Acetaldehyde in the Enders triple cascade reaction via acetaldehyde dimethyl acetal

• Alessandro Brusa,
• Debora Iapadre,
• Maria Edith Casacchia,
• Alessio Carioscia,
• Giuliana Giorgianni,
• Giandomenico Magagnano,
• Fabio Pesciaioli and
• Armando Carlone

Beilstein J. Org. Chem. 2023, 19, 1243–1250, doi:10.3762/bjoc.19.92

• as a reagent has always been challenging. The low boiling point and high volatility pose a problem with its handling and safety. The small steric hindrance gives rise to a high reactivity both as an electrophile and as a pro-nucleophile, hampering chemoselectivity (further to side reactions such as

• self-aldol condensations, polymerization and Tishchenko-type processes) and stereoselectivity [20]; the activation of acetaldehyde via aminocatalysis, furthermore, suffers from a lack of proper steric hindrance for the enantio-discrimination process. However, some methodologies enabling the use of

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Linker, loading, and reaction scale influence automated glycan assembly

• Marlene C. S. Dal Colle,
• Manuel G. Ricardo,
• Nives Hribernik,
• José Danglad-Flores,
• Peter H. Seeberger and
• Martina Delbianco

Beilstein J. Org. Chem. 2023, 19, 1015–1020, doi:10.3762/bjoc.19.77

• /g to yield supports with low (0.3–0.4 mmol/g) or high (0.7–0.8 mmol/g) loadings (see Supporting Information File 1, section 2.3, module A). The latter allows for a larger synthesis scale, but steric hindrance and chain–chain interactions could negatively influence the AGA outcome, as observed for

Copper-catalyzed N-arylation of amines with aryliodonium ylides in water

• Kasturi U. Nabar,
• Bhalchandra M. Bhanage and
• Sudam G. Dawande

Beilstein J. Org. Chem. 2023, 19, 1008–1014, doi:10.3762/bjoc.19.76

• –h in 57–65% yields. Also, the halogen-substituted arylamines such as p-bromo, o-bromo, p-chloro, and p-fluoroanilines reacted smoothly to produce the corresponding diarylamine products 3i–l with 65–73% yields. To identify the effect of steric hindrance we treated 2,6-dimethylaniline under optimal

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• steric hindrance. Conclusion In summary, this work illustrates, once more, the synthetic potential of an Ir-polypyridyl complex as a photoredox catalyst that can efficiently convert visible light into chemical energy. In addition, this catalyst was applied to demonstrate the proposed radical mechanism

Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structure

• Demet Demirci Gültekin,
• Arif Daştan,
• Yavuz Taşkesenligil,
• Cavit Kazaz,
• Yunus Zorlu and
• Metin Balci

Beilstein J. Org. Chem. 2023, 19, 764–770, doi:10.3762/bjoc.19.56

• are formed from the intermediate 10. Since the bromine atom attached to the C7 carbon atom poses steric hindrance at the exo face of the double bond, bromine attacks the double bond also from the endo face to form the intermediate 8. The endo-stereochemistry of the bromide attack can be rationalized

Construction of hexabenzocoronene-based chiral nanographenes

• Ranran Li,
• Di Wang,
• Shengtao Li and
• Peng An

Beilstein J. Org. Chem. 2023, 19, 736–751, doi:10.3762/bjoc.19.54

• –Alder cycloaddition to afford compound 45 in a 79% yield. Due to the steric hindrance from two bulky tert-butyl groups on the benzene rings in the adjacent hexaphenylbenzene monomers in precursor 45, two [5]helicenes were formed in the oxidative cyclodehydrognation reaction, which gave compound 46 as

pH-Responsive fluorescent supramolecular nanoparticles based on tetraphenylethylene-labelled chitosan and a six-fold carboxylated tribenzotriquinacene

• Nan Yang,
• Yi-Yan Zhu,
• Wei-Xiu Lin,
• Yi-Long Lu and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2023, 19, 635–645, doi:10.3762/bjoc.19.45

