Aryl-substituted acridanes as hosts for TADF-based OLEDs

• Naveen Masimukku,
• Dalius Gudeika,
• Oleksandr Bezvikonnyi,
• Ihor Syvorotka,
• Rasa Keruckiene,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 989–1000, doi:10.3762/bjoc.16.88

• prepared using simple synthetic procedures and characterized as hosts for TADF-based OLEDs. Results and Discussion Synthesis and characterization The synthetic routes for acridan derivatives 3–6 are outlined in Scheme 1. The key intermediate, 2,7-dibromo-9,9-dimethyl-9,10-dihydroacridine (1) was prepared

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• -phospholenium chlorides 3 was only postulated. Herein, two additional derivatives, the 4-methylphenyl- and ethyl-1-chloro-3-methyl-2-phospholenium chlorides 3c and 3h were isolated and characterized, which confirmed the key intermediate of the proposed mechanism. The chloro-2-phospholenium salts 3 were then

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• the cis-disubstituted double bond in the latter was performed under a high pressure of hydrogen, leading to the saturated tricyclic scaffold that was used as a key intermediate in the total synthesis of lycoflexine (15, Scheme 18). Manzamine alkaloids A highly interesting application of a metathesis

• the corresponding bicyclic dienic scaffolds. The subsequent hydroboration and aminohydroxylation carried out on these bicyclic dienes provided the AB subunit as a key intermediate component of manzamines A (16a) and E (16b, Scheme 19). Eventually, several highly elaborated transformations of the AB

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• resulted in 99% of the borylated product 414, which may indicate the presence of a radical intermediate in the second, protodeboronation step. Therefore, the key intermediate is the 1,4-adduct 415, which in the presence of base and water affords the saturated product (e.g., 410, 411; Scheme 66) [129]. The

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• the key intermediate aldehyde 25 (Scheme 4). Initially, we explored the Suzuki coupling reaction for substrate 4. Gratifyingly, the reaction product 24 was produced in 41% yield from our developed synthetic strategy. Then, compound 24 was subjected to an SeO2 oxidation reaction. The oxidation reaction

Synthesis of triphenylene-fused phosphole oxides via C–H functionalizations

• Md. Shafiqur Rahman and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2020, 16, 524–529, doi:10.3762/bjoc.16.48

• and the carbohelicene moieties (Scheme 1) [16]. The approach focused on the regioselective one-pot synthesis of a 7-hydroxybenzo[b]phosphole derivative from an 3-alkoxyphenylzinc reagent, an alkyne, and dichlorophenylphosphine [17]. The hydroxy group of this key intermediate served as a handle for the

• strong blue fluorescence in solution. The absorption and emission profiles of the π-extended phosphole oxide revealed their characteristics as hybrids of 2,3-dialkoxytriphenylene and 1-phenyl-2,3-dialkylbenzo[b]phosphole. We anticipate that the key intermediate of the present synthesis, 3, and related

• ) side view). UV–vis absorption (solid lines) and fluorescence (dashed lines) spectra of compounds 8a–c. Syntheses of PAH-fused phospholes featuring a 7-hydroxybenzo[b]phosphole as a key intermediate. Synthesis of phosphole-fused ortho-teraryl compounds 7. Oxidative cyclization of phosphole-fused ortho

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

• Faïma Lazreg,
• Marie Vasseur,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

• catalytic strategy for the one-pot synthesis of N-sulfonylamidines is described. The cationic copper(I) complexes were found to be highly active and efficient under mild conditions in air and in the absence of solvent. A copper acetylide is proposed as key intermediate in this transformation. Keywords

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• arylcopper(I) species was the key intermediate. Terminal alkynes were also investigated under similar reaction conditions (Scheme 13) [37]. Aromatic and π-activated aliphatic substrates led to the desired products in moderate to very good yields. Moreover, vinyl sulfone derivatives were formed when the

• alkynes. The latter was also a key intermediate for the formation of α-trifluoromethylselenylated vinylsulfone. It is worth noting that the strategy for the trifluoromethylselenolation of boronic acid developed in our laboratory was applied in 2019 for the synthesis of the selenylated analog 30 of

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• -coumarins are a key intermediate for diverse natural products, and they have already been synthesized by various research groups with different procedures [132][133][134][135][136][137][138]. Inspired by previous work, Gomez and co-workers reported the preparation of benzo-3,4-coumarins using photoredox

