Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• indolinonaphthoxazoles. Herein, we present the synthesis of, and investigation on the conjugates 3a and 3b, as well as mechanistic studies on the metal ion-induced formation of the derivatives 4a and 4b, along with the pertinent spectroscopic data of the products. Results and Discussion Synthesis The spirooxazine

Copper catalysis with redox-active ligands

• Agnideep Das,
• Yufeng Ren,
• Cheriehan Hessin and
• Marine Desage-El Murr

Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77

• to benzoxepines and 2,2’-biphenols through catalyst control (Scheme 5, top) [20]. Extensive mechanistic studies evidenced a biomimetic pathway involving a key CuII-semiquinone intermediate in which the substrate becomes activated as a redox-active ligand (Scheme 5, bottom) [21]. This radical CuII

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• irradiation, supporting the other two pathways. Also, mechanistic studies by Cui et al. showed that the energy levels of the reactions (1) and (2) in Scheme 5 were closely tied, so distinguishing them is not always trivial [32]. The triplet state quenching of 8 and related compounds, such as aryl ketones, has

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• more and more dominant role as the catalysis of the 3-phospholene oxide (1) 2-phospholene oxide (4) rearrangement, which explains the change in the reaction rate in the kinetic experiments. Mechanistic studies of the isomerization of 3-phospholene oxides 1 under acidic conditions The isomerization of 3

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• featuring a 1,4-borylation of α,β-unsaturated compounds 405 was reported by Hosomi in the presence of Cu(OTf)2·C6H6/(t-Bu)3P in DMF. No reaction occurred using (CuOTf)2·C6H6 in the absence of (t-Bu)3P. Mechanistic studies showed that the coordination of phosphorus(III) to Cu(I) accelerated the reaction, as

• an appropriate electrophile led to C–C bond formation, ultimately delivering chiral tertiary alcohols. Mechanistic studies and DFT calculations showed that an in situ-formed borylcopper(I) species is responsible for the 1,2-addition (Scheme 73) [136]. C,O-Diboration of ketones 464 was explored using

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• isolated in moderate to good yields. Using the more reactive allyl sulfone, a panel of symmetrical diaryliodonium salts was reacted, giving the products in good yields. The authors conducted some mechanistic studies and suggested a plausible catalytic cycle involving [Cu(I)]/[Cu(I)]*/[Cu(II)] species. The

• conducted mechanistic studies and demonstrated the role of [Cu(dap)2]Cl as a precatalyst since the catalytically active species was a [Cu(II)] complex. To explain the formation of the product, the authors suggested that after excitation, the [Cu(I)] catalyst is oxidized to a [Cu(II)] species along with the

• , probably due to their intrinsic reduction potential. Interestingly, the bromide substrate derived from menthol was readily reduced in an excellent 74% isolated yield. The authors conducted some mechanistic studies (including cyclic voltammetry and Stern–Volmer quenching experiments, for instance), and

Room-temperature Pd/Ag direct arylation enabled by a radical pathway

• Amy L. Mayhugh and
• Christine K. Luscombe

Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36

• paper, we investigated the mechanism of room-temperature direct arylation and DArP by extending the method reported by Larrosa to synthesize a conjugated polymer, polyindole (PIn). Small molecule mechanistic studies were undertaken that will help future development of mild, efficient DArP conditions

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• sulfonylethanone oxime derivatives were less reactive than the PNP one [10]. Due to the similarity in DNA photocleavage by p-pyridine amidoxime, ethanome oxime and aldoxime carbamoyl derivatives, mechanistic studies were performed for two active compounds from the series of amidoximes and aldoximes, 12 and 26

• derivatives, of both amidoxime, ethanone oxime and aldoxime derivatives showed, similarly, significant DNA photocleavage. Mechanistic studies on DNA photocleavage showed that these “synthetic nucleases” act independently of oxygen and pH. As photobase generators, upon the homolysis of their N–O bond, oxime

• 32.3% of the initial EB–DNA fluorescence intensity for 11 and 31.5% for 12). DNA photocleavage of amidoxime carbamates at a concentration of 500 μM and mechanistic studies of aldoxime carbamate 26. Gel electrophoreses pictures. For (A) and (B) wells 1 and 2 represent DNA in dark and DNA UV irradiated

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• ]. From mechanistic studies it can be inferred that the photoredox catalysis process is independent from the C–H activation process. They also successfully demonstrated the importance of a photoredox catalysts in the generation of superoxide radicals. On the other hand, recently, Xiong and co-workers

