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

• (tert-butyl)-9H-carbazol-9-yl]-5-methylpyrimidines 2a–d General procedure. 4,6-Bis(3,6-di-tert-butyl-carbazol-9-yl)-5-methyl-2-methylthiopyrimidine (50 mg, 0.072 mmol), the corresponding boronic acid (0.094 mmol), CuMeSal (34 mg, 0.158 mmol), Pd(PPh3)4 (4.2 mg, 0.0036 mmol), Cs2CO3 (46.8 mg, 0.144 mmol

• , in case of meta-substituted boronic acid, 1 equiv) and dioxane (3 mL) were placed in a screw-cap vial equipped with a magnetic stirring bar and flushed with argon for 10 min. The reaction mixture was heated at 130 °C under stirring for 4 h. Then, dioxane was removed by distillation under reduced

Borylated norbornadiene derivatives: Synthesis and application in Pd-catalyzed Suzuki–Miyaura coupling reactions

• Robin Schulte and
• Heiko Ihmels

Beilstein J. Org. Chem. 2022, 18, 368–373, doi:10.3762/bjoc.18.41

• all, as neither the reaction of 2a with NaIO4 and hydrochloric acid, nor the reaction of 2a with LiOH and subsequent addition of acid (ammonium chloride, hydrochloric acid) gave the desired boronic acid, but led to decomposition, instead. Obviously, the 2-borylated norbornadiene derivatives are acid

• -labile, so that the synthesis of the boronic acid was not further investigated. In addition, the 4,4,5,5-tetramethyl-2-(3-methylbicyclo[2.2.1]heptadien-2-yl)-1,3,2-dioxaborolane (2b) was obtained by conversion of the known 2-bromo-3-methylbicyclo[2.2.1]heptadiene (1b) [27] to the metalated intermediate

• catalyst and additive. The 1H NMR-spectroscopic analysis of the reaction showed that in both attempts no reaction occurred. It may be concluded that the nucleophilicity of the boronic ester is not sufficient, however, under the employed conditions, it can be hydrolyzed to the more reactive boronic acid

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• -diaminobutyric acid (Dab), ornithine (Orn), or lysine (Lys). Utilising the Alloc protecting group allowed the coupling of 4-carboxyphenylboronic acid once the linear sequence had been synthesised (Scheme 2C). The intramolecular SMC between 6- or 7-bromotryptophan and the boronic acid afforded the stapled

• , 1 h. In panel C), amino acids in R1 and R2 are with protecting groups and R2 is resin-bound (Rink amide resin); R3 = 4-phenylboronic acid or (4-ethylphenyl)boronic acid (P2–P5). Supporting Information Supporting Information File 6: Details on the amino acid and peptide synthesis, analytical data of

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• in nearly quantitative yield according to known protocols [63]. Although O-unprotected hydroxyphenylboronic acids similar to 18 have been reported in the literature [64], we found the synthesis of the more lipophilic O-TBS-protected boronic acid 18 to proceed more facile in a yield of 66% via an

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• catalytic systems, namely arylboronic acid alone, its dual combination with chiral thiourea and integrated catalyst having boronic acid functionality in the chiral thiourea molecule. The dual combination of arylboronic acid with chiral thiourea was found as effective as arylboronic acid alone for the

• intermolecular asymmetric Michael addition of alk-2-enoic acids 68 with O-benzylhydroxylamine (69) giving racemic mixture of the product in poor yield. However, the integrated catalyst having boronic acid functionality in the chiral thiourea molecule gave the desired β-benzyloxyamino acid as the single product

• yields ranged 57–89% with ee 70–97% [52]. A similar chiral multifunctional thiourea/boronic acid was used as an organocatalyst by Michigami et al. for the enantioselective synthesis of N-hydroxyaspartic acid derivatives 76 with perfect regioselectivity and high enantioselectivity (Table 17) [53

Synthesis of new substituted 7,12-dihydro-6,12-methanodibenzo[c,f]azocine-5-carboxylic acids containing a tetracyclic tetrahydroisoquinoline core structure

• Agnieszka Grajewska,
• Maria Chrzanowska and
• Wiktoria Adamska

Beilstein J. Org. Chem. 2021, 17, 2511–2519, doi:10.3762/bjoc.17.168

• products was formed. Then, N-2,3-methylenedioxybenzylamino acid 6b and N-3,4,5-trimethoxybenzylamino acid 6c were prepared from boronic acid 5a, glyoxylic acid hydrate (4) and aminoacetals 3b and 3c, in 99% and 90% yield, respectively (Scheme 4). Under the Pomeranz–Fritsch conditions compounds 6b and 6c

