Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• epoxides are formed through oxidation reactions in vivo, that occur in protein processes dependent on vitamin K [96][97]. Dwyer and co-workers described a procedure using sugar-derived hydroperoxides for the synthesis of epoxides in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base [98][99

• anomeric hydroperoxides (HPO) to obtain epoxides 40 with moderate ees (Scheme 11B) [100][101]. Bunge and co-workers used the enantiomerically pure dihydroperoxide 41 in the DBU-mediated epoxidation of menadione (10) for the enantioselective synthesis of epoxide 42 (92% yield and 45–66% ee) (Scheme 11C

Synthesis of piperidine and pyrrolidine derivatives by electroreductive cyclization of imine with terminal dihaloalkanes in a flow microreactor

• Yuki Naito,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2022, 18, 350–359, doi:10.3762/bjoc.18.39

• -diazabicyclo[5,4,0]-7-undecene (DBU), which has the strongest basicity among these bases, was used, the yield of 3a increased significantly, while the formation of 4 was suppressed. In particular, when more than 1.0 equiv of DBU was added, the yield of 3a reached almost 80%. The reactivity of the radical

• mol−1; current density, 12.7 mA cm−2; solvent, THF; substrate, 0.06 M benzylideneaniline (1) and 0.12 M 1,4-dibromobutane (2a); base added, 0.06M DBU; supporting electrolyte, 0.14 M n-Bu4N∙ClO4; flow rate, 11 mL h−1 (residence time, 3.9 s); collection volume and time for each fraction, 2 mL, 10 min 55

• suppress the formation of the hydromonomeric product, which is a main byproduct. Among the various bases, DBU suppressed the formation of byproducts and the desired cyclization products such as piperidine and pyrrolidine derivatives were obtained in good yields. Moreover, in the electrochemical flow

Chemoselective N-acylation of indoles using thioesters as acyl source

• Tianri Du,
• Xiangmu Wei,
• Honghong Xu,
• Xin Zhang,
• Ruiru Fang,
• Zheng Yuan,
• Zhi Liang and
• Yahui Li

Beilstein J. Org. Chem. 2022, 18, 89–94, doi:10.3762/bjoc.18.9

• of the N(sp2)–H bond by using a catalytic amount of DBU for the preparation of indoleamides [14] (Scheme 1, A2). Subsequently, Sundén reported an efficient chemoselective method for the synthesis of indoleamide by oxidative organocatalytic reaction of indole derivatives and conjugated aldehydes under

Total synthesis of the O-antigen repeating unit of Providencia stuartii O49 serotype through linear and one-pot assemblies

• Tanmoy Halder and
• Somnath Yadav

Beilstein J. Org. Chem. 2021, 17, 2915–2921, doi:10.3762/bjoc.17.199

• (TCCA) in aqueous acetone [51] resulting in compound 11. Treatment of compound 11 with trichloroacetonitrile and DBU in dry DCM resulted in the formation of the desired trichloroacetimidate donor 12 in 93% yield (Scheme 4). The first stage of the one-pot synthesis was carried out using donor 12 and

A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones

• Yuki Yamamoto,
• Akihiro Tabuchi,
• Kazumi Hosono,
• Takanori Ochi,
• Kento Yamazaki,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 2906–2914, doi:10.3762/bjoc.17.198

• , triethylamine, DBU, or Cs2CO3 was less effective (Table 3, entries 6–9); furthermore, the reaction did not proceed in the absence of a base (Table 3, entry 10). This investigation revealed that medium-chain tetraalkylammonium hydroxides, namely n-Bu4N+OH− and n-Pr4N+OH−, effectively transform 2a into 3a through

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• -toluenesulfonylmethyl isocyanide (TosMIC) by using respectively zinc iodide and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as catalysts were developed. The distinguishing feature of this method is that TosMIC plays a dual role from the same substrates in the reaction: as a sulfonyl source or as an isonitrile source. The

