Cu(OTf)₂-catalyzed multicomponent reactions

• Sara Colombo,
• Camilla Loro,
• Egle M. Beccalli,
• Gianluigi Broggini and
• Marta Papis

Beilstein J. Org. Chem. 2025, 21, 122–145, doi:10.3762/bjoc.21.7

• additive. Some control experiments support a mechanism whose key intermediates are the formation of the iminium ion XIX, originated from aniline with formaldehyde which serves as the C1 building block, and the generation of the cyclic α,β-unsaturated ethers XX by Cu(OTf)2-catalyzed dehydrogenation of the

• process by using α-diazoketones, nitroalkenes and primary amines, in the presence of air as oxidant. The mechanism involved the formation of α-ketocarbene XXVI from α-diazoketone, able to react with the amine affording imine XXV after copper-catalyzed oxidative dehydrogenation. The subsequent [3 + 2

Non-covalent organocatalyzed enantioselective cyclization reactions of α,β-unsaturated imines

• Sergio Torres-Oya and
• Mercedes Zurro

Beilstein J. Org. Chem. 2024, 20, 3221–3255, doi:10.3762/bjoc.20.268

• cyclic derivatives. Conjugated imines are usually synthesized from the corresponding carbonyl precursors by reaction with a sulfonamide in the presence of Lewis acids and a dehydrating agent such as molecular sieves [3]. Also, recently a palladium-catalyzed dehydrogenation of aliphatic imines was

N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240

• ). Dehydrogenation of the latter with DDQ afforded the anomerically pure indol-N-glycoside β-26a which upon benzylation and methylation gave products β-27a and β-27b, respectively. Iodination gave products β-28a and β-28b, however, due to the basic reaction conditions (I2, NaOH, DMF), ether rather than ester

Deuterated reagents in multicomponent reactions to afford deuterium-labeled products

• Kevin Schofield,
• Shayna Maddern,
• Yueteng Zhang,
• Grace E. Mastin,
• Rachel Knight,
• Wei Wang,
• James Galligan and
• Christopher Hulme

Beilstein J. Org. Chem. 2024, 20, 2270–2279, doi:10.3762/bjoc.20.195

• , Scheme 10. In line with all prior MCRs, good yields were observed with no deuterium scrambling. Calcium channel blockers derived from this methodology are heavily metabolized by CYP3A4 via dehydrogenation to afford inactive pyridines, Scheme 11 [54]. As such, bio-isosteric deuterium–hydrogen exchange at

• scrambling. GBB reaction products, no deuterium scrambling was observed. aA 70% [D2]-isocyanide was used in 7a and 7b. Ar = 4-PhPh, Ar1 = 4-MePh. Modified Hantzsch pyridine synthesis to afford 1,4-dihydropyridines. No deuterium scrambling was observed. CYP3A4 mediated dehydrogenation of dihydropyridines

Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis

• Akiya Ogawa and
• Yuki Yamamoto

Beilstein J. Org. Chem. 2024, 20, 2114–2128, doi:10.3762/bjoc.20.182

• isocyanides forms the imidoyl radicals, which undergo intramolecular cyclization and oxidative dehydrogenation to give phenanthridines (Scheme 27) [100]. Conclusion In this Perspective, the addition and cycloaddition reactions of heteroatom radicals with isocyanides have been described in detail and their

A facile three-component route to powerful 5-aryldeazaalloxazine photocatalysts

• Ivana Weisheitelová,
• Radek Cibulka,
• Marek Sikorski and
• Tetiana Pavlovska

Beilstein J. Org. Chem. 2024, 20, 1831–1838, doi:10.3762/bjoc.20.161

• Discussion Regarding the synthesis of 5-aryldeazaalloxazines 2 (5-arylpyrimido[4,5-b]quinoline-2,4(1H,3H)-diones), the data in the literature are quite limited, and the known methodology describes the dehydrogenation of initially formed 5,10-dihydro analogues (5-aryl-5,10-dihydropyrimido[4,5-b]quinoline-2,4

Oxidation of benzylic alcohols to carbonyls using N-heterocyclic stabilized λ³-iodanes

• Thomas J. Kuczmera,
• Pim Puylaert and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 1677–1683, doi:10.3762/bjoc.20.149

• experiment no formation of an alkoxyiodane was observed, indicating that the formation of this ligand-exchanged intermediate is slower than the dehydrogenation. As a consequence, we attempted to accelerate the ligand exchange through the addition of a Lewis acid and the performance of the NHIs was compared

Methyltransferases from RiPP pathways: shaping the landscape of natural product chemistry

• Maria-Paula Schröder,
• Isabel P.-M. Pfeiffer and
• Silja Mordhorst

Beilstein J. Org. Chem. 2024, 20, 1652–1670, doi:10.3762/bjoc.20.147

• cyanoborohydride as a mild reducing agent, and paraformaldehyde as a methylating agent [36]. Methanol can be used as the methylating reagent in other methods. Here, a palladium on carbon (Pd/C) catalyst processes the dehydrogenation of the alcohol to form the corresponding aldehyde. The subsequently formed imine

Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• synthesized via the Cannizzaro reaction. Proposed catalytic cycle for the dehydrogenation of alcohols. Intramolecular Cannizzaro reaction of aryl glyoxal hydrates using TOX catalysts. Intramolecular Cannizzaro reaction of aryl methyl ketones using ytterbium triflate/selenium dioxide. Intramolecular Cannizzaro

Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer

• Mohd Farhan Ansari,
• Atul Kumar Maurya,
• Abhishek Kumar and
• Saravanakumar Elangovan

Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98

• to the scientific community [10][11][12]. In this process, first, the metal-catalyzed dehydrogenation of the alcohol provides a reactive substrate for coupling with nucleophiles and the active metal hydride species. Later, the borrowed hydrogen is used in the final step to reduce unsaturated

• achieving both selective dehydrogenation and hydrogenation is highly important. A typical BH process is demonstrated in Scheme 1. Several precious transition-metal catalysts have been used successfully in this area, including iridium, rhodium, ruthenium, and osmium [4]. However, these noble metals are toxic

• Milstein [17] in hydrogenation and dehydrogenation reactions with pincer-decorated manganese complexes, significant progress has been made in manganese catalysis [18][19][20]. Notably, well-defined low-valent diamagnetic manganese(I) complexes have been studied in many catalytic transformations, and

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

Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

• Ekaterina V. Kolupaeva,
• Narek A. Dzhangiryan,
• Alexander F. Pozharskii,
• Oleg P. Demidov and
• Valery A. Ozeryanskii

Beilstein J. Org. Chem. 2024, 20, 243–253, doi:10.3762/bjoc.20.24

• pyridine rings, the naphthalene core at positions 5(8) and the CH2CH2 bridge (dehydrogenation) undergo chemical modifications under mild conditions, giving the corresponding acenaphthylenes. The latter can also be obtained in an unusual way by tele-elimination from 5,8-dibromodipyridoacenaphthene by

• effect of functional groups on the further chemistry and basicity of the newly synthesized derivatives is also considered. Results and Discussion Amination, dehydrogenation, and supramolecular aggregation Direct amination of quinoquinoline 5 could potentially lead to 2(11)-substituted amines 6 (Figure 1

• activity/inactivity in amination reactions. It is known that acenaphthylenes are usually readily formed from acenaphthenes by dehydrogenation with chloranil, dichlorodicyanobenzoquinone (DDQ) or active MnO2 on reflux in toluene/xylene and other inert solvents. However, attempts to obtain acenaphthylene 8

Biphenylene-containing polycyclic conjugated compounds

• Cagatay Dengiz

Beilstein J. Org. Chem. 2023, 19, 1895–1911, doi:10.3762/bjoc.19.141

• reaction, followed by a Au(I)-catalyzed [4 + 2] cycloaddition reaction to afford the target substrate 96 and its regioisomer 95 in a 2:1 ratio (Scheme 20). POA 87 was obtained on Au(111) at 610 K after Ullmann-type coupling and aromatic dehydrogenation of compound 96. Apart from these studies, the

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• interest in developing novel methodologies in this field of organic chemistry. Keywords: alkylation; cross-dehydrogenation coupling; ether; non-noble metals; Introduction Since the 1970s, organic chemists have developed many selective cross-coupling methods for the construction of C–C bonds, such as the

• , tetrahydrofuran or tetrahydropyran can smoothly react with many methyl aryl ketones to obtain the desired coupling products (Scheme 6a) [54]. The mechanism of the dehydrogenation cross-coupling reaction may undergo a radical pathway. Initially, the tert-butoxy radical produced by the dissociation of t-BuOOH may

• synthesis of compounds with quaternary centers and natural products with high structural complexity. In 2014, Li et al. reported a CuCl2-catalyzed cross-dehydrogenation coupling reaction of C(sp3)–H bonds adjacent to an ether oxygen and the C(sp3)–H bonds at the α-position of a carbonyl functionality in the

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• electrochemical hydrogenation methods might be more appropriate [41][42]. There is already work on electrochemical dehydrogenation of LOHCs [76][77]. In one example, DDQ was used to remove hydrogen from secondary amines by oxidizing them, followed by reoxidation of the hydrogenated DDQ at the electrode to

Strategies in the synthesis of dibenzo[b,f]heteropines

• David I. H. Maier,
• Barend C. B. Bezuidenhoudt and
• Charlene Marais

Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51

• of o-nitrotoluene (22) Reduction to 2,2'-diaminobibenzyl (20) Ring-closing via amine condensation Catalytic dehydrogenation 1.1 Oxidative coupling of o-nitrotoluene (22) and reduction to 2,2'-diaminobibenzyl (20) The preparation of dinitrobibenzyl (21) can be achieved by the oxidative coupling of

