Continuous flow synthesis of azobenzenes via Baeyer–Mills reaction

• Jan H. Griwatz,
• Anne Kunz and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2022, 18, 781–787, doi:10.3762/bjoc.18.78

• synthesis of AB 1i from m-anisidine (2i) gave only 7% yield, due to the formation of large amounts of azoxybenzene and purification issues therefrom. The moderate product yields from the ortho-substituted aniline derivatives are presumably caused by the higher steric hindrance of the nucleophilic attack

Structural basis for endoperoxide-forming oxygenases

• Takahiro Mori and
• Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

• . Then, the abstraction of a hydrogen atom from C13 is catalyzed by the Fe(IV)=O species. Here, the active site residue Glu208 would contribute to determining the position of the hydrogen atom abstraction, by forming steric hindrance with the A-ring of the substrate. Subsequently, further conformational

Direct C–H amination reactions of arenes with N-hydroxyphthalimides catalyzed by cuprous bromide

• Dongming Zhang,
• Bin Lv,
• Pan Gao,
• Xiaodong Jia and
• Yu Yuan

Beilstein J. Org. Chem. 2022, 18, 647–652, doi:10.3762/bjoc.18.65

• products. Electron-donating alkyl-substituted arenes were generally more prone to give ortho and para products. When the reaction was carried out with cumene under standard conditions, due to steric hindrance resulting from the alkyl group on the arene’s ring, only the single product 3d was observed in 55

Substituent effect on TADF properties of 2-modified 4,6-bis(3,6-di-tert-butyl-9-carbazolyl)-5-methylpyrimidines

• Irina Fiodorova,
• Tomas Serevičius,
• Rokas Skaisgiris,
• Saulius Juršėnas and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 497–507, doi:10.3762/bjoc.18.52

• were of similar molecular geometry with partially twisted carbazole units (in the order of 45–47°). The steric hindrance between the carbazole fragments and the pyrimidine core was enhanced by introducing a methyl group in position 5 of the latter [29], enabling sufficient HOMO–LUMO decoupling. Single

Bioinspired tetraamino-bisthiourea chiral macrocycles in catalyzing decarboxylative Mannich reactions

• Hao Guo,
• Yu-Fei Ao,
• De-Xian Wang and
• Qi-Qiang Wang

Beilstein J. Org. Chem. 2022, 18, 486–496, doi:10.3762/bjoc.18.51

• reacted with two equiv 3-nitro-5-(trifluoromethyl)benzyl bromide (2) in the presence of a base to afford the dinitro compounds 3a–f in moderate to excellent yields (Scheme 1a). The diminished yield for product 3d was probably caused by the large steric hindrance of the 3-pentyl substituent. Reduction of

Tosylhydrazine-promoted self-conjugate reduction–Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives

• Sayan Pramanik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 469–478, doi:10.3762/bjoc.18.49

• formed by multistep reaction progression where, to overcome severe steric hindrance, two oxindole moieties are in trans orientation. HPLC data of compound 3o ensures >95:5 dr (Supporting Information File 1). The structure was further confirmed by NOESY spectra of compounds 3e (Figure 3) and 3j

Comparative study of thermally activated delayed fluorescent properties of donor–acceptor and donor–acceptor–donor architectures based on phenoxazine and dibenzo[a,j]phenazine

• Saika Izumi,
• Prasannamani Govindharaj,
• Anna Drewniak,
• Paola Zimmermann Crocomo,
• Satoshi Minakata,
• Leonardo Evaristo de Sousa,
• Piotr de Silva,
• Przemyslaw Data and
• Youhei Takeda

Beilstein J. Org. Chem. 2022, 18, 459–468, doi:10.3762/bjoc.18.48

• [17]. It is noted that the solubility of the D–A compound 1 in organic solvents is lower than that of the D–A–D compound, indicating a more aggregated state of the D–A molecules in the solid state, due to less steric hindrance on the acceptor plane arising from breaking the symmetry. The synthesized

• , the one-less number of donor units in the molecular scaffold led to lower solubility in organic solvents and thermal stability, presumably due to the less steric hindrance around the π-extended conjugated acceptor unit with the unsymmetric molecule structure. The OLEDs fabricated with the D–A emitter

Cs₂CO₃-Promoted reaction of tertiary bromopropargylic alcohols and phenols in DMF: a novel approach to α-phenoxyketones

• Ol'ga G. Volostnykh,
• Olesya A. Shemyakina,
• Anton V. Stepanov and
• Igor' A. Ushakov

Beilstein J. Org. Chem. 2022, 18, 420–428, doi:10.3762/bjoc.18.44

• and 9) failed. Employing the reaction conditions similar to those given in entries 4 and 6 (Table 1), we examined the substrate scope of the process relative to other phenols (Scheme 1). It was found that the electronic character of the substituents and the steric hindrance affected the reaction