• with 67% yield (53% overall yield from 3d), while the reaction carried out in 20% HCl led to a mixture of products, among which 7f was not detected (Scheme 5). It should be also mentioned that the amino acid 6g with a benzyloxy-substituted aromatic ring, obtained in the Petasis reaction of boronic acid

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

• yield (Table 1, entries 8 and 9). However, increasing the amount of K3PO4 to 4 equivalents gave a nearly quantitative yield (Table 1, entry 12). We believe that a supplementary activation of the boronic acid, by adding a high amount of base, improved the nucleophilicity and facilitated the

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

• Songeziwe Ntsimango,
• Kennedy J. Ngwira,
• Moira L. Bode and
• Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

• was demonstrated to be useful for the synthesis of the natural product trisphaeridine (3) [17]. Exposure of 1-bromo-2,4,5-trimethoxybenzene (19) to Suzuki–Miyaura coupling reaction conditions with boronic acid 20 resulted in the formation of aldehyde 21 (Scheme 5). Treatment of 21 with hydroxylamine

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• the previous sections. For example, catalyst 25 bearing a nucleophilic aminoalcohol functionality interacts with the boronic acid reagent in the Reissert-type reaction with acylated quinolines (Scheme 5b) [36], while the phosphine moiety in the bifunctional phosphinothiourea catalyst 31 allows for

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• -dibromo-[2-(3-dodecylthien-2-yl)]azulene (46) by using two successive Suzuki coupling reactions with thiophene boron ester 47 and biphenyl-4,4’-diboronic acid bis(pinacol) ester 49 (Scheme 11), whereas the Suzuki coupling of 46 with 2,1,3-benzothiadiazole-4,7-bis(boronic acid pinacol ester) 51 yielded the

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• ]. Hongtao and co-workers reported the synthesis of tetrakisindole species 13 through the coupling of aniline (12) and indole-2-boronic acid pinacol ester 11 using the Buchwald–Hartwig method (Scheme 3a) [42]. In a similar fashion, Han reported the syntheses of the symmetric and unsymmetric triaryl

• -mediated coupling of N-silylated 6-hydroxyindole 174 with the corresponding boronic acid 173 (Scheme 24) [114]. For further synthetic transformations of 175, N-protection with bromo esters 176 followed by hydrolysis towards acids 177a and 177b were performed. The products 177a and 177b are potent anti-HIV

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• given combination of enone and arylboronic acid. Keywords: asymmetric reaction; boronic acid; conjugated enones; chromones; enantioselective catalysis; Michael addition; Pd complexes; Introduction The asymmetric 1,4-addition of arylboronic acids to conjugated cyclic enones and chromones is a very

• of the boronic acid to Pd. This enhanced catalytic system showed a great turnover number (TON) up to 9,900. The authors described additions to cyclic substrates with high yields (90–99%) and enantioselectivities (89–94% ee; entries 1–5, Table 2). Also, a library of linear enones was tested giving

• -hydroxyaryl)enones underwent cyclization to ketals (chromanols) after the addition of boronic acid. The prepared chromanols afforded the chromenes through elimination upon treatment with p-TsOH. A series of different β-(2-hydroxyaryl)enones and boronic acids was tested and provided the substituted chromenes

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• the Cu2+-catalyzed coupling reaction with the boronic acid (Scheme 2). The regioselectivity of the latter reaction step is most likely determined by a stronger nucleophilicity of the oxyanion in the 10-position of 6 that is caused by the particular electron distribution in the intermediate 6

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• EDA complex was formed by 2-iodophenyl thiocarbonate 152, bis(catecholato)diboron, and triethylamine, which afforded boronic acid ester derivative 153 under blue-light irradiation. Simultaneously, pinacol boronic acid ester derivative 154 can be yielded by subsequent processing (Scheme 53). The

• initiated by an EDA complex. Synthesis of boration product 151 initiated by an EDA complex. Synthesis of boronic acid ester derivative 154 initiated by an EDA complex. Synthesis of β-azide product 157 initiated by an EDA complex. Decarboxylation reaction initiated by an EDA complex. Synthesis of amidated