• [36] via the polyphosphoric acid (PPA) catalysed cyclisation of 2,2'-diaminobibenzyl (20) at elevated temperatures (Scheme 3) [37][38]. 1.3 Catalytic dehydrogenation An early synthesis of 5H-dibenzo[b,f]azepine (1a) involved the gas phase dehydrogenation of 10,11-dihydro-5H-dibenzo[b,f]azepine (2a) to

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• oxanorbornenes; however, the latter two substrates did not undergo dehydrogenation, generating cis-selective annulated coumarins (10b and 10d). In 2006, the same group applied this methodology for the total synthesis of arnottin I (10h), a coumarin-type natural product isolated from the bark of the Xanthoxylum

• 10. The selectivity for the non-dehydrogenated coumarins 10d is not understood, but 10b likely does not undergo dehydrogenation because there is no formation of aromaticity to drive the reaction forward. When the bicyclic alkene is substituted unsymmetrically at the bridgehead position, the reaction

Germacrene B – a central intermediate in sesquiterpene biosynthesis

• Houchao Xu and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18

• ., by heating with sulphur, to the blue azulene derivative 62 (Scheme 16C) [121][122][124][125][126], but the structure elucidation of this compound was only completed in 1936 [127]. Based on a comparison of IR spectra of natural terpenes, their hydrogenation and dehydrogenation products, the correct

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

• condensation of enals 6 with aldehydes 7a or ketones 7b [6][7][8][9][10][11], isomerization of alkynones 8 [12][13][14][15], Horner–Wadsworth–Emmons reaction of unsaturated phosphonates 9 and aldehydes 10 [16][17], and dehydrogenation of enones 11 [18]. Further, Claisen rearrangement of vinyl propargylic

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• alternative approaches exist. The direct dehydrogenation of 1,4-dithiane is somewhat cumbersome [25], and, moreover, 1,4-dithiane (1) is surprisingly not available in large quantities at a reasonable cost, in spite of its apparent simplicity. Our lab has found that the synthetic method for dihydrodithiins

• then brominated with an excess of bromination reagent, which effects the 1,2-sulfur-migratory ring expansion, followed by bromination-induced dehydrogenation to the aromatic ring [31]. At the time of writing this review, the resulting benzoannelated dithiane 5 is also commercially available in small

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• opening of the epoxide (15%). From 41 having the correct tetracyclic skeleton, a transient protection followed by Petasis olefination, deprotection, selenide-mediated α,β-dehydrogenation and Mukaiyama oxidation afforded an advanced intermediate 42 bearing most of the target’s functionalities. A sequence

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• activation for hydrogenation of various organic substrates. More recently, SET reactivity of FLP was discovered [155]. The FLP-catalyzed dehydrogenation of N-protected indolines with H2 release [156] is depicted in Scheme 39. According to the proposed mechanism, the reaction starts with a hydride transfer

• heterocyclizations. Electrochemical N-ammonium ylide-catalyzed CH-oxidation. Oxidative dimerization of aryl- and alkenylmagnesium compounds catalyzed by quinonediimines. FLP-catalyzed dehydrogenation of N-substituted indolines. Funding This work was supported by the Russian Science Foundation (Grant no. 21-13-00205).

Cyclometalated iridium complexes-catalyzed acceptorless dehydrogenative coupling reaction: construction of quinoline derivatives and evaluation of their antimicrobial activities

• Hongling Shui,
• Yuhong Zhong,
• Renshi Luo,
• Zhanyi Zhang,
• Jiuzhong Huang,
• Ping Yang and
• Nianhua Luo

Beilstein J. Org. Chem. 2022, 18, 1507–1517, doi:10.3762/bjoc.18.159

• ][42], we found that cyclometalated iridium catalysts can effectively catalyze the dehydrogenation of alcohols to produce carbonyl compounds and hydrogen gas. Therefore, we used cyclometalated iridium complex (TC-6) to catalyze the ADC reaction of o-aminobenzyl alcohols 1 and aryl/heteroaryl/alkyl

• released from the dehydrogenation of 2-aminobenzyl alcohol/1-phenylethanol according to the previous literature [28]. Lastly, the desired product 3aa was obtained by the condensation and cyclization of the aldehyde 5 with acetophenone (6) under base conditions. The potential antimicrobial activity of the

Cytochrome P450 monooxygenase-mediated tailoring of triterpenoids and steroids in plants

• Karan Malhotra and
• Jakob Franke

Beilstein J. Org. Chem. 2022, 18, 1289–1310, doi:10.3762/bjoc.18.135

• (12) scaffold to 7β-hydroxythalianol, while CYP705A5 is a desaturase and introduces a double bond at C15 [41]. The related Arabidopsis CYP705A1 (also from clan 71) accepts a slightly different scaffold, arabidiol (11), triggering cleavage of the side chain at the same C15 instead of dehydrogenation

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

• applications. NiO2, on the other hand, was used to achieve the dehydrogenation of amines (to nitriles) and to perform the α,β dehydrogenation of ketones 61. 3.2.3 Using chemically active fixed beds (catalysts): Copper metal in the form of wires or turnings can also be inductively heated when placed inside flow