Synthesis and properties of 6-alkynyl-5-aryluracils

• Ruben Manuel Figueira de Abreu,
• Till Brockmann,
• Alexander Villinger,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 898–911, doi:10.3762/bjoc.20.80

• stronger electron-withdrawing groups, as can be seen in case of product 4d. The yield of 4b was comparatively lower, which may be due to the higher steric hindrance of the used arylacetylene. Product 4f could not be synthesized, due to decomposition during the reaction. Furthermore, no precursor could be

• deactivates the compound for the subsequent Suzuki reaction. Furthermore, lower yields were generally observed when a strong electron-donor or -acceptor was attached to the phenyl group at position 5. Higher yields could be obtained by reducing the steric hindrance at position 5 by introducing a 5-membered

• between the layers varies periodically between 3.373 Å and 3.662 Å. This results in different interactions between the layers, as depicted in Figure 3. Furthermore, the layers are arranged in an anti-parallel face-to-face order to reduce the steric hindrance. Within the shorter distance layers (3.373 Å

Skeletal rearrangement of 6,8-dioxabicyclo[3.2.1]octan-4-ols promoted by thionyl chloride or Appel conditions

• Martyn Jevric,
• Julian Klepp,
• Johannes Puschnig,
• Oscar Lamb,
• Christopher J. Sumby and
• Ben W. Greatrex

Beilstein J. Org. Chem. 2024, 20, 823–829, doi:10.3762/bjoc.20.74

• at C4 determined the resultant ring system, as the σ* orbital is not accessible to external nucleophiles due to steric hindrance and the rigid conformation of the bicyclic ring system. When the C4–OH was equatorial, O8 migrated as it was aligned with the σ* orbital giving a 3,8-dioxabicyclo[3.2.1

• some sulfites 13b,d,e, attributed to the reduced steric hindrance in the chlorosulfite intermediate allowing for the second alcohol to approach prior to rearrangement. The isolation of these materials suggested that dialkyl sulfite formation could compete with the rearrangement if the neighbouring

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• worked well in the transformation, affording homopropargylic azides 4n–q in 60–77% yield. The reaction appears to be sensitive to the steric hindrance of the nucleophile: addition of a mesitylalkyne only formed 33% of 4r. Pleasingly, heteroaryl substituents were tolerated, 4s bearing a thiophene was

Palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines

• Geng-Xin Liu,
• Xiao-Ting Jie,
• Ge-Jun Niu,
• Li-Sheng Yang,
• Xing-Lin Li,
• Jian Luo and
• Wen-Hao Hu

Beilstein J. Org. Chem. 2024, 20, 661–671, doi:10.3762/bjoc.20.59

• next turned to evaluate the scope of 1,3-dienes. Although the regioselectivity control of allylic substitution can be attributed to many factors, it is agreed that steric hindrance generally is the primary factor affecting the regioselectivity of nucleophilic attack [54][55][56][57]. Monoalkyl

• , the corresponding 1,2-addition products 4p–t were formed with high selectivity (E/Z > 20:1, 1,2-/1,4-addition >20:1), presumably due to steric hindrance by the phenyl group. Furthermore, the 1,3-diene bearing a 1-furan group with smaller steric hindrance afforded product 4u with moderate

Possible bi-stable structures of pyrenebutanoic acid-linked protein molecules adsorbed on graphene: theoretical study

• Yasuhiro Oishi,
• Motoharu Kitatani and
• Koichi Kusakabe

Beilstein J. Org. Chem. 2024, 20, 570–577, doi:10.3762/bjoc.20.49

• ) linkers on graphene. The activation barrier between two bi-stable conformations exhibited by PASE is confirmed to be based on the steric hindrance effect between a hydrogen on the pyrene group and a hydrogen on the alkyl group of this molecule. Even after the protein is supplemented, this steric hindrance

• the steric hindrance effect between two hydrogen atoms in the molecule. A discussion on how the activation barrier between possible conformations of a protein immobilized on graphene by linkers appears is also provided. We consider the adsorption of the linker molecule forming a bond with a protein

• about 1.8 Å (Table 1). If we compare this distance with the distance between the same hydrogen pairs in conformation 1 and conformation 2, we can see that 1.8 Å is indeed very short compared with that for the others (about 2.2 Å). Therefore, we conclude that a local steric hindrance occurs at the

Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Irina V. Dubonosova,
• Olga Yu. Karlutova,
• Oleg P. Demidov,
• Alexander D. Dubonosov and
• Vladimir A. Bren

Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47

• -wavelength absorption at 458 nm, while acylation led to a hypsochromic shift of the maximum in compounds 2a–c to 423–426 nm (Table 1). The intensity of this absorption band decreased with increasing steric hindrance in the order R = acetyl (i.e., 2a) > propionyl (i.e., 2b) > phenylacetyl (i.e., 2c). N

