Synthesis and optoelectronic properties of benzoquinone-based donor–acceptor compounds

• Daniel R. Sutherland,
• Nidhi Sharma,
• Georgina M. Rosair,
• Ifor D. W. Samuel,
• Ai-Lan Lee and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2019, 15, 2914–2921, doi:10.3762/bjoc.15.285

• temperature, it is also carried out in benign acetone as solvent and does not require any additional oxidant. It circumvents the additional prefunctionalization of the BQ step usually required for Pd cross-couplings [15], while also showing greater functional group tolerance than radical-based methods [16][17

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• developed an electrochemical approach for a Sharpless asymmetric dihydrohydroxylation of alkenes using an osmium complex [63]. In this protocol, the traditional chemical oxidant was replaced by an anode that regenerates [FeCN)6]3− via an Os(VIII) to Os(VI) interconversion. Similarly, Torri and co-workers

• oxidant required for this process was initially generated through anodic oxidation of aqueous Na2CO3 in an undivided cell under constant current electrolysis. A catalytic amount of chiral iminium salt 103 and olefinic substrate 71' were added to the same reaction mixture, and chiral epoxides 73' were

• obtained via oxidation by electrogenerated CO42− [73]. Moreover, they showed that electrogenerated persulfate generated in situ via a similar anodic oxidation of H2SO4 could act as an even better oxidant in presence of catalyst 103 to achieve the epoxidation of 71'c with higher ee values (Scheme 36). In

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• behaviour can be ascribed to the fact that Ag(SbF6) acts as a stronger oxidant in DCM compared to THF solution [98]. Well-defined catalysts for alkyne metathesis. Examples for a ferrrocenic thiacrown ether complexing palladium (IV), and a dicationic ferrocenophane (V) featuring a diyne bridge for ion

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• (H2O2/NaOH) proceeded with the low yield (32%). Application of m-chloroperbenzoic acid (mCPBA) as an oxidant, similarly to Knochels findings [19], gave the higher yield (56%) of (((1R,2R,3R,4R,5R)-4-hydroxypinan-3-yl)methyl)diphenylphosphine oxide (22). Next, phosphine oxide 22 was reduced to the

Experimental and computational electrochemistry of quinazolinespirohexadienone molecular switches – differential electrochromic vs photochromic behavior

• Eric W. Webb,
• Jonathan P. Moerdyk,
• Kyndra B. Sluiter,
• Benjamin J. Pollock,
• Amy L. Speelman,
• Eugene J. Lynch,
• William F. Polik and
• Jason G. Gillmore

Beilstein J. Org. Chem. 2019, 15, 2473–2485, doi:10.3762/bjoc.15.240

• 2b. The addition of benzoquinone (a chemical oxidant) to the electrochemically reduced solution under argon gave similar results, consistent with our hypothesis. When the yellow solution remained open to the atmosphere during electrolysis, the initially yellow solution turned green at first

• reduction potential between PSHD and QSHD for eLW was much less. For 5b Eored was 28 mV more positive than 2b indicating that 5b is a slightly better oxidant than the parent PSHD. But Eored of eLW 5a was surprisingly shifted 10 mV more negative than PSHD LW 2a, meaning it was actually harder to oxidize

• chemical oxidant (benzoquinone) added to complete the reduction of the dianion to the LW isomer. NMR spectroscopy was performed on samples 5 mm NMR tubes (Wilmad) made of clear quartz (photolyzed samples) or amber pyrex (dark samples) on a Varian Mercury or Bruker AvanceIII 400 MHz NMR. 1H NMR experiments

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• the relatively cheap complex (p-cymene)ruthenium(II) chloride dimer, in the presence of copper(II) acetate as oxidant under conventional heating. Despite all effort put in this attempt, the isolated yields were in the range of 14–62%, with the highest yield achieved after 24 h of reaction using 10 mol

• efficiently. The use of the nonhygroscopic and cheaper sodium acetate decreased the yield (Table 1, entry 5), whereas the absence of the acetate salt additive led to a very low reaction yield (Table 1, entry 6). Neither removal of the oxidant (Table 1, entry 7) nor further modification of the reaction

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

• Ronja Driller,
• Daniel Garbe,
• Norbert Mehlmer,
• Monika Fuchs,
• Keren Raz,
• Dan Thomas Major,
• Thomas Brück and
• Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

