Five new sesquiterpenoids from agarwood of Aquilaria sinensis

• Hong Zhou,
• Xu-Yang Li,
• Hong-Bin Fang,
• He-Zhong Jiang and
• Yong-Xian Cheng

Beilstein J. Org. Chem. 2023, 19, 998–1007, doi:10.3762/bjoc.19.75

• . The known compounds are readily identified as eudesm-4(15)-ene-7β,11-diol (6) [17], rel-(2R,8S,8aR)-2-(1,2,6,7,8,8a-hexahydro-8,8a-dimethyl-2-naphthyl)propan-2-ol (7) [18], γ-costol (8) [19], (+)-9-hydroxyselina-4,11-dien-14-oic acid (9) [20] and 1β-hydroxyeremophila-7(11),9-dien-8-one (10) [21] by

• powder, possesses a molecular formula of C16H24O3 (5 degrees of unsaturation) derived from its HRESIMS (m/z 287.1614, calcd 287.1618 [M + Na]+). Comparing the NMR data of 1 with those of 4 indicates that the Δ4,5 double bond migrates to Δ3,4 and the carboxylic acid group becomes a methyl ester derivative

• (Table 3). The difference is that the carboxylic acid at C-4 in 3 undergoes reduction to form a hydroxymethyl group at C-4 in 5. This alteration is supported by the analysis of the HMBC correlations (Figure 2) of H-3/C-4 (δC 128.6), C-14 (δC 63.5) and H-14/C-4, C-5 (δC 141.9). Thus, the planar structure

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• system. Like the classical Friedel–Crafts reaction, the aza-Friedel–Crafts reaction also requires the presence of a Lewis acid catalyst for rate acceleration. The reaction can be very easily modulated by different Lewis acidic metallic compounds which effectively form a coordinate bond by accepting the

• 2004. In this methodology, a 1,1’-bi-2-naphthol (BINOL)-derived chiral phosphoric acid P1 was used as the catalytic reagent to couple 2-methoxyfuran (1) and N-Boc-protected aldimines 2 to incorporate an aza-tertiary stereocenter into the 2’ position of the heteroaromatic products 3 (Scheme 1) [24

• aza-Friedel–Crafts process between indoles 4 and cyclic N-sulfonyl ketimines 5. The authors employed the BINOL-based chiral phosphoric acid P2 bearing two imidazoline moieties at the ortho-positions as the catalyst which activates both reactants through H-bonding where the NH group of the nucleophile

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

• acid catalysts and transition metal catalysts. The goal of this review is to summarize the synthesis of various N-substituted pyrrole derivatives using a modified Clauson–Kaas reaction under diverse conventional and greener reaction conditions. Keywords: catalyst; Clauson–Kaas pyrrole synthesis; 2,5

• -assisted reactions in water, solvent-free conditions and in other organic solvents. Clauson–Kaas reaction and its mechanism The Clauson–Kaas reaction refers to the synthesis of various N-substituted pyrroles via an acid-catalyzed reaction between aromatic or aliphatic primary amines and 2,5

• -dialkoxytetrahydrofuran. This reaction was originally discovered by N. Clauson–Kaas and Z. Tyle in 1952 [37] (Scheme 2a). Initially, acetic acid was used as a catalyst in this classic reaction; however, diverse modifications have been reported for this procedure using various Brønsted acid catalysts, metal catalysts, and

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• selectively targeted by photoredox catalysis to enable unprecedented modification of the amino acid. In this context, it is worth mentioning that the single-electron oxidation of the indole moiety in tryptophan provides the radical cation, which enables selective C-radical generation at the weaker benzylic

• : 1) it functions as the central intermediate in the biosynthetic pathways leading to numerous prenylated indole alkaloids, such as ergot alkaloids in normal biosynthesis and clavicipitic acid in derailment biosynthesis [68][69][70][71]; and 2) the mechanism of the fundamental central C-ring formation

• photoredox cycle (Figure 1b). Alternatively, we envisioned a more established approach expecting the direct oxidative photoredox decarboxylation of the carboxylic acid/carboxylate (by SET from the activated photocatalyst) of DMAT to generate the α-aminoalkyl radical that might readily be captured/trapped

Intermediates and shunt products of massiliachelin biosynthesis in Massilia sp. NR 4-1

