Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• shaking a 1:1 mixture of chalcone (4.1) and 1,1,6,6-tetraphenylhexa-2,4-diyne-1,6-diol (4.2) with a test-tube shaker under irradiation with a high-pressure Hg lamp, the [2 + 2] syn-head-to-tail dimer product 4.3 was obtained selectively in 80% yield after 10 h (Scheme 4) [66]. In detail, 4.2 works as a

Chemical structure metagenomics of microbial natural products: surveying nonribosomal peptides and beyond

• Thomas Ma and
• John Chu

Beilstein J. Org. Chem. 2024, 20, 3050–3060, doi:10.3762/bjoc.20.253

• , respectively. Based on the position of the nucleophile, a NRP can be cyclized head-to-tail, via an amino acid side-chain, a nucleophilic heteroatom on the N-terminal fatty acyl chain, or as a multimer of repeating sub-structures (Figure 5b). The ring size, ratio of ʟ- and ᴅ-amino acids, etc. may also be the

Cyclodextrin-based rotaxanes for polymer materials: challenge on simultaneous realization of inexpensive production and defined structures

• Yosuke Akae

Beilstein J. Org. Chem. 2024, 20, 3026–3049, doi:10.3762/bjoc.20.252

• microscopy (STM) [44], clarifying that 80% of the CDs formed the head-to-head and tail-to-tail repeating patterns in which the wheels were located next to each other on the same cavity side, whereas 20% of the CDs exhibited the head-to-tail structure. This direction was induced by the different strengths of

Chemo-enzymatic total synthesis: current approaches toward the integration of chemical and enzymatic transformations

• Ryo Tanifuji and
• Hiroki Oguri

Beilstein J. Org. Chem. 2024, 20, 1693–1712, doi:10.3762/bjoc.20.151

• , (2) a second intramolecular Michael reaction forming a head to tail formal [4 + 4] cycloadduct, and (3) sequential hemiketal formations to furnish the densely-functionalized and complicated pentacyclic scaffold of trichodimerol (2). Alternatively, the 2,4-cyclohexadienone moiety of 34 undergoes

Chemoenzymatic synthesis of macrocyclic peptides and polyketides via thioesterase-catalyzed macrocyclization

• Senze Qiao,
• Zhongyu Cheng and
• Fuzhuo Li

Beilstein J. Org. Chem. 2024, 20, 721–733, doi:10.3762/bjoc.20.66

• -century [32][33][34][35]. Biosynthetically, the corresponding cluster consists of three NRPS, TycA-C, and at the C-terminus of TycC, the TE domain can catalyze a head-to-tail macrocyclization and deliver tyrocidines [30]. With a comprehensive understanding of its biosynthetic mechanism, Walsh and co

Inclusion complexes of the steroid hormones 17β-estradiol and progesterone with β- and γ-cyclodextrin hosts: syntheses, X-ray structures, thermal analyses and API solubility enhancements

• Alexios I. Vicatos,
• Zakiena Hoossen and
• Mino R. Caira

Beilstein J. Org. Chem. 2022, 18, 1749–1762, doi:10.3762/bjoc.18.184

• γ-CD molecules (A, B, C) comprise the major structural motif in the γ-CD·PRO crystal, and they stack to form infinite columns, arranging themselves in a head-to-tail motif between molecules C and A, a tail-to-tail motif between molecules B and C, and a head-to-head motif between molecules A and B

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

• torsion angle of 10.28°. 2-Phenylimidazo[1,2-a]pyridine moieties of neighboring molecules were arranged into slipped-parallel π-stacks with head-to-tail or head-to-head orientations. The distances between parallel mean planes were 3.427 and 3.428 Å (Figure 2b). To demonstrate the efficiency and to broaden

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• order to construct polyazulenes with the head-to-tail alignment of dipoles, azulene should be functionalized at the 2,6-positions, which are diagonally opposite to each other. This will lead to an alternate arrangement of seven and five-membered rings along the polymer backbone and can facilitate

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

•  20C) and the bromine tolyl interaction in a head-to-tail alignment (Figure 20D), which combine to form the packing illustrated in Supporting Information File 1, Figure S45. By substituting the bromine atoms with a TMS-acetylene group the apparent lateral alignment of 16A is distorted due to the larger

• steric demand of the TMS moiety (Supporting Information File 1, Figure S46A). Additionally, while this structure expresses the same head-to-tail overlap between stacked moieties (separation between layers at 3.573(3) Å), shows a greater degree of overlap (Supporting Information File 1, Figure S46B). In

• compound 17, the stacking has alternated to a head-to-tail overlap with 3.562(5) Å separation between the porphyrin layers (Supporting Information File 1, Figure S47A). Moreover, there is a head-to-tail linear network (Supporting Information File 1, Figure S47B) which is tied together with a Br···H contact