• [1][2][3]. Sesqui- and diterpenes are a diverse class of secondary metabolites derived predominantly from plants, marine invertebrates, fungi and some prokaryotes [4][5][6][7][8]. Properties of these natural products include antitumor, anti-oxidant, anti-inflammatory, antiviral, antimalarial

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• fluoride source and PhI(OPiv)2 as a hypervalent iodine oxidant (Scheme 8). Very recently, they [44] optimized this transformation and achieved the benzylic C–H radiofluorination with no-carrier-added Ag[18F]F. This method was applied to the radiolabeling of diversely substituted 8-methylquinoline

• –H fluorination of benzaldehydes. Notably, these transformations were achieved with orthanilic acids as new transient directing groups (TDGs) in DCE in the presence of air (Scheme 23). This approach employed 1-fluoro-2,4,6-trimethylpyridinium salts as a bystanding F+ oxidant or an electrophilic

• catalyst, AgF as fluoride source, NMO as oxidant, and DMF as solvent, they achieved the selective mono- or difluorination in high yields (Scheme 34). Notably, pyridine as an additive could prevent the decomposition of an amide substrate in a long-time reaction. Meanwhile, the group of Sanford [79

Characterization of two new degradation products of atorvastatin calcium formed upon treatment with strong acids

• Jürgen Krauß,
• Monika Klimt,
• Markus Luber,
• Peter Mayer and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2085–2091, doi:10.3762/bjoc.15.206

• experiments” the drug is submitted to more drastic conditions (e.g., strong acid or base, strong oxidant, very high temperature), and potential degradation products can be identified in very short time [2][3]. However, forced degradation experiments are highly artificial in nature, and thus one has to keep in

Naphthalene diimides with improved solubility for visible light photoredox catalysis

• Barbara Reiß and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201

• strength of chemical redox agents [60], cNDI 2 in the excited state is a strong oxidant and a mild reductant. We assume based on literature-known cNDIs that the different alkyl groups of the other cNDIs 3–6 have no or only very little influence on the electrochemical properties in comparison with those of

Metal-free mechanochemical oxidations in Ertalyte^® jars

• Andrea Porcheddu,
• Francesco Delogu,
• Lidia De Luca,
• Claudia Fattuoni and
• Evelina Colacino

Beilstein J. Org. Chem. 2019, 15, 1786–1794, doi:10.3762/bjoc.15.172

• compounds under very mild conditions [6][7]. Initially used in a stoichiometric amount [8], over the last 20 years it has been exploited successfully in catalytic quantities in combination with other oxidants [9]. A diverse range of co-oxidant agents (N-chlorosuccinimide, NaOCl, Oxone®, PhIO, PhICl2, PhI

• a catalytic amount of KBr promotes the in situ generation of HOBr, which is a stronger oxidant than HOCl [57]. The results improved remarkably by using as oxidant a 6% aqueous solution of NaOCl (1.14 mL, 1.1 mmol) adsorbed on NaHCO3 (6.5 g) in the presence of a catalytic amount of TEMPO (5.0 mol

• reactions of hydantoins [41][59]. However, also using this oxidant, we observed low conversions (31%) and the formation of significant amounts of byproducts, mainly halides and olefins (elimination byproducts). The use of liquid-assisted grinding (LAG) procedures [60][61][62] by adding small quantities of

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• *: pentamethylcyclopentadiene) [28], FeCl3 [29], NiFe2O4 [30], CuO [31], mixed-metal oxides [32] etc. Some of the reactions have utilized metal salts like Cu(OAc)2, Ag2CO3, AgOAc, etc. (reference papers of this review) as an oxidant to carry out the synthesis among which preference was given to the use of oxygen and air as

• served the role of oxidant for generating a Cu(III) intermediate during the reaction. The absence of oxygen atmosphere gave the yield in a slightly lesser amount with increased loading of catalyst to almost 1 equivalent. This reaction avoided the use of any additive; moreover, the presence of bases in

• the first step which was converted to the final product via radical cation intermediate 17 in the second step (Scheme 6). This additive-free approach offered an easy separation and reusability of heterogeneous catalyst along with the use of air as environmentally benign oxidant. The use of zinc and

Synthesis of 9-O-arylated berberines via copper-catalyzed C_Ar–O coupling reactions

• Qiaoqiao Teng,
• Xinhui Zhu,
• Qianqian Guo,
• Weihua Jiang,
• Jiang Liu and
• Qi Meng