Allylic cross-coupling using aromatic aldehydes as α-alkoxyalkyl anions

• Akihiro Yuasa,
• Kazunori Nagao and
• Hirohisa Ohmiya

Beilstein J. Org. Chem. 2020, 16, 185–189, doi:10.3762/bjoc.16.21

• ) species B. The 1,2-addition of silylcopper(I) B to the aromatic aldehyde 1 [15][16][17][18][19] and the subsequent [1,2]-Brook rearrangement from the obtained α-silyl-substituted copper(I) alkoxide C forms the key intermediate, an α-silyloxybenzylcopper(I) species D. The transmetallation between D and an

Attempted synthesis of a meta-metalated calix[4]arene

• Christopher D. Jurisch and
• Gareth E. Arnott

Beilstein J. Org. Chem. 2019, 15, 1996–2002, doi:10.3762/bjoc.15.195

• 5 in 44% yield which was comparable to the yields reported by Albrecht [20]. Synthesis of the calix[4]arene ruthenacycle Satisfied that the published methods worked in our hands, we then set about synthesizing the targeted mesoionic calix[4]arene ruthenacycle. Our first key intermediate was

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• grams without losing of yield) for the synthesis of key intermediate 8. In order to further improve the synthesis of the key intermediate triptophenolide methyl ether (8), van Tamelen and co-workers further developed a synthesis as shown in Scheme 4 (Figure 2, route F) [70]. This synthesis features two

• key cyclization precursor ketoester 15, which was cyclized in the presence of SnCl4 to give tricyclic intermediate 83, followed by steps of functional group modification to install the butenolide (D-ring), and to finish the racemic synthesis of the key intermediate triptophenolide methyl ether (8) in

• conversion of 89 to vinyl triflate 90, followed by reduction and palladium-catalyzed carbonylation–lactone formation to give key intermediate 8 [75][76][77]. After that, the three successive epoxides were installed by known procedures with some modification. The highlights were the introduction of the second

Application of chiral 2-isoxazoline for the synthesis of syn-1,3-diol analogs

• Juanjuan Feng,
• Tianyu Li,
• Jiaxin Zhang and
• Peng Jiao

Beilstein J. Org. Chem. 2019, 15, 1840–1847, doi:10.3762/bjoc.15.179

• well tolerate PTSA-catalyzed methanolysis. Conclusion In conclusion, we synthesized tert-butyl (3S,5R)-6-hydroxy-3,5-O-isopropylidene-3,5-dihydroxyhexanoate (16), which is enantiomeric to a key intermediate for atorvastatin, from a chiral 2-isoxazoline (3). The β-hydroxy ketone 7 obtained from 3 could

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• selective desilylation and N-debenzylation with simultaneous N-Boc protection and served as a key intermediate for installation of a dimethylhexylene fragment in Julia–Kocienski olefination [56]. Pyrrolidine alkaloids (−)-hygrine ((S)-61) and (−)-hygroline ((2S,2'S)-62) were isolated from many natural

• hydrolysis. Installation of the allyl group at the nitrogen atom required prior derivatization as an oxazolidin-2-one and Birch reduction to furnish 204. To construct a properly functionalized piperidine ring olefin metathesis was performed to supply the key intermediate 205. Taking advantage of the steric

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Enantioselective PCCP Brønsted acid-catalyzed aza-Piancatelli rearrangement

• Gabrielle R. Hammersley,
• Meghan F. Nichol,
• Helena C. Steffens,
• Jose M. Delgado,
• Gesine K. Veits and
• Javier Read de Alaniz

Beilstein J. Org. Chem. 2019, 15, 1569–1574, doi:10.3762/bjoc.15.160

• hypothesized that a PCCP-derived catalyst could be used. It is proposed that the chiral anion moieties serve to interact with the key intermediate 5 during the enantiodetermining electrocyclization step [35][36][37]. A tentative mechanistic hypothesis for the asymmetric aza-Piancatelli is shown in Figure 1

Synthesis and biological evaluation of truncated derivatives of abyssomicin C as antibacterial agents

• Leticia Monjas,
• Peter Fodran,
• Johanna Kollback,
• Carlo Cassani,
• Thomas Olsson,
• Maja Genheden,
• D. G. Joakim Larsson and
• Carl-Johan Wallentin