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• stacked in a slipped anti- or syn-head-to-tail (HT) fashion) to afford the successive photocyclodimerization, which mimics a catalytic antibody. Therefore, various head-to-head (HH)- or HT-photodimers could be obtained. Particularly, the 21–AC complex could be involved in the photolysis and produced the

• stereochemistry as catalysts [27]. The stereochemical properties were sensitive to the linker size and length, and the yield of the syn-head-to-tail-9,10:9',10'-cyclodimer could reach 97–98%. Traditional thiol-functionalized organic ligands decorated on the surface of gold nanoclusters (AuNCs) tend to generate a

Chiral anion recognition using calix[4]arene-based ureido receptors in a 1,3-alternate conformation

• Tereza Horáčková,
• Jan Budka,
• Vaclav Eigner,
• Wen-Sheng Chung,
• Petra Cuřínová and
• Pavel Lhoták

Beilstein J. Org. Chem. 2020, 16, 2999–3007, doi:10.3762/bjoc.16.249

• same time, the carbonyl groups from the neighbouring receptor urea moieties interacted with the C–H bonds of the DMSO methyl group (the C=O···H–C distances were 2.486 and 2.452 Å), thus forming the calixarene dimer with a head-to-tail mutual orientation. The overall supramolecular binding motif was

Naphthalonitriles featuring efficient emission in solution and in the solid state

• Sidharth Thulaseedharan Nair Sailaja,
• Iván Maisuls,
• Jutta Kösters,
• Alexander Hepp,
• Andreas Faust,
• Jens Voskuhl and
• Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

• some intermolecular CH…π interactions between the C–H units of the residual tolyl group and the central ring of the naphthalonitrile bearing two nitrile groups with a CH/π-ring distance of 2.780 Å (Figure 2A). Even though the naphthalonitrile planes of two adjacent head-to-tail-arranged molecules are

A consensus-based and readable extension of Linear Code for Reaction Rules (LiCoRR)

• Benjamin P. Kellman,
• Yujie Zhang,
• Emma Logomasini,
• Eric Meinhardt,
• Karla P. Godinez-Macias,
• Austin W. T. Chiang,
• James T. Sorrentino,
• Chenguang Liang,
• Bokan Bao,
• Yusen Zhou,
• Sachiko Akase,
• Isami Sogabe,
• Thukaa Kouka,
• Elizabeth A. Winzeler,
• Iain B. H. Wilson,
• Matthew P. Campbell,
• Sriram Neelamegham,
• Frederick J. Krambeck,
• Kiyoko F. Aoki-Kinoshita and
• Nathan E. Lewis

Beilstein J. Org. Chem. 2020, 16, 2645–2662, doi:10.3762/bjoc.16.215

• structure is repeated and the repeating unit is not connected “head to tail,” the MS where the repeating units are connected is marked between 2 dashes “ - - ” (RR2). An example is {nGa6Ga4(-Ab3-)Ub2Ha3Ha3Ha3}. Additionally, Banin et al. specify that a cyclic motif, a form of repetition, is expressed using

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

• of the ε-isomer in 4: (1) the initial (Z)-configuration of the oxazolones 2 is retained during the C–H bond activation step to give 3; (2) the relative transoid arrangement in 3 establishes the 1,3-head-to-tail coupling of the exocyclic C=C bonds; (3) the template effect of the Pd2(O2CCF3)2 moiety

Formal preparation of regioregular and alternating thiophene–thiophene copolymers bearing different substituents

• Atsunori Mori,
• Keisuke Fujita,
• Chihiro Kubota,
• Toyoko Suzuki,
• Kentaro Okano,
• Takuya Matsumoto,
• Takashi Nishino and
• Masaki Horie

Beilstein J. Org. Chem. 2020, 16, 317–324, doi:10.3762/bjoc.16.31

• head-to-tail (HT) orientation with respect to the substituent at the 3-position are extensively studied to date since they generally show superior performances as materials [1][2][3][4][5][6]. Cross-coupling polymerization catalyzed by a transition metal complex has been recognized as an effective tool

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• methoxy-substituted styrylquinolizinium derivatives form the corresponding syn head-to-tail cyclobutanes in a selective [2 + 2] photocycloaddition, as revealed by X-ray diffraction analysis of the reaction products. These photodimers bind to DNA only weakly by outside-edge association, but they release

• triclinic space group . Both XRD analyses clearly showed that both cyclobutane products were formed as rctt configured dimers 4b and 4c (Figure 8). The products 4b and 4c may have formed by a syn head-to-tail dimerization of the E-configured substrate 3a and 3b or by an anti head-to-tail photodimerization

