Photoswitches beyond azobenzene: a beginner’s guide

• Michela Marcon,
• Christoph Haag and
• Burkhard König

Beilstein J. Org. Chem. 2025, 21, 1808–1853, doi:10.3762/bjoc.21.143

• strong as in the previous examples, a deeper analysis is usually needed to predict the photophysical properties of the azoheteroarenes. While the Z-isomer of 6-membered rings is always in a twisted conformation, it was discovered in the case of 5-membered rings that also a T-shaped conformation could be

• of T-shaped 8a and 9a the Z-isomer was more thermally stable thanks to the weak interaction between the hydrogen and the π-system. However, the high symmetry weakens the intensity of the nπ* absorption band, which is the excitation band for the Z–E isomerisation, resulting in a lower E-PSS. Basic

• heterocyclic imines [36][37][38]. The Z-isomers of the unsubstituted derivatives adapt different conformations: T-shaped for the N-phenyl and twisted for the N-pyrazoles. The half-lives follow the same trends already discussed beforehand. In contrast with the azopyrazoles, mono- and di-ortho-amination of the

Supramolecular assembly of hypervalent iodine macrocycles and alkali metals

• Krishna Pandey,
• Lucas X. Orton,
• Grayson Venus,
• Waseem A. Hussain,
• Toby Woods,
• Lichang Wang and
• Kyle N. Plunkett

Beilstein J. Org. Chem. 2025, 21, 1095–1103, doi:10.3762/bjoc.21.87

• durability, low harmful, and convenient alternative to heavy-metal reagents [10][11]. Hypervalent iodine compounds exist as trivalent (λ3-iodanes) or pentavalent (λ5-iodanes) species. The λ3-iodanes have an T-shaped structure [12], with the energetically preferred arrangement of the two most electronegative

Reactivity of hypervalent iodine(III) reagents bearing a benzylamine with sulfenate salts

• Beatriz Dedeiras,
• Catarina S. Caldeira,
• José C. Cunha,
• Clara S. B. Gomes and
• M. Manuel B. Marques

Beilstein J. Org. Chem. 2024, 20, 3281–3289, doi:10.3762/bjoc.20.272

• distorted T-shaped geometry, consistent with previously reported N–bound hypervalent iodine reagents. Additionally, the N–I bond distance is 2.0454(5) Å, which aligns with our previously reported values [4]. The two aromatic rings are nearly coplanar, exhibiting a dihedral angle of 0.7(3)°. All other bond

Structure and thermal stability of phosphorus-iodonium ylids

• Andrew Greener,
• Stephen P. Argent,
• Coby J. Clarke and
• Miriam L. O’Duill

Beilstein J. Org. Chem. 2024, 20, 2931–2939, doi:10.3762/bjoc.20.245

• bipyramidal (T-shaped) with the least electronegative group and the two nonbonding electron pairs occupying the equatorial positions, and the most electronegative substituents forming a hypervalent 3-centre-4-electron (3c-4e) bond in the axial position (Figure 1A) [17][18]. The LUMO of this bond is

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

Photoswitchable glycoligands targeting Pseudomonas aeruginosa LecA

• Yu Fan,
• Ahmed El Rhaz,
• Stéphane Maisonneuve,
• Emilie Gillon,
• Maha Fatthalla,
• Franck Le Bideau,
• Guillaume Laurent,
• Samir Messaoudi,
• Anne Imberty and
• Juan Xie

Beilstein J. Org. Chem. 2024, 20, 1486–1496, doi:10.3762/bjoc.20.132

• , with Kd values from micromolar (for monovalent galactosides) to nanomolar range (for di- and multivalent derivatives) [5][6][7][8]. For the monovalent system, it has been shown that aromatic aglycons favored “T-shaped” CH...π interactions with the protons of the His50 imidazole in the carbohydrate