• Till Steinmetz,
• Blaise Kimbadi Lombe and
• Markus Nett

Beilstein J. Org. Chem. 2023, 19, 909–917, doi:10.3762/bjoc.19.69

• Burkholderia gladioli, which possesses an unprecedented citrate-derived fatty acid moiety [11]. Furthermore, lipopeptide siderophores with photocleavable moieties, like taiwachelin, were reported from bacteria of the genera Cupriavidus and Variovorax [12][13][14]. The β-proteobacterial genus Massilia was

• substituent at C-2 of the phenol moiety. The final carbon atom at 171.9 ppm (C-15) could be attributed to a carboxylic acid function with HMBC correlations from H-13 and H-14, thereby completing the determination of the planar structure of 1. To determine the configuration of 1, we measured its optical

• rotation. The obtained value ( = +37°) was consistent with the value of (S)-dihydroaeruginoic acid (8, = +47°) which is structurally almost identical to 1 except for the presence of the n-pentyl side chain [21]. We thus propose that 1 is also S-configured. Compound 2 (0.4 mg) was obtained as a brown oil

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• Pharmaceutical Sciences, Osaka University, Yamadaoka 1-6, Suita, Osaka 565-0871, Japan 10.3762/bjoc.19.67 Abstract Although nitrocyclopropanedicarboxylic acid esters are widely used in organic syntheses, nitrocyclopropanes with an acyl group have not yet been synthesized. When adducts of β-nitrostyrene and 1,3

• bulkier. The obtained nitrocyclopropane was transformed into furan upon treatment with tin(II) chloride via a ring-opening/ring-closure process. Keywords: acetoxyiodine; conjugate addition; dihydrofuran; nitroalkene; nitrocyclopropane; Introduction 3-Arylated 2-nitrocyclopropane-1,1-dicarbonylic acid

• example, when esters 1a are subjected to Lewis acid-induced denitration, highly electron-deficient enones (reaction b) [4] are obtained. The latter compounds are highly reactive and undergo reaction with, e.g., mercaptoacetaldehyde affording thiophenes (reaction c) [5] or with activated (hetero)aromatic

Asymmetric tandem conjugate addition and reaction with carbocations on acylimidazole Michael acceptors

• Brigita Mudráková,
• Renata Marcia de Figueiredo,
• Jean-Marc Campagne and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 881–888, doi:10.3762/bjoc.19.65

• of −7.13 eV and an even more negative NBO charge of −0.368 at the C-2 position. We can confer from these data that Zn enolates obtained from acylimidazoles are somewhat less reactive than silyl enol ethers obtained in the Lewis acid-promoted conjugate addition of Grignard reagents [23]. This finding

Light-responsive rotaxane-based materials: inducing motion in the solid state

• Adrian Saura-Sanmartin

Beilstein J. Org. Chem. 2023, 19, 873–880, doi:10.3762/bjoc.19.64

• the interlocked arrangement. As an illustrative example, cucurbit[8]uril-based pseudorotaxanes having a pair of styrylpyridinium threads bearing carboxylic acid groups were employed in the preparation of the uranium-organic framework U-CB[8]-MPyVB (Figure 4a) [63]. The solid structure of the MOFs

• shows the styrene-based derivatives coordinated in an antiparallel manner through the carboxylic acid group placed at the end of each thread, thus avoiding the dethreading process. Two identical intertwined scaffolds were formed differing in the photoactivities due to different conformations. In the

A fluorescent probe for detection of Hg²⁺ ions constructed by tetramethyl cucurbit[6]uril and 1,2-bis(4-pyridyl)ethene

• Xiaoqian Chen,
• Naqin Yang,
• Yue Ma,
• Xinan Yang and
• Peihua Ma

Beilstein J. Org. Chem. 2023, 19, 864–872, doi:10.3762/bjoc.19.63

• mol·L−1 hydrochloric acid solution, heated at 70 °C, cooled and filtered. The filtrate was slowly evaporated in air (about 10 days) to obtain colorless crystals. Ultraviolet–visible absorption and fluorescence spectroscopy An aqueous solution of TMeQ[6] and G@TMeQ[6] at 3.0 × 10−5 mol L−1 was prepared

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• ). A direct selective C4-alkylation of pyridine has been reported by the groups of Hiyama [62] (Scheme 12a) and Zhang [63] (Scheme 12c) in 2010 and 2020, respectively. The Hiyama group developed a C-4-selective alkylation of pyridines using a Ni/Lewis acid cooperative catalytic system in combination

• with a bulky N-heterocyclic carbene ligand and (2,6-t-Bu2-4-Me-C6H2O)2AlMe (MAD) as the Lewis acid which allowed the direct C-4 alkylation of pyridines 1 (Scheme 12a). With the optimized reaction conditions in hand the group also screened the alkene and pyridine substrate scope which resulted C4

• nickel Lewis acid catalyst with amino pendant linked NHC complex (Scheme 21). In addition, the authors were able to isolate the bimetallic intermediate structure η2,η1-pyridine–Ni(0)–Al(III) complex 112, as a support for their mechanism for the para-C–H functionalization. They further investigated the

Eschenmoser coupling reactions starting from primary thioamides. When do they work and when not?

