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

• catalytic hydrogenation to 27, dehydration to a mixture of alkenes (28) and hydrogenation to selinane (29) it was concluded that 11 was a selinane sesquiterpene alcohol (Scheme 9B) [75]. Four years later, based on NMR data Bhattacharyya and co-workers suggested a cis-ring junction for 11 [76], but 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

• ]. Since the early work by Wailes, Schwartz and Buchwald on the Schwartz reagent Cp2Zr(H)Cl and its reactivity towards alkynes, alkenes, and C–X double bonds particularly hydrozirconation has gained much attention [25][26][27][28][29][30]. It has been successfully employed in methodology studies [31][32

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

• dienophiles 7 and 27. 4 Alkylation chemistry of 1,4-dithianes and 1,4-dithiins: stereocontrolled synthesis of Z-alkenes As mentioned in chapter 2 of this review, Palumbo and co-workers found that 5,6-dihydro-1,4-dithiins are relatively resistant to β-elimination in their lithiated form (Scheme 6e), and this

• should be noted that the three-step strategy (dithiolane protection, oxidative rearrangement, and hydrodesulfurization) can be used to treat carbonyl functional groups as synthetic equivalents of cis-alkenes (Scheme 10c), as is shown by the highly stereoselective conversion of α-phenylacetophenone (60

• some experimentation, the desired chemoselective transformation can be achieved in almost all cases, including for sensitive substrates such as yohimbine-derived compound 102 [30]. A common problem is the concomitant hydrogenation of alkenes, which can be hard to avoid, as seen in the

Practical synthesis of isocoumarins via Rh(III)-catalyzed C–H activation/annulation cascade

• Qian-Ci Gao,
• Yi-Fei Li,
• Jun Xuan and
• Xiao-Qiang Hu

Beilstein J. Org. Chem. 2023, 19, 100–106, doi:10.3762/bjoc.19.10

• approach towards isocoumarins [17][18]. Pioneering examples relying on the Pd, Ru, and Ir-catalyzed C–H cross coupling of benzoic acids with alkenes and alkynes were realized by the groups of Miura [19], Lee [20], Ackermann [21], Zhang [22], Jiang [23], and Jeganmohan [24] et al. Despite these impressive

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• future synthetic developments [61][62][63][64][65][66][67]. The NaI/PPh3 system has been further broadly applied to the functionalization of alkenes [68][69][70], as well as to decarboxylative C(sp3)–X bond formation [71], cyclization of 1,7-enynes [72][73] and other reactions [74][75][76][77]. Inspired

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• reactions of transition metal hydrides (Fe, Co, Mn, etc) with alkenes (e.g., Mukaiyama hydration) [20]. The last decade saw the development of milder methods for generating carbon-centered radicals as the advancement of their reactivity in cross-coupling reactions, the concept of photoredox catalysis [21

• ) [30]. HAT reductions of the C9–C11 alkene followed to deliver arisugacin F (35), phenylpyropene C (36), pyripyropene E (38), and phenylpyropene F (41). The steric bulk of the manganese catalyst employed suppressed the undesired reaction with tetrasubstituted alkenes and led to the exclusive reaction

• -step sequence. The cyclization of the formed radical is 6-exo-trig and leads to the formation of a benzyl radical that is further oxidized to 188. From this common scaffold, the group managed to access several natural products of the class, majorly by utilizing the ability of conjugated alkenes to be

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

• active oxidative agent. Asymmetric quaternary ammonium phase-transfer catalysts proved to be effective in the asymmetric nucleophilic epoxidation of electron-poor alkenes by hydroperoxides [70] and the asymmetric hydroxylation of enolizable carbonyl compounds employing O2 or H2O2 as terminal oxidants [71

• perform the CH-functionalization of alkanes by electron-deficient alkenes. Photoredox catalysis was employed for the one-electron oxidation of the DABCO-derived organocatalyst to the dication radical. The authors noted that the introduction of a substituent X near the radical center further improves the

• (for example, amines, alkenes, benzyl ethers) by electron-deficient aryl cyanides under photoredox conditions. An example of such process is presented in Scheme 23 [122]. The key stages of the proposed mechanism include the photoredox-catalyzed generation of a thiyl radical and anion radical from ArCN

Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone

• Motoyuki Isoda,
• Kazuyuki Sato,
• Kenta Kameda,
• Kana Wakabayashi,
• Ryota Sato,
• Hideki Minami,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1642–1648, doi:10.3762/bjoc.18.176

• formed the corresponding E-silylenolate via 1,4-reduction at 0 °C [46], even if the reaction was performed at −45 °C (Scheme 3). Also in relation to this result, Mikami and his group reported a rhodium-catalyzed carboxylation of alkenes or activated alkenes by using CO2 with Et2Zn, and a similar Rh–H