Introduction of peripheral nitrogen atoms to cyclo-meta-phenylenes

• Koki Ikemoto and
• Hiroyuki Isobe

Beilstein J. Org. Chem. 2024, 20, 1207–1212, doi:10.3762/bjoc.20.103

• configurations preferred over T-shaped stackings [22]. In our study, we observed that pyridine–pyridine stacks were preferred in the crystal stacking (Figure 3), which might be attributed to the biased ESPs on the macrocycles. Finally, we found that nitrogen locations altered chemical characteristics of nitrogen

Rapid gas–liquid reaction in flow. Continuous synthesis and production of cyclohexene oxide

• Kyoko Mandai,
• Tetsuya Yamamoto,
• Hiroki Mandai and
• Aiichiro Nagaki

Beilstein J. Org. Chem. 2022, 18, 660–668, doi:10.3762/bjoc.18.67

• ratio of aldehyde and oxygen to 1:9. The liquid and gas phases were combined at a T-shaped mixer with a 1 mm inner diameter and flowed through a stainless-steel tube reactor immersed in heated silicon oil for reaction temperature control. The inner pressure was maintained at 0.9 MPa using a back

• with air in the flow microreactor A flow microreactor system consisting of a T-shaped micromixer, and one microtube reactor was used for epoxidation of cyclohexene with air. A solution of cyclohexene (0.065 M), isobutyraldehyde (0.195 M), and tridecane as an internal standard in 1,2-dichloroethane

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• indole ring of TOI4 was also contorted upward, forming a T-shaped π–π interaction with Phe-207 while both the indole rings of TOI1 and TOI2 were shown to be flipped downward forming a T-shaped π–π interaction with Phe-208. TOI4 is the only diazine compound having two nitrogens directly next to each other

• -rev is tilted downward forming a T-shaped π–π interaction with Phe-208. In review of the computational results, the inclusion of the nitrogen atoms in the core ring structure of panobinostat produced compounds with predicted binding affinities similar to panobinostat. Thus, aiming to develop improved

Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

• Hoang Huy Do,
• Saif Ullah,
• Alexander Villinger,
• Joanna Lecka,
• Jean Sévigny,
• Peter Ehlers,
• Jamshed Iqbal and
• Peter Langer

Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276

• involved in hydrogen bonding were His380, Asn277, Ser378, Ser381, Tyr382, Lys391, Ser387 and Ser386. In addition, the study also showed binding with the zinc ion and π-interactions, in particular, π–π T-shaped and amide–π shaped coupling with Ser377 and Tyr382. The molecular docking study of compound 5c

• exhibited π–π T-shaped interactions connecting the indole and furan rings with Tyr340. However, π–alkyl linkage was observed between the benzofuran moiety of compound 5c and amino acid Lys295. The fluorine atom of the 4-fluorophenyl group was involved in the binding with the zinc ion and Ser377. Hydrogen

• . However, the zinc–metal interaction was exhibited by the substituted phenyl moiety on the indole ring. The oxygen atom of the furan ring of dual inhibitor 6e showed a single hydrogen bond with Phe548. Asp423 was found to be involved in two π–cation bindings with the indole ring, whereas π–π stacked, π–π T

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• consistent with our previous studies on 4pzH compared to 4pzMe [18], significantly larger half-lives are predicted for 4pzH-X derivatives compared to the dimethylated 4pzMe-X derivatives, which can be rationalized by the stabilizing short CH···π interactions in the T-shaped conformation of Z-4pzH-X (Figure 2

• 4pzH-Pyr compounds, the destabilizing nature of the Cl···pyrazole interaction is evidenced by the absence of heteroring tilting in the T-shaped Z-isomers of the 4pzH-X family (θ = 97° and 94° for 4pzH-Cl1 and 4pzH-Cl2), and the systematic decrease in θ for the 4pzMe-X series in going from 4pzMe (138

• highly depends on the molecular conformation, significantly increasing for T-shaped structures (4pzH-X) compared to twisted arrangements (4pzMe-X), and thus leading to larger n–π* band separation for the 4pzH-X series [18]. On the other hand, the intense π–π* transition of the Z-isomer is generally found

Adhesion, forces and the stability of interfaces

• Robin Guttmann,
• Johannes Hoja,
• Christoph Lechner,
• Reinhard J. Maurer and
• Alexander F. Sax

