Towards an asymmetric β-selective addition of azlactones to allenoates

• Behzad Nasiri,
• Ghaffar Pasdar,
• Paul Zebrowski,
• Katharina Röser,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1504–1509, doi:10.3762/bjoc.20.134

• investigated the generality of this protocol. As outlined in Scheme 2, differently substituted allenoates were reasonably well tolerated (see products 5a–d), albeit some erosion in enantioselectivity was observed when using a tert-butyl ester containing allenoate (product 5d). Various α-arylmethyl-substituted

Synthesis of 2-benzyl N-substituted anilines via imine condensation–isoaromatization of (E)-2-arylidene-3-cyclohexenones and primary amines

• Lu Li,
• Na Li,
• Xiao-Tian Mo,
• Ming-Wei Yuan,
• Lin Jiang and
• Ming-Long Yuan

Beilstein J. Org. Chem. 2024, 20, 1468–1475, doi:10.3762/bjoc.20.130

• study began with the preparation of the (E)-2-arylidene-3-cyclohexenones 2 via DMAP-catalyzed elimination reaction of 2-cyclohexenone-MBH alcohols 1 and di-tert-butyl dicarbonate [22] as depicted in Scheme 2. Starting materials 2 were prepared in moderate to high yields. Next, we chose (E)-2

Synthesis of 4-functionalized pyrazoles via oxidative thio- or selenocyanation mediated by PhICl₂ and NH₄SCN/KSeCN

• Jialiang Wu,
• Haofeng Shi,
• Xuemin Li,
• Jiaxin He,
• Chen Zhang,
• Fengxia Sun and
• Yunfei Du

Beilstein J. Org. Chem. 2024, 20, 1453–1461, doi:10.3762/bjoc.20.128

• substituents (R2 and R3), albeit the reaction afforded product 2n in a much lower yield, possibly caused by steric congestion. In addition, when the aryl substituent of R1 was replaced with a tert-butyl group, this method also worked well to give product 2o in moderate yield. Notably, when the C3 and C5

Rapid construction of tricyclic tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine via isocyanide-based multicomponent reaction

• Xiu-Yu Chen,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2024, 20, 1436–1443, doi:10.3762/bjoc.20.126

• . Under the optimized reaction conditions, the scope of the reaction was developed by using various substrates. The results are summarized in Table 2. At first, several alkyl isocyanides such as cyclohexyl, tert-butyl and benzyl isocyanide have been successfully employed in the reaction. Dimethyl but-2

Synthesis of cyclic β-1,6-oligosaccharides from glucosamine monomers by electrochemical polyglycosylation

• Md Azadur Rahman,
• Hirofumi Endo,
• Takashi Yamamoto,
• Shoma Okushiba,
• Norihiko Sasaki and
• Toshiki Nokami

Beilstein J. Org. Chem. 2024, 20, 1421–1427, doi:10.3762/bjoc.20.124

• the thioglycoside monomer 14 (Scheme 3) [17][18]. The electrochemical polyglycosylation of 14 was carried out in the presence of 2,6-di-tert-butyl-4-methylpyridine (DTBMP) to ensure the formation of a β-glycosidic bonds [19]. Although we could suppress formation of 1,6-anhydrosugar 15, cyclic

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• components, such as various acrylates, α,β-unsaturated acids, enones, enals, acrylamides, vinyl phosphonates, and vinyl sulfones. Various cesium salts of oxalates also performed well using this protocol. Isopropyl and tert-butyl groups present in an adjacent position of oxalates do not disturb the reaction

Transition-metal-catalyst-free electroreductive alkene hydroarylation with aryl halides under visible-light irradiation

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

Beilstein J. Org. Chem. 2024, 20, 1327–1333, doi:10.3762/bjoc.20.116

• found to be suitable coupling partners. Aryl chloride 1a reacted with tert-butyl acrylate (2b) without any difficulty, providing 3ab in a high yield. Methacrylamide (2c) and acrylonitrile (2d) were transformed into the corresponding products in high yields, but with slightly lower Faradaic efficiency

Synthesis of indano[60]fullerene thioketone and its application in organic solar cells

• Yong-Chang Zhai,
• Shimon Oiwa,
• Shinobu Aoyagi,
• Shohei Ohno,
• Tsubasa Mikie,
• Jun-Zhuo Wang,
• Hirofumi Amada,
• Koki Yamanaka,
• Kazuhira Miwa,
• Naoyuki Imai,
• Takeshi Igarashi,
• Itaru Osaka and
• Yutaka Matsuo

