Innovative synthesis of drug-like molecules using tetrazole as core building blocks

• Jingyao Li,
• Ajay L. Chandgude,
• Qiang Zheng and
• Alexander Dömling

Beilstein J. Org. Chem. 2024, 20, 950–958, doi:10.3762/bjoc.20.85

• involves the hazardous chemicals NaN3, DIBAL-H, and CCl4 [25]. Moderhack described the synthesis of 1-substituted tetrazole-5-carbaldehyde through a Kröhnke reaction involving lengthy to access 5-chloromethyltetrazole and the well-known carcinogen p-nitrosodimethylaniline [27]. Also Ugi described the

• synthesis of 5-hydroxymethyltetrazoles through a Passerini reaction, however, in low yields, with very long reaction times, and using hazardous aluminum azide [30]. Clearly our novel access to this elusive substance class of 1-substituted tetrazole-5-carbaldehyde outperforms all hitherto described synthetic

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• synthetic pathways in organic chemistry [32][33][34]. Common organic syntheses require the use of harmful chemicals, such as toxic solvents, hazardous reagents, catalysts and reaction conditions, which contribute to environmental pollution and soil degradation [35][36]. Wanting to enhance the sustainability

• is an intriguing solid support, since it is a low cost, commercially available and non-hazardous support, that can be employed in tandem with various traditional catalysts [70]. Some examples in literature are ZrOCl2·8H2O/SiO2 [71], P2O5/SiO2 [72], LiHSO4/SiO2 [73], (PhCH2PPh3)+Br−/SiO2 [74], H2SO4

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• chemistry is well documented [1][2]. Traditional approaches for radical generation relied on hazardous reagents and harsh conditions, resulting in low reaction efficiency and undesired byproduct formation [3][4][5][6]. As a consequence, the utility of radicals in organic synthesis remained limited for many

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• possibility of obtaining the products of alkyne hydration with analogous or improved yields, using less hazardous precursors to generate the reactive species in situ. In particular, for terminal arylalkynes, the electrochemical route proved to be advantageous, yielding preferentially the hydration products vs

One-pot nucleophilic substitution–double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

• Hans-Ulrich Reissig and
• Fei Yu

Beilstein J. Org. Chem. 2023, 19, 1399–1407, doi:10.3762/bjoc.19.101

• the Nobel Prize in 2022 to M. Meldal, K. B. Sharpless and C. R. Bertozzi did not come as a surprise. In most cases the (3 + 2) cycloadditions were performed with isolated (and purified) organic azides, but it was early found that one-pot processes generating the potentially hazardous azides [22] in

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• solvent and reaction time. The environmental impacts are manifold, including excessive utilization of organic solvents, high-temperature reactions, the production of hazardous byproducts, and by the use of traditional purification techniques. Therefore, green chemistry methods in Clauson–Kaas synthesis

Honeycomb reactor: a promising device for streamlining aerobic oxidation under continuous-flow conditions

• Masahiro Hosoya,
• Yusuke Saito and
• Yousuke Horiuchi

Beilstein J. Org. Chem. 2023, 19, 752–763, doi:10.3762/bjoc.19.55

• , their harsh and hazardous conditions impede their application to complex molecules. Thus, a variety of mild and chemoselective oxidations have been developed, including Swern oxidation [5], tetrapropylammonium perruthenate (TPAP) oxidation [6], Pinnick oxidation [7], and 2,2,6,6-tetramethylpiperidinyl-1

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• chemistry heralded for synthetic chemistry are minimization or ideally the complete prevention of chemical waste. In this vein, the use of innocuous chemicals, replacement of hazardous reagents, atom efficient reactions and overall safer chemical processes are desirable [1][2]. Therefore, one current

Investigation of cationic ring-opening polymerization of 2-oxazolines in the “green” solvent dihydrolevoglucosenone

• Solomiia Borova and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2023, 19, 217–230, doi:10.3762/bjoc.19.21

• ]. Therefore, choosing environmentally benign solvents becomes ever more relevant [27]. Accordingly, some research groups have been also looking for "green" and safer solvents suitable for CROP of 2-oxazolines. "Green" solvents are considered environmentally friendly, less hazardous solvents that make a

Sequential hydrozirconation/Pd-catalyzed cross coupling of acyl chlorides towards conjugated (2E,4E)-dienones

• Benedikt Kolb,
• Daniela Silva dos Santos,
• Sanja Krause,
• Anna Zens and
• Sabine Laschat