Beilstein J. Org. Chem. 2019, 15, 1575–1580, doi:10.3762/bjoc.15.161

• 100 °C (Supporting Information File 1, Figure S2). To promote this process I2 was used as the oxidant and provides the anion at the same time [22]. Following this procedure, the oxidation went to completion within 6 h as indicated by TLC (Scheme 3, Scheme 4), and no substitution on the aromatic

• backbone was observed as with Br2 [5]. This makes I2 a better oxidant for the oxidation of tetrahydroberberines. Compounds 3a–o are yellow solids, which are soluble in CH2Cl2, CH3CN, DMSO and MeOH. In contrast, the phenylene-bridged dimer 5 is only sparingly soluble in DMSO and MeOH. The formation of the

Transient and intermediate carbocations in ruthenium tetroxide oxidation of saturated rings

• Manuel Pedrón,
• Laura Legnani,
• Maria-Assunta Chiacchio,
• Pierluigi Caramella,
• Tomás Tejero and
• Pedro Merino

Beilstein J. Org. Chem. 2019, 15, 1552–1562, doi:10.3762/bjoc.15.158

• typically performed by preparing ruthenium tetroxide in situ from ruthenium species in lower oxidation states (RuCl3 or RuO2) and an oxidant such as NaIO4 [8]. Under these conditions RuO4 reacts with the alkane to form intermediate species I that evolves to the alcohol and RuO3, which is re-oxidized to re

• -start the catalytic cycle (Scheme 1) [12]. Depending on the substrates and reaction conditions (re-oxidant, solvent, temperature) the alcohol can be oxidized to the corresponding carbonyl derivative [13][14]. The rate-limiting step of the catalytic cycle illustrated in Scheme 1 is the initial reaction

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• -methyl-2-pyrrolidone (NMP) was disadvantageous for the reaction (Table 2, entry 10). It is well-known that at elevated temperatures sulfur may act as an oxidant, which in this case may have compromised the reaction [97][98][99]. Therefore, the molar excess of sulfur was decreased, providing a positive

Synthesis of pyrrolo[1,2-a]quinolines by formal 1,3-dipolar cycloaddition reactions of quinolinium salts

• Anthony Choi,
• Rebecca M. Morley and
• Iain Coldham

Beilstein J. Org. Chem. 2019, 15, 1480–1484, doi:10.3762/bjoc.15.149

• adduct 10 was performed using the oxidant 2,3-dichloro-5,6-dicyanoquinone (DDQ) to give the fully unsaturated product 13. To expand the range of products and explore the scope of the reaction further, we prepared the salts 14a and 14b (from 6-chloroquinoline and 6-bromoquinoline) and these were heated

Mechanochemical synthesis of hyper-crosslinked polymers: influences on their pore structure and adsorption behaviour for organic vapors

• Sven Grätz,
• Sebastian Zink,
• Hanna Kraffczyk,
• Marcus Rose and
• Lars Borchardt

Beilstein J. Org. Chem. 2019, 15, 1154–1161, doi:10.3762/bjoc.15.112

• Information File 1, Figure S2) at around 310 °C. The residual mass of only 1.9% confirms the absence of both, excessive abrasion and oxidant inside the polymer. This is further supported by the SEM-EDX (scattering electron microscope, energy-dispersive X-ray spectroscopy) measurements showing both Cl and Fe

• surface area) achieved with the classical solvent-based approach (Sol-HCP, SSABET = 1450 m2g−1, Vp = 1.55 cm−3g−1) [11] could not be reached. In order to improve this property, we varied the mechanochemical reaction parameters such as milling time and amount of oxidant in a systematic (DOE) design of

Extending mechanochemical porphyrin synthesis to bulkier aromatics: tetramesitylporphyrin

• Qiwen Su and
• Tamara D. Hamilton

Beilstein J. Org. Chem. 2019, 15, 1149–1153, doi:10.3762/bjoc.15.111

• placing reactants in a sealed tube at high temperatures (150 °C or higher) for 24 to 48 hours in the absence of air or any oxidant. Not every substituted benzaldehyde could survive this process and yield the porphyrin. Adler and Longo later introduced refluxing propionic acid (141 °C) open to air as a

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• acid derivative as one of the substrates of the reaction, together with an amine and a third reagent that provides the carbon atom needed to complete the cyclic moiety. Thus, Shi et al. [76] reacted benzoic acid derivatives 1, amides 2 and DMSO (3) in the presence of DDQ as oxidant and without any