Beilstein J. Org. Chem. 2024, 20, 1270–1277, doi:10.3762/bjoc.20.109

• para-substituents were used and the reaction from FIDO to FIDS was found to tolerate both electron-donating and -withdrawing functional groups as shown in Table 2. It is well known that functional groups with larger steric hindrance can reduce intermolecular forces. Consequently, a tert-butyl

• ) was determined by analyzing the onset of weight loss for these compounds. Tsub was lower for t-Bu-FIDO and t-Bu-FIDS, at 410 °C and 417 °C, respectively, than for C60, which began to sublimate at 460 °C (Table 3). The lower sublimation temperature was attributed to the steric hindrance of the tert

• -butyl groups, which disrupted the π–π stacking between the fullerene cages. The slight difference in sublimation temperature between t-Bu-FIDO and t-Bu-FIDS might be due to the slightly higher electron density of the sulfur atom compared with the oxygen atom. Additionally, data on the degradation

Bismuth(III) triflate: an economical and environmentally friendly catalyst for the Nazarov reaction

• Manoel T. Rodrigues Jr.,
• Aline S. B. de Oliveira,
• Ralph C. Gomes,
• Amanda Soares Hirata,
• Lucas A. Zeoly,
• Hugo Santos,
• João Arantes,
• Catarina Sofia Mateus Reis-Silva,
• João Agostinho Machado-Neto,
• Leticia Veras Costa-Lotufo and
• Fernando Coelho

Beilstein J. Org. Chem. 2024, 20, 1167–1178, doi:10.3762/bjoc.20.99

• decarboxylation directed by bismuth triflate at 100 °C. Synthesis of 3-aryl-1-indanones. aIsolated yield after purification using silica gel column chromatography. bReaction performed at 60 °C. cFrom tert-butyl Knoevenagel derivative. Basic protocol: The Knoevenagel product 9 (0.5 mmol), dry acetonitrile (2 mL

Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer

• Mohd Farhan Ansari,
• Atul Kumar Maurya,
• Abhishek Kumar and
• Saravanakumar Elangovan

Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98

• way, alkylation of tert-butyl acetate with numerous alcohols was also tested using catalyst Mn18 (5 mol %), t-BuOK (2 equiv) in toluene at 100 °C for 4 h and gave moderate yields of 39 to 61%. Compared to the alkylation of amides, the alkylation of esters required higher catalyst and base loading

• . However, the reaction proceeded at a low temperature and less reaction time (Scheme 51). In addition, Balaraman and co-workers reported the C-alkylation of unactivated amides and tert-butyl acetate using primary alcohols as alkylating agents catalyzed by an aliphatic PNP-Mn pincer catalyst [79]. Various

• alcohols, including aliphatic alcohols, were coupled with N,N-dimethylacetamide using low catalyst loading (0.5 mol % Mn21) and t-BuOK as base (1.2 equiv) at 110 °C for 16 h and furnished the products in good yields (up to 88%). The alkylation of tert-butyl acetate with alcohols under the same reaction

Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO–LUMO gaps

• Qian Liu and
• Glen P. Miller

Beilstein J. Org. Chem. 2024, 20, 1099–1110, doi:10.3762/bjoc.20.97

• substituents, respectively, were also attempted but without success. In these cases, the sterically congesting ortho isopropyl and tert-butyl groups stymie the Friedel–Crafts acylation step leading to diketone (Scheme 1). Experimental and computational studies of 1,3-diarylisoacenofurans Purified

• isoacenofurans. Thus, unless there is a need for improved kinetic stabilization of the most reactive 1,3-carbons on the furan ring, there appears little benefit of utilizing highly hindered 2’,4’,6’-triisopropyl (compound 24) or 2’,4’,6’-tri-tert-butyl (compound 25) substituents, especially as these compounds

Carbonylative synthesis and functionalization of indoles

• Alex De Salvo,
• Raffaella Mancuso and
• Xiao-Feng Wu

Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87

• the presence of Ni(dme)Cl2 (a nickel(II) chloride ethylene glycol dimethyl ether complex), dtbbpy (4,4-di-tert-butyl-2,2-dipyridyl), Zn(0) and ZnI2 in DMF at 120 °C [42] (Scheme 22). The nickel catalyst catalyzed the oxidative addition and CO insertion on aryl iodide compounds, while the Zn/ZnI2

Innovative synthesis of drug-like molecules using tetrazole as core building blocks

