Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• material 11 and dehalogenation was in parallel observed as competitive reaction pathway. Thus, mostly diiodobiselenophene 13 and 2,2’-biselenophene were isolated as main products. Independent reaction of deprotected diiodobiselenophene 13, which was alongside prepared from TMS-biselenophene 11 by

Gold-catalyzed ethylene cyclopropanation

• Silvia G. Rull,
• Andrea Olmos and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7

• ], electroreductive dehalogenation [7] and decarboxylation of diethyl 1,1-cyclopropyldicarboxylate [8]. Other methods include the transesterification of other alkyl cyclopropanecarboxylates [9] and the esterification with ethanol of the cyclopropanecarboxylic acid [10]. This product finds applications as lubricant

N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• become a precious class of organic molecules, not only due to their widespread use in medicinal chemistry [13] but also because of their fascinating electronic properties. Recently their use in photoredox catalysis allowed for the development of some novel transformations, namely dehalogenation [14] as

Pd-Catalyzed microwave-assisted synthesis of phosphonated 13α-estrones as potential OATP2B1, 17β-HSD1 and/or STS inhibitors

• Rebeka Jójárt,
• Szabolcs Pécsy,
• György Keglevich,
• Mihály Szécsi,
• Réka Rigó,
• Csilla Özvegy-Laczka,
• Gábor Kecskeméti and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 2838–2845, doi:10.3762/bjoc.14.262

• the yields of the C–P couplings. Reactions with catalyst precursor Pd(OAc)2 gave the desired phosphonate 8a in moderate yields (Table 1, entries 1–8). Starting from 2-iodo compound 1I, dehalogenation, an unwanted side reaction occurred, in particular, at elevated temperature (Table 1, entries 3, 4, 7

• , 8). Pd(PPh3)4, used as catalyst in the classical Hirao reaction [26], proved to be more efficient concerning the yields of the desired arylphosphonate (8a, Table 1, entries 9–16). K2CO3 as inorganic base seemed to be superior to organic Et3N (Table 1, entries 1–4, 9–12). The extent of dehalogenation

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• also described, with a focus on radical-involved reactions in terms of organic synthesis. Keywords: dehalogenation; electrolysis; green chemistry; heptamethyl cobyrinate; methyl transfer; 1,2-migration; photosensitizer; vitamin B12; Review 1. Introduction 1-1. Redox and coordination chemistry of B12

• to AB in the presence of GSH and iodoacetic acid in phosphoric acid–citric acid buffer at 37 °C, a safe and eco-friendly detoxification of inorganic arsenics was developed via methyl transfer reactions mediated by biomimetic vitamin B12. 4. Dehalogenation reactions “Dehalorespiration” is also a model

• of good catalysts for chemists because the anaerobic metabolism of microbes couples the dehalogenation of organic halides with energy conservation [85]. In some electron transport chains, reductive dehalogenases contain B12 derivatives as cofactors [86]. The reductive dehalogenase originating from

A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols

• Anna Czarnecka,
• Emilia Kowalska,
• Agnieszka Bodzioch,
• Joanna Skalik,
• Marek Koprowski,
• Krzysztof Owsianik and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2018, 14, 1229–1237, doi:10.3762/bjoc.14.105

• , ether cleavage and dehalogenation (I but not Cl and Br) are common, side reactions due to either the high acidity which is necessary to generate carbocationic species or due to the use of strongly reducing reaction conditions [28][29][30][46][47][48][49][50][51][52]. In this context, a serious challenge

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

The first Pd-catalyzed Buchwald–Hartwig aminations at C-2 or C-4 in the estrone series

• Ildikó Bacsa,
• Dávid Szemerédi,
• János Wölfling,
• Gyula Schneider,
• Lilla Fekete and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 998–1003, doi:10.3762/bjoc.14.85

• in low to high yields (Table 1, entries 1, 2, 4, 7–9) except when using Cs2CO3 as the base (Table 1, entries 6 and 10). In the latter cases only dehalogenation of the starting aryl halide was observed in around 20–60% yield. The use of KOt-Bu (Table 1, entries 2 and 8) or NaOt-Bu (Table 1, entries 4

• formation of compound 5, but in very low yields. The starting aryl halide 1 was mostly recovered, and neither dehalogenation nor C(sp2)–N coupling occurred. After finding the best set of reaction conditions (Table 1, entries 2 and 4), the temperature was lowered to 100 °C (Table 1, entries 3 and 5) in order

• to suppress the dehalogenation side reaction. The efficiency of the couplings was found to be similar to that observed at higher temperature with improved yields. Nevertheless, reaction with KOt-Bu (Table 1, entry 3) proved to be slightly more efficient. In order to compare the efficiency and

Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66

• , PR China 10.3762/bjoc.14.66 Abstract A mechanically-activated chemoselective Heck coupling for the synthesis of 3-vinylindazoles has been developed with the aid of catalytic amounts of TBAB and NaBr as both dehalogenation restrainer and grinding auxiliary. After tuning of the chemical conditions and

