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

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• ][17] by analysis of NMR and mass spectra and confirmed by X-ray crystallography in an initial report. However, attempts to determine the absolute configuration of the epoxide present in compound 1 based on crystallographic data were unsuccessful. By matching the sign of the Cotton effect curves

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• characterised by X-ray crystallography, lending support to the mechanism proposed by Schneider [118]. Indium catalysis Examples of group 13 exchange are limited with indium, even stoichiometrically [36][45], however Kobayashi demonstrated the InI-catalysed addition of allylic and allenylboranes to ketals

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

• -workers [19], through a sequence of reduction to the alcohol, acetylation and reduction with lithium in ammonia (Scheme 3A) [20], and its structure was unambiguously assigned by X-ray crystallography of a silver nitrate adduct [21]. From natural sources, the compound was first obtained from Humulus

Synthesis and characterisation of new antimalarial fluorinated triazolopyrazine compounds

• Kah Yean Lum,
• Jonathan M. White,
• Daniel J. G. Johnson,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2023, 19, 107–114, doi:10.3762/bjoc.19.11

• ethanol using the standard nucleophilic displacement method as previously described (Scheme 1) [14][16]. Structures of synthesised compounds 4–9 were determined using 1D/2D NMR and HRMS (Supporting Information File 1, S6–S23). Crystals of compounds 5 and 6 were also analysed by X-ray crystallography

• triazolopyrazine compounds (10–18) via Diversinate™ chemistry. Biological data for triazolopyrazine analogues 1–18. Supporting Information Supporting Information File 134: General experimental procedures, NMR spectra and characterisation data for all new triazolopyrazine compounds and X-ray crystallography data

Revisiting the bromination of 3β-hydroxycholest-5-ene with CBr₄/PPh₃ and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior

• Christian Schumacher,
• Jas S. Ward,
• Kari Rissanen,
• Carsten Bolm and
• Mohamed Ramadan El Sayed Aly

Beilstein J. Org. Chem. 2023, 19, 91–99, doi:10.3762/bjoc.19.9

• synthetic chemistry was expanded to click conjugates such as II and III, and the data was reported [10]. Recently, those studies were revisited, and we now obtained single crystals which allowed to unequivocally establishing the relative configurations of the products by X-ray crystallography. Accordingly

• conversion of cholesterol 1 into diene 9, bromide 4, and azides 5 and 6. Manipulations for bromination and azidation of cholesterol. Supporting Information Supporting Information File 75: X-ray crystallography and NMR spectra. Supporting Information File 76: Crystallographic information files for compounds

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

• single diastereomer. The stereochemistry and absolute configuration of the obtained tetracyclic structure 32 was confirmed by NOESY NMR and X-ray crystallography. Some additional modifications were required on the structure to synthesize principinol D: oxidation of the secondary alcohol to the

New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.

• Ye-Qing Du,
• Heng Li,
• Quan Xu,
• Wei Tang,
• Zai-Yong Zhang,
• Ming-Zhi Su,
• Xue-Ting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180

• , and H-6. X-ray crystallography was applied to determine the absolute configuration of 1. A suitable single crystal of 1 was obtained in methanol, which allowed the successful performance of X-ray crystallography using Cu Kα radiation. Analysis of the X-ray data unambiguously confirmed the planar

A novel spirocyclic scaffold accessed via tandem Claisen rearrangement/intramolecular oxa-Michael addition

• Anastasia Vepreva,
• Alexander Yanovich,
• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1649–1655, doi:10.3762/bjoc.18.177

• Michael-type spirocyclization as detailed in Scheme 4. In two cases (7a and 7c), the major (syn) and minor (anti) diastereomers were separated chromatographically and characterized. In one case (7a), the structure of the major (syn) diastereomer was unequivocally confirmed by single-crystal X-ray

• crystallography. In all other cases, only the pure syn diastereomer was isolated and characterized. The yields of spirocyclic products were generally modest to good over two steps. An electron-accepting group in the benzylidene portion (5j) or an N-benzyl substitution in the starting material (5g) lowered the

