Rotaxanes with integrated photoswitches: design principles, functional behavior, and emerging applications

• Jullyane Emi Matsushima,
• Khushbu,
• Zuliah Abdulsalam,
• Udyogi Navodya Kulathilaka Conthagamage and
• Víctor García-López

Beilstein J. Org. Chem. 2025, 21, 2345–2366, doi:10.3762/bjoc.21.179

• an acyclic Hamilton-like receptor with terminal anthracene moieties on both ends. Therefore, upon irradiation with light, the anthracene undergoes photodimerization, forming a macrocycle and capturing the axle to afford the [2]rotaxane. Notably, the photoclipping approach is thermally reversible

C2 to C6 biobased carbonyl platforms for fine chemistry

• Jingjing Jiang,
• Muhammad Noman Haider Tariq,
• Florence Popowycz,
• Yanlong Gu and
• Yves Queneau

Beilstein J. Org. Chem. 2025, 21, 2103–2172, doi:10.3762/bjoc.21.165

• irradiation was proven to be thermally, chemically and sunlight stable. The esterification of trans-3-(2-furyl)acrylic acid with ethanol, provided (1α,2α,3β,4β)-2,4-di(furan-2-yl)cyclobutane-1,3-dicarboxylic acid (CBDA-5) via a solvent-free [2 + 2] photodimerization from ethyl 2-furanacrylate and subsequent

Deep-blue emitting 9,10-bis(perfluorobenzyl)anthracene

• Long K. San,
• Sebastian Balser,
• Brian J. Reeves,
• Tyler T. Clikeman,
• Yu-Sheng Chen,
• Steven H. Strauss and
• Olga V. Boltalina

Beilstein J. Org. Chem. 2025, 21, 515–525, doi:10.3762/bjoc.21.39

• to suppress undesirable fluorescence self-quenching [15]. Not only do bulky substituents disrupt intermolecular interactions of this type, they can also provide higher chemical stability and reduce or prevent the photodimerization and photo-oxidation to which all acenes are prone [13]. Furthermore

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

• spectroscopy (Scheme 1). During the reaction progress, the C=C bonds of bpe ligands undergo pedal-like motion prior to photodimerization [63]. For the single-crystal irradiation, the slow reactivity can be attributed to the hindered pedal motion in the single crystals, likely due to the presence of

• surface area exposed to light but also to allow the motions within the crystal. In another instance, MacGillivray and colleagues reported the synthesis of rctt-tetrakis(4-pyridyl)cyclobutane (2.3) via [2 + 2] photodimerization of trans-1,2-bis(4-pyridyl)ethylene (2.1) via supramolecular catalysis by 4,6

• obtained as a single stereoisomer and in quantitative yield after 80 h of irradiation. The role of 2.2 is to create a close-packed environment via hydrogen-bond interactions where the [2 + 2] photodimerization can occur stereoselectively. Next, the authors evaluated the possibility of using the template

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

• photoactive arrangement, a single-crystal-to-single-crystal regioselective [2 + 2] photodimerization reaction was accomplished by irradiating at 365 nm using a 6 W UV lamp. This light-triggered reaction led to the photoconversion of the threaded styrylpyridinium motifs into the corresponding interlocked

• cyclobutanes (Figure 4b). Interestingly, the changes in the crystalline array as a consequence of this photodimerization within the cucurbituril macrocycles also induced a macroscopic deformation of the metal-organic material, promoting a photomechanical bending of the crystals. This photomechanical

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• photodimerization [55][56][57], photocleavage [58][59], and cis–trans photoisomerization [60][61][62][63][64][65]. While it had been well-established to access oligomer formation and gelation, a light-switchable particle size has remained a challenge until realized through the mentioned electrostatic self-assembly

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

• reactions, including photopolymerization, photohydrolysis, and photodimerization [42][43][44][45][46]. Chemical transformations assisted by nanosized reaction vessels have gained attention in the field of supramolecular photocatalysis. Therefore, Sivaguru et al. performed the photodimerization of coumarin

• /22 ratio of 1:2, which revealed that the singlet spin-state of coumarin could be involved in the photodimerization process within the CB[8] cavity and that the triplet state could be shielded from external quenchers (O2 as a triplet quencher). These results also indicated that photodimerization could

• . Srinivasan “Fabrication of anti-poisoning core-shell TiO2 photocatalytic system through a 4-methoxycalix[7]arene film’’ pages 1–6, Copyright (2016), with permission from Elsevier. (a) Photodimerization of 6-methylcoumarin (22). (b) Catalytic cycle for the photodimerization of 22, mediated by CB[8

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• 1а with pinacol 2-phenylethynyl boronate. The meta-methoxystyryl derivative 5c was found to easily undergo photodimerization in solid state upon sunlight exposure, leading to the formation of compound 8 with a central cyclobutane ring (see Supporting Information File 1). As proved previously for

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

• ; photodimerization; photoswitches; Introduction The association of DNA-targeting drugs with nucleic acids [1][2][3][4][5][6][7][8] is considered one of the essential properties that determine their biological activity [9]. Specifically, a ligand may occupy particular binding sites of DNA or induce significant