A Se···O bonding catalysis approach to the synthesis of calix[4]pyrroles

• Qingzhe Tong,
• Zhiguo Zhao and
• Yao Wang

Beilstein J. Org. Chem. 2022, 18, 325–330, doi:10.3762/bjoc.18.36

• obtained in 58% and 42% yield, respectively. Further investigation revealed that cyclobutanone was reactive in this transformation to give product 2f, albeit with 30% yield. However, benzophenone and 2,4-dimethylpentan-3-one with high steric hindrance failed to give desirable products 2g and 2h. Further

Anomeric 1,2,3-triazole-linked sialic acid derivatives show selective inhibition towards a bacterial neuraminidase over a trypanosome trans-sialidase

• Peterson de Andrade,
• Sanaz Ahmadipour and
• Robert A. Field

Beilstein J. Org. Chem. 2022, 18, 208–216, doi:10.3762/bjoc.18.24

• differentiate both enzymes. Moreover, such selectivity might be reasoned based on a possible steric hindrance caused by a bulky hydrophobic loop that sits over the TcTS active site and may prevent the hydrophobic inhibitors from binding. The present study is a step forward in exploiting subtle structural

• buried in a deep and narrow cavity. Such conformational change could potentially prevent the hydrophobic inhibitors from entering the TcTS active site due to steric hindrance. In this context, our results suggest that the key interactions with the hydrophobic substituents at C-2 have occurred in the less

• site causing steric hindrance, probably preventing the hydrophobic inhibitors from entering its active site. Also, the absence of TcTS inhibition could potentially be attributed to the lack of flexibility of the substituents, thus compromising key favourable orientations for strong binding in the

Bifunctional thiourea-catalyzed asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins

• Jiang-Song Zhai and
• Da-Ming Du

Beilstein J. Org. Chem. 2022, 18, 25–36, doi:10.3762/bjoc.18.3

• (>20:1 dr, 84–>99% ee). Possibly due to the influence of steric hindrance, reactions involving substrate 2 with ortho-substitution on the benzene ring has lower yields and worse enantioselectivities than those with meta-substitution and para-substitution. Meanwhile, the enantioselectivities of the

Efficient N-arylation of 4-chloroquinazolines en route to novel 4-anilinoquinazolines as potential anticancer agents

• Rodolfo H. V. Nishimura,
• Thiago dos Santos,
• Valter E. Murie,
• Luciana C. Furtado,
• Leticia V. Costa-Lotufo and
• Giuliano C. Clososki

Beilstein J. Org. Chem. 2021, 17, 2968–2975, doi:10.3762/bjoc.17.206

• ). As expected, substituents at the ortho-position of the anilines affected the N-arylation reactions due to the steric hindrance exerted by these groups. In fact, reactions with 2-methoxy-substituted N-methylaniline 9c were slower, but we obtained high conversions within 20 min under microwave heating

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• products in diminished yields. This transformation was sensitive to steric hindrance, as ortho-substituted aryl species and bulky alkyl carbazates failed to react under these reaction conditions. Based on control experiments, the authors proposed a tentative catalytic cycle. Initially, in the presence of

Biological properties and conformational studies of amphiphilic Pd(II) and Ni(II) complexes bearing functionalized aroylaminocarbo-N-thioylpyrrolinate units

• Samet Poyraz,
• Samet Belveren,
• Sabriye Aydınoğlu,
• Mahmut Ulger,
• Abel de Cózar,
• Maria de Gracia Retamosa,
• Jose M. Sansano and
• H. Ali Döndaş

Beilstein J. Org. Chem. 2021, 17, 2812–2821, doi:10.3762/bjoc.17.192

• postulated that the longer metal–O and metal–S distances of the palladium atom, compared to nickel, placed the substituents of the pyrrolidine ring far enough to reduce the steric hindrance that destabilized nickel-conformer B complexes. The results obtained for L3-M complexes showed that, independently of

• intramolecular hydrogen-bonding interactions (Figure 2). Additional steric hindrance in conformer B, compared to conformer A (as found in L1-Ni complexes), raises the energy of the latter. Thus, in L3-M complexes, only one set of signals was expected in the NMR spectra. Due to the high number of possible

Me₃Al-mediated domino nucleophilic addition/intramolecular cyclisation of 2-(2-oxo-2-phenylethyl)benzonitriles with amines; a convenient approach for the synthesis of substituted 1-aminoisoquinolines

• Krishna M. S. Adusumalli,
• Lakshmi N. S. Konidena,
• Hima B. Gandham,
• Krishnaiah Kumari,
• Krishna R. Valluru,
• Satya K. R. Nidasanametla,
• Venkateswara R. Battula and
• Hari K. Namballa

Beilstein J. Org. Chem. 2021, 17, 2765–2772, doi:10.3762/bjoc.17.186

• can be rationalized by the steric hindrance created by the ortho-substituents. It is also worth mentioning that secondary anilines also reacted with 2-(2-oxo-2-phenylethyl)benzonitrile (3a) and delivered the corresponding product 5m, albeit in lesser yields. Later, the substrate scope of 2-(2-oxo-2

