Unraveling the role of prenyl side-chain interactions in stabilizing the secondary carbocation in the biosynthesis of variexenol B

• Moe Nakano,
• Rintaro Gemma and
• Hajime Sato

Beilstein J. Org. Chem. 2023, 19, 1503–1510, doi:10.3762/bjoc.19.107

• hyperconjugative interactions, through-space interactions, and C–H–π interactions, have been intensively investigated by Tantillo and co-workers, who have contributed greatly to revealing the intriguing nature of carbocations [7][19][20]. We have also elucidated various new insights of carbocation chemistry, such

Comparison of crystal structure and DFT calculations of triferrocenyl trithiophosphite’s conformance

• Ruslan P. Shekurov,
• Mikhail N. Khrizanforov,
• Ilya A. Bezkishko,
• Tatiana P. Gerasimova,
• Almaz A. Zagidullin,
• Daut R. Islamov and
• Vasili A. Miluykov

Beilstein J. Org. Chem. 2022, 18, 1499–1504, doi:10.3762/bjoc.18.157

• )3PS [7] (Figure 4). All three compounds form crystals belonging to the monoclinic syngony. In all three cases, the molecules in the crystals form a herringbone motif. In (FcS)3P, C–H···π interactions dominate, while in (FcS)3PS and (FcS)3PO, in addition to C–H···π interactions, by one C–H···S and two

• has the highest energy. Most obviously the latter is stabilized by intermolecular C–H···π interactions (Figures S4 and S5 in Supporting Information File 1). The bulky Fc moieties do not allow to form such type of dimers. Conclusion Triferrocenyl trithiophosphite (FcS)3P was studied by X-ray single

Experimental and theoretical studies on the synthesis of 1,4,5-trisubstituted pyrrolidine-2,3-diones

• Nguyen Tran Nguyen,
• Vo Viet Dai,
• Nguyen Ngoc Tri,
• Luc Van Meervelt,
• Nguyen Tien Trung and
• Wim Dehaen

Beilstein J. Org. Chem. 2022, 18, 1140–1153, doi:10.3762/bjoc.18.118

• (Figure S1 in Supporting Information File 1) is characterized by C7–H7···O12i hydrogen bonds resulting in chain formation along the a direction [C7–H7: 0.93 Å, H7···O12: 2.42 Å, C7···O12: 3.325(3) Å, C7–H7···O12: 164˚; symmetry code: (i) 1 + x, y, z]. Neighboring chains connect by C–H···π interactions

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• hydrogen bonding, which was found for these and the other cycloaddends between a proton of the benzene ring of the diene and an oxygen atom of the dienophile (Table 7), also stabilize the endo TS. Therefore, this theoretical study indicated that the non-covalent π···π and C–H···π interactions control the

Towards triptycene functionalization and triptycene-linked porphyrin arrays

• Gemma M. Locke,
• Keith J. Flanagan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2020, 16, 763–777, doi:10.3762/bjoc.16.70

• molecule in the asymmetric unit with the bridgehead substituents being almost 180° to each other (Figure 2, for labelling see Figure S33 in Supporting Information File 1). Unlike the unsubstituted triptycene 1 crystal structure which exhibits a high degree of C–H···π interactions between the aromatic rings

• omitted for clarity (thermal displacement 50%); (b) expanded view showing the π-stacking between the i and ii rings (thermal displacement 50%). Bridgehead substituents have been omitted for clarity; (c) expanded view showing C–H···π interactions between the TIPS group of one molecule and the third pocket

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• encapsulated two molecules of E-1 (in agreement with the NMR spectra), arranged in an antiparallel fashion (Figure 3). The binding of E-1 within 2 is driven by a combination of π–π stacking, van der Waals forces, and C–H···π interactions (vide infra); in addition, the encapsulation is likely facilitated by the

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

• Esther Nieland,
• Oliver Weingart and
• Bernd M. Schmidt

Beilstein J. Org. Chem. 2019, 15, 2013–2019, doi:10.3762/bjoc.15.197

• , connected by C–H···F contacts. The azobenzenes A2 interact by lamellar 2D π-stacking, anthracene U1 interact predominantly by C–H···π interactions as both the solubilizing mesitylene group and the two perpendicular lutidine acceptors effectively prevent stacking of the anthracenes body (Supporting

Complexation of 2,6-helic[6]arene and its derivatives with 1,1′-dimethyl-4,4′-bipyridinium salts and protonated 4,4'-bipyridinium salts: an acid–base controllable complexation

