One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

• Ji Ma,
• Yubin Fu,
• Junzhi Liu and
• Xinliang Feng

Beilstein J. Org. Chem. 2020, 16, 791–797, doi:10.3762/bjoc.16.72

• twofold [3 + 2] cyclopentannulation and subsequent twofold [4 + 2] benzannulation. The structure of 1 is unambiguously confirmed by X-ray crystallography; 1 adopted a twisted geometry due to the steric hindrance of the phenyl rings and the hydrogen substituents at the bay regions. Notably, compound 1

• [4 + 2] benzannulation, instead of the desired tetracyclopenta[cd,fg,jk,mn]pyrene (2). The selective formation of 1 could be rationalized by the steric hindrance of the phenyl rings after the twofold [3 + 2] alkyne pentannulated intermediate (Scheme S2, Supporting Information File 1), and the sequent

• -diphenylpyrene is the key step. The single crystal X-ray diffraction analysis revealed a twisted structure of 1 due to the steric hindrance at the bay positions. From the bond length analysis and DFT calculations, CP-PAH 1 consists of the aromatic peropyrene core with two slightly antiaromatic peri-fused five

Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas

• Zhenghui Liu,
• Peng Wang,
• Zhenzhong Yan,
• Suqing Chen,
• Dongkun Yu,
• Xinhui Zhao and
• Tiancheng Mu

Beilstein J. Org. Chem. 2020, 16, 645–656, doi:10.3762/bjoc.16.61

• substituents (F, Cl, Br), these were also compatible with the reaction system, affording 79−89% yields of the halogenated aromatic aldehydes 8–16. Iodobenzene derivatives with phenyl or tert-butyl groups displaying larger steric hindrance in the para-position still provided the corresponding aldehydes 17 and

• 18 in relatively high yields (85% and 81%, respectively). 2-Iodonaphthalene with smaller steric hindrance performed a little better than 1-iodonaphthalene (19, 84% and 20, 77%). However, starting iodides having methyl substituents in both ortho-positions afforded the corresponding aldehydes in much

Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

• Faïma Lazreg,
• Marie Vasseur,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

• conversion with respectively 96% (10a), 95% (10c) and 93% (10g) isolated yields, in reaction times of 3 to 4.5 hours. Regarding the 2,4,6-triisopropylsulfonyl azide, a slight decrease in the reactivity was observed (66%, 10f), presumably due to the steric hindrance of the substrate. Electron-withdrawing

Synthesis of 4-amino-5-fluoropyrimidines and 5-amino-4-fluoropyrazoles from a β-fluoroenolate salt

• Tobias Lucas,
• Jule-Philipp Dietz and
• Till Opatz

Beilstein J. Org. Chem. 2020, 16, 445–450, doi:10.3762/bjoc.16.41

• producing alkyl-substituted pyrimidine derivatives was investigated (Scheme 2). Starting from formamidine hydrochloride, compound 10a was synthesized in 85% yield. A variety of amidines with different steric hindrance such as methyl, cyclopropyl and tert-butyl substitution was used, and all substituents

Synthesis of six-membered silacycles by borane-catalyzed double sila-Friedel–Crafts reaction

• Yafang Dong,
• Masahiko Sakai,
• Kazuto Fuji,
• Kohei Sekine and
• Yoichiro Kuninobu

Beilstein J. Org. Chem. 2020, 16, 409–414, doi:10.3762/bjoc.16.39

• transformed into phenoxasilin 3g in 80% yield. Also, the chloro-substituted diaryl ether gave its corresponding phenoxasilin 3h in 94% yield without affecting the chlorine substituent. The methyl-substituted phenoxasilin derivatives 3i and 3j were formed in good yield despite of the steric hindrance of the

Six-fold C–H borylation of hexa-peri-hexabenzocoronene

• Mai Nagase,
• Kenta Kato,
• Akiko Yagi,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2020, 16, 391–397, doi:10.3762/bjoc.16.37

• bonds of HBC (Figure 3a). An equivalent amount of pentane for 1 was co-crystallized. As illustrated in Figure 3b and 3c, 1 is slightly distorted to have S6 symmetry, and no π–π interaction is observed in the packing mode reflecting the steric hindrance of boryl groups. This result corresponds with the

Copper-catalyzed enantioselective conjugate addition of organometallic reagents to challenging Michael acceptors