• systems and antiparallel alignment of dipole moments is realized in a syn head-to-tail complex where irradiation would lead directly to the photodimers 4b and 4c in a topochemical reaction (Scheme 2). Notably, the cyclobutane derivatives 4b and 4c were not persistent in solution for extended periods of

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• pyrophosphate synthase, and GFPP geranylfarnesyl pyrophosphate. Mechanisms for type I, type II, and type II/type I tandem terpene cyclases. a) Tail-to-head class I germacrene A (13) cyclase. b) Head-to-tail type II brasilicardin (14) cyclase. c) Type II ent-copalyl diphosphate (15) synthase and type I ent

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• ) cation was coordinated to two sulfur atoms with (R)- and (S)-configuration, respectively (head-to-tail ligand coordination mode). These diastereoisomeric crystals presented a slightly different spatial arrangement. The head-to head macrocycle 1a had a parallelepiped shape (Figure 1a): the interplanar

• distance between two anthracenes was ca. 6.31 Å and the dihedral angle between the anthracene core and its 9,10-aryl substituents was 89° and 104°, respectively. The head-to-tail macrocycle 1a adopted a V-shape (Figure 1b): the angle between the planes of the two anthracenes was 73.2° and the dihedral

• the coordinated ligands (head-to-head or head-to-tail) resulting into different spatial arrangements. In solution, the architectures of silver(I) complexes with ligand syn-1 seemed to be similar to the solid-state structures. The silver(I) complexes were evaluated as homogeneous catalysts in two

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• component in a [6 + 3] cycloaddition with p-benzoquinone to afford cycloadduct 9 [32]. Proposed mechanism for the [6 + 4] cycloaddition of tropone with dimethylfulvene via an ambimodal [6 + 4]/[4 + 6] transition state. Triafulvene dimerization through the proposed 'head-to-tail' mechanism. The dipolar

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs₂CO₃-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

• Mio Matsumura,
• Yuki Kitamura,
• Arisa Yamauchi,
• Yoshitaka Kanazawa,
• Yuki Murata,
• Tadashi Hyodo,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

• independent molecules, and the benzimidazole and the fused benzoselenophene rings are virtually coplanar (mean deviation 0.0169 and 0.0359 Å, respectively) to each other. The molecules show head-to-tail (antiparallel) stacking with π···π interactions, with distances between the nearest neighbor atoms on

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• 1,4-polybutadiene or natural polyisoprene and olefin-containing polyester or polyurethane prepared via step-growth polymerization (Figure 4B and C) [83][84][85]. The multiblock copolymers from polybutadiene and olefin-containing polyurethane demonstrated improved mechanical properties [85]. Head-to

• -tail regioregular and E-stereoregular multiblock copolymers and heterotelechelic polymers were successfully synthesized by the cross metathesis between different ROMP-derived poly(3-substituted cyclooctenes), (Figure 4D) [86]. The MCM between immiscible commercial polybutadiene and polyisoprene led to

Calixazulenes: azulene-based calixarene analogues – an overview and recent supramolecular complexation studies

• Paris E. Georghiou,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Hidetaka Nishimura,
• Jaehyun Lee,
• Atsushi Wakamiya and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2018, 14, 2488–2494, doi:10.3762/bjoc.14.225

• columnar arrays [17]. In this type of array the host molecules which are in 1,3-alternate conformations align in a “head-to-tail” fashion with the C60 molecules able to be accommodated within the opposite clefts. Furthermore, within such an arrangement, in addition to the “face-to-face” π–π interactions

Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions

• Siva Sankar Murthy Bandaru,
• Darinka Dzubiel,
• Heiko Ihmels,
• Mohebodin Karbasiyoun,
• Mohamed M. A. Mahmoud and
• Carola Schulzke

Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161

• composition, however, was unanimously proven by the data. Derivative 2b crystallizes with one molecule of CHCl3 as lattice solvent in the highly symmetric orthorhombic space group I2/a with 8 molecules in the unit cell. Both cations are essentially planar and π-stacked in an anti-head-to-tail (ht) arrangement

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• ). This has been attributed to strong self-association (dimerization) in an antiparallel, head-to-tail orientation in aqueous solution during complex formation with duplex DNA oligomers verified via NOE experiments [61]. They further reported several structurally diverse MGBs, derived from distamycin, in

Polarization spectroscopy methods in the determination of interactions of small molecules with nucleic acids – tutorial

• Tamara Šmidlehner,
• Ivo Piantanida and
• Gennaro Pescitelli

Beilstein J. Org. Chem. 2018, 14, 84–105, doi:10.3762/bjoc.14.5