• competent organic photoredox catalyst 9,10-dihydroacridine (1) under mild conditions at room temperature [128]. As usual, no reaction was observed without photoredox catalyst 1 or LED light. Mechanistic studies showed that the reaction proceeded via the generation of an aryl radical. As such, a list of

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

• Abhijit Paul,
• Debnath Chatterjee,
• Srirupa Banerjee and
• Somnath Yadav

Beilstein J. Org. Chem. 2020, 16, 140–148, doi:10.3762/bjoc.16.16

• . Mechanistic studies have unambiguously proven the heterogeneous nature of the catalysis. The ability of the nanocatalyst to activate the C–H bond is due to the presence of minimal stabilising groups on its surface. Studies of the surface morphology of the catalyst have revealed the presence of surface oxides

Potent hemithioindigo-based antimitotics photocontrol the microtubule cytoskeleton in cellulo

• Alexander Sailer,
• Franziska Ermer,
• Yvonne Kraus,
• Rebekkah Bingham,
• Ferdinand H. Lutter,
• Julia Ahlfeld and
• Oliver Thorn-Seshold

Beilstein J. Org. Chem. 2020, 16, 125–134, doi:10.3762/bjoc.16.14

• azobenzenes or styrylbenzothiazoles) is desirable, in particular for cell-free mechanistic studies [33]. More broadly, this work also shows that the HTI scaffold robustly enables the photoswitchable use of resonance-capable substituents that can establish high-affinity interactions (such as para-hydroxy

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

• Katarzyna Włodarczyk,
• Piotr Borowski and
• Marek Stankevič

Beilstein J. Org. Chem. 2020, 16, 88–105, doi:10.3762/bjoc.16.11

• control experiments and DFT calculations. Keywords: Brønsted and Lewis acids; DFT; mechanistic studies; rearrangement; stereochemistry; sulfur atom migration; Introduction Among all organic reactions, rearrangements are an exciting class of transformations where unusual or even unexpected products can

Construction of trisubstituted chromone skeletons carrying electron-withdrawing groups via PhIO-mediated dehydrogenation and its application to the synthesis of frutinone A

• Qiao Li,
• Chen Zhuang,
• Donghua Wang,
• Wei Zhang,
• Rongxuan Jia,
• Fengxia Sun,
• Yilin Zhang and
• Yunfei Du

Beilstein J. Org. Chem. 2019, 15, 2958–2965, doi:10.3762/bjoc.15.291

• yields are given. Control experiments for mechanistic studies. Proposed reaction mechanism. Application of the reported method to the synthesis of frutinone A. Optimization of reaction conditions.a Supporting Information Supporting Information File 586: Synthetic details and compound characterization

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

• and his group developed an electrochemical strategy for the asymmetric alkylation of 2-acylimidazole derivatives 94 with substituted para-methylphenols 95 using Ni(OAc)2 as a Lewis acid catalyst in presence of chiral diamine ligand 96 (Scheme 34) [71]. Based on their detailed mechanistic studies, the

AgNTf₂-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives

• Ziping Cao,
• Jiekun Zhu,
• Li Liu,
• Yuanling Pang,
• Laijin Tian,
• Xuejun Sun and
• Xin Meng

Beilstein J. Org. Chem. 2019, 15, 2623–2630, doi:10.3762/bjoc.15.255

• carbene pathway presumed by mechanistic studies and theoretical calculations. Following our ongoing interest in the alkyne chemistry [36][37][38], we recently envisaged that the reaction of ynamides with isoxazoles could proceed under silver catalysis conditions, involving the generation of α-imino silver

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

• (Scheme 60). Also, mechanistic studies, a radical clock experiment, revealed the intermediacy of −Cu(CF3)3Me, which undergoes reductive elimination and subsequent oxidation to give the active species Cu(CF3)2. Meanwhile, aliphatic carboxylic acids give the corresponding alkyl radicals via Ag(II)-mediated

• ) as an additive (Scheme 78). Mechanistic studies revealed that this reaction probably proceeds through a radical pathway. Copper-catalyzed trifluoromethylation of arenes and heteroarenes: In 2013, Xi et al. [142] reported a CuCl-catalyzed direct trifluoromethylation of sp2 C–H bonds with Togni reagent

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs₂CO₃-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

• Mio Matsumura,
• Yuki Kitamura,
• Arisa Yamauchi,
• Yoshitaka Kanazawa,
• Yuki Murata,
• Tadashi Hyodo,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

• parent tetracyclic compound 2a features a nearly coplanar ring. Absorption spectroscopy data revealed the λmax was dependent on the number of rings. Detailed mechanistic studies of this cyclization and the applications of this reaction to other heterocycles are currently underway in our laboratory

