Entry to new spiroheterocycles via tandem Rh(II)-catalyzed O–H insertion/base-promoted cyclization involving diazoarylidene succinimides

• Alexander Yanovich,
• Anastasia Vepreva,
• Ksenia Malkova,
• Grigory Kantin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2024, 20, 561–569, doi:10.3762/bjoc.20.48

• 1H NMR spectroscopy data, one of its components was the product of the migration of the double bond of the benzylidene fragment into the succinimide cycle – compound 22. Finally, a compound with a longer side chain 24, obtained from 2-(2-bromoethoxy)ethanol (23), underwent exclusively isomerization

Optimizations of lipid II synthesis: an essential glycolipid precursor in bacterial cell wall synthesis and a validated antibiotic target

• Milandip Karak,
• Cian R. Cloonan,
• Brad R. Baker,
• Rachel V. K. Cochrane and
• Stephen A. Cochrane

Beilstein J. Org. Chem. 2024, 20, 220–227, doi:10.3762/bjoc.20.22

• using established procedures from the literature, commencing with ᴅ-glucosamine and benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-ᴅ-glucopyranoside as the starting materials, respectively [40][41][42][43]. Imidate donors 1a and 1e were obtained exclusively as α-anomers, and 1b and 1g as a 1:1 α:β

Synthesis of the 3’-O-sulfated TF antigen with a TEG-N₃ linker for glycodendrimersomes preparation to study lectin binding

• Mark Reihill,
• Hanyue Ma,
• Dennis Bengtsson and
• Stefan Oscarson

Beilstein J. Org. Chem. 2024, 20, 173–180, doi:10.3762/bjoc.20.17

• , taking care not to affect the Troc group, to afford acceptor 5 in a 96% yield. Earlier optimizations of the introduction of the β-linked galactose moiety using 2-azidoethyl 2-acetamido-4,6-O-benzylidene-2-deoxy-α-ᴅ-galactopyranoside as acceptor showed an acetylated thioglycoside donor to be the best

Synthesis of 5-arylidenerhodanines in L-proline-based deep eutectic solvent

• Stéphanie Hesse

Beilstein J. Org. Chem. 2023, 19, 1537–1544, doi:10.3762/bjoc.19.110

• scaffolds is the introduction of a benzylidene moiety on C5 via a Knoevenagel reaction. Here, a facile synthesis of 5-arylidenerhodanines via a Knoevenagel reaction in an ʟ-proline-based deep eutectic solvent (DES) is reported. This method is fast (1 h at 60 °C), easy, catalyst-free and sustainable as no

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

• 24.5. In addition to the stereocontrolled synthesis of AMG reported in Figure 21 [116] and Figure 22 [118], another possibility uses dimethyl-ᴅ-tartrate (25.1) as chiral precursor (Figure 25) [81]. This 8-step synthesis starts with the protection of the diol to form the benzylidene tartrate 25.2. Then

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

• 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

Radical cation Diels–Alder reactions of arylidene cycloalkanes

• Kaii Nakayama,
• Hidehiro Kamiya and
• Yohei Okada

Beilstein J. Org. Chem. 2022, 18, 1100–1106, doi:10.3762/bjoc.18.112

• benzylidene cycloalkanes and therefore, the results described herein may support a detailed mechanistic understanding. Further experimental and theoretical studies of radical cation cycloadditions of arylidene cycloalkanes are under investigation in our laboratory. Experimental Photoelectrochemical: The

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

• should be pointed out that the exocyclic benzylidene group exists on the C3-position in the newly formed cyclohexyl ring, while it exists on the C6-position in the above obtained spiro compounds 3a–z. This result clearly indicated that these two reactions have the opposite regioselectivity. Another kind

Unusual highly diastereoselective Rh(II)-catalyzed dimerization of 3-diazo-2-arylidenesuccinimides provides access to a new dibenzazulene scaffold

• Anastasia Vepreva,
• Alexander S. Bunev,
• Andrey Yu. Kudinov,
• Grigory Kantin,
• Mikhail Krasavin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2022, 18, 533–538, doi:10.3762/bjoc.18.55

• other hand, their specific geometry enables intriguing transformations with simultaneous involvement of the diazo function and the benzylidene fragment. DAS were first described in 2020 and were involved in a [2 + 1] cycloaddition to aldehydes to give oxiranes [1]. Later on, we developed a convenient

• benzylidene fragment (1g) led to the deactivation of the diazo substrate ‒ after 1 hour the conversion did not exceed 30% and even after 3 days the starting DAS 1g was still present in the mixture. At the same time, only a trace amount of the expected dimerization product 2g was detected along unidentified