• not proceed (Table 1, entry 9). Then, we investigated the effect of a catalytic amount of DBU on the reaction and found that reaction efficiency did not decrease, indicating that the reaction could also be catalyzed by DBU (Table 1, entry 10). When DABCO (triethylene diamine) was used instead of DBU

• , the reaction also proceeded, however, the reaction efficiency was lower compared to DBU (Table 1, entry 11). After identifying the optimal conditions, we first evaluated the substrate scope of the sulfonylation reaction. As shown in Scheme 2, various substituted p-QMs were readily transformed in this

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• followed by esterification with 3-butenoic acid (37) under Steglich conditions (Scheme 3). The resulting product 38 was isolated in 86% yield. A subsequent ring-closing metathesis reaction and DBU-assisted double bond migration then furnished the anticipated structure 39. The PMB functionality was removed

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• ]acene-2,3-dicarbaldehydes 91 and the Wittig reagents 92; DBU was employed to produce the corresponding substituted [n+1]acene-2,3-diethyl diesters 93. Then, in two steps (reduction and Swern oxidation), the authors converted the diesters 93 to the dialdehydes 94, which could be transformed into the

• fumaronitrile to produce the Wittig reagents. Despite the limitations, the authors noted that DBU was no longer required in these reactions. The scope of these reactions included five examples of substituted anthracene-2,3-dicarbonitriles 96 (40–62% yield) [57]. BN arenes include analogs in which a C=C bond has

• OMe, NO2, or Cl groups, and epoxides (149 and 150), DBU as catalyst, CTAB as surfactant, and water as solvent. The use of cyclohexene oxide (149) provided oxa-aza-benzo[a]anthracene derivatives 151 in excellent yields (90–96%). On the other hand, the use of styrene oxide (150) provided oxa-aza

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

• Ryan M. Alam and
• John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

• solubility of Cs2CO3 in toluene and 1,4-dioxane [24]. Using K2CO3 in MeCN, Longworth et al. have obtained 10 with a similar degree of N-1 regioselectivity (ratio N-1:N-2 = 2.8:1) [26]. However, altering solvent polarity when employing 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a base (Table 1, entries 15–17

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• -containing 1,2,3-triazole derivatives 30 from the reaction of glycosyl azides 28 with enolates of active ketones and esters 29 in the presence of DBU in DMF at 70 °C (Scheme 12) [43]. Diverse monosaccharide and disaccharide azides were successfully reacted with a variety of enolates of active ketones and

• the use of a catalytic amount of DBU in DMSO at room temperature [46]. The cyclic enones 43 were reacted with the α-azidostyrenes 44 containing groups such as Cl, F, and OMe to form the corresponding products (Scheme 16). The o-, m-, and p-tolylvinyl azides facilitated a good to excellent yield of the

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• inorganic bases, such as Et3N, K2CO3, and DBU. Along with the “traditional” reaction performed in solution, a mechanochemical approach using ball milling was also tested. The obtained results are collected and compared in Table 1. They show that the best results were achieved using dry THF as a solvent and

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• were formed that were still insufficient for complete characterization. Intending to improve the yield of 3aa, we screened various solvents, non-nucleophilic organic bases such as triethylamine and DBU, and several inorganic bases like K2CO3, Cs2CO3, and NaH (Table 1, entries 2–6). After systematic

• inert atmosphere prior to use. Organic bases, including DIPEA, Et3N, and DBU, were stored over anhydrous KOH pellets. In vitro cytotoxicity studies Cytotoxicity analysis in cancer and macrophage cells Cancer (MCF7, A431, A549, HEK293 or HeLa cell lines) or RAW264.7 cells were seeded in a 96-well plate

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• industrialized total synthesis of a nontrivial natural product. The original experimental protocol was recently improved by replacing the inorganic base (KOH, NaOH) with the amidine base diazobicycloundecane (DBU) as well as ethanol with n-propanol [49]. The type-III Guareschi reaction is a three-component