• highly efficient route for the synthesis of axitinib. Keywords: axitinib; ball-milling; dehalogenation; Heck reaction; indazoles; Introduction The palladium-catalyzed vinylation of alkenes in the presence of a base, known as the Heck reaction (Mizoroki–Heck reaction), is one of the most important

• dehalogenation of aryl bromides, wherever possible. Herein, 3-bromoindazoles were chosen as model substrates not only for their low activity and easy dehalogenation properties, but also for their potential applications in the synthesis of natural products and pharmaceuticals, such as gamendazole [31][32], YC-1

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• oxide Ce0.99Pd0.01O2–δ showed to be least efficient for the explored Suzuki–Miyaura couplings. Regarding the selectivity of the catalysts in the selected cross-coupling reactions, no bromoarene-deriving side products (dehalogenation product Ar’ and bromoarene homocoupling product Ar’Ar’) could be

Fluorescent nucleobase analogues for base–base FRET in nucleic acids: synthesis, photophysics and applications

• Mattias Bood,
• Sangamesh Sarangamath,
• Moa S. Wranne,
• Morten Grøtli and
• L. Marcus Wilhelmsson

Beilstein J. Org. Chem. 2018, 14, 114–129, doi:10.3762/bjoc.14.7

• or 2-aminophenol afforded compounds 5 and 6, respectively. Refluxing 5 with t-BuOK in EtOH generated 7 in 38% isolated yield. When 6 was treated with the same cyclization conditions as 5 only dehalogenation was observed. Compound 8 was obtained by first removing the acetyl protecting groups using

Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents

• Josef Jansa,
• Ramona Schmidt,
• Ashenafi Damtew Mamuye,
• Laura Castoldi,
• Alexander Roller,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2017, 13, 895–902, doi:10.3762/bjoc.13.90

• -pyridineboronic acid, respectively) in the course of a Suzuki cross-coupling procedure [27][28] under different reaction conditions (for instance Cs2CO3/DMF; Na2CO3/DMF; Cs2CO3/dioxane–H2O; Na2CO3/dioxane–H2O; Pd(PPh3)4) always led to dehalogenation and thus to the isolation of 2a as the main reaction product

• h reflux, [29]) (Scheme 4). The reaction of 3a with phenylmagnesium bromide under modified ‘Kumada’-conditions [30] (Scheme 4) once more gave 2a (dehalogenation) and biphenyl. Subjecting 3a and phenyllithium under the conditions of a ‘Feringa’-coupling [31] resulted in a complex mixture with 2a as

• coupling products 6a,b and 9a,b–11a,b in variable yields (19–87%). Firstly, the Pd(PPh3)4 was employed as the catalyst for the reaction of 3a to 9a but low conversion and considerable dehalogenation were observed. Utilization of Pd(dppf)Cl2 as catalyst in THF brought much better selectivity, because

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• both methods (34h) but, with the bromo counterpart, dehalogenation also occurs. 2-Cyanothiophene results in quantitative yield of thiophene 60 with both methods but cyanopyridines are not converted, probably due to the coordination abilities of the pyridine. Finally, decanenitrile is decyanated with

Flow carbonylation of sterically hindered ortho-substituted iodoarenes

• Carl J. Mallia,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1503–1511, doi:10.3762/bjoc.12.147

• dehalogenation pathway becomes dominant resulting in overall lower yields of the carbonylated product. In principle, increasing the carbon monoxide concentration (by increasing the carbon monoxide pressure) together with an increase in temperature, should promote the carbonylation. However, an increase in carbon

• yields obtained in batch when compared to the reactions conducted in flow, most probably arises from the fact that not enough carbon monoxide is being delivered to the reaction mixture. The dehalogenation pathway is then preferred yielding chlorobenzene as the main product. The second batch reaction set

• -dehalogenation pathway becomes preferred, giving 1,3-dimethoxybenzene as the main product, which was isolated in 31% yield in the case of 29 and 3-chlorotoluene in the case of 30 which was isolated in 52% yield (Scheme 4). To demonstrate the potential scalability of the reaction conditions, the synthesis of

A convenient route to symmetrically and unsymmetrically substituted 3,5-diaryl-2,4,6-trimethylpyridines via Suzuki–Miyaura cross-coupling reaction

• Dariusz Błachut,
• Joanna Szawkało and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2016, 12, 835–845, doi:10.3762/bjoc.12.82

• 3,4,5-triarylpyridines. Additionally, the dehalogenation of 68–71 may provide 3,5-diarylo-2,6-dimethylpyridines. These compounds can be regarded as "route specific markers" for amphetamine analogues synthesized by the Leuckart method. We choose 3-bromo-4-chloro-2,6-dimethyl-5-phenylpyridine (67) as a