• TBTQ-C6 in water at pH 5.3 due to the more pronounced steric hindrance and the stronger charge repulsion on their complex surface [29][30]. Moreover, we propose that TBTQ-C6/CS-TPE supra-amphiphiles connected by electrostatic interactions self-assemble in water layer-by-layer with the outer surface

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• of zirconium enolates, presumably, due to the considerable steric hindrance caused by bulky ligands around the Zr center. Fletcher investigated the formylation of zirconium enolates with the Vilsmeier–Haack reagent [70]. Interestingly, the reaction afforded chloroformylation rather than simple

C3-Alkylation of furfural derivatives by continuous flow homogeneous catalysis

• Grédy Kiala Kinkutu,
• Catherine Louis,
• Myriam Roy,
• Juliette Blanchard and
• Julie Oble

Beilstein J. Org. Chem. 2023, 19, 582–592, doi:10.3762/bjoc.19.43

• to ring tension, gave endo product 2f with an isolated yield of 49%. On the other side, disubstituted vinylsilanes proved to be ineffective, certainly because of the steric hindrance of the double bond decreasing the kinetics of the hydroruthenation step. We also wanted to extend this alkylation

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

• Ita Hajdin,
• Romana Pajkert,
• Mira Keßler,
• Jianlin Han,
• Haibo Mei and
• Gerd-Volker Röschenthaler

Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39

• ortho and meta-positions on the phenyl ring (6e, 6f, 6h, 6i), decelerated the process. In the case of α-methylstyrene, complete conversion of diazo reagent 5 to compound 6b was observed only after 48 hours of heating, which might result from the steric hindrance around the reaction centre. In almost all

• the reaction with tert-butyl-N-allyl carbamate 7g (1:6) while the reaction with allylcyclohexane resulted with the lowest yield (7f, 28%), probably due to the steric hindrance of the reagents. In the case of N-Boc-allylamine, improved diastereoselectivity might result from the coordination of the

Computational studies of Brønsted acid-catalyzed transannular cycloadditions of cycloalkenone hydrazones

• Manuel Pedrón,
• Jana Sendra,
• Irene Ginés,
• Tomás Tejero,
• Jose L. Vicario and
• Pedro Merino

Beilstein J. Org. Chem. 2023, 19, 477–486, doi:10.3762/bjoc.19.37

• materials and the conditions used [5]. Some common types of TCRs include Diels–Alder reactions [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], photocycloadditions [21][22][23][24][25][26][27][28], and other types of multistep cycloadditions [29]. Steric hindrance can have a significant effect on

Asymmetric synthesis of a stereopentade fragment toward latrunculins

• Benjamin Joyeux,
• Antoine Gamet,
• Nicolas Casaretto and
• Bastien Nay

Beilstein J. Org. Chem. 2023, 19, 428–433, doi:10.3762/bjoc.19.32

• %). This compound results from the transposition of the para-nitrobenzoyl (PNBz) group onto the 13-OH, which could be favoured by the steric hindrance of C-15 and a possible π–π stacking with the OPMB group. These PNBz esters were readily hydrolyzed to furnished diol 24 in 97% yield. The oxydation of the

Discrimination of β-cyclodextrin/hazelnut (Corylus avellana L.) oil/flavonoid glycoside and flavonolignan ternary complexes by Fourier-transform infrared spectroscopy coupled with principal component analysis

• Nicoleta G. Hădărugă,
• Gabriela Popescu,
• Dina Gligor (Pane),
• Cristina L. Mitroi,
• Sorin M. Stanciu and
• Daniel Ioan Hădărugă

Beilstein J. Org. Chem. 2023, 19, 380–398, doi:10.3762/bjoc.19.30

• FA moieties interact with the β-CD host molecules. This was the reason to use such non-equimolar ratios. If a theoretical 3:1 interaction can be considered, the formation of such β-CD/triglyceride supramolecular system in practice is limited by the steric hindrance. On the other hand, ternary

Synthesis and reactivity of azole-based iodazinium salts

• Thomas J. Kuczmera,
• Annalena Dietz,
• Andreas Boelke and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2023, 19, 317–324, doi:10.3762/bjoc.19.27