• Jing Li,
• Qiang Shi,
• Ying Han and
• Chuan-Feng Chen

Beilstein J. Org. Chem. 2019, 15, 1795–1804, doi:10.3762/bjoc.15.173

• Information File 1, Figure S92). The calculation results revealed the C–H···π interactions between the protons on the pyridinium ring of G1 and the benzene ring units of the host H4 and C–H···O hydrogen bonds between the protons of the methyl group and pyridinium rings of G1 and the oxygen atom of H4 with

• distances ranging from 2.052 to 2.769 Å. Likewise, DFT calculations at the B3LYP/6-31G level of theory for the complexes H4·G3 and H5·G3 were also performed. As shown in Figure 6, in the optimized structure, the pyridinium ring of the guest is surrounded by the cavity of the host. There are C–H···π

• interactions between the protons on the pyridinium ring of G3 and the benzene rings encompassing the cavity of H4, and C–H···O hydrogen bonding between the protons of the pyridinium ring of G3 and the oxygen atom of H4 with distances ranging from 2.052 to 2.769 Å. Similar to H4·G3, complex H5·G3 also shows the

2,3-Dibutoxynaphthalene-based tetralactam macrocycles for recognizing precious metal chloride complexes

• Li-Li Wang,
• Yi-Kuan Tu,
• Huan Yao and
• Wei Jiang

Beilstein J. Org. Chem. 2019, 15, 1460–1467, doi:10.3762/bjoc.15.146

• distance: 2.21, 2.38 and 2.46 Å). C–H···π interactions (H···π distance: 2.75 and 2.83 Å) between the methyl group of CH3CN and the naphthalene panels of the host are also detected. This suggests that the 2.3-dibutoxynaphthalene tetralactam macrocycle, just like other tetralactam macrocycles, may use

Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

• Andrew T. King,
• Hugh G. Hiscocks,
• Lidia Matesic,
• Mohan Bhadbhade,
• Roger Bishop and
• Alison T. Ung

Beilstein J. Org. Chem. 2019, 15, 1347–1354, doi:10.3762/bjoc.15.134

• -3H-indazole core of 8 carries both benzhydryl and germinal diphenyl groups. These aromatic substituents make significantly different intermolecular contacts in the crystal. The phenyl rings of the former (C1A to C6A, and C1B to C6B) make complementary C–H···π interactions with the related molecule

• across a centre of inversion. Hydrogen atoms C2A–H2A and C3A–H3A make an almost perpendicular approach to ring B at C2B and C6B, respectively: H2A···C2B = 3.04 Å and H3A···C6B = 2.96 Å (Figure 4a). One of the gem-diphenyl rings (C1C to C6C) also employs C-H···π interactions across a centre of inversion

Synthesis of 3-aminocoumarin-N-benzylpyridinium conjugates with nanomolar inhibitory activity against acetylcholinesterase

• Nisachon Khunnawutmanotham,
• Cherdchai Laongthipparos,
• Patchreenart Saparpakorn,
• Nitirat Chimnoi and
• Supanna Techasakul

Beilstein J. Org. Chem. 2018, 14, 2545–2552, doi:10.3762/bjoc.14.231

• chromene ring moved away from Tyr72 in the PAS; thus, compounds 9e and 9i lost H-bond interactions to Tyr72. Moreover, the C–H–π interactions of compounds 9e and 9i to Tyr72 became weaker. All other H-bonds, C–H–π and π–π interactions of 9e and 9i to amino acid residues in the binding site were similar to

• substituents on the chromene ring, no H-bonds and C–H–π interactions to Tyr72, Trp286, and Tyr341 are observed. In compound 10a, one additional methylene group between the pyridinium and the carbonyl groups caused the chromene ring to flip in the binding pocket. The other parts of the structure also shifted

• the amide group and dimethoxy substituents on the chromene ring to the amino acid residues Tyr72, Tyr124, Trp286, and Tyr341 in the PAS; and (5) the hydrogen atoms of phenyl ring to Glu202 and a methoxy group to Ser293. Moreover, C–H–π and π–π interactions were found for compound 9h. The C–H–π

Evaluation of dispersion type metal···π arene interaction in arylbismuth compounds – an experimental and theoretical study

• Ana-Maria Preda,
• Małgorzata Krasowska,
• Lydia Wrobel,
• Philipp Kitschke,
• Phil C. Andrews,
• Jonathan G. MacLellan,
• Lutz Mertens,
• Marcus Korb,
• Tobias Rüffer,
• Heinrich Lang,
• Alexander A. Auer and
• Michael Mehring

