metal catalysis, are often avoided, especially if the metal contamination in the product exceeds certain limits. This is particularly true for the pharmaceutical industry. A continuous flow protocol for

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• recovered and reused, but it could also result in a reduced metal contamination of the products. However, most of the immobilized catalysts suffer from some problems like catalyst deactivation, low turnover numbers, and also leaching of metal. A new heterogeneous cobalt catalyst (Co@imine-porous organic

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• since any pharmaceutically relevant compounds must not contain any metal contamination [5], the use of organic dyes is quite popular and can substitute the use of metal-based photocatalysts [6]. An alternative solution is the use of organic molecules as photocatalysts. There are already many reviews

Mechanochemical amorphization of chitin: impact of apparatus material on performance and contamination

• Thomas Di Nardo and
• Audrey Moores

Beilstein J. Org. Chem. 2019, 15, 1217–1225, doi:10.3762/bjoc.15.119

• : amorphization; biomass; chitin; hardness; mechanochemistry; metal contamination; Introduction The last decade has seen a tremendous development in the field of mechanochemistry, which was notably covered in the New York Times in 2016 [1]. Yet, mechanochemistry is hardly a novel concept, since it is likely

• frequency 29.5 Hz. Correlation between the ball mass (orange line) or kinetic energy (blue line) with the crystallinity of chitin after milling in SS jar fitted with 1 SS ball. Experimental conditions: 200 mg of chitin, milling time: 30 min, frequency 29.5 Hz. Metal contamination of milled chitin determined

Catalyst-free synthesis of 4-acyl-NH-1,2,3-triazoles by water-mediated cycloaddition reactions of enaminones and tosyl azide

• Lu Yang,
• Yuwei Wu,
• Yiming Yang,
• Chengping Wen and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2018, 14, 2348–2353, doi:10.3762/bjoc.14.210

• with activated dipolarophiles. As synthetic tools being able to provide 1,2,3-triazoles using an organocatalyst or other non-metal catalysts, this method shows distinctive advantages in enabling the production of 1,2,3-triazoles free of any heavy metal contamination [36][37][38]. Generally, the

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

• Carmen Moreno-Marrodan,
• Francesca Liguori and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73

• of utmost importance for the reduction of metal residues in the food and pharmaceuticals manufacture industry [96]. The choice of appropriate support materials is therefore critical to this purpose. Alternative strategies to reduce metal contamination include the use of metal scavengers, usually in

Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

• Maximilian Koy,
• Hagen J. Altmann,
• Benjamin Autenrieth,
• Wolfgang Frey and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 1632–1638, doi:10.3762/bjoc.11.178

• as the organic solvent. While Ru-2 showed low RCM activity, it turned out to be active in ROMP reactions of strained cyclic olefins like norbornenes, 7-oxanorbornenes, norbornadiene and cis-cyclooctene allowing for the synthesis of the corresponding polymers with unprecedented low metal contamination

Highly enantioselective access to cannabinoid-type tricyles by organocatalytic Diels–Alder reactions

• Stefan Bräse,
• Nicole Volz,
• Franziska Gläser and
• Martin Nieger

Beilstein J. Org. Chem. 2012, 8, 1385–1392, doi:10.3762/bjoc.8.160

• , organocatalytic methods are especially attractive for the preparation of compounds that do not tolerate metal contamination, e.g., active pharmaceutical ingredients. MacMillan’s imidazolidinone-based organocatalysts are general catalysts for a variety of asymmetric transformations. The first highly

Nano copper oxide catalyzed synthesis of symmetrical diaryl sulfides under ligand free conditions

• K. Harsha Vardhan Reddy,
• V. Prakash Reddy,
• A. Ashwan Kumar,
• G. Kranthi and
• Y.V.D. Nageswar

Beilstein J. Org. Chem. 2011, 7, 886–891, doi:10.3762/bjoc.7.101

• and ligands [43], long reaction times [43][44], metal contamination of the final product, and non recyclability of the catalyst. This leads to increased costs as well as limiting the scope of the reaction. From the synthetic point of view, it is desirable to find novel recyclable catalytic systems

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• tetrazole decomposition in the stainless steel coils is connected to metal contamination as a result of steel corrosion phenomena, a series of inductively coupled plasma mass spectrometry (ICPMS) experiments were performed. ICPMS analysis of a NMP/AcOH/H2O (5:3:2) mixture pumped through the continuous flow

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

Ring opening metathesis polymerization-derived block copolymers bearing chelating ligands: synthesis, metal immobilization and use in hydroformylation under micellar conditions

• Gajanan M. Pawar,
• Jochen Weckesser,
• Siegfried Blechert and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2010, 6, No. 28, doi:10.3762/bjoc.6.28

• can be further enhanced by adding free ligand that again accumulates inside the micelle. Further advantages in favor of a micellar setup are the low metal contamination of the products as well as the possibility of reuse. Experimental All manipulations were performed under a N2 atmosphere in a glove

From discovery to production: Scale- out of continuous flow meso reactors

• Peter Styring and
• Ana I. R. Parracho

Beilstein J. Org. Chem. 2009, 5, No. 29, doi:10.3762/bjoc.5.29

• reaction. This makes catalyst recovery and re-cycling problematic if not impossible. It also leads to the possibility of metal contamination at trace levels in the final product. Furthermore, added phosphines and other activating agents tend to be expensive and also difficult to recover, adding both an

Hydrogenation of aromatic ketones, aldehydes, and epoxides with hydrogen and Pd(0)EnCat™ 30NP

• Steven V. Ley,
• Angus J. P. Stewart-Liddon,
• David Pears,
• Remedios H. Perni and
• Kevin Treacher

Beilstein J. Org. Chem. 2006, 2, No. 15, doi:10.1186/1860-5397-2-15

• product (entry 3). It is worth mentioning that the crude product obtained in Table 1, Entry 1 was analysed for metal contamination to determine the exent of leaching. Inductively coupled plasma (ICP) analysis indicated the level of palladium (in the reaction mixture after filtration) to be under 6 ppm. In