• Delphine Pichon,
• Jennifer Morvan,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2020, 16, 212–232, doi:10.3762/bjoc.16.24

• enantioselectivities (up to 99% ee, Scheme 7), depending on the steric hindrance of the reagent. Unfortunately, the addition of PhMgBr remained unsuccessful. This powerful catalytic protocol was illustrated by Bates and Sridhar in the enantioselective total synthesis of (−)-mintlactone [27]. The key step, furnishing

Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• presence of camphorsulfonic acid did not give the desired amine, supporting the hypothesis of steric hindrance at such position [57]. Similarly, Simmons–Smith cyclopropanation reaction [58] did not work, and so as for the cycloaddition reaction with Danishefsky’s diene, possibly due to steric hindrance

Construction of trisubstituted chromone skeletons carrying electron-withdrawing groups via PhIO-mediated dehydrogenation and its application to the synthesis of frutinone A

• Qiao Li,
• Chen Zhuang,
• Donghua Wang,
• Wei Zhang,
• Rongxuan Jia,
• Fengxia Sun,
• Yilin Zhang and
• Yunfei Du

Beilstein J. Org. Chem. 2019, 15, 2958–2965, doi:10.3762/bjoc.15.291

• noticeably higher yields than those with electron-withdrawing groups, 2b–g. The product 2g, with an electron-withdrawing group in ortho position, was formed in a much lower yield, most likely due to steric hindrance. When the phenyl group was replaced by a naphthyl group, less of the corresponding substrate

Facile regiodivergent synthesis of spiro pyrrole-substituted pseudothiohydantoins and thiohydantoins via reaction of [e]-fused 1H-pyrrole-2,3-diones with thiourea

• Aleksandr I. Kobelev,
• Nikita A. Tretyakov,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Michael Rubin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2019, 15, 2864–2871, doi:10.3762/bjoc.15.280

• thiohydantoins 7 required longer time in comparison with unsubstituted thiourea and 1,3-dibutylthiourea. Possible reasons for this are the influence of the steric hindrance induced by the phenyl substituents and weakening of the nucleophilic properties of the phenyl-substituted nitrogen atom, which prevented a

Carbazole-functionalized hyper-cross-linked polymers for CO₂ uptake based on Friedel–Crafts polymerization on 9-phenylcarbazole

• Dandan Fang,
• Xiaodong Li,
• Meishuai Zou,
• Xiaoyan Guo and
• Aijuan Zhang

Beilstein J. Org. Chem. 2019, 15, 2856–2863, doi:10.3762/bjoc.15.279

• the molar ratio of FDA to 9-PCz could not result in a higher BET specific surface area, because the high steric hindrance prevented further crosslinking reaction [39], the raised C/N ratio (Table 3) maybe because of the tail end groups of FDA. The BET specific surface area of P3 was much higher than

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• oxidation of methyl 3-aminobenzoate (17a) using Oxone® to obtain a crude nitroso product 18a, which was used in a Mills reaction with an iodoaniline (19a–c) at 100 °C to obtain azobenzenes 20g,h in high yields and ortho-analogue 20f in a decreased yield presumably due to steric hindrance. The methyl ester

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• rearrangement reaction may be the rigid bicyclic structure of the substrate and steric hindrance on one side of the molecule caused by the gem-dimethyl bridge. Conclusion Regioisomeric exocyclic allylic alcohols were synthesized from natural α-pinene. (1R,2R,4S,5R)-3-Methyleneneoisoverbanol and (1R,2R,3R,5R)-4

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

• steric hindrance also induced the access to a racemic mixture of (R,R)- and (S,S)-complexes where triphenylphosphine groups were located at the opposite sides of the anthracene core. The crystallographic structures of 1a, 1c and 1d showed that both ligand syn-1 and the nature of silver anion impacted on

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• substituent was present in the meta-position, only a single regiosomer of compound 4j was obtained. It is important to note that when R2 is different than H (i.e., iPr or Bn), no products (4n and 4o) were formed, presumably due to the steric hindrance at the neighboring position of the amide and the tetrazole

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• larger counteranion (BArF4−) because of steric hindrance but instead forms a conventional ion pair, resulting in a smaller potential splitting. A polar solvent should interfere with the N–H···F H-bonding in the present MV state. Indeed, in MeCN/CH2Cl2 9:1 containing n-Bu4NPF6, 1a showed a 13 mV smaller