• ortho-methyl substituent in the benzylidene fragment. In this case, along with conventional reaction products ‒ dimer 2r and indene 3r, unexpectedly the cyclobutane 5, a product of the formal [2 + 2] cycloaddition, was isolated in low yield (Scheme 1); its structure was confirmed by single-crystal X-ray

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

• catalyst for the oxidation of 2-methylnaphthalene (16) with H2O2 [59]. The complex L1-Fe(III) (L1 = (2-((2-(2-((2-((2-hydroxyphenylimino)methyl)phenoxy)methyl)benzyloxy)benzylidene)amino)phenol) showed the best catalytic activity with 58.54% selectivity and 79.11% conversion (Table 1, entry 13) [59

Asymmetric organocatalytic Michael addition of cyclopentane-1,2-dione to alkylidene oxindole

• Estelle Silm,
• Ivar Järving and
• Tõnis Kanger

Beilstein J. Org. Chem. 2022, 18, 167–173, doi:10.3762/bjoc.18.18

• to synthesise indoloquinolizidines [5]. Moreover, six-membered and five-membered cyclic 1,3-diketones have been investigated in reactions with acetates of nitroalkenes [6], cyanoacrylates and benzylidene malononitriles [7], ortho-hydroxy-benzhydryl alcohols [8], α,β-unsaturated pyrazolamides [9] and

• in carbohydrate chemistry [15]. Cyclic six-membered 1,2-diketones have been shown to react with benzylidene malononitriles [7][16], β-nitrostyrenes [17] and substituted propionaldehydes [18]. For a while, there were no examples related to cyclopentane-1,2-dione (CPD). In 2004, the first instance of

• thiourea catalysts were screened in a model reaction between CPD 1 and Boc-protected benzylidene oxindole 2a at room temperature in the presence of 10 mol % of catalyst (Figure 2). First, the quinidine-derived squaramide A was used and the desired product was obtained as a mixture of chromatographically

Total synthesis of the O-antigen repeating unit of Providencia stuartii O49 serotype through linear and one-pot assemblies

• Tanmoy Halder and
• Somnath Yadav

Beilstein J. Org. Chem. 2021, 17, 2915–2921, doi:10.3762/bjoc.17.199

• on the hydroxy groups. First, the concomitant removal of the Troc group and the N-acetylation was achieved using Zn/AcOH/Ac2O 3:2:1 as reagent in one pot (Scheme 6) [52]. Then, O-deacetylation was accomplished by using a catalytic amount of NaOMe in MeOH at room temperature. Finally, the benzylidene

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF₃·OEt₂ catalysis

• Karthikeyan Soundararajan,
• Helen Ratna Monica Jeyarajan,
• Raju Subimol Kamarajapurathu and
• Karthik Krishna Kumar Ayyanoth

Beilstein J. Org. Chem. 2021, 17, 2186–2193, doi:10.3762/bjoc.17.140

• arrangement would facilitate the intramolecular Friedel–Crafts cyclization of the MBH adducts. Cycloaddition of azomethine imine 7a with 2-substituted-1H-indenes 6b and 6c was attempted to ascertain the structure of the synthesized 1H-indenes (Scheme 3). The azomethine imine, 1-benzylidene-3-oxopyrazolidin-1

• ; found, 174.0706 Synthesis of 1-benzylidene-3-oxopyrazolidin-1-ium-2-ide (7a) A methyl acrylate (0.0225 mol) solution was added drop-wise to the solution of hydrazine monohydrate (0.0205 mol) in 20 mL of ethanol. This solution was stirred at 78 °C for 4 hours; the solvent was evaporated and the residue

• (6C, aro-C), 57.92 (1C, N-CH2), 29.38 (1C, CO-CH2); HRMS (m/z): [M + H]+ calcd for C10H10N2O, 174.0793; found, 174.0818. Typical procedure for synthesis of compounds 8a and 8b Indene 6b (1 mmol) in 2 mL of toluene was successively added to 1-benzylidene-3-oxopyrazolidin-1-ium-2-ide (1.2 mmol). The

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• dramatic when 2,4-di-O-acyl groups are present, sometimes leading to exclusive formation of α-anomers [128][129]. PGs like 2-O-ADMB (4-acetoxy-2,2-dimethylbutanoate) [130] or 2,2’-O-benzylidene [131] were introduced to solve this issue. Several reports highlighted the importance of the 4,6-O-benzylidene

• group on the glycosyl donor and the acceptor for the stereoselective formation of the β(1–3) linkage (Figure 4) [132]. Interestingly, oligomers bearing several 4,6-O-benzylidene groups show anomalously small coupling constants for some of the C-1 hydrogens. NMR [133] and X-ray [134] studies revealed