Beilstein J. Org. Chem. 2023, 19, 176–185, doi:10.3762/bjoc.19.17

• ethers 12 [19] and metal-catalyzed cross coupling of alkenes 13 and enones 14 [20][21] have been reported. However, these reactions face multiple disadvantages such as limited substrate scope, use of hazardous solvents and harsh reaction conditions such as high temperatures or acidic/basic conditions

Modern flow chemistry – prospect and advantage

• Philipp Heretsch

Beilstein J. Org. Chem. 2023, 19, 33–35, doi:10.3762/bjoc.19.3

• pressurized gaseous alkanes employed in the abovementioned transformations. Enhanced safety profiles of continuous flow reactors have been widely appreciated in industrial laboratories, while hazardous reactions still tend to be addressed subordinately or are even marginalized in academia [9]. The comparably

Two-step continuous-flow synthesis of 6-membered cyclic iodonium salts via anodic oxidation

• Julian Spils,
• Thomas Wirth and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2023, 19, 27–32, doi:10.3762/bjoc.19.2

• -established reagents for synthetic chemists. They are portrayed as an alternative to otherwise hazardous transition metals. This is due to their great reactivity in electrophilic group transfers [1][2][3][4], photo- or organocatalysis [5][6][7][8][9][10][11][12][13][14][15], and their utility as building

A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• reports found in the literature suffer from the requirement of hazardous intermediates and harsh reaction conditions. Here, we report a new six-step synthesis for c1G base, starting from 6-iodo-1-deazapurine. The key transformations are copper catalyzed C–O-bond formation followed by site-specific

• synthesis of 1-deazaguanine and 1-deazahypoxanthine. Previously published routes toward these compounds focused on ring closure of the imidazole part of the purine system after the pyrimidine core had been functionalized, however, the drawback of this approach is the passage of rather hazardous/explosive

• (H-C(8)), 149.08 (H-C(4)), 160.86 (H-C(6)); ESIMS (m/z): [M − H]− calcd for 134.04; found, 134.03. Syntheses of C4-substituted diethyl 2,6-pyridinedicarbamates 4, passing hazardous and explosive diacylazide intermediates 3 that are required for Curtius rearrangement in the final step [19]. Synthesis

A one-pot electrochemical synthesis of 2-aminothiazoles from active methylene ketones and thioureas mediated by NH₄I

• Shang-Feng Yang,
• Pei Li,
• Zi-Lin Fang,
• Sen Liang,
• Hong-Yu Tian,
• Bao-Guo Sun,
• Kun Xu and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2022, 18, 1249–1255, doi:10.3762/bjoc.18.130

• ketones and thiourea via an oxidative cyclization initiated by a radical process and a following condensation reaction (Scheme 1c) [29]. Although these methods are practical, most of these strategies require stoichiometric or excess amounts of halogenating reagents or oxidants, which are toxic, hazardous

Lewis acid-catalyzed Pudovik reaction–phospha-Brook rearrangement sequence to access phosphoric esters

• Jin Yang,
• Dang-Wei Qian and
• Shang-Dong Yang

Beilstein J. Org. Chem. 2022, 18, 1188–1194, doi:10.3762/bjoc.18.123

• with highly air-sensitive and hazardous phosphorus halides, with the assistance of a suitable base [19][20][21][22][23][24]. As an alternative pathway, the phospha-Brook rearrangement [25][26][27][28][29][30] represents a green approach to phosphoric esters since it uses α-hydroxyphosphonates, which

Automated grindstone chemistry: a simple and facile way for PEG-assisted stoichiometry-controlled halogenation of phenols and anilines using N-halosuccinimides

• Dharmendra Das,
• Akhil A. Bhosle,
• Amrita Chatterjee and
• Mainak Banerjee

Beilstein J. Org. Chem. 2022, 18, 999–1008, doi:10.3762/bjoc.18.100

• , pharmaceuticals, agrochemicals, and advanced materials [10][11][12][13][14]. The ubiquity of halogen atoms in these synthetic building blocks urges the development of efficient, sustainable, and mild methods for aromatic halogenation. The century-old classical method of using hazardous and corrosive reagents X2

Cathodic generation of reactive (phenylthio)difluoromethyl species and its reactions: mechanistic aspects and synthetic applications

• Sadanobu Iwase,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2022, 18, 872–880, doi:10.3762/bjoc.18.88