Beilstein J. Org. Chem. 2018, 14, 2125–2145, doi:10.3762/bjoc.14.187

• and C–H···π interactions in organobismuth compounds and therefore the crystal structures are described and discussed in the following chapter. Please note that the term C–H···π is used as a structure descriptor rather than to describe a special type of bonding. Thus we follow the criticism given by

• is built up via C–HPh···π intermolecular contacts of T-shape. Noteworthy, polymorph 2a showed bismuth···π and π···π interactions leading to 1D ribbons in the solid state, while 2b did not reveal Bi···π interactions. Thus, it is concluded that Bi···π, π···π and C–H···π interactions must be of similar

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• ···O distance = 3.10 Å; average N–H···O angle = 157°). In addition, C–H···π interactions were detected among the methylene groups of the axle 2+ inside the calix cavity, and the aromatic rings of 1 [42], ( average C–H···πcentroid distance = 3.17 Å [42]; average C–H···πcentroid angle = 160° [43]). In

• addition, the biphenyl portion of 2+ hosted inside the calix cavity was involved in π···π interactions with the aromatic walls (Figures S11–S13, Supporting Information File 1) and C–H···π interactions with the tert-butyl groups of the calixarene wheel (Figure S13, Supporting Information File 1

Host–guest complexes of conformationally flexible C-hexyl-2-bromoresorcinarene and aromatic N-oxides: solid-state, solution and computational studies

• Rakesh Puttreddy,
• Ngong Kodiah Beyeh,
• S. Maryamdokht Taimoory,
• Daniel Meister,
• John F. Trant and
• Kari Rissanen

Beilstein J. Org. Chem. 2018, 14, 1723–1733, doi:10.3762/bjoc.14.146

• , aiding in the binding of polar guests such as N-oxides. Keywords: aromatic N-oxides; C–H···π Interactions; ditopic receptors; endo/exo complexation; host–guest chemistry; resorcinarenes; Introduction Resorcinarenes are macrocyclic compounds with a bowl-shaped cavity stabilised by circular

• encapsulation in the bowl-shaped upper rim (endo complexation) due to size complementarity between host cavity and guest shape, and are generally stabilised through multiple C–H···π interactions [26][27][28]. The cavity capacity to undergo induced conformational changes in response to the incorporation of

• -acidity of aromatic protons assist in orienting the N-oxide guest by C–H···π interactions, and that the HB accepting N–O group is positioned “up”, extending out beyond the cavity to interact with solvent molecules. Our work, investigating the interactions of PyNO guests with various resorcinarene hosts

Complexation of molecular clips containing fragments of diphenylglycoluril and benzocrown ethers with paraquat and its derivatives

• Leonid S. Kikot',
• Catherine Yu. Kulygina,
• Alexander Yu. Lyapunov,
• Svetlana V. Shishkina,
• Roman I. Zubatyuk,
• Tatiana Yu. Bogaschenko and
• Tatiana I. Kirichenko

Beilstein J. Org. Chem. 2017, 13, 2056–2067, doi:10.3762/bjoc.13.203

• weak C–H···π interactions of the hydrogen atoms of the methylene groups and dipyridinium fragments of paraquat (the corresponding H···π distances are ≈2.84 Å). In the crystal phase molecules form infinite rows in such way that the neighboring molecules are turned to each other on 180° within the row

• complexes with paraquat (7), the host–guest complexes 2@8 and 3@8 are stabilized by π–π stacking, C–H···O and C–H···π interactions. So far as the structures of these complexes are very similar the main attention will be paid to some differences only. The presence of the terminal hydroxy groups creates the

Organofluorine chemistry: Difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring

• Mathew J. Jones,
• Ricardo Callejo,
• Alexandra M. Z. Slawin,
• Michael Bühl and
• David O'Hagan

Beilstein J. Org. Chem. 2016, 12, 2823–2827, doi:10.3762/bjoc.12.281

• interactions between the non-fluorine face of the cyclohexyl ring and the phenyl group of a neighbouring molecule (Figure 2). These C-H···π interactions are a feature of the solid state packing found in phenyl derivatives of 2 [29]. This electrostatic ordering was reinforced by an NMR shift experiment in

Friedel–Crafts-type reaction of pyrene with diethyl 1-(isothiocyanato)alkylphosphonates. Efficient synthesis of highly fluorescent diethyl 1-(pyrene-1-carboxamido)alkylphosphonates and 1-(pyrene-1-carboxamido)methylphosphonic acid