Total synthesis of pyrrolo[2,3-c]quinoline alkaloid: trigonoine B

• Takashi Nishiyama,
• Erina Hamada,
• Daishi Ishii,
• Yuuto Kihara,
• Nanase Choshi,
• Natsumi Nakanishi,
• Mari Murakami,
• Kimiko Taninaka,
• Noriyuki Hatae and
• Tominari Choshi

Beilstein J. Org. Chem. 2021, 17, 730–736, doi:10.3762/bjoc.17.62

• -iodo-5-methoxyaniline (24), was synthesized according to the procedure previously reported by Wetzel and co-workers [31]. The Suzuki–Miyaura coupling of 2-iodoaniline derivative 24 and pyrrole-3-boronic acid pinacol ester 13 was carried out in the presence of Pd(OAc)2 and SPhos, followed by the

Helicene synthesis by Brønsted acid-catalyzed cycloaromatization in HFIP [(CF₃)₂CHOH]

• Takeshi Fujita,
• Noriaki Shoji,
• Nao Yoshikawa and
• Junji Ichikawa

Beilstein J. Org. Chem. 2021, 17, 396–403, doi:10.3762/bjoc.17.35

• ) in the teraryl structure, because the diborylated arenes were less available. Either (a) the coupling of boronic acid esters bearing one acetal moiety with dihalogenated arenes or (b) the coupling of dihalogenated arenes bearing two acetal moieties with arylboronic acids were conducted for the

• ]. Herein, we synthesized two types of ortho-fused seven-hexagon benzenoids with two [4]helicene structures. According to the strategy illustrated in Scheme 3, route b, double helical helicenes 5 were synthesized using (naphthyl-1-yl)boronic acid (7) and dibromobenzenes 6 with two (1,3-dioxolan-2-yl)methyl

• boronic acid ester 17 with a biphenyl structure and an acetal moiety, to afford bisacetal 18 in 92% yield. Thus, tandem cycloaromatization of 18 effectively proceeded to afford thia[6]helicene 15 in 63% yield. Conclusion In summary, we developed a facile and efficient method for the synthesis of several

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• corresponding pyrimidines. An efficient C–N bond-forming process is also observed by using boronic acid pinacol esters as coupling partners in the presence of Cu(II) acetate and boric acid. The 4-fluoroalkyl group on the pyrimidine ring significantly assists in the formation of the target N1-substituted

• expected, the ortho-substituent on the phenyl ring of the boronic acid impeded N1-arylation by steric hindrance. However, the methoxy and methyl groups at the ortho position did not prevent the formation of the corresponding products 3o and 3p, which were isolated in moderate yields of 52 and 35

• further the range of reagents, we subjected phenylboronic acid pinacol ester (6а) to a similar model conversion. Boronic acid pinacol esters are generally known to be much less reactive than the corresponding boronic acids in the Chan–Evans–Lam reaction having, on the other hand, the important advantage

The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

• Patrizia Andreozzi,
• Lorenza Tamberi,
• Elisamaria Tasca,
• Gina Elena Giacomazzo,
• Marta Martinez,
• Mirko Severi,
• Marco Marradi,
• Stefano Cicchi,
• Sergio Moya,
• Giacomo Biagiotti and
• Barbara Richichi

Beilstein J. Org. Chem. 2020, 16, 2272–2281, doi:10.3762/bjoc.16.188

• the mechanochemical approach (the B & B, ball milling for boronic acid conjugation) as bioconjugation strategy for the labeling of biocompatible carbohydrates. Fluorescent labeling is of key importance to follow up the fate of molecules and (nano)materials inside cells and in the human body. In this

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

Regioselective cobalt(II)-catalyzed [2 + 3] cycloaddition reaction of fluoroalkylated alkynes with 2-formylphenylboronic acids: easy access to 2-fluoroalkylated indenols

• Tatsuya Kumon,
• Miroku Shimada,
• Jianyan Wu,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 2193–2200, doi:10.3762/bjoc.16.184

• cycloaddition reaction using a fluoroalkylated alkyne having a 4-biphenyl group as R1 took place smoothly, giving the corresponding indenol 3eA in a good yield. Though bulkier groups as R1, such as 1-naphthyl or 3-chlorophenyl, reduced the reactivity (see 3fA and 3gA), an excess loading of the boronic acid