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• , nitrosoquinoxaline 3 was synthesized in a two-step procedure starting from 2-chloroquinoxaline (1), which was transformed into its oxime 2 using hydroxylammonium chloride [64]. The subsequent oxidation was performed using periodic acid as oxidant [65]. The subsequent reaction with differently substituted anilines in

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• cyclisation in a basic medium of 2 then occurred to generate 4,5-dihydroisobenzofuran-5-ol (3) [19]. At this step, Cao et al. [17] have chosen the direct oxidation of 4,5-dihydroisobenzofuran-5-ol (3) to obtain 4-HO-OPA by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an oxidant. However, the yield

Selective benzylic C–H monooxygenation mediated by iodine oxides

• Kelsey B. LaMartina,
• Haley K. Kuck,
• Linda S. Oglesbee,
• Asma Al-Odaini and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55

• hypervalent iodine species as a terminal oxidant. Combinations of ammonium iodate and catalytic N-hydroxyphthalimide (NHPI) were shown to be effective in the selective oxidation of n-butylbenzene directly to 1-phenylbutyl acetate in high yield (86%). This method shows moderate substrate tolerance in the

• ) scaffold have been intensely studied for their ability to mediate hydrogen atom abstraction using a terminal oxidant of molecular oxygen [40][41][42][43][44][45]. NHPI has also been used in the effective C–H to C–O functionalization of benzylic positions using oxidants other than molecular oxygen including

• hydrocarbons [53], was also able to catalyze the reaction yielding compound 3a in 81% yield. The NHPI-catalyzed oxidation of n-butylbenzene (1a) was shown to be compatible with a variety of iodine(V) and iodine(VII) oxidants. As shown in Table 1, the use of potassium periodate as the terminal oxidant in the

Tandem copper and photoredox catalysis in photocatalytic alkene difunctionalization reactions

• Nicholas L. Reed,
• Madeline I. Herman,
• Vladimir P. Miltchev and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2019, 15, 351–356, doi:10.3762/bjoc.15.30

• describe a method for alkene oxyamination and diamination that utilizes simple carbamate and urea groups as nucleophilic heteroatom donors. This method uses a tandem copper–photoredox catalyst system that is operationally convenient. The identity of the terminal oxidant is critical in these studies. Ag(I

• ligand sets might be required, as in enantioselective catalytic oxidation reactions or certain cross-coupling applications. We wondered, therefore, if catalytic loadings of copper(II) salts might be used in these reactions by adding a secondary terminal oxidant to turn over the intermediate copper(I

• dioxygen for this purpose is frequently exploited to effect synthetically useful copper-catalyzed aerobic oxidation reactions [27][28]. However, the use of molecular oxygen as a terminal oxidant presents unique challenges in photoredox chemistry. Triplet dioxygen rapidly quenches the excited state of most

Metal-free C–H mercaptalization of benzothiazoles and benzoxazoles using 1,3-propanedithiol as thiol source

• Yan Xiao,
• Bing Jing,
• Xiaoxia Liu,
• Hongyu Xue and
• Yajun Liu

Beilstein J. Org. Chem. 2019, 15, 279–284, doi:10.3762/bjoc.15.24

• showed it served not only as a solvent but also as an oxidant. The developed reaction system required neither a metal catalyst nor a ligand. This simple method is expected to have potential application in both laboratory and industry. Representative examples of biologically active 2-mercaptobenzoxazoles

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• [2,3-c]dihydrocarbazoles 70 and [2,3-c]carbazoles 71 (Scheme 15) [91]. This process permitted the use of readily available and cheap AgOAc as the catalyst and oxidant, and DMF as the solvent. Notably, the product 70 was easily transformed into 71 in the presence of chloranil (1.4 equiv) at 120 °C under

• using AgF2 as both oxidant and fluorine atom source via the silver(II)-mediated ring-opening and fluorination of cyclopropanols 91 (Scheme 32) [112]. Through this method, a fluorine atom could easily be introduced in the β-position of a ketone. The mechanism is outlined in Scheme 32, the Ag-alkoxide

• ring-opening and difluoromethylthiolation of cyclopropanols 91 with PhSO2SCF2H 142 for the synthesis of difluoromethylthioethers 143 was reported by Shen and co-workers (Scheme 38) [118]. AgNO3 was utilized as catalyst, K2S2O8 as oxidant, and SDS (sodium dodecyl sulfate) as addictive in water. The SDS