• Lukáš Marek,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2023, 19, 808–819, doi:10.3762/bjoc.19.61

• solutions (DMSO-d6, MeOD-d4, D2O), it was impossible to measure its NMR spectra and the only characterization involves MALDI–MS, IR, and melting point. The salt 6a was then treated in various solvents with or without additive (thiophile, base/acid) to give diverse products of cyclization (8a or 8a-Me), ECR

• phosphite does not give 8a-Me at all. The combined yield of 8a and 8a-Me can be increased when trifluoroacetic acid is added (Table 1, entry 9). Its role probably involves an acid-catalyzed elimination of a water molecule from 7a or 7a-Me. On the other hand, the addition of a stronger base (triethylamine

• lactam 2 structure involving the replacement of a quaternary carbon carrying two electron-donating methyl groups with an electron-withdrawing carbonyl group (2b → 3). The starting isoquinoline-1,3(2H,4H)-dione was prepared [31] from homophthalic acid and then brominated with NBS to give 4

Non-peptide compounds from Kronopolites svenhedini (Verhoeff) and their antitumor and iNOS inhibitory activities

• Yuan-Nan Yuan,
• Jin-Qiang Li,
• Hong-Bin Fang,
• Shao-Jun Xing,
• Yong-Ming Yan and
• Yong-Xian Cheng

Beilstein J. Org. Chem. 2023, 19, 789–799, doi:10.3762/bjoc.19.59

• , accompanied by two known flavan derivatives 5 and 6 and a known olefine acid (9) were isolated from whole bodies of Kronopolites svenhedini (Verhoeff). The structures of the new compounds were determined by 1D and 2D nuclear magnetic resonance (NMR) and other spectroscopic methods, as well as computational

• (δC 43.8), and H-12/C-10, C-11. The presence of a conjugated carboxylic acid was verified by the HMBC correlation of H2-2 to C-1 (δC 177.1). Concerning the geometry of 7, the ROESY correlation (Figure 2 and Figure S32 in Supporting Information File 1) of H-10/H2-12 disclosed that the ∆10,11

• above mentioned compounds, three known compounds were identified as daphnegiralin C1 (5) [23], daphnegiranol C1 (6) [29], and (E)-oct-2-enoic acid (9) [30] by comparing their spectroscopic data with those in the literature. Biological evaluation To explore the bioactive potential of the isolated

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

• temperature derived from the heat of reaction accelerated the reaction. The quantitative yield by HPLC was 98.3% and the byproduct carboxylic acid 3a was 1.3%. 3a was easily purged by extraction with a weak base such as NaHCO3. From the above discussion, the throughput was improved to 1.4 kg/day (= 57 g/h

Construction of hexabenzocoronene-based chiral nanographenes

• Ranran Li,
• Di Wang,
• Shengtao Li and
• Peng An

Beilstein J. Org. Chem. 2023, 19, 736–751, doi:10.3762/bjoc.19.54

• -dicyano-p-benzoquinone (DDQ) and methanesulfonic acid in dichloromethane, the helical structure 7 was obtained in a 72% yield [34]. The possible reason for this incomplete cyclization is the electronic effect of the alkoxy groups. Meanwhile, the methoxy version was also synthesized from precursor 5. The

• dibenzocyclooctyne 8 and tetracyclone 2 in a 91% yield. After a subsequent sequence of deprotection and oxidation, ketone 10 was obtained. Through the oxidative cyclodehydrogenation reaction of 10 in the presence of DDQ and trifluoromethanesulfonic acid (TfOH), a saddle-helix hybrid nanographene 11, bearing an

• ]azepine and tetrabromothiophene-S,S-dioxide, followed by oxidative aromatization in the presence DDQ to afford compound 25 in an overall 75% yield. Suzuki−Miyaura cross-coupling reaction of compound 25 with (4-ethylphenyl)boronic acid in the presence of Pd(CH3CN)2Cl2, SPhos, and K3PO4 then furnished the