Simple synthesis of multi-halogenated alkenes from 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane)

• Yukiko Karuo,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1567–1574, doi:10.3762/bjoc.18.167

A facile approach to spiro[dihydrofuran-2,3'-oxindoles] via formal [4 + 1] annulation reaction of fused 1H-pyrrole-2,3-diones with diazooxindoles

• Pavel A. Topanov,
• Anna A. Maslivets,
• Maksim V. Dmitriev,
• Irina V. Mashevskaya,
• Yurii V. Shklyaev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2022, 18, 1532–1538, doi:10.3762/bjoc.18.162

• investigated for FPDs: the [4 + 2] cycloaddition with alkenes resulting in pyran-annulated products [27][28][29][30][31][32][33][34] and the [3 + 2] cycloaddition with nitrones resulting in isoxazole-annulated products [35][36][37] (Scheme 2). However, formal [4 + 1] cycloaddition reactions for FPDs remain to

Dissecting Mechanochemistry III

• Lars Borchardt and
• José G. Hernández

Beilstein J. Org. Chem. 2022, 18, 1454–1456, doi:10.3762/bjoc.18.150

• Margetić used dibrominated polycyclic imides as substrates to generate reactive alkenes, which could be trapped in situ by several dienes through Diels−Alder cycloadditions by ball milling (Scheme 3) [7]. Further, Moores and co-workers synthesized phosphorus-bridged heptazine-based carbon nitrides (g-h-PCN

Reductive opening of a cyclopropane ring in the Ni(II) coordination environment: a route to functionalized dehydroalanine and cysteine derivatives

• Oleg A. Levitskiy,
• Olga I. Aglamazova,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2022, 18, 1166–1176, doi:10.3762/bjoc.18.121

• reactions with electrophiles, intramolecular cyclization and disproportionation process. The synthetic viability of the approach will be considered. A one-pot multistep synthetic protocol is suggested, based on addition of thiols to the mixture of isomeric alkenes formed in an electroreductive opening of a

• analysis of the reaction mixture showed that two isomeric alkenes (containing the α-β or β-γ double bond) are formed. In the isomers, two protons of the amino acid side chain create an AB system; in the α-β isomer, both protons show correlations in the HMBC spectrum with the C atoms of the COOMe groups

• , whereas in the β-γ isomer, only one H correlates with the COOMe and the other H atom correlates with the Schiff and carboxylic carbons (see Figure 3 and Supporting Information File 1). The experimental ratio of the isomeric alkenes (1.5:1) is close to the calculated value predicted from their relative

Electrochemical hydrogenation of enones using a proton-exchange membrane reactor: selectivity and utility

• Koichi Mitsudo,
• Haruka Inoue,
• Yuta Niki,
• Eisuke Sato and
• Seiji Suga

Beilstein J. Org. Chem. 2022, 18, 1055–1061, doi:10.3762/bjoc.18.107

• ]. For instance, they recently reported a stereoselective reduction of alkynes to Z-alkenes using a PEM reactor. The use of a Pd/C cathode catalyst and the appropriate cathode potential realize the selective synthesis of Z-alkenes [22][23][24]. They also reported the stereoselective hydrogenation of α,β

Synthesis of bis-spirocyclic derivatives of 3-azabicyclo[3.1.0]hexane via cyclopropene cycloadditions to the stable azomethine ylide derived from Ruhemann's purple

• Alexander S. Filatov,
• Olesya V. Khoroshilova,
• Anna G. Larina,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2022, 18, 769–780, doi:10.3762/bjoc.18.77

• (Scheme 3). Notably, it took longer reaction times (6 h) for achieving full consumption of 1 while significant amounts of alkenes 2f and 2g remained unreacted. In turn, both the ester 2h and acid 2i [35] proved to be totally unreactive towards PRP (1) under the optimized reaction conditions (THF, reflux

Structural basis for endoperoxide-forming oxygenases

• Takahiro Mori and
• Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

• the synthesis of chemical reagents with an endoperoxide bridge have been reported [77][78]. The classical method for endoperoxide synthesis is through cycloadditions of dienes and alkenes, using singlet oxygen. Furthermore, cyclizations of hydroperoxides with pendant alkenes or alkynes have also been

Tri(n-butyl)phosphine-promoted domino reaction for the efficient construction of spiro[cyclohexane-1,3'-indolines] and spiro[indoline-3,2'-furan-3',3''-indolines]

• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 669–679, doi:10.3762/bjoc.18.68

• the construction of diverse carbocyclic systems [17][18][19][20][21][22][23][24]. In these reactions, the tertiary phosphine firstly adds to electron-deficient alkenes, alkynes, and allenes to give active ionic intermediates. Then, the in situ-generated ionic intermediates further react with various

Sesquiterpenes from the soil-derived fungus Trichoderma citrinoviride PSU-SPSF346