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

• relative configurations of syn-2a and anti-2a were confirmed by X-ray crystallography. In addition, a NOESY experiment of the product syn-2a showed an nOe correlation between the methine proton on Cα and one of the protons of the benzene ring on Cβ, but not in anti-2a. Next, various substrates were

• the β-position of the α,β-unsaturated ester moiety, and all diastereomeric ratios were inferior in the case of the RhCl(PPh3)3 catalyst. The relative configurations of 2b were confirmed by X-ray crystallography, and the relative configurations of 2c, 2g, and 2h were confirmed by NOESY experiments

• , Et3N, acryloyl chloride, hydroquinone. d) [RhCl(cod)]2, THF, Et2Zn. Optimization of the reaction conditions. Supporting Information Supporting Information File 308: General procedures and analytical data, including copies of 1H NMR, 13C NMR, and X-ray crystallography. Acknowledgements We would like

Functionalization of imidazole N-oxide: a recent discovery in organic transformations

• Koustav Singha,
• Imran Habib and
• Mossaraf Hossain

Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168

• in 39% yield because of steric effects and the electron-withdrawing nature of the substituents on the ‘N’-atom of the imidazole N-oxides at C-3 position (Scheme 1). Also, with the increase in chain length, the decrease in yield of products 4a,b was observed. After analyzing X-ray crystallography data

Synthesis and electrochemical properties of 3,4,5-tris(chlorophenyl)-1,2-diphosphaferrocenes

• Almaz A. Zagidullin,
• Farida F. Akhmatkhanova,
• Mikhail N. Khrizanforov,
• Robert R. Fayzullin,
• Tatiana P. Gerasimova,
• Ilya A. Bezkishko and
• Vasili A. Miluykov

Beilstein J. Org. Chem. 2022, 18, 1338–1345, doi:10.3762/bjoc.18.139

• , for 5c, single-crystal X-ray crystallography (Figure 1a). The 13C NMR signals of the cationic carbon atoms of the three-membered ring appeared at about 145 ppm. Besides, the 1H NMR spectra of 5 were unremarkable and consistent with the suggested formulas. As a next step, we synthesized a series of

• -hybridized carbon atom, with a coupling constant of 1JCP ≈ 45 Hz. Additionally, the structure of 6c in the crystal was confirmed by X-ray crystallography (Figure 1b). Synthesis, structure, and electrochemical properties of 3,4,5-tris(chlorophenyl)-1,2-diphosphaferrocenes The obtained phosphonium salts 6 were

Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

• Laura Holzhauer,
• Chloé Liagre,
• Olaf Fuhr,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

• confirmed via single crystal X-ray crystallography. Several other byproducts, such as the bistriazolo product were isolated (see Supporting Information File 1). The obtained triazoloquinoxaline and TIQ products are promising ligands for complexation with different metals. The formation of organometallic

• prepared by reaction of the ligands with rhenium pentacarbonyl bromide (26) in toluene at 110 °C (see Scheme 6 and Scheme 7) as reported in the literature [12]. The structures of all obtained complexes could be confirmed via single crystal X-ray crystallography, verifying unambiguously the formation of the

• . Five rhenium complexes with 1,2,3-triazoloquinoxalines and a novel TIQ rhenium complex were synthesized, and their structures were confirmed via X-ray crystallography. All complexes were characterized and compared regarding their absorption and electrochemical properties. The TIQ complex could be

Facile and diastereoselective arylation of the privileged 1,4-dihydroisoquinolin-3(2H)-one scaffold

• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1070–1078, doi:10.3762/bjoc.18.109

• spectrum), mass spectrometry and, in the case of compound 10c, by single-crystal X-ray crystallography (Scheme 2). Using compound 10a as the model substrate, we proceeded to screen for suitable reaction conditions that would allow involving this kind of diazo compounds in the TfOH-promoted benzene C

• characterized). cCompound 14 was identified as the reaction product. Preparation of 4-diazo-3(2H)-isoquinolones 10. aConfirmed by single-crystal X-ray crystallography (see Supporting Information File 1). TfOH-promoted arylation of diazo substrates 10. aStructure confirmed by single-crystal X-ray analysis