• out using 3.0 equiv of the boronic acid 2A and 20 mol % each of Co(acac)2·2H2O and dppp at 110 °C, the desired 2-fluoroalkylated indenol 3iA was obtained in 43% yield. Subsequently, we investigated the [2 + 3] cycloaddition reaction of the fluoroalkylated alkyne 1a (R1 = 4-ClC6H4) with variously

• the reaction time, and a higher reaction temperature were applied. However, the exposure of the fluoroalkylated alkynes 1a to electron-rich substrates, e.g., 2D and 2E, lead to the indenols in approximately 30% yield, and the use of an excessive amount of boronic acid, Co(acac)2·2H2O, or dppp improved

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties

• Nuray Altinolcek,
• Ahmet Battal,
• Mustafa Tavasli,
• William J. Peveler,
• Holly A. Yu and
• Peter J. Skabara

Beilstein J. Org. Chem. 2020, 16, 1066–1074, doi:10.3762/bjoc.16.93

• potassium acetate (KOAc) and dichlorobis(triphenylphosphine)palladium(II) in 1,4-dioxane [36][37]. Upon chromatography (9-hexylcarbazole-3-yl)boronic acid pinacol ester (5) was obtained as a liquid in good yield. (9-Hexylcarbazole-3-yl)boronic acid pinacol ester (5) was subjected to Suzuki–Miyaura reaction

• ), 0.86 (t, J = 7.0 Hz, 4H). (9-Hexylcarbazole-3-yl)boronic acid pinacol ester (5): 5 was synthesised as reported previously [36][37]. Bis(pinacolato)diboron (423 mg, 1.7 mmol), potassium acetate (446 mg, 4.5 mmol) and dichlorobis(triphenylphosphine)palladium(II) (35 mg, 0.05 mmol) catalyst were added to

• ) δ (ppm) 8.60 (s, 1H), 8.13 (d, J = 7.6 Hz, 1H), 7.91 (dd, J = 8.1, 2.5 Hz, 1H), 7.46 (t, J = 7.4 Hz, 1H), 7.42–7.36 (m, 2H), 7.23 (d, J = 7.6 Hz, 1H), 4.30 (t, J = 7.0 Hz, 2H), 1.86 (t, J = 7.6 Hz, 2H), 1.49–1.15 (m, 18H), 0.85 (t, J = 7.1 Hz, 3H). Compound 7a: (9-Hexylcarbazol-3-yl)boronic acid

Pd-catalyzed asymmetric Suzuki–Miyaura coupling reactions for the synthesis of chiral biaryl compounds with a large steric substituent at the 2-position

• Yongsu Li,
• Bendu Pan,
• Xuefeng He,
• Wang Xia,
• Yaqi Zhang,
• Hao Liang,
• Chitreddy V. Subba Reddy,
• Rihui Cao and
• Liqin Qiu

Beilstein J. Org. Chem. 2020, 16, 966–973, doi:10.3762/bjoc.16.85

• decreased with the increase of the substituent on the boronic acid. When a methyl or methoxy group were present at the ortho-position of 1-naphthaleneboronic acid, the reactions were hard to move on even at 70 °C. By replacing the 3-methyl group of the amide with a 3-methoxy or a 3-benzyloxy group, the

• hindrance of the 4-substituted boronic acid. Next, in order to confirm our speculation, the amide group of the aryl bromide was replaced with other functional groups, as shown in Scheme 2. When the amide group was changed into an amine, coupling product 5a was obtained quantitatively but without any

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

• performed a Suzuki coupling reaction between boronic acid 15 with chloro compound 2 (Scheme 2). To the best of our knowledge, there is no report of a Suzuki coupling reaction using boronic acid 15 in the literature. However, we generated this required boronic acid from the corresponding methyl propiolate

• [38]. Next we investigated reaction conditions for the reaction of compound 2 with boronic acid 15 using different variables (Supporting Information File 1, Table S1). Gratifyingly, after surveying several reaction conditions, we successfully obtained the desired product 16 in 35% yield using PdCl2

• , 1.1 equiv), TEA (2 equiv), rt, 63%; f) NaOH at −10 °C, NH2OH·H2O at −10 °C, MeOH , rt, 12 h, 55%. Reaction conditions: a) boronic acid 15 (1.3 equiv), PdCl2(PPh3)2 (0.1 equiv), dioxane/H2O (3:1), Na2HPO4 (2.0 equiv), TEA (4.0 equiv), 90 °C, 15 h, 55% for 16 and 71% for 18; b) SeO2 , different