• Wiriya Yaosanit,
• Vatcharin Rukachaisirikul,
• Souwalak Phongpaichit,
• Sita Preedanon and
• Jariya Sakayaroj

Beilstein J. Org. Chem. 2022, 18, 479–485, doi:10.3762/bjoc.18.50

• functional groups, respectively [10]. The 1H NMR spectrum (Table 1) displayed characteristic signals for two olefinic protons of two trisubstituted alkenes (δH 6.64, d, J = 10.5 Hz, and 5.31, s, each 1H), two methine protons (δH 3.06 and 1.35, each m, 1H), one set of equivalent oxymethylene protons (δH 3.92

Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides

• Md Imran Hossain,
• Md Imdadul H. Khan,
• Seong Jong Kim and
• Hoang V. Le

Beilstein J. Org. Chem. 2022, 18, 446–458, doi:10.3762/bjoc.18.47

• organocatalysts (Figure 1) [26][27]. This enolate-mediated cycloaddition, however, requires long reaction time in organic solvents at high temperatures. Our current work was inspired by a recent report by Kesornpun et al., in which a cycloaddition of nitrile oxides and alkenes or alkynes was carried out in 0.1 M

• oxide and strained alkenes has been used to achieve the high-density functionalization of oligodeoxyribonucleotides [29]. However, the alkenes need to be highly strained in order for this reaction to occur without the need for an additional metal catalyst. As an alternative to the mild acidic conditions

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

Synthesis of piperidine and pyrrolidine derivatives by electroreductive cyclization of imine with terminal dihaloalkanes in a flow microreactor

• Yuki Naito,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2022, 18, 350–359, doi:10.3762/bjoc.18.39

• ]. Conventional synthetic methods for piperidine derivatives include nucleophilic substitution (route (1) in Scheme 1), reductive amination (route (2)), intramolecular cyclization of amines and alkenes (route (3)), the Diels–Alder reaction and subsequent reduction (route (4)), and the radical cyclization reaction

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• , azides, halides and alkenes, oxidation of remote C–H bonds and alkenes, and substitution reactions involving ring-opening cyclization of epoxides, nucleophilic substitution of allylic chlorides, and hydrolysis reactions. The product selectivity is interpreted as the consequence of the space shape and

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• -opening reactions of heterobicyclic alkenes are of particular interest [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53], as they provide access to a broad family of synthetic building blocks bearing multiple stereocenters in a single step 2 [54]. Application of these functionalized

• catalyzed by rhodium/diene to afford the 1,2,4-trisubstituted naphthalene framework 8 with complete regio- and stereocontrol (Scheme 1) [62][63]. In 2015, the Nishimura group reported the first iridium-catalyzed addition of salicylaldehydes 14 to bicyclic alkenes 11 (Scheme 1) [64]. Although a variety of

• carbo- and heterobicyclic alkenes was investigated, the study was limited by the number of unsymmetrical coupling partners. In their seminal report, the authors were able to produce hydroacylated adducts 15a and 15b in good yield. On the basis of the aforementioned literature, several different products

Synthesis of novel [1,2,4]triazolo[1,5-b][1,2,4,5]tetrazines and investigation of their fungistatic activity

• Anna V. Korotina,
• Svetlana G. Tolshchina,
• Rashida I. Ishmetova,
• Natalya P. Evstigneeva,
• Natalya A. Gerasimova,
• Natalya V. Zilberberg,
• Nikolay V. Kungurov,
• Gennady L. Rusinov,
• Oleg N. Chupakhin and
• Valery N. Charushin

Beilstein J. Org. Chem. 2022, 18, 243–250, doi:10.3762/bjoc.18.29

• labeling proteins and visualizing cancer due to the ability of s-tetrazine to fast and biocompatible ligation with alkenes via the inverse electron demand Diels–Alder reactions [29][30][31]. At the same time, azolo-annulated 1,2,4,5-tetrazines remain to be a scarcely studied class of compounds, mainly due

Trichloroacetic acid fueled practical amine purifications

• Aleena Thomas,
• Baptiste Gasch,
• Enzo Olivieri and
• Adrien Quintard

Beilstein J. Org. Chem. 2022, 18, 225–231, doi:10.3762/bjoc.18.26

• isolated in its pure form starting from model mixtures containing various aromatics, phenols, alkanes or alkenes in overall purification yields ranging from 53 to 98%. The lower yields are observed for coordinating phenol and catechol (Table 2, entries 3 and 4), probably impacting the crystallization

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• -oxazoles are: the 1,3-dipolar cycloaddition of alkenes and alkynes with nitrile oxides, and the reaction of a three-carbon atom component, such as a α,β-unsaturated ketone or a 1,3-diketone with hydroxylamine hydrochloride [33]. Recently, Rosa et al. reported a useful procedure for the synthesis of various