• , these methods require various metal and organometallic reagents. On the other hand, electrochemical organic synthesis is a metal-free process and does not require any hazardous reagents and it produces less waste than conventional chemical syntheses. Therefore, electrochemical synthesis is desirable

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

• is a three-step flow-through protocol leading to macrocycles with musk-like olfactoric properties, which was realized under extreme conditions. These include the use of safety-hazardous reaction mixtures, the handling of explosive intermediates, and their pyrolysis at high temperatures (Scheme 17

• be established as a batch protocol due to the hazardous conditions. Conclusion Inductive heating and flow chemistry are an ideal combination for performing continuously operated high-temperature and high-pressure syntheses. The technical setup is quite simple compared to corresponding microwave

Rapid gas–liquid reaction in flow. Continuous synthesis and production of cyclohexene oxide

• Kyoko Mandai,
• Tetsuya Yamamoto,
• Hiroki Mandai and
• Aiichiro Nagaki

Beilstein J. Org. Chem. 2022, 18, 660–668, doi:10.3762/bjoc.18.67

• performing the reaction in a continuous flow system. To the best of our knowledge, this is for the first time to achieve the epoxidation of cyclohexene using air within only 1.4 min by carefully avoiding any unwanted release which could result in a hazardous situation. In our flow conditions, the volume of

Synthesis of 5-unsubstituted dihydropyrimidinone-4-carboxylates from deep eutectic mixtures

• Sangram Gore,
• Sundarababu Baskaran and
• Burkhard König

Beilstein J. Org. Chem. 2022, 18, 331–336, doi:10.3762/bjoc.18.37

• bearing two aryl groups at the C4 and C6 positions was also reported [26]. Although several synthetic routes to 5-unsubstituted DHPM have been reported, there is still need for improvements in terms of higher yields, shorter reaction times, less hazardous or corrosive reagents, and fewer synthetic steps

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• products and processes that reduce or eliminate the use and generation of hazardous substances, as well as increase the atom economy of the reaction [9]. Among the transition-metal (TM) catalysts often used, the late transition metals like rhodium [10][11][12][13][14], palladium [15][16][17][18][19

Synthesis of new bile acid-fused tetrazoles using the Schmidt reaction

• Dušan Đ. Škorić,
• Olivera R. Klisurić,
• Dimitar S. Jakimov,
• Marija N. Sakač and
• János J. Csanádi

Beilstein J. Org. Chem. 2021, 17, 2611–2620, doi:10.3762/bjoc.17.174

• . Intramolecular Schmidt reaction of alkyl azides and ketones, which follows the first pathway in the mechanism, found especially broad application in the synthesis of different lactams [23][24]. Serious drawbacks of the Schmidt reaction for tetrazole synthesis are the need for a large excess of the hazardous

• hazardous [26][27]. Some recent studies employ this reagent in the Schmidt synthesis of tetrazoles from ketones that are smaller in size and simpler than the steroidal ketones in this work [28][29]. For the synthesis of steroidal tetrazoles, most often 1,3-dipolar cycloadditions are being used. In this way

• chromatographic purification. A lactam byproduct was detected in a small quantity, the isolation and purification of which proved to be problematic. Further work was directed towards reactions using less hazardous TMSN3 as an azide source. Data for entries 2–8 in Table 1 are showing that trimethylsilyl

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• effectiveness of our strategy, the necessity of isolating the potentially hazardous diazonium salt may be seen as an important disadvantage. Arylating the quinone starting directly from the aniline in a one-pot procedure would effectively avoid the need for isolation of the potentially explosive salt and

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• synthetic perspective, coumarin derivatives have received much attention due to their pivotal role in organic synthesis [16][17][18]. The development of efficient synthetic processes with eco-friendliness and sustainability that avoid the extensive use of toxic and hazardous reagents and solvents, as well

Cascade intramolecular Prins/Friedel–Crafts cyclization for the synthesis of 4-aryltetralin-2-ols and 5-aryltetrahydro-5H-benzo[7]annulen-7-ols

• Jie Zheng,
• Shuyu Meng and
• Quanrui Wang

Beilstein J. Org. Chem. 2021, 17, 1481–1489, doi:10.3762/bjoc.17.104

• alcohol using Dess–Martin periodinane [19][20]. The reported methods involved the use of ethylene oxide, a hazardous and carcinogenic gas. This prompted us to work out a more practical and flexible method to access the aromatic enal compounds 13. At the offset, we examined the synthesis of 2-(2