Beilstein J. Org. Chem. 2019, 15, 106–129, doi:10.3762/bjoc.15.12

• series starts with dipoles, whereas in non-polar molecules it starts with quadrupoles or higher multipoles. Accordingly, there will always be electrostatic interactions of different ranges between molecules with static multipoles. For example, the T-shaped equilibrium structure of the benzene dimer is

Metal-free formal synthesis of phenoxazine

• Gabriella Kervefors,
• Antonia Becker,
• Chandan Dey and
• Berit Olofsson

Beilstein J. Org. Chem. 2018, 14, 1491–1497, doi:10.3762/bjoc.14.126

• the neat crude product at rt, along with 52% of 4-iodoanisol (see Supporting Information File 1). This observation is in line with a ligand-coupling (LC) mechanism [30][35][36] where the observed byproduct could be the T-shaped intermediate 9 or the corresponding 4-coordinated species with two

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• arylation protocols [18][19][20][21][22]. While in solid state they clearly have a T-shaped pseudotrigonal bipyramid structure, the common structural motif for λ3-iodanes, recent theoretical investigations revealed a potential role of the cationic, normal valent tetrahedral form, in atom transfer processes

Preparation, structure, and reactivity of bicyclic benziodazole: a new hypervalent iodine heterocycle

• Akira Yoshimura,
• Michael T. Shea,
• Cody L. Makitalo,
• Melissa E. Jarvi,
• Gregory T. Rohde,
• Akio Saito,
• Mekhman S. Yusubov and
• Viktor V. Zhdankin

Beilstein J. Org. Chem. 2018, 14, 1016–1020, doi:10.3762/bjoc.14.87

• distorted T-shaped geometry with an N(1)–I(1)–N(2) angle of 153.90 (15)°. Compared to other reported bicyclic hypervalent iodine compounds [23][25][37], this is the most bent structure at the N(1)–I(1)–N(2) angle. An additional relatively weak intermolecular coordination between the iodine atom and the

Synthesis of fluoro-functionalized diaryl-λ³-iodonium salts and their cytotoxicity against human lymphoma U937 cells

• Prajwalita Das,
• Etsuko Tokunaga,
• Hidehiko Akiyama,
• Hiroki Doi,
• Norimichi Saito and
• Norio Shibata

Beilstein J. Org. Chem. 2018, 14, 364–372, doi:10.3762/bjoc.14.24

• SF5-diaryliodonium salts 3p, 4b, 5a and 6a were characterized spectroscopically. The single crystal X-ray structure of 3p was also analysed. The SF5-diaryliodonium salt 3p has a T-shaped geometry at the iodine centre, consistent with the general structure of diaryliodonium salts [33] (Figure 3

Aggregation behaviour of a single-chain, phenylene-modified bolalipid and its miscibility with classical phospholipids

• Simon Drescher,
• Vasil M. Garamus,
• Christopher J. Garvey,
• Annette Meister and
• Alfred Blume

Beilstein J. Org. Chem. 2017, 13, 995–1007, doi:10.3762/bjoc.13.99

• DPPC/DHPC systems [49], or for mixtures of phospholipids with other amphiphilic substances, e.g., in PEG-stabilized bilayer systems [50][51], for phospholipids with membrane scaffold proteins [52][53] or in combination with copolymers [54][55], or for DPPC in mixture with a T-shaped amphiphile [56

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• using the B3LYP hybrid functional and a different basis set. The computed geometric parameters for the molecules are very close to each other. One Pt–C bond is short (2.10 Å) while the other two flanking bonds are 2.52 Å. Thus, 20 strongly resembles an η1 14 electron complex with a “T” shaped geometry

Biosynthesis of α-pyrones

• Till F. Schäberle

Beilstein J. Org. Chem. 2016, 12, 571–588, doi:10.3762/bjoc.12.56

• chain is placed into the proximal cavity, orienting the α-carbon in a position suitable for the nucleophilic attack by the cysteine-tethered, activated chain. Thereby, the second chain is still attached to the ACP, the phosphopantetheine residue reaching into the T-shaped catalytic cavity, enabling the