• that, for some residues, the 4,6-O-benzylidene group stabilizes a boat conformation (1,4B or B2,5), in contrast to the standard chair (4C1). This unexpected conformation did not affect the stereoselectivity of the glycosylation, permitting the preparation of linear β(1–3)-glucans of different lengths

Copper-mediated oxidative C−H/N−H activations with alkynes by removable hydrazides

• Feng Xiong,
• Bo Li,
• Chenrui Yang,
• Liang Zou,
• Wenbo Ma,
• Linghui Gu,
• Ruhuai Mei and
• Lutz Ackermann

Beilstein J. Org. Chem. 2021, 17, 1591–1599, doi:10.3762/bjoc.17.113

• column chromatography on silica gel (petroleum/EtOAc 5:1 to 2:1, with 1% Et3N), yielding the desired product 3. (Z)-3-Benzylidene-2-(methyl[pyridin-2-yl]amino)isoindolin-1-one (3aa) The general procedure was followed using hydrazide 1a (68.2 mg, 0.30 mmol) and alkyne 2a (91.9 mg, 0.90 mmol). Purification

Organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones

• Chandrakanta Parida and
• Subhas Chandra Pan

Beilstein J. Org. Chem. 2021, 17, 1447–1452, doi:10.3762/bjoc.17.100

• ). Finally, nitroketone 2n with a cyclohexyl group was engaged in the reaction and a moderate enantioselectivity was detected for product 3n (Table 2, entry 14). In the next step, we investigated the scope of the reaction of substrate 2a with a variety of pyrrolidine-2,3-diones 1 having different benzylidene

Synthesis of multiply fluorinated N-acetyl-D-glucosamine and D-galactosamine analogs via the corresponding deoxyfluorinated glucosazide and galactosazide phenyl thioglycosides

• Vojtěch Hamala,
• Lucie Červenková Šťastná,
• Martin Kurfiřt,
• Petra Cuřínová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2021, 17, 1086–1095, doi:10.3762/bjoc.17.85

• ). 4,6-O-Benzylidenation of diol 18 followed by regioselective opening of the benzylidene acetal produced compound 35. Subsequent DAST deoxyfluorination delivered the desired thioglycoside 36 (Scheme 3). For both compounds 18 and 35, deoxyfluorination of the C4 hydroxy group occurred with inversion of

An atom-economical addition of methyl azaarenes with aromatic aldehydes via benzylic C(sp³)–H bond functionalization under solvent- and catalyst-free conditions

• Divya Rohini Yennamaneni,
• Vasu Amrutham,
• Krishna Sai Gajula,
• Rammurthy Banothu,
• Murali Boosa and
• Narender Nama

Beilstein J. Org. Chem. 2020, 16, 3093–3103, doi:10.3762/bjoc.16.259

• achieved from other starting materials, such as 2-methyl-6-(phenylethynyl)pyridine [36], 2,6-dimethylpyridine (1a) and (E)-N-benzylidene-4-methylbenzenesulfonamide [22], 2-bromo-6-methylpyridine and (E)-styrylboronic acid [37], as well as 2-methylpyridine and phenylmethanamine [38]. Most recently

One-pot synthesis of oxazolidinones and five-membered cyclic carbonates from epoxides and chlorosulfonyl isocyanate: theoretical evidence for an asynchronous concerted pathway

• Esra Demir,
• Ozlem Sari,
• Yasin Çetinkaya,
• Ufuk Atmaca,
• Safiye Sağ Erdem and
• Murat Çelik

Beilstein J. Org. Chem. 2020, 16, 1805–1819, doi:10.3762/bjoc.16.148

• polymerization of the compounds containing cyclic carbonates such as methyl 4,6-O-benzylidene-2,3-O-carbonyl-α-ᴅ-glucopyranoside (MBCG) (5) [19][20] and glycerol carbonate (6) [21] were also reported (Scheme 1). Therefore, numerous synthetic approaches have been developed to date for the preparation of

Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• bioactive natural products and pharmaceutical drugs [20][21][22]. Thioaurones (2-benzylidene benzo[b]thiophen-3(2H)-one) are sulfur-containing heterocyclic compounds, an important subclass of flavonoids which were first introduced by O’Sullivan in 1977 [23]. Specifically, thioaurones and their analogs show

Synthesis of the tetrasaccharide repeating unit of the O-specific polysaccharide of Azospirillum doebereinerae type strain GSF71^T using linear and one-pot iterative glycosylations

• Arin Gucchait,
• Pradip Shit and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2020, 16, 1700–1705, doi:10.3762/bjoc.16.141

• led to the formation of disaccharide acceptor 5 in 73% yield. The quantity of HClO4-SiO2 present in the reaction mixture was very low, which allowed the selective deprotection of the highly acid labile PMB group without affecting the benzylidene acetal in the molecule in dichloromethane as the solvent