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• hand the ability to alter the configuration of a newly created stereocenter by changing only the catalyst configuration is a quite unprecedented phenomenon in singlet oxygen reactions. Usually in those reactions the introduction of a steric hindrance much larger than the phenyl ring (i.e., adamantyl

• observed for reactions of singlet oxygen with substrates that do not possess chiral auxiliary or do not impose significant steric hindrance. Experimental General information 1H and 13C NMR spectra were recorded at rt on Bruker 400 and Varian 600 MHz instruments with TMS as an internal standard. The

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• study 3,6-dihydroxyphthalimide derivatives as aromatic diols to construct functionalized O6-corona[3]arene[3]tetrazins. Being different from terephthalate in terms of substitution pattern, we envisioned that the phthalimide unit would flip freely owing to the less steric hindrance. In addition, N

Synthesis of a [6]rotaxane with singly threaded γ-cyclodextrins as a single stereoisomer

• Jason Yin Hei Man and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2019, 15, 1829–1837, doi:10.3762/bjoc.15.177

• bound in the cavity of a γ-CD to form a [4]pseudorotaxane consisting of one γ-CD and two CB[6], and that because of the steric hindrance provided by the CB[6], inclusion of a second guest in the γ-CD cavity is discouraged [46]. The observation that no rotaxane product derived from a 2:1 complex of 1/γ

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

• Rosana Ribić,
• Ranko Stojković,
• Lidija Milković,
• Mariastefania Antica,
• Marko Cigler and
• Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

• , a powerful supramolecular nanoparticle carrier for targeted drug delivery [38]. Previous research suggested a design of mannosylated desmuramyl peptides with adamantane at the C-terminus in order to facilitate the incorporation into the hydrophobic layer of the cavity because of the minor steric

• hindrance of the mannose and peptide part during the inclusion process of the adamantane [37][39]. It is well known that vaccine adjuvants can enhance or modulate the Th1/Th2-bias of an induced immune response. Interferon-γ (as a Th1 cytokine) and IL-4 (as a Th2 cytokine) induce isotype switching to IgG2a

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

• diffusion of isopropyl ether into a chloroform/acetone 1:1 (v/v) solution of the 1:1 mixture of H3 and G1, we only obtained a single crystal of H3 instead of the host–guest complex. The steric hindrance of the n-butoxy groups in H3 (Supporting Information File 1, Figure S90) might lead to weak complexation

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• . Removing these methyl groups is an effective way to reduce the dihedral angle between the meso substituent and the BODIPY core by lowering the steric hindrance between the two latter. It has been previously reported that a better molecular planarity usually originates a higher charge injection efficiency

• level may arise from the overall size of the molecule BOD-TTPA-alk that displays 4 alkyl chains and 2 ethylene glycol chains. The bigger size of BOD-TTPA-alk can eventually prevents its diffusion through all the pores of the TiO2 layer or decreases the density of grafted molecules due to steric

• hindrance. 4. Electrochemical characterization Cyclic voltammetry of both BODIPY dyes was carried out in deoxygenated DCM solutions containing tetrabutylammonium hexafluorophosphate as salt (see Figure S24 and S25 in Supporting Information File 1), to investigate their oxidation and reduction processes as

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• the same direction, are the most stable conformers due to the steric-hindrance effect of the substituents in other conformers. In general, the Sp and Rp conformers can interconvert from each other in solution through the oxygen-through-annulus rotation along the methylene bridges [18], and the

• quantum yield was only slightly decreased. This should be mainly due to the steric hindrance of the 9- and 10-phenyl groups, which inhibited the π–π stacking of the anthracene core in DPA. The fluorescent lifetimes of P5A-Py and P5A-DPA were compared with Py-6 and DPA-6. As shown in Figure 2, the lifetime

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• excellent yield (94%) demonstrating that no steric hindrance occurs during the reaction. Taking into account aliphatic derivatives, O-methyl cyclohexylcarbamothioate (3e) was formed in good yield (82%), however, O-methyl tert-butylcarbamothioate (3f), partly due to the volatile nature of the isocyanide and

• %, respectively) that might be attributed either to steric hindrance or the growing instability of the conjugate base of the secondary and tertiary alcohol, respectively. The present method provided the allylic derivative 3j in 72% yield, however, applying ethylene glycol resulted in 3k in 34% yield only. In the