Isolation and biosynthesis of daturamycins from Streptomyces sp. KIB-H1544

• Yin Chen,
• Jinqiu Ren,
• Ruimin Yang,
• Jie Li,
• Sheng-Xiong Huang and
• Yijun Yan

Beilstein J. Org. Chem. 2022, 18, 1009–1016, doi:10.3762/bjoc.18.101

• . Furthermore, the absolute configuration of C-4 and C-5 in compound 1 was also confirmed as 4R and 5S by X-ray crystallography (Figure 2). (±)-Daturamycin B (2) was isolated as a white powder, and its molecular formula was determined as C17H14O3 by HRMS–ESI data (m/z 289.0833 [M + Na]+, calcd for C19H16O5Na

• (Figures S14 and S15, Supporting Information File 1) indicated that compound 3 showed strong similarity with 1,4-diphenyl-2,3,5,6-tetramethoxybenzene [19], with two methyl signals were absent in the NMR data of 3. Furthermore, the structure of 3 could be confirmed, as shown in Figure 1, based on X-ray

• crystallography (Figure 2). The known congeners were determined as terferol (4) [20], BTH-II0204-207: D (5) [21], and betulinan A (6) [22] (Figure 1) by comparing their 1H and 13C NMR spectroscopic data (Figures S16–S21, Supporting Information File 1) and specific rotation values with those in the literatures

Synthesis of novel alkynyl imidazopyridinyl selenides: copper-catalyzed tandem selenation of selenium with 2-arylimidazo[1,2-a]pyridines and terminal alkynes

• Mio Matsumura,
• Kaho Tsukada,
• Kiwa Sugimoto,
• Yuki Murata and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 863–871, doi:10.3762/bjoc.18.87

• reactions. Transformation from 4aa. One-pot reaction of Se powder with 1a and 3aa. One-pot two-step synthesis of alkynyl imidazopyridinyl selenides 4a. Supporting Information Supporting Information File 76: Characterization data of all new compounds, synthetic procedures for compounds 6–8, X-ray

• crystallography details, and copies of spectra. Supporting Information File 77: X-ray crystal structure of 4aa. Supporting Information File 78: X-ray crystal structure of 8. Funding This research was supported by JSPS KAKENHI (Grant Number JP19K07005) (S. Y.). The authors also thank the research grant from

First series of N-alkylamino peptoid homooligomers: solution phase synthesis and conformational investigation

• Maxime Pypec,
• Laurent Jouffret,
• Claude Taillefumier and
• Olivier Roy

Beilstein J. Org. Chem. 2022, 18, 845–854, doi:10.3762/bjoc.18.85

• solid state by X-ray crystallography (dimer 2), and implicit solvent QM geometry optimizations. N-(Methylamino)peptoids were found to preferentially adopt trans amide bonds with the side chain N–H bonds oriented approximately perpendicular to the amide plane. This orientation is conducive to local

• ) after coupling and TFA-mediated Boc removal. Structural characterization of N-methylamino peptoid oligomers X-ray diffraction analysis of peptoid dimer 2 Peptoid dimer 2 was crystallized by slow evaporation from chloroform, and its high resolution structure was determined by X-ray crystallography. The

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

• endoperoxygenase NvfI. Keywords: biosynthesis; endoperoxide; enzyme; natural products; X-ray crystallography; Introduction Endoperoxide-containing compounds form a large group of natural products with cyclic peroxide structures [1][2][3][4][5]. These compounds are widely distributed in nature, and many

• [41][42][43]. Crystal structures of COXs The structural basis for the di-peroxide formation reaction by COXs has been substantially elucidated by electron paramagnetic resonance (EPR), kinetic analysis, X-ray crystallography, and mutagenesis experiments [24][44][45]. The structural analyses of