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• a parallel direction, as the bulky -OMe groups are located outside the tweezer’s cavity to avoid steric hindrance with each other. When protonated, the pyridinium group acts as a hydrogen-bond donor for the two methoxy groups and triggers the rotation of the respective benzene rings along with the

• ]. In the neutral state, the tweezers 34 adopt an anti-conformation because of steric hindrance between the N–H and the tert-butyl groups. Again, the N–H proton of the indole can bind to anions through hydrogen bonds and causes the system to adopt a cis-conformation, closing the tweezers. This closed

Development of a chemical scaffold for inhibiting nonribosomal peptide synthetases in live bacterial cells

• Fumihiro Ishikawa,
• Sho Konno,
• Hideaki Kakeya and
• Genzoh Tanabe

Beilstein J. Org. Chem. 2024, 20, 445–451, doi:10.3762/bjoc.20.39

• and 9 exhibited lower affinity than inhibitors 1, 2, 4, 5, and 7. This result suggests that the incorporation of the pegylated functionality at the 2′-OH group of the adenosine skeleton particularly perturbs binding via steric hindrance. Next, we investigated whether ʟ-Phe-AMS derivatives could

Mono or double Pd-catalyzed C–H bond functionalization for the annulative π-extension of 1,8-dibromonaphthalene: a one pot access to fluoranthene derivatives

• Nahed Ketata,
• Linhao Liu,
• Ridha Ben Salem and
• Henri Doucet

Beilstein J. Org. Chem. 2024, 20, 427–435, doi:10.3762/bjoc.20.37

• , carbon 2 should be more reactive than carbon 4 in the Pd-catalyzed direct arylation, but we previously observed that the main product of the reaction was C4-arylated 1,3-dichlorobenzene [32]. This selectivity could be due to the steric hindrance of the chloro substituents. As a result, in the presence of

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

Synthesis of spiropyridazine-benzosultams by the [4 + 2] annulation reaction of 3-substituted benzoisothiazole 1,1-dioxides with 1,2-diaza-1,3-dienes

• Wenqing Hao,
• Long Wang,
• Jinlei Zhang,
• Dawei Teng and
• Guorui Cao

Beilstein J. Org. Chem. 2024, 20, 280–286, doi:10.3762/bjoc.20.29

• spiropyridazine-benzosultams. The electronic effects of substituents and the influence of steric hindrance on the reaction were explored. The configuration of the product was determined by X-ray single crystal diffraction. This method has the advantages of mild reaction conditions, wide substrate scope, and high

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• -9a and Z-9d in benzene solution. Interestingly, the order of acceleration was primarily dependent on the basicity of the catalyst, unless the steric hindrance of the amine became a significant factor, as is the case of diisopropylamine and trimethylamine. Compounds 9d and 9e are the first examples of

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

• Youlong Du,
• Haibo Mei,
• Ata Makarem,
• Ramin Javahershenas,
• Vadim A. Soloshonok and
• Jianlin Han

Beilstein J. Org. Chem. 2024, 20, 212–219, doi:10.3762/bjoc.20.21

• groups, including alkyl (4a–e), halogen (4h–l), and phenyl (4m), were all suitable substrates for this reaction. However, the benzoic acid with ortho-substituent did not afford the expected product (4f) mainly due to the steric hindrance effect. Notably, substrates with electron-withdrawing groups (4h–l

Chiral phosphoric acid-catalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles

• Yumei Wang,
• Guangzhu Wang,
• Yanping Zhu and
• Kaiwu Dong

Beilstein J. Org. Chem. 2024, 20, 205–211, doi:10.3762/bjoc.20.20

• obtained in 98% yield with 20% ee after 12 h (Table 1, entry 1). Then, the effect of steric hindrance of the CPA catalyst and solvents on the stereochemistry of this transfer hydrogenation were investigated in detail. Among various 3,3’-disubstituted CPA catalysts (Table 1, entries 2–6), chiral phosphoric

• acid CPA-6 containing 2,4,6-triisopropylphenyl-substituents at the 3,3’-positions of the binaphthyl skeleton performed best giving the target product in 99% yield with 91% ee (Table 1, entry 6). This suggested, that the steric hindrance of the CPA catalyst at the 3,3’-position is important for

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• 1f decreased the selectivity with respect to formation of the hydration product 2f, favouring the condensation product 3f (Table 4, entry 6). On the other hand, an ortho methyl group in 1g favoured formation of the ketone 2g, with a good yield, probably due to the steric hindrance of the aldol

Long oligodeoxynucleotides: chemical synthesis, isolation via catching-by-polymerization, verification via sequencing, and gene expression demonstration

• Yipeng Yin,
• Reed Arneson,
• Alexander Apostle,
• Adikari M. D. N. Eriyagama,
• Komal Chillar,
• Emma Burke,
• Martina Jahfetson,
• Yinan Yuan and
• Shiyue Fang