Beilstein J. Org. Chem. 2019, 15, 1468–1474, doi:10.3762/bjoc.15.147

• allyldioxazaborolidine 11), respectively. The tetronate building blocks 4 and 5 were further converted to the corresponding enolates using lithium diisopropylamide and allowed to react with the common key intermediate 3 to afford the hydroxyalkylated products 18 and 19, in 78% and 59% yield, respectively (Scheme 4

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• ) complexes [56]. The above considerations lead to the use of β-ketosulfones in the Ni(II)-catalyzed reaction, since the proposed mechanism [47], that involves the formation of cyclic Ni enolate, and the high CH acidity of ketosulfones (pKa 9.8–10.5 [4]). The formation of the key intermediate can be provided

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• ). For this reason, another strategy of obtaining high % ee of d was employed. Chiral resolution of racemic-d with (R)-menthyl chloroformate gave a high % ee of this key intermediate d. After column chromatographic purification of the crude reaction mixture, the corresponding diastereomers (R)-e or (S)-e

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• the addition of a protecting step of the unstable key intermediate 4,5-dihydroisobenzofuran-5-ol. Oxidation and deprotection steps were also studied in order to provide an effective availability of these two dialdehyde compounds that may increase their future applications. Keywords: demethylation

• ). To our delight, the remarkable stability of the methoxy group under the same synthesis conditions introduces the key intermediate 4-methoxyphthalaldehyde (5b) with an excellent conversion rate and minimal OPA formation (Table 2, entry 6). Compound 5b was then isolated by column chromatography in 63

• key intermediate 4,5-dihydroisobenzofuran-5-ol (3) before reaching the oxidation step. The methoxy protecting group and the DDQ oxidation reagent were found to be the most efficient. Moreover, deprotection of 4-methoxy-ortho-phthalaldehyde (5b) was successfully achieved using [Bmim]Br and p-TsOH on

Homo- and hetero-difunctionalized β-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry

• Gábor Benkovics,
• Mihály Bálint,
• Éva Fenyvesi,
• Erzsébet Varga,
• Szabolcs Béni,
• Konstantina Yannakopoulou and
• Milo Malanga

Beilstein J. Org. Chem. 2019, 15, 710–720, doi:10.3762/bjoc.15.66

• -identical functional groups on the primary side. Three different types of reactions were investigated to obtain 6A-monoazido-6X-monotosyl-β-CD (a key intermediate for the preparation of various hetero-difunctionalized β-CDs), having three possible regioisomers and consequently three pairs of

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• as key intermediate. A [2 + 2] cycloaddition with a second olefin leads to the formation of intermediate IV, followed by a retro [2 + 2] cycloaddition that regenerates catalyst I and releases the metathesis product. This visionary mechanistic proposal was later confirmed by experimental studies [17

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• key intermediate of the domino sequence (Scheme 1, reaction 1). Taking into account the capability of 2-iminochromenes to perform as Michael acceptors [39][40][41], we envisioned the diversification of the substitution pattern at the chromene ring to be a realizable and an appealing target

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• yield for two steps. The silyl group of compound 22 was cleaved using tetrabutylammonium fluoride (TBAF) in THF to form alcohol 23 which was used directly in the next step [48]. At this stage, we envisioned that 23 could be also a key intermediate to access the ristosamine derivative by reversing the

• for access to 3-amino glycals. Synthesis of key intermediate 23 for the C-3 unbranched amino glycals preparation. Access to diastereoisomeric compounds 3 and 4 from 23. Supporting Information Supporting Information contains detailed experimental procedures with full characterization of all compounds

Synthesis of pyrrolidine-based hamamelitannin analogues as quorum sensing inhibitors in Staphylococcus aureus

• Jakob Bouton,
• Kristof Van Hecke,
• Reuven Rasooly and
• Serge Van Calenbergh

Beilstein J. Org. Chem. 2018, 14, 2822–2828, doi:10.3762/bjoc.14.260

• pyrrolidine-based hamamelitannin analogues is depicted in Scheme 1. The synthesis of 4 as a key intermediate allows to gain access to a diverse set of analogues by chemoselective late-stage derivatization of the pyrrolidine nitrogen. Previously, we used the iminosugar 5 to prepare a series of 2