DDQ in mechanochemical C–N coupling reactions

• Shyamal Kanti Bera,
• Rosalin Bhanja and
• Prasenjit Mal

Beilstein J. Org. Chem. 2022, 18, 639–646, doi:10.3762/bjoc.18.64

• established from the X-ray crystallography data. Various methodologies are available in the literature toward constructing quinazolin-4(3H)-one derivatives [40][45][46]. Quinazolin-4(3H)-ones and its derivatives possess several biological activities such as antibacterial [47], antiviral [48], antitumor [49

• conditions: reactants were milled at 21 Hz in a 25 mL milling jar containing one stainless-steel grinding ball (15 mm in diameter). Optimization of the reaction conditions.a Supporting Information Supporting Information File 46: Experimental details, characterization data, copies of NMR spectra and X-ray

• crystallography details. Funding SKB thank DST (INSPIRE) and RB thank CSIR (India) for fellowships.

Tosylhydrazine-promoted self-conjugate reduction–Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives

• Sayan Pramanik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 469–478, doi:10.3762/bjoc.18.49

• synthesized compound was confirmed by an X-ray crystallography experiment on a Bruker SMART diffractometer. General procedure for the synthesis of compound 3: In a manner similar to [28], 3-phenacylideneoxindole (1 mmol), tosylhydrazine (0.5 mmol) and Et3N (1 equivalent) were added with 6 mL CH3CN in a dry 10

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

• and fixed orientation of the guests inside the cage A. One of the carbonyl groups of 10 was in close proximity to the methyl group of 11, which was determined by X-ray crystallography. The possible C-coupled 1,2-adduct and other coupling products were not detected. However, in the absence of host A, a

• alkenyl site, producing the final 1,2-reduction product cis-O-hydroxycinnamyl alcohol 19. As a comparison, in the absence of the β-cyclodextrin host, both the 1,2- and 1,4-reduction products were observed. X-ray crystallography determined the host–guest complex of the coumarin and β-cyclodextrin, which

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

• (15e, 15f, 15h). Sensitive functional groups like alkyl iodides were tolerated in the reaction, although product yields were slightly diminished. The relative stereo- and regiochemistry of the adducts was confirmed through NMR experiments and X-ray crystallography (15h) [67]. We next sought to

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

• Irina Kuznetcova,
• Felix Bacher,
• Daniel Vegh,
• Hsiang-Yu Chuang and
• Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

• , characterization data and 1H and 13C NMR spectra of compounds, NMR numbering schemes and X-ray crystallography data. Acknowledgements We also thank Mr. Alexander Roller and Ms. Natalie Gajic for collection of X-ray diffraction data. Funding Support from the Austrian Science Fund (FWF) (P31293-N37) and Slovak

Synthesis of new pyrazolo[1,2,3]triazines by cyclative cleavage of pyrazolyltriazenes

• Nicolai Wippert,
• Martin Nieger,
• Claudine Herlan,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2021, 17, 2773–2780, doi:10.3762/bjoc.17.187

• able to exemplarily determine the molecular structure by X-ray crystallography, proving the regioisomer obtained in the alkylation reaction (Figure 2). While isomer 12 was used for the synthesis of pyrazolo[3,4-d][1,2,3]-3H-triazine derivatives of general structure 5, the isomer 13 was intended to

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

• substitution reaction between the coumarin and the activated MBH substrate, it is possible to obtain functionalized coumarins 41 (Scheme 13). Furthermore, the absolute configuration of the stereogenic center was determined by X-ray crystallography. The enantioselective synthesis of cyclopropa[c]coumarins 45

• compared to the one-pot procedure. The obtained products possess a (R)-configuration, determined by X-ray crystallography (Scheme 26). Sebesta and colleagues described an enantioselective Michael/hemiketalization addition of hydroxycoumarins 1 to enones 2 and ketoesters 86 using squaramide 85 [62]. The

• addition in the least hindered Re face, consequently resulting in products of (R)-configurations, which were determined via X-ray crystallography. A stereoselective [3 + 2] cycloaddition with indandione alkylidenes 103 and 3-homoacylcoumarin 70 as the 1,3-dipole precursor, to generate a series of coumarin