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• elimination as opposed to styrenyl selectivity. In addition, the methacrylates were used as allyl surrogates to overcome the reactivity problem caused by steric hindrance of 1,1,-disubstituted alkenes, and the electron-withdrawing esters enhance the migratory insertion to form palladacycle I-2. The CPA

• electronic properties of the substituents on the aromatic rings of the indole have limited influence on the reactivity and remarkable effects on the enantioselectivity. For example, in the case of indole 20b, the enantioselectivity was drastically reduced due to steric hindrance present at the 2-position of

Solvent-free synthesis of enantioenriched β-silyl nitroalkanes under organocatalytic conditions

• Akhil K. Dubey and
• Raghunath Chowdhury

Beilstein J. Org. Chem. 2021, 17, 2642–2649, doi:10.3762/bjoc.17.177

• enantioselectivity (52% ee). β-Silylenone 2n bearing a o-chloro substituent in the aromatic ring remained unreactive under the optimized reaction conditions probably due to steric hindrance. The facile synthesis of both enantiomers of the targeted compounds is of paramount importance since biological activities are

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• cooperative steric hindrance based on bulky substituents at the 2,9-position of the phenanthroline moiety [32][33]. Alternatively, heteroleptic CuI complexes with phenanthroline and bulky chelating phosphine ligands were also synthesized [30][34][35]. The photophysical properties are dramatically modified by

Copper-catalyzed monoselective C–H amination of ferrocenes with alkylamines

• Zhen-Sheng Jia,
• Qiang Yue,
• Ya Li,
• Xue-Tao Xu,
• Kun Zhang and
• Bing-Feng Shi

Beilstein J. Org. Chem. 2021, 17, 2488–2495, doi:10.3762/bjoc.17.165

• functionalities, such as ester 4f, cyano 4g and ketal 4i, were well tolerated. Unfortunately, 1,2,3,4-tetrahydroquinoline (2k) was proved unreactive under our conditions, probably due to the steric hindrance. Thiomorpholine (2l) was compatible with this reaction, albeit with significantly dropped yield (29

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• including dihedral angles and bonding and non-bonding distances (Table 3). It can be seen from Figure 7 that the four obtained structures are non-planar, due to steric hindrance and electronic repulsions. For compound 4a, considerable distortions of −38.61 and −49.60 degrees between the tetrahydroacridine

A novel methodology for the efficient synthesis of 3-monohalooxindoles by acidolysis of 3-phosphate-substituted oxindoles with haloid acids

• Li Liu,
• Yue Li,
• Tiao Huang,
• Dulin Kong and
• Mingshu Wu

Beilstein J. Org. Chem. 2021, 17, 2321–2328, doi:10.3762/bjoc.17.150

• motif allowed to access the corresponding product 3l in a higher yield. Notably, phosphate 2a with no substitution on the aromatic ring and on the nitrogen atom showed a good reactivity, furnishing the corresponding product 3a in the highest yield, possibly owing to not having steric hindrance. It

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• , explaining the lowered yield. The reaction also required six equivalents and 72 h of reaction time to produce the product. ortho-Substituted anilines are interesting substrates as the product enables several possibilities for post-functionalization. Despite the inherent steric hindrance originating from the

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• alkanes were preferentially functionalized at the 2-position due to the less steric hindrance. In addition to alkanes, a variety of ethers and amines were also compatible and selectively functionalized at the α-heteroatom positions in moderate to good yields and excellent regioselectivity. Interestingly

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF₃·OEt₂ catalysis

• Karthikeyan Soundararajan,
• Helen Ratna Monica Jeyarajan,
• Raju Subimol Kamarajapurathu and
• Karthik Krishna Kumar Ayyanoth

Beilstein J. Org. Chem. 2021, 17, 2186–2193, doi:10.3762/bjoc.17.140

• (15 mol %)/BF3·OEt2 (2.5 mol %) in 10 mL dichloromethane (Table 2). A series of indene derivatives were obtained from moderate to excellent yield (58–85%). The steric hindrance and electronic effect of electron-withdrawing substituents such as nitriles and methyl/ethyl esters did not significantly

• the Cr(salen)/BF3·OEt2 catalytic system (5m–r, Table 2). This could be an outcome of steric hindrance exerted by the substitutents at the arene moiety of the MBH adducts. Thereafter, to inspect the utility of the reaction for a gram-scale reaction, we endeavoured a model reaction using the optimized

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• (transformation of the vinyl group at C-6 was preferred, except for the reactions of isoxazoline (±)-4 with 7f and 7g), while all CM reactions of (±)-6 were completely regioselective (the vinyl group at C-6 was transformed first). This can be explained by steric hindrance: the substituent at C-3 on the

• . Some commercial Ru-based catalysts used in the current work. Synthesis of divinylated cyclopentane-fused isoxazolines [41]. Various fluorine-containing olefins used in the current work. Chemoselective CM reaction due to steric hindrance. Cross-metathesis of divinylated isoxazoline (±)-4 with