• % yields. In the latter case, the initially generated hydroxy-iodonium salt is stabilized via the indazole nitrogen [26] and the steric hindrance by the methyl group is likely destabilizing this intermediate by an out-of-plane distortion [28][34] and hence accelerating the cyclization. The dicationic

• result obtained when using the stabilized salt 12 (Scheme 2b) [44]. Here, no counter-ion exchange to chloride was observed. The favored counter ion is determined by the pKa value of the corresponding acids but not by halogen bonding due to the steric hindrance at the iodines’ σ-holes. The reaction of

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• a TBDPS substituent in compound 40 was assumed unfavorable, since this bulky residue generates a steric hindrance precluding the cyclization (Scheme 6, path A) [27]. Its replacement by a sterically less demanding benzyl protecting group (compound 44) allowed the reaction to occur (Scheme 6, path B

• steric hindrance, alcohol 47 was converted into triene 48 upon dehydration, and further engaged in the RCM reaction. In this case, the use of HG-II catalyst proved to be the best choice to achieve cyclooctene ring formation giving rise to intermediate 49, providing entries for further functionalization

• methylene in compound 74 and the formation of a trisubstituted alkene in 75 were assumed to cause an important steric hindrance unfavorable for the cyclization process. As a solution, the RCM was envisaged on 76 which possesses two terminal double bonds and successfully produced cyclooctene 77 in 65–80

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• to 2 in the presence of n-BuLi, the direct transfer of the crotyl appendage failed, likely compromised by the steric hindrance of the nucleophile [31]. To alleviate this shortcoming, the crotyl appendage of 8 was assembled by methylation of the allylic pyrone counterpart (Scheme 5). Implemented by

• the steric hindrance of the electrophile and potentially facilitate the 1,4-addition, 2,5-cyclohexadienone 14, deprived of a methyl group, was prepared and tested but the reactivity was not significantly improved compared to 5. Both compounds appeared thus mostly reluctant to 1,4-addition and, when it

Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene

• Konstantin Lebedinskiy,
• Volodymyr Lobaz and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170

• and unsubstituted CD, in our case, the Me–O–C6 groups could have changed the situation due to the steric hindrance. The interaction of the triazole proton with the protons inside the cavity was not observed in the spectra of compound 9, which is acetyl-protected 10 (Figure 1c). However, it shares with

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence

• Kaiyue Ye,
• Liyuan Cao,
• Davita M. E. van Raamsdonk,
• Zhijia Wang,
• Jianzhang Zhao,
• Daniel Escudero and
• Denis Jacquemin

Beilstein J. Org. Chem. 2022, 18, 1435–1453, doi:10.3762/bjoc.18.149

• potential of the PTZ moiety. NI-PTZ has a linkage at the 3-position of the NI moiety, for the recently reported analogous dyad, however, the substitution is at the 4-position [20]. For the current NI-PTZ dyad, the torsion between the NI and PTZ has a larger freedom, due to the reduced steric hindrance

• was observed for the triad NI-PTZ2. For the dyads containing a phenyl linker between the NI and the PTZ moieties, the steric hindrance imposed by the methyl substituents on the phenyl linker is significant: the dihedral angle between the NI and the phenyl linker is 37° only in NI-Ph-PTZ, but it

Mechanochemical synthesis of unsymmetrical salens for the preparation of Co–salen complexes and their evaluation as catalysts for the synthesis of α-aryloxy alcohols via asymmetric phenolic kinetic resolution of terminal epoxides

• Shengli Zuo,
• Shuxiang Zheng,
• Jianjun Liu and
• Ang Zuo

Beilstein J. Org. Chem. 2022, 18, 1416–1423, doi:10.3762/bjoc.18.147

• between 1g (81%) and 1h (76%). Yields of 1d (79%), 1e (81%), and 1f (72%) were less than 1a‒c, caused by the steric hindrance of di-tert-butyl groups. In the aspect of characterization of salens, two singlets were shown at around 8 ppm in the 1H NMR spectrum, indicating two unsymmetrical imines. The broad