Beilstein J. Org. Chem. 2023, 19, 1957–1965, doi:10.3762/bjoc.19.146

• File 1 for details). To block any hydroxy groups on the surface of CPG that were not capped, including those resulted from mechanical breakage of CPG, before commencing a synthesis, the CPG was subjected to typical capping conditions for 20 minutes. To reduce steric hindrance within the pores of CPG

• much longer than 1,000 nt. Second, to maintain high average stepwise yields as the ODNs grow longer, the problem of steric hindrance needs to be addressed. Our syntheses were conducted in the pores of CPG. Even though we reduced the loading to address the steric hindrance problem, there is a limit to

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

• Dayanne Martins,
• Roberta Lamosa,
• Talis Uelisson da Silva,
• Carolina B. P. Ligiero,
• Sérgio de Paula Machado,
• Daphne S. Cukierman and
• Nicolás A. Rey

Beilstein J. Org. Chem. 2023, 19, 1713–1727, doi:10.3762/bjoc.19.125

• only one NH signal around 12 ppm, indicating the presence exclusively of the (E)-isomer in solution. Furthermore, steric hindrance in these cases allow only for the formation of the antiperiplanar conformation around the conjugated amide single bond. Full assignments, with the chemical shifts and

Quinoxaline derivatives as attractive electron-transporting materials

• Zeeshan Abid,
• Liaqat Ali,
• Sughra Gulzar,
• Faiza Wahad,
• Raja Shahid Ashraf and
• Christian B. Nielsen

Beilstein J. Org. Chem. 2023, 19, 1694–1712, doi:10.3762/bjoc.19.124

• chlorination effects on the Qx20 series, resulting in four new NFAs, i.e., Qx22–Qx25 (Figure 4). The research revealed the strategic balance between molecular crystallinity, packing, and optical properties. Qx24 and Qx25, with lower steric hindrance in the alkyl side chains, showed slightly decreased

Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

• Xiaofeng Zhang,
• Xiaoming Ma and
• Wei Zhang

Beilstein J. Org. Chem. 2023, 19, 1677–1693, doi:10.3762/bjoc.19.123

• Ar and CF3 groups can localize the negative charge and also provide steric effects to afford stereoselective cycloaddition products with 3:1 to 6:1 dr. The steric hindrance also prevents products 9 from undergoing a second cycloaddition. The control reactions of methyl ketone or benzaldehydes gave

• , serine, and norvaline to give products 11a–f in 53–88% yields with greater than 8.5 dr (Scheme 7). The reactions with leucine and phenylglycine (R2 = iPr and Ph) as amino acids gave mainly mono-cycloaddition products and very little double cycloaddition products 11g and 11h due to the steric hindrance of

Lewis acid-promoted direct synthesis of isoxazole derivatives

• Dengxu Qiu,
• Chenhui Jiang,
• Pan Gao and
• Yu Yuan

Beilstein J. Org. Chem. 2023, 19, 1562–1567, doi:10.3762/bjoc.19.113

• good to excellent yields, which showed that the steric hindrance has little effect on the reaction (3j–n). Furthermore, some heteroaromatic and aliphatic alkynes were also utilized, and the corresponding products 3o and 3p were isolated in good yields. We also tried 1,2-diphenylethyne as sustrate

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• loading. Substrates with electron-withdrawing groups are tolerated, whereas strong electron-releasing groups decrease the reactivity. Steric hindrance also plays a crucial role, with ortho-substitution resulting in reduced catalytic activity. Mankad and co-worker [89] developed dehydrogenative borylation

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

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

• possesses a twisted orientation between the donor (benzoguanidine) and acceptor (benzonitrile) ligands (Figure 2) due to steric hindrance imposed by benzoguanidine ligands and reflected by the torsion angle (α) laying in the range of 42.5(2)–64.3(2)º. We compared it with the more narrow torsion angle range

Acetaldehyde in the Enders triple cascade reaction via acetaldehyde dimethyl acetal

• Alessandro Brusa,
• Debora Iapadre,
• Maria Edith Casacchia,
• Alessio Carioscia,
• Giuliana Giorgianni,
• Giandomenico Magagnano,
• Fabio Pesciaioli and
• Armando Carlone

Beilstein J. Org. Chem. 2023, 19, 1243–1250, doi:10.3762/bjoc.19.92

• as a reagent has always been challenging. The low boiling point and high volatility pose a problem with its handling and safety. The small steric hindrance gives rise to a high reactivity both as an electrophile and as a pro-nucleophile, hampering chemoselectivity (further to side reactions such as

• self-aldol condensations, polymerization and Tishchenko-type processes) and stereoselectivity [20]; the activation of acetaldehyde via aminocatalysis, furthermore, suffers from a lack of proper steric hindrance for the enantio-discrimination process. However, some methodologies enabling the use of