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

Switchable selectivity in Pd-catalyzed [3 + 2] annulations of γ-oxy-2-cycloalkenones with 3-oxoglutarates: C–C/C–C vs C–C/O–C bond formation

• Yang Liu,
• Julie Oble and
• Giovanni Poli

Beilstein J. Org. Chem. 2019, 15, 1107–1115, doi:10.3762/bjoc.15.107

• met always with failure. Mechanistic studies Considering that the change of reaction outcome of the dimethyl 3-oxoglutarate (1a) only depends on the variation of temperature in DMSO, we surmised that in the above annulation the C–C/O–C adducts 4 are the kinetic products, while the C–C/C–C adducts 5

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

• . Results and Discussion We have recently reported a system of simple combinations of an iodine (III, V, or VII) oxide with a catalytic amount of chloride for the direct oxygenation of methane to its methyl ester [49][50]. Mechanistic studies of this system have indicated that these chloride-iodate

• benzylic C–H bonds. Moreover, substrates with tertiary benzylic C–H bonds were unreactive despite having a weaker C–H bond strength. Preliminary mechanistic studies indicate that the reaction occurs via H-atom abstraction mediated by the PINO radical followed by trapping with molecular iodine. The formed

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• ]. Mechanistic studies of Na2S2O4 reduction of pyridinium salts, including NR+ derivatives, suggest that this reaction proceeds through the formation of sulfinic acid adducts (1,4-dihydro-4-pyridine sulfinates) I. This adduct is generated from the completely regioselective attack of the dithionite ion on the 4

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• from Vikse et al. [53]. Mechanistic studies: 1H NMR experiments 1H NMR experiments of reaction R1 (Scheme 3) show the temporal progress of the reaction which is easily tracked by the concentrations of substrate 2, acetone and product 3 (Figure 2, and Figures S1 and S2 in Supporting Information File 1

• for the Diels–Alder reaction to proceed. Mechanistic studies: ESIMS experiments As ESIMS has a lower limit of detection than NMR, we also studied the proceeding reaction with ESIMS. In its simplest version, i.e., without charge-tagged components (R1, Scheme 3) and at a low concentration (0.005 mmol/mL

Copper(I)-catalyzed tandem reaction: synthesis of 1,4-disubstituted 1,2,3-triazoles from alkyl diacyl peroxides, azidotrimethylsilane, and alkynes

• Muhammad Israr,
• Changqing Ye,
• Munira Taj Muhammad,
• Yajun Li and
• Hongli Bao

Beilstein J. Org. Chem. 2018, 14, 2916–2922, doi:10.3762/bjoc.14.270

• %), DCM (2 mL), 50 °C, 10 h. Yields of the isolated products are given. Preliminary mechanistic studies. Plausible reaction mechanism. Optimization of the reaction conditionsa. Supporting Information Supporting Information File 280: Detailed experimental procedures and characterization data for all new

Efficient catalytic alkyne metathesis with a fluoroalkoxy-supported ditungsten(III) complex

• Henrike Ehrhorn,
• Janin Schlösser,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2018, 14, 2425–2434, doi:10.3762/bjoc.14.220

• for W2F3·(NHMe2), W2F3 and WPhF3. Acknowledgements H.E. wishes to thank the Fonds der Chemischen Industrie (FCI) for a Chemiefonds Fellowship. This work was funded by the Deutsche Forschungsgemeinschaft (DFG) through project TA 189/12−1 (“Mechanistic studies on the catalytic metathesis of internal

The enzymes of microbial nicotine metabolism

• Paul F. Fitzpatrick

Beilstein J. Org. Chem. 2018, 14, 2295–2307, doi:10.3762/bjoc.14.204

• catalyzes oxidation of the C2–N bond, not the C2–C3 bond, in line with the typical reactions catalyzed by members of the MAO family [18]. In addition, mutagenesis of His187, Glu300, and Tyr407 established that they are not involved in catalysis. Subsequent mechanistic studies of the reaction using pH and

• /vanillyl oxidase family catalyze an extremely diverse set of reactions, including oxidation of non-aromatic alcohols and amines [30], and DALI [31] identifies several enzymes catalyzing oxidation of nonaromatic substrates as having similar structures to DHNO. Indeed, recent mechanistic studies of DHNO are

• -hydroxypseudooxynicotine dehydrogenase being a molybdopterin protein, and the recombinant Kdhc (also known as KdhL) contains Mo and a cofactor derived from CTP [33]. While no mechanistic studies of the enzyme have been reported, its mechanism is likely to resemble those of nicotine dehydrogenase (Scheme 2) and other