• Anna Wrona-Piotrowicz,
• Janusz Zakrzewski,
• Anna Gajda,
• Tadeusz Gajda,
• Anna Makal,
• Arnaud Brosseau and
• Rémi Métivier

Beilstein J. Org. Chem. 2015, 11, 2451–2458, doi:10.3762/bjoc.11.266

• , apart from the H1 atom which was involved in intermolecular hydrogen bond formation. (a) Dimers of π-stacked and hydrogen-bonded molecules of 3a represented in single figures; (b) network of weak C–H…O and C–H…π interactions stabilizing H-bonded dimer strings and (c) crystal packing along the

Direct alkenylation of indolin-2-ones by 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles: a novel approach

• Sandeep Kumar,
• Ramendra Pratap,
• Abhinav Kumar,
• Brijesh Kumar,
• Vishnu K. Tandon and
• Vishnu Ji Ram

Beilstein J. Org. Chem. 2013, 9, 809–817, doi:10.3762/bjoc.9.92

• , respectively. The angles C−H…π interactions (Figure 3) that led to the formation of a centrosymmetric dimer. The C–H…π interaction distance is

Structural conditions required for the bridge lithiation and substitution of a basic calix[4]arene

• Conrad Fischer,
• Wilhelm Seichter and
• Edwin Weber

Beilstein J. Org. Chem. 2011, 7, 1602–1608, doi:10.3762/bjoc.7.188

• stabilized by weak C–H···π interactions [14] involving methoxy groups and arene units of the neighbouring calixarene molecules (C33A–H33D···centroid C: 3.460(6) Å; C38–H38A···centroid B: 3.707(6) Å; C52A–H52D···centroid A: 3.619(6) Å). The resulting channel-like voids between any two calixarene layers are

A convenient method for preparing rigid-core ionic liquid crystals

• Julien Fouchet,
• Laurent Douce,
• Benoît Heinrich,
• Richard Welter and
• Alain Louati

Beilstein J. Org. Chem. 2009, 5, No. 51, doi:10.3762/bjoc.5.51

• spectra at 10.45 ppm and 134.97 ppm respectively. Single crystals of 1a suitable for X-ray diffraction were obtained by slow diffusion of ether into a CH2Cl2 solution. The compound 1a crystallizes in the triclinic space group P1. A partly labelled ORTEP view showing non-classical hydrogen bonds and C-H..π

• interactions is given in Figure 1 (the interactions also being listed in Table 1). The alkyloxy chains are quite parallel, as is clear from the crystal packing given in Figure 2, with segregation between the rigid part (including iodine atoms) and the alkyloxy chains (≈20 Å, see Figure 2). The length of the

Variations in product in reactions of naphthoquinone with primary amines

• Marjit W. Singh,
• Anirban Karmakar,
• Nilotpal Barooah and
• Jubaraj B. Baruah

Beilstein J. Org. Chem. 2007, 3, No. 10, doi:10.1186/1860-5397-3-10

• interactions N-H. . . O, C-H. . . O and C-H. . . π interactions play roles in the self-assembly formation as illustrated in Figure 2. Some of the important weak bonds responsible for hydrogen bonding assemblies in 3 C6-H. . . O1 (3.303Å, 153.07°), C11-H. . . O1 (3.540Å, 143.41°), N2-H. . . O2 (2.877Å, 140.18

Crystal engineering of analogous and homologous organic compounds: hydrogen bonding patterns in trimethoprim hydrogen phthalate and trimethoprim hydrogen adipate

• Packianathan Thomas Muthiah,
• Savarimuthu Francis,
• Urszula Rychlewska and
• Beata Warżajtis

Beilstein J. Org. Chem. 2006, 2, No. 8, doi:10.1186/1860-5397-2-8

• compound 2, the bond angles at carboxylate group, C18-C17-O5 and C18-C17-O4 are 120.1(2)° and 116.5(2)° respectively, whereas the angle at the carboxyl group C21-C22-O6, C21-C22-O7 are 123.1(2)° and 113.1(2)° respectively. The crystal structure of compound 2 is further stabilized by two C-H...π

• interactions [38] [C16-H161...Cg1(atoms N1-C6) (2.923Å, 137°) and C20-H201...Cg2 (atoms C8-C13) (2.779Å, 156°)] and the pyrimidine stacking interactions. The interplanar and centroid to centroid distances are 3.381Å and 3.738Å, respectively, and the angle between the centroid vector and normal to the plane is