• without the isolation and purification of the intermediate glycosylation products. Finally, compound 7 was subjected to a set of reactions involving (a) transformation of the azido group to an acetamido group by the treatment with thioacetic acid [33]; (b) removal of the benzylidene acetal by the

• -20 column using CH3OH/H2O 6:1 as eluent to give pure compound 1 (90 mg, 50%). p-Methoxyphenyl (2,4-di-O-benzyl-α-ʟ-rhamnopyranosyl)-(1→3)-2-azido-4,6-O-benzylidene-2-deoxy-β-ᴅ-glucopyranoside (5): To a solution of compound 2 (600 mg, 1.5 mmol) and compound 3 (800 mg, 1.57 mmol) in anhydrous CH2Cl2

Synthesis of Streptococcus pneumoniae serotype 9V oligosaccharide antigens

• Sharavathi G. Parameswarappa,
• Claney L. Pereira and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2020, 16, 1693–1699, doi:10.3762/bjoc.16.140

• reducing-end monosaccharide 14 equipped with the linker in 70% yield as a mixture of anomers (α:β = 2:1) (Scheme 2). The reductive opening of the benzylidene protecting group in 14 enabled the separation of anomers and furnished acceptor 15α [28], that was reacted with thioglucoside 11 to yield exclusively

• was modified into compound 6 via benzylidene ring opening followed by benzoylation of the free C-4 secondary hydroxy group in 27. The disaccharide imidate 29 was synthesized from 6 by anomeric desilylation to afford 28 that was converted to the corresponding imidate in an excellent yield. The final [2

• mannosamine was obtained from 33, that in turn was a product of the benzylation of 32. Cleavage of the benzylidene group in 33 yielded 34 that was selectively acetylated at the primary alcohol at low temperature to obtain 35 [30]. The subsequent removal of the benzyl groups using hydrogenation with Pd/C in an

Distinctive reactivity of N-benzylidene-[1,1'-biphenyl]-2-amines under photoredox conditions

• Shrikant D. Tambe,
• Kwan Hong Min,
• Naeem Iqbal and
• Eun Jin Cho

Beilstein J. Org. Chem. 2020, 16, 1335–1342, doi:10.3762/bjoc.16.114

• unprecedented reductive coupling of N-benzylidene-[1,1'-biphenyl]-2-amines with an aliphatic amine. The presence of a phenyl substituent in the aniline moiety of the substrate was critical for the reactivity. The reaction proceeded via radical–radical cross-coupling of α-amino radicals generated by proton

• -coupled single-electron transfer in the presence of an Ir photocatalyst. On the other hand, symmetrical 1,2-diamines were selectively produced from the same starting materials by the judicious choice of the reaction conditions, showcasing the distinct reactivity of N-benzylidene-[1,1'-biphenyl]-2-amines

• of other valuable structural motifs via the careful control of the reaction conditions for the reaction of the biphenyl imine derivative N-benzylidene-[1,1'-biphenyl]-2-amine. Results and Discussion With the initial results in hand, we attempted the optimization of the reaction conditions to improve

Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore

• Esteban P. Urriolabeitia,
• Pablo Sánchez,
• Alexandra Pop,
• Cristian Silvestru,
• Eduardo Laga,
• Ana I. Jiménez and
• Carlos Cativiela

Beilstein J. Org. Chem. 2020, 16, 1111–1123, doi:10.3762/bjoc.16.98

• ) and the (E)-configuration of the styryl moiety (C11–C12) are clearly seen, thus confirming the results obtained in solution. It is worth noting the orientation of the chlorine atom Cl1, which is syn with respect to the benzylidene proton. This orientation minimizes steric repulsions in the molecule

• and allows the establishment of an intramolecular contact between Cl1 and H7A. The non-bonding distance Cl1–H7A is 2.565(3) Å, which is much shorter than the sum of the van der Waals radii (2.95 Å) [51]. The same syn arrangement between the ortho-substituent and the benzylidene proton has also been

Convenient synthesis of the pentasaccharide repeating unit corresponding to the cell wall O-antigen of Escherichia albertii O4

• Tapasi Manna,
• Arin Gucchait and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2020, 16, 106–110, doi:10.3762/bjoc.16.12

• ) hydrogenolysis of benzyl ethers and benzylidene acetals over Pearlman’s catalyst [36] to furnish the desired pentasaccharide 1 in 49% overall yield (Scheme 4). The structure of compound 1 was unambiguously characterized by its NMR spectral analysis [signals at δ 5.37 (d, J = 2.0 Hz, H-1A), 5.29 (d, J = 3.5 Hz, H