Synthesis of imidazo[1,2-a]pyridine-containing peptidomimetics by tandem of Groebke–Blackburn–Bienaymé and Ugi reactions

• Oleksandr V. Kolomiiets,
• Alexander V. Tsygankov,
• Maryna N. Kornet,
• Aleksander A. Brazhko,
• Vladimir I. Musatov and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2023, 19, 727–735, doi:10.3762/bjoc.19.53

• peptidomimetic chain was already described in 2010 [32]. Thus, the corresponding acid components were synthesized with GBB-3CR and used in Ugi and Paserini reactions with various aldehydes, amines (for Ugi) and isocyanides. Moreover, in 2016 [33], an alternative route to use GBB-3CR products in Ugi reaction as

• . Taking into account all these facts, we solved the task of developing a new approach for the synthesis of hybrid molecules containing substituted pharmacophoric heterocyclic and peptidomimetic fragments. An approach based on the preparation of an imidazo[1,2-a]pyridine-containing heterocyclic acid and

• its introduction as an acid component in the Ugi reaction was chosen. The route to the synthesis of the target molecules can be divided into two stages, with GBB-3CR in the first stage and the Ugi reaction in the second stage using the product of the first stage. Results and Discussion A model

Palladium-catalyzed enantioselective three-component synthesis of α-arylglycine derivatives from glyoxylic acid, sulfonamides and aryltrifluoroborates

• Bastian Jakob,
• Nico Schneider,
• Luca Gengenbach and
• Georg Manolikakes

Beilstein J. Org. Chem. 2023, 19, 719–726, doi:10.3762/bjoc.19.52

• Bastian Jakob Nico Schneider Luca Gengenbach Georg Manolikakes Department of Chemistry, RPTU Kaiserslautern-Landau, Erwin-Schrödinger-Str. Geb. 54, D-67663 Kaiserslautern, Germany 10.3762/bjoc.19.52 Abstract A palladium-catalyzed enantioselective three-component reaction of glyoxylic acid

• imine species provide a very flexible approach to the arylglycine scaffold [2][9]. The Petasis borono-Mannich reaction constitutes a prominent example for such an imine-based multicomponent reaction (Scheme 1a). The reaction of glyoxylic acid, an amine component and an arylboronic acid offers a highly

• situ generation of reactive imine species, we have disclosed iron- and bismuth-catalyzed three-component reactions for the synthesis of α-arylglycines [14][15][16], in which the arylboronic acid could be replaced with an electron-rich (hetero)arene as nucleophile. In parallel, we have developed

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

• [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

• good yield (80%) by heating 23 in polyphosphoric acid (Scheme 5). Independently, in an effort to synthesise phenothiazine isosteres, Craig et al. [39] prepared 1a via a Wagner–Meerwein rearrangement of 23 with P2O5 (Scheme 5) the following year. The method was used to successfully synthesise

• 24 was reported by Cong et al. [45] as a method for the synthesis of substituted dibenzo[b,f]oxepines 25 (Scheme 6). Treatment of the malonate derivative 24 with Mn(OAc)3 in 90% acetic acid gave C-10 carboxylate derivatives of dibenzo[b,f]oxepine 25. The authors proposed a one-electron oxidation of

Synthesis of medium and large phostams, phostones, and phostines

• Jiaxi Xu

Beilstein J. Org. Chem. 2023, 19, 687–699, doi:10.3762/bjoc.19.50

• )butyl)phosphonic acid (28) in 45% yield as a byproduct, which was generated from the Pd-catalyzed arylmethylic cleavage under hydrogenolysis conditions (Scheme 5) [22]. To avoid the formation of the acyclic byproduct, the same research group designed a new inhibitor with a reverse phosphonate bond

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• were obtained in good yields regardless of the substituent R in the benzene ring. Treatment of the latter with fluoroboric acid in dichloromethane gave double salts 11a–e. X-ray structures Slow evaporation of solutions of butadiynes 5 in the CHCl3/EtOAc system made it possible to grow single crystals

• -terminated butadiyne 5 gradually underwent demethylation/acid-catalyzed heterocyclization involving one of the dimethylamino groups and the adjacent C≡C bond of the butadiyne linker, forming the corresponding benzo[g]indole derivative. Proton sponge-based 1,4-diaryl-1,3-butadiynes synthesized previously and

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• ]. Finally, the reaction of 5 with benzoic acid and zinc acetate (in a 1:1 ratio) under standard reaction protocol resulted in the competitive formation of products 4a and 10 (Scheme 3E), indicating the susceptibility of other acids towards this method. These results, along with the Stern–Volmer fluorescence

pH-Responsive fluorescent supramolecular nanoparticles based on tetraphenylethylene-labelled chitosan and a six-fold carboxylated tribenzotriquinacene