• -tethered chains are interconnected by the catalytic activity of a free-standing KS. In the second step the lactonization takes place, facilitated by the keto–enol tautomerism. Thereby the α-pyrone 78 is formed. Structures of csypyrones. Schematic drawing of the T-shaped catalytic cavities of the related

• enzymes CorB and MxnB. The two cavities, each harboring one chain are depicted in green and blue, respectively. The phosphopantetheine arm of the ACP reaches into the T-shaped catalytic cavity through a third hydrophobic channel. The oxyanion hole is highlighted by a pink circle. In that way the two

Synthesis of dinucleoside acylphosphonites by phosphonodiamidite chemistry and investigation of phosphorus epimerization

• William H. Hersh

Beilstein J. Org. Chem. 2015, 11, 184–191, doi:10.3762/bjoc.11.19

• contrast, did not yield a trigonal planar transition state, but rather gave a T-shaped transition state. In fact, such a result has been reported for PF3 [59][60] and is due to the presence of the highly electronegative atoms bound to phosphorus. While the alkoxy groups of the phosphite triester are

• calculations were then carried out on the chiral acylphosphonite 21 with the expectation that a high phosphite-like barrier might occur. In fact, the barrier of 41.7 kcal/mol was slightly higher than the phosphite triester calculation. Unlike the phosphite T-shaped transition state, this occurs via a trigonal

Synthesis and properties of novel star-shaped oligofluorene conjugated systems with BODIPY cores

• Clara Orofino-Pena,
• Diego Cortizo-Lacalle,
• Joseph Cameron,
• Muhammad T. Sajjad,
• Pavlos P. Manousiadis,
• Neil J. Findlay,
• Alexander L. Kanibolotsky,
• Dimali Amarasinghe,
• Peter J. Skabara,
• Tell Tuttle,
• Graham A. Turnbull and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2704–2714, doi:10.3762/bjoc.10.285

• -shaped molecules. The other series (T-Bn, n = 1–4) represents star-shaped systems with the arms in the meso- and β-positions, providing T-shaped molecules. Results and Discussion Synthesis For the synthesis of the Y-B1–Y-B4 series a convergent strategy was chosen (Scheme 1). The modified Suzuki coupling

• bathochromically shifted optical transitions compared with their T-shaped analogues. The phenyl linker attached to the meso-position is also more twisted in T-B1 (80.8°) than in Y-B1 (58.0°) because the methyl groups in the 1,7-positions exert greater steric hindrance than the hydrogen substituents of Y-B1. The

Carbenoid-mediated nucleophilic “hydrolysis” of 2-(dichloromethylidene)-1,1,3,3-tetramethylindane with DMSO participation, affording access to one-sidedly overcrowded ketone and bromoalkene descendants^§

• Rudolf Knorr,
• Thomas Menke,
• Johannes Freudenreich and
• Claudio Pires

Beilstein J. Org. Chem. 2014, 10, 307–315, doi:10.3762/bjoc.10.28

• (2.80 g, 11.0 mmol), dimethyl sulfoxide (45 mL), and a magnetic stirring bar were placed in a round-bottomed flask carrying either a wide-bore connection to a cooled trap or a T-shaped glass-tube with a bubbler and gas inlet. This suspension was stirred at 60 °C until 6 was completely dissolved. Freshly

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

• organometallic transformations. Although very few authenticated three-coordinate Pt(II) complexes have been characterized, a much larger number of complexes can be described as operationally three-coordinate in a kinetic sense. In these compounds, which we have called masked T-shaped complexes, the fourth

• position is occupied by a very weak ligand (agostic bond, solvent molecule or counteranion), which can be easily displaced. This review summarizes the structural features of the true and masked T-shaped Pt(II) complexes reported so far and describes synthetic strategies employed for their formation

• . Moreover, recent experimental and theoretical reports are analyzed, which suggest the involvement of such intermediates in reaction mechanisms, particularly C–H bond-activation processes. Keywords: C–H bond activation; intermediate; platinum(II); reactive intermediates; three-coordinate; T-shaped; Review