• Jingyao Li,
• Ajay L. Chandgude,
• Qiang Zheng and
• Alexander Dömling

Beilstein J. Org. Chem. 2024, 20, 950–958, doi:10.3762/bjoc.20.85

• isocyanide component (Scheme 1). Aliphatic isocyanides, such as tert-octyl and tert-butyl isocyanide (1b and 1c) were well-tolerated in the Passerini-tetrazole reaction, leading to the corresponding tetrazole products in moderate to good yields of 74% and 52%, respectively. β-Cyanoethyl isocyanide (1d) was

• also well tolerated providing a good yield (62%). The tolerability of different isocyanides, and the possibility to remove the cleavable isocyanides under different reaction conditions (acidic for the tert-octyl and tert-butyl isocyanide, basic for β-cyanoethyl isocyanide, or reductive for the benzyl

• smoothly and provided moderate to excellent yields of 58–83%. Among this, the tert-octyl-substituted aldehyde exhibited excellent product transformation with a yield of 83% of 3e. Various isocyanides such as benzyl, phenylethyl, tert-octyl and tert-butyl isocyanides participated in the reaction with

One-pot Ugi-azide and Heck reactions for the synthesis of heterocyclic systems containing tetrazole and 1,2,3,4-tetrahydroisoquinoline

• Jiawei Niu,
• Yuhui Wang,
• Shenghu Yan,
• Yue Zhang,
• Xiaoming Ma,
• Qiang Zhang and
• Wei Zhang

Beilstein J. Org. Chem. 2024, 20, 912–920, doi:10.3762/bjoc.20.81

• the reported procedures [41], the Ugi-azide reaction of 2-bromobenzaldehyde (1a, 1 mmol), allylamine hydrochloride (2, 1 mmol), trimethylsilyl azide (3, 1 mmol) and tert-butyl isocyanide (4a, 1 mmol) in MeOH at 40 °C for 24 h afforded 1,5-DS-1H-T 5a in 92% yield after chromatography purification. Our

• mmol), trimethylsilyl azide (3, 1 mmol), and tert-butyl isocyanide (4a, 1 mmol) was stirred in MeOH at 40 °C for 24 h, and after the reaction was completed, the solvent was evaporated under vacuum to give crude Ugi adduct 5a which was used for the intramolecular Heck reaction without further

• . Experimental General procedure for the synthesis of Ugi-azide adduct 5a A solution of 2-bromobenzaldehyde 1 (1 mmol, 1 equiv), allylamine hydrochloride (2, 1 mmol, 1 equiv), trimethylsilyl azide (3, 1 mmol, 1 equiv) and tert-butyl isocyanide 4a (1 mmol, 1 equiv) in MeOH (5 mL) with Et3N (1.5 mmol) was heated

(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• -workers, and was accessed over 8 steps from diene 161 (Scheme 17A) [51]. Diels–Alder reaction of diene 161 and di-tert-butyl azodicarboxylate (160) followed by palladium-assisted elimination of acetic acid gave diene 162. A sequence of 4π-electrocyclisation and electrophilic transcarbamation (to 163

Ortho-ester-substituted diaryliodonium salts enabled regioselective arylocyclization of naphthols toward 3,4-benzocoumarins

• Ke Jiang,
• Cheng Pan,
• Limin Wang,
• Hao-Yang Wang and
• Jianwei Han

Beilstein J. Org. Chem. 2024, 20, 841–851, doi:10.3762/bjoc.20.76

• 3au and 3av were produced in 34% and 39% yields, respectively, in which methoxy and tert-butyl groups were located in the para position to the hydroxy group (Table 2, entries 20 and 21). In the case of 3al, the mono-arylation of naphthol generated 3al’ in 20% isolated yield, which is the reason for

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• carbenium ions are highly energetic species which tend to react unselectively according to the reactivity–selectivity principle. In contrast, MH HAT produces relatively stable radicals which is demonstrated by, e.g., the strong difference of heat of formation of the tert-butyl radical and cation (Figure 7B

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• work [45], and will be only shortly described in a summarized form (Scheme 3). Styrene substituted with a tert-butyl at the para position afforded 4b in 78% yield. Using a styrene bearing a sterically hindered aryl afforded 4c in a similar yield. Homopropargylic azides possessing oxygen substituents

HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines

• Luan A. Martinho and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2024, 20, 628–637, doi:10.3762/bjoc.20.55

• our hands, when we tried to reproduce the reaction between 2-aminopyridine (1a), benzaldehyde (2), and tert-butyl isocyanide (3a), following in detail the reported protocol using exactly the same reaction conditions, the reaction failed completely in 20 minutes (followed by TLC) and after 72 h only 46