• Nan Yang,
• Yi-Yan Zhu,
• Wei-Xiu Lin,
• Yi-Long Lu and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2023, 19, 635–645, doi:10.3762/bjoc.19.45

• reported procedures [16][23]. The 1H NMR spectra were recorded by use of a Bruker AV 400 spectrometer in D2O and CDCl3. Synthesis of CS-TPE. The TPE-CHO [23] (2 mol %, 10 mol %, and 20 mol %) solution in THF (20 mL) was added to the CS (143.1 mg, 0.9 mmol) solution in 1% glacial acetic acid (30 mL), and

• nanoparticles. CS-TPE was dissolved in 1% (v/v) acetic acid by stirring. The pH was increased by adding sodium hydroxide solution dropwise until it reached 5.3. The pH value was verified with a pH meter calibrated with two standard buffer solutions. Then, the TBTQ-C6 solution was dropped into the CS-TPE

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• Following the seminal work of Feringa in 1997 [21], the tandem asymmetric organozinc conjugate addition followed by subsequent aldol reaction was scarcely applied in the last decade. Welker and Woodward studied the reaction of zinc enolates 2 with chiral acetals 3 (Scheme 2) [22]. The Lewis acid (TiCl4 or

• the transient iminium species 68 to afford the corresponding aminomethylation products 69 (Scheme 18) [50]. As seen from Table 2, the diastereoselectivities were somewhat compromised compared to what one can expect from the reactions of cyclic enolates. This erosion was likely caused by Lewis acid

• developed a Lewis acid-promoted conjugate addition to unreactive Michael acceptors such as amides or vinyl heterocycles [60]. Trimethylsilyl triflate or boron trifluoride-activated unsaturated amides underwent highly efficient and enantioselective addition of Grignard reagents. When this methodology was

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• electrochemically induced oxidative modification of the amino acid side chain. Experimental and DFT studies showed that the additional tert-butyl group increases the dispersion interactions in the Ni coordination environment making the complexes more conformationally rigid and provides a higher level of

• complex. Solubility of the t-Bu-containing ligand and its Schiff base complexes is increased, facilitating scaling-up the reaction procedure and isolation of the functionalized amino acid. Keywords: asymmetric synthesis; chiral auxiliaries; cysteine derivatives; Ni–Schiff base complexes; voltammetry

• )) and includes a chiral auxiliary, an amino acid, and a bifunctional linker capable to arrange the components in the Schiff base complex. Such templates provide a significant C–H acidity at the α-amino acid carbon and a possibility for recycling of the chiral auxiliaries (for reviews see [5][14][15][16

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• Biotechnology, Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia 10.3762/bjoc.19.40 Abstract Two novel conjugate molecules were designed: pyrene and phenanthridine-amino acid units with a different linker length between the aromatic fragments. Molecular

• formed an exciplex [15], and conjugates formed of pyrene and an amino acid-fluorescent nucleobase derivative qAN1, differing in length and flexibility between fluorophores [16]. Due to pre-organization, both conjugates strongly interacted with ds-DNA/RNA grooves with similar affinity but opposite

• ), differing only in the linker length between the aromatic units, have been prepared by condensation of two different pyrenecarboxylic acids with phenanthridine-labelled amino acid (Scheme 2). The influence of the linker length on the molecule flexibility, intramolecular conformation, spectroscopic properties

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

• 25. Transmetalation of 25 with the organoboronic acid gives intermediate 26, which upon reductive elimination affords the difunctionalized product 21 and regenerates the Ni(0) catalyst. In 2019, the Stanley laboratory explored the Ni-catalyzed intermolecular three-component carboacylation of

• final ring-opened adduct 37. Copper-catalyzed reactions In 2009, Pineschi and co-workers explored the Cu-catalyzed rearrangement/allylic alkylation of 2,3-diazabicyclo[2.2.1]heptenes 47 with Grignard reagents 48 (Scheme 8) [41]. The reaction is thought to proceed via the Lewis acid-catalyzed [3,4

• success of the reaction, hypothesizing it inhibited the classical [3,3]-sigmatropic Lewis acid-catalyzed rearrangement often observed. Both alkyl and aryl Grignard reagents were amenable to the reaction; however, heteroaryl Grignard reagents resulted in poor conversion. The Cu-catalyzed borylative