• 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

• . Supporting Information File 1) that may have been followed by a [2 + 2] photodimerization (Scheme 2). However, it is difficult to explain why the photocycloaddition of the Z-isomers Z-3b and Z-3c led exclusively to the dimer, because such a selectivity has not been reported so far for (Z)-stilbenes. On the

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• . Chiral solvents The only report on asymmetric electrochemical reaction in chiral solvent was published by Seebach and Oei in 1975 [53]. The asymmetric photodimerization of acetone to pinacol was conducted using amino-ether DDB 54 as a chiral solvent. Under the optimized reaction conditions, this

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• . In 2008, they have established a [2 + 2] photodimerization through solid-state grinding either in neat or liquid-assisted conditions [93]. To achieve 100% stereospecific products they considered resorcinol derivatives as hydrogen-bond donors for the photodimerization of 1,2-di(pyridin-4-yl)ethylene

• ]-cycloaddition methodology. They used the vertex grinding technique where solid-state grinding and UV irradiation was done simultaneously [111] and verified co-crystal formation of a resorcinol derivative with dipyridylethylene in the solid state. Also, the supramolecular catalysis of [2 + 2] photodimerization

Synthesis of carbohydrate-scaffolded thymine glycoconjugates to organize multivalency

• Anna K. Ciuk and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 668–674, doi:10.3762/bjoc.11.75

• protecting group was observed whereas the Boc-protection remained untouched. Thus, the title glycocluster 13 was obtained in a single deprotection step. The new divalent glycoconjugate 13 shows good water solubility and is thus suited for biological testing. For photodimerization of 13, it was irradiated for

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• -to-head dimer. The degree of complexation of coumarin could be increased by employing the salting out effect. Keywords: acenaphthylene; anthracene; coumarin; cyclodextrins; photodimerization; quantum yield; stereoselectivity; Introduction Photochemical reactions have been considered highly

• paid to both the quantum yields Φ and stereoselectivities of the photodimerizations. Results and Discussion Photodimerization of anthracene Due to the fact that the inclusion compounds of ANT in native β-CD or γ-CD are completely insoluble in water, only the aqueous photochemistry of hydrophilic ANT

• derivatives, such as anthracene-2-carboxylate (ANT-2-COONa) [12], and anthracene-2-sulfonate (ANT-2-SO3Na) [26], have been investigated so far. The quantum yields of photodimerization increase dramatically from 5 to up to 50% by complexation of these guests with β-CD or γ-CD, as found by Tamaki et al. [26][27

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• amination reactions [53][54], photodimerization studies [55], MnO2 oxidations [56] and during phase-transfer reactions [57]. The use of high-resolution cameras to specifically examine physical effects during the merging of sonochemistry and microfluidic techniques, leading to improved reactor design, was

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

• Henning Hopf,
• Vitaly Raev and
• Peter G. Jones

Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

• ), photodimerization to the corresponding cyclobutane derivative occurs readily, and the photoproduct can be saponified to the corresponding pseudo-geminal diamine and truxinic acid (6) in excellent yield, thus allowing its stereospecific synthesis. We believe that the use of the [2.2]paracyclophane scaffold as a

• 30% probability levels. [2.2]Paracyclophanes as scaffolds for intraannular photodimerization reactions in solution. Stereospecific intramolecular [2+2]photoadditions using [2.2]paracyclophane spacers. Different conformations of pseudo-geminal divinyl[2.2]paracyclophane. Preparation of tetraene 11

Supramolecular FRET photocyclodimerization of anthracenecarboxylate with naphthalene-capped γ-cyclodextrin

• Qian Wang,
• Cheng Yang,
• Gaku Fukuhara,
• Tadashi Mori,
• Yu Liu and
• Yoshihisa Inoue

Beilstein J. Org. Chem. 2011, 7, 290–297, doi:10.3762/bjoc.7.38

• modification of γ-CD causes a dramatic switching of stereoselectivity in AC photodimerization [12][22]. Thus, by using native γ-CD the chiral cyclodimer 2 is obtained in 41% enantiomeric excess (ee), whereas biphenyl-capped γ-CD 5 yields antipodal 2 in −57% ee (Scheme 1) [22]: Where the positive/negative sign

Exceptionally small supramolecular hydrogelators based on aromatic–aromatic interactions

• Junfeng Shi,
• Yuan Gao,
• Zhimou Yang and
• Bing Xu

Beilstein J. Org. Chem. 2011, 7, 167–172, doi:10.3762/bjoc.7.23

• 2.5 to 2.9 ppm (Figure S1, Supporting Information File 1), photopolymerization or photodimerization are unlikely. Furthermore, the result shown in Figure S2 (Supporting Information File S2) also supports the contention that heating is insufficient to cause conversion of the trans-isomer to the cis

Synthesis of 2a,8b-Dihydrocyclobuta[a]naphthalene-3,4-diones

• Kerstin Schmidt and
• Paul Margaretha

Beilstein J. Org. Chem. 2010, 6, No. 76, doi:10.3762/bjoc.6.76

• . In the same experiment with 1c, the MeO-group apparently tends to increase the efficiency in photodimerization vs mixed photocycloaddition, otherwise there is no obvious explanation for this result. Experimental 1. General. Acetals 1 were synthesized according to [8]. Both 1b, m.p. 60–62 °C, and 1c