• -Aminopyridine (1a), 4-nitrobenzaldehyde (2a), and tert-butyl isocyanide (3a) were chosen as model substrates and different conditions were screened (Table 1). Glycerol, a green and sustainable solvent, was tried first, but unfortunately, the expected intense orange solid product 4a was obtained in low yields

• -position gave moderate product yields (4c and 4d). Furthermore, cyclohexyl isocyanide gave higher yields compared to tert-butyl isocyanide. Ortho-substituted aromatic aldehydes were very efficient, regardless the type of substituents used, and good to excellent yields (74–99%) of products 4k–r were

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• tweezers with tert-butyl groups positioned farther from the salphen via alkyne spacers were synthesized [42]. While, like in the parent tweezers 12, no intercalation of aromatic guests was observed in the closed form, strong intramolecular and intermolecular Pt–Pt bonds were achieved in the solid state

• ]. In the neutral state, the tweezers 34 adopt an anti-conformation because of steric hindrance between the N–H and the tert-butyl groups. Again, the N–H proton of the indole can bind to anions through hydrogen bonds and causes the system to adopt a cis-conformation, closing the tweezers. This closed

Ligand effects, solvent cooperation, and large kinetic solvent deuterium isotope effects in gold(I)-catalyzed intramolecular alkene hydroamination

• Ruichen Lan,
• Brock Yager,
• Yoonsun Jee,
• Cynthia S. Day and
• Amanda C. Jones

Beilstein J. Org. Chem. 2024, 20, 479–496, doi:10.3762/bjoc.20.43

• amounts of water (Table 3, entries 12–14) [39]. The same decelerating effect of water in MeOH solvent was seen with [JPhosAu(NCCH3)]SbF6 (5) (Table 3, entries 15–17). Substrate effect The rate of hydroamination to cyclized 3a–c was measured for three substrates, tert-butylurea 1a, tert-butyl carbamate 1b

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• hydrogen atom to terminate the radical reaction. The proposed mechanism of the hydroalkylation cascade is depicted in Scheme 13B. Upon excitation of complex 59 with blue light, intra-complex SET takes place from the HE to the NHPI ester, leading to the formation of tert-butyl radical 64 and radical cation

• isonicotinate tert-butyl ester) in C(sp2)-borylation methods under photochemical and thermal conditions, respectively [65][66]. The activation of NHPI esters through EDA complex formation is also possible by employing a catalytic donor species, which enables a range of redox neutral transformations. In 2019

• absorption spectra of PTH1 was observed, suggesting the formation of a charge transfer complex of the type 88 [68] (Scheme 17A). tert-Butyl radical (64), along with additional 2° and 3° alkyl radicals, resulting from these EDA complexes were harnessed in C(sp3)-heteroatom bond forming reactions [69], and in

Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3H-phenoxazin-3-one with ortho-substituted anilines

• Eugeny Ivakhnenko,
• Vasily Malay,
• Pavel Knyazev,
• Nikita Merezhko,
• Nadezhda Makarova,
• Oleg Demidov,
• Gennady Borodkin,
• Andrey Starikov and
• Vladimir Minkin

Beilstein J. Org. Chem. 2024, 20, 336–345, doi:10.3762/bjoc.20.34

• condensation and Schiff base formation, which is then cyclized [12][16]. The reaction of 1 with arylamines 2a is performed in toluene solution in the presence of a catalytic amount of p-toluenesulfonic acid. This readily affords 6,8-di-tert-butyl-N-aryl-3H-phenoxazin-3-imines 3 but proceeds smoothly only with

• highly basic amines (Scheme 1) [6]. The choice for one of the other two possible reaction pathways (nucleophilic additions to either the C(1) or C(2) center) critically depends on the electrophilicity. Figure 1 shows the distribution of electronic density in 6,8-di-tert-butyl-3H-phenoxazin-3-one (1

• ). This is also the basic compound used in the transformations that are studied in this work due to the high kinetic stability and good solubility ensured by the tert-butyl groups. The largest positive charge of the C(1)–C(2)–C(3) segment is concentrated at the C(2) atom. The charge at the other

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• structure induced by the embedded heteropine ring. By way of example, the solubility of SeO-doped seco-HBC 29c is more than 100-fold higher than pristine HBC carrying four tert-butyl groups in both dichloromethane and ethanol. Ring contraction was next attempted on the series of heteropines synthesized