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• -Michael reaction, it was possible to reach either cis- or trans-isoindolines, 69 and 70, respectively, from the same precursor 68. The authors proposed that the thermodynamically more stable cis-isomer 69 is formed when TBAF was used. Meanwhile, working under kinetic conditions (DBU as base), trans-isomer

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

• , Fu and colleagues [35] received the target product 40 with 23 W CFL irradiation of a solution containing 1-(4′-hydroxy-[1,1′-biphenyl]-2-yl)ethanone O-(2,4-dinitrophenyl)oxime (39) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in CH3CN (Scheme 13). Ready-made DBU serves two roles: base and electron

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• CBr4 or I2, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or NaH as the base, and a malonate-derived substrate. The adduct is synthesized in a slightly higher yield by direct treatment of fullerene with malonates. As noted above, a decrease in the strain of the fullerene core is the driving force of its

1,2,3-Triazoles as leaving groups: S_NAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

• Dace Cīrule,
• Irina Novosjolova,
• Ērika Bizdēna and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

• regioselectivity of SNAr reactions was proved by 13C NMR comparison of the products 3a–i with similar compounds from literature [61]. Intriguingly, we were able to conserve the acetate protecting groups in product 3j, when the SNAr reaction was performed in the presence of DBU used as base. The artificial

Facile preparation and conversion of 4,4,4-trifluorobut-2-yn-1-ones to aromatic and heteroaromatic compounds

• Takashi Yamazaki,
• Yoh Nakajima,
• Minato Iida and
• Tomoko Kawasaki-Takasuka

Beilstein J. Org. Chem. 2021, 17, 132–138, doi:10.3762/bjoc.17.14

• as a Michael acceptor. Stronger bases, such as NaH and t-BuOK seemed to be preferable (Table 2, entries 3 and 6), and amines such as DBU and 1,1,3,3-tetramethylguanidine (TMG) were found to be insufficient (Table 2, entries 10 and 11). Judging from the possible mechanism, this process was considered

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• [80], compound (Z)-(+)-143a delivered the bromodiene (Z,Z)-(+)-145a in good yield and stereoselectivity. Isomerization of (Z)-(+)-143a to (E)-(+)-143b was carried out successfully using sterically hindered base DBU or DABCO. Treatment of (E)-(+)-143b with 144 using the boron-Wittig reaction [79

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• , 70%, 97.3% ee; iii) 1. DMAP, Et3N, MsCl, CH2Cl2; 2. DBU, CH2Cl2, 70% over two steps; iv) CH2=CHCH2MgCl, THF; v) HCl (4.0 M in dioxane), CH2Cl2, 78% over two steps; vi) PdCl2, CuCl, DMF/H2O (20:1), 23 °C, 93%; vii) KOSiMe3, 23 °C, 35 min; viii) NOPF6, DME, 80% over two steps; ix) 2-butanone ethylene

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• tetracyclic compound 56. Dihydroxylation of freshly prepared 56 with OsO4 and then selective tosylation afforded 57 in 39% yield over two steps. Exposure of 57 to DBU upon heating gave the elimination product 58, which was subjected to an oxidative rearrangement with PDC to give enone 59 in 68% yield. Copper

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

•  3). Thioamides 1f,g,t were converted to 5-arylamino-1,2,3-triazoles 1i–k by heating at reflux in n-propanol in the presence of DBU and these rearranged thioamides were then treated with sulfonyl azide 2c,f and kept at the same temperature for 17‒31 h. After flash column chromatography, pure N

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• the complex [Zn(49)]2+. The liberated zinc(II) ions replaced the Li+ ions in the nanoswitch [Li(35)]+ and translocated them onto the luminophore 36, thus finally generating the state SelfSORT-II composed of 49•H+, [Zn(35)]2+, and [Li(36)]+. In the return process, the deprotonation of 49•H+ by DBU