Ferrocenoyl-adenines: substituent effects on regioselective acylation

• Mateja Toma,
• Gabrijel Zubčić,
• Jasmina Lapić,
• Senka Djaković,
• Davor Šakić and
• Valerije Vrček

Beilstein J. Org. Chem. 2022, 18, 1270–1277, doi:10.3762/bjoc.18.133

• the N7 atom. As a consequence, the formation of N7-isomer is a kinetically less feasible process, i.e., the corresponding transition state structure increases in relative energy (compared to the formation of the N9-isomer). In cases where the steric hindrance is negligible, the electronic effect of

• applied to quantify the fraction of the defined sphere around a reaction center [46]. It was introduced for ligands on metals [47], but may be adapted to estimate the steric hindrance of substituents in different chemical environments (see Supporting Information File 1 for more details). As expected

• approach of an electrophile (e.g., FcCOCl) towards the N7 atom. In the course of N9-isomer formation no similar steric hindrance is encountered. This is supported by our quantum-chemical calculations which compared the two transition state structures for the ferrocenoylation of the N6,N6-di-tert

Lewis acid-catalyzed Pudovik reaction–phospha-Brook rearrangement sequence to access phosphoric esters

• Jin Yang,
• Dang-Wei Qian and
• Shang-Dong Yang

Beilstein J. Org. Chem. 2022, 18, 1188–1194, doi:10.3762/bjoc.18.123

• phenyl ring were well tolerated, and the phosphinate products 3ab–ah were obtained in moderate to good yield. The steric hindrance effect had a significant influence on the outcome of the reaction. For the phosphine oxide substrate 1i bearing an ortho-methyl-substituted phenyl group, the desired product

• yield (see 3ar–au). Next, we studied the scope with respect to the α-pyridinecarboxaldehyde by using 1a as the reaction partner (Scheme 3). Firstly, we investigated the effect of steric hindrance on the pyridine ring of the α-pyridinealdehyde. Under standard conditions, a methyl group was introduced at

• in moderate to good yield. Delightfully, in addition to aldehydes, a ketone was also applicable under standard conditions, albeit affording the product in a comparably lower yield, probably due to the lower reactivity and steric hindrance of the substrate (see 3bl). Moreover, pyridine bearing two

Experimental and theoretical studies on the synthesis of 1,4,5-trisubstituted pyrrolidine-2,3-diones

• Nguyen Tran Nguyen,
• Vo Viet Dai,
• Nguyen Ngoc Tri,
• Luc Van Meervelt,
• Nguyen Tien Trung and
• Wim Dehaen

Beilstein J. Org. Chem. 2022, 18, 1140–1153, doi:10.3762/bjoc.18.118

• due to the steric hindrance of the C6H5-groups attached to the 1- and 5-position of the heterocyclic ring. The 3D-optimized structures of substances on the PES are illustrated in Figures S2, S3, S4, S5, S6 and S7 in Supporting Information File 1. For the reaction pathway starting from 4a, firstly, it

Radical cation Diels–Alder reactions of arylidene cycloalkanes

• Kaii Nakayama,
• Hidehiro Kamiya and
• Yohei Okada

Beilstein J. Org. Chem. 2022, 18, 1100–1106, doi:10.3762/bjoc.18.112

• decrease the steric hindrance at the β-position and improve the reaction. Unfortunately, the arylidene cyclopropane 4 was found to be totally unreactive under both conditions (Scheme 3). However, to our surprise, the arylidene cyclobutane 5 was found to be productive and the corresponding spiro ring

Electrochemical formal homocoupling of sec-alcohols

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masashi Shiota,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2022, 18, 1062–1069, doi:10.3762/bjoc.18.108

• (2f and 2g). On the other hand, the reaction of 1-(4-cyanophenyl)ethanol (1h) resulted in a decrease in both the yield and the dl:meso ratio. While steric hindrance of substituents on the meta-position of the aryl moiety did not impede the present transformation (2i and 2j), the ortho-substituted