An improved procedure for the preparation of Ru(bpz)₃(PF₆)₂ via a high-yielding synthesis of 2,2’-bipyrazine

• Danielle M. Schultz,
• James W. Sawicki and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2015, 11, 61–65, doi:10.3762/bjoc.11.9

• yields of bpz we were able to obtain resulted from a Pd-catalyzed procedure reported by Plé (Scheme 1) [31]. Using this protocol, we were able to obtain only 40% yield of the desired 2,2-bipyrazine ligand on milligram scale, accompanied by a significant degree of undesired reductive dehalogenation

Efficient routes toward the synthesis of the D-rhamno-trisaccharide related to the A-band polysaccharide of Pseudomonas aeruginosa

• Aritra Chaudhury,
• Sajal K. Maity and
• Rina Ghosh

Beilstein J. Org. Chem. 2014, 10, 1488–1494, doi:10.3762/bjoc.10.153

• thioglycosides directly. Moreover, the use of stoichiometric amounts of the toxic tin hydride for radical-based reductive dehalogenation as required by the above method appeared undesirable especially in the preparative stages where reactions have to be set up on a large scale. On the other hand, Kiefel’s method

Pd/C-catalyzed aerobic oxidative esterification of alcohols and aldehydes: a highly efficient microwave-assisted green protocol

• Marina Caporaso,
• Giancarlo Cravotto,
• Spyros Georgakopoulos,
• George Heropoulos,
• Katia Martina and
• Silvia Tagliapietra

Beilstein J. Org. Chem. 2014, 10, 1454–1461, doi:10.3762/bjoc.10.149

• selectivity were achieved in most cases, apart from 3,5-dimethoxybenzaldehyde and 4-chlorobenzaldehyde. Pd-catalyzed dehalogenation reaction of 4-chlorobenzaldehyde (120 °C for 1.5 h) gave methyl benzoate as main product besides traces of the desired product (detected by GC–MS analysis). Aiming to reduce this

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• light-mediated reductions such as reductive dehalogenation [47][48][49][50][51], reductive radical cyclization [52][53][54], reduction of activated ketones [49], and reduction of aromatic azides [55]. The third mode involves deprotonation of amine radical cation 2 to form α-amino radical 3, which is

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• fulvenes are produced as side products [25]. The formation of fulvene derivatives and other compounds containing five-membered rings has often been noted in this type of approach [26]. These cyclic products are formed by mechanisms involving carbene (generated during the dehalogenation step of the

trans-2-(2,5-Dimethoxy-4-iodophenyl)cyclopropylamine and trans-2-(2,5-dimethoxy-4-bromophenyl)cyclopropylamine as potent agonists for the 5-HT₂ receptor family

• Adam Pigott,
• Stewart Frescas,
• John D. McCorvy,
• Xi-Ping Huang,
• Bryan L. Roth and
• David E. Nichols

Beilstein J. Org. Chem. 2012, 8, 1705–1709, doi:10.3762/bjoc.8.194

• to the amine by a Curtius type rearrangement (Scheme 2). In our previous synthesis [2] we had employed an N-carbobenzoxy intermediate, followed by catalytic debenzylation over Pd(C); but those conditions would lead to dehalogenation in the present series, so we instead employed acid-catalyzed removal

Branching out at C-2 of septanosides. Synthesis of 2-deoxy-2-C-alkyl/aryl septanosides from a bromo-oxepine

• Supriya Dey and
• Narayanaswamy Jayaraman

Beilstein J. Org. Chem. 2012, 8, 522–527, doi:10.3762/bjoc.8.59

• increase the yields, although dehalogenation of 2 to oxepine was found to occur to a minor extent when the reaction time was increased to several days. 13C NMR spectra of 11 and 12 showed resonances for the newly formed C–C bond at 11: 108.4 ppm (C-2) and 95.8 ppm (C≡C-Ph); 12: 109.9 ppm (C-2) and 97.4 ppm

Continuous flow hydrogenation using polysilane-supported palladium/alumina hybrid catalysts

• Hidekazu Oyamada,
• Takeshi Naito and
• Shū Kobayashi

Beilstein J. Org. Chem. 2011, 7, 735–739, doi:10.3762/bjoc.7.83

• palladium/alumina (Pd/(PSi–Al2O3)) hybrid catalysts were developed. Our original Pd/(PSi–Al2O3) catalysts were used successfully in these systems and the hydrogenation of unsaturated C–C bonds and a nitro group, deprotection of a carbobenzyloxy (Cbz) group, and a dehalogenation reaction proceeded smoothly

• could also be carried out successfully in water (Scheme 4). The reduction of aqueous maleic acid proceeded quantitatively. Dehalogenation of p-chlorobenzoic acid in basic aqueous solution also proceeded smoothly and benzoic acid was obtained after acid treatment. In the case of p-chlorophenol, the

• ., the reduction of unsaturated C–C bonds and a nitro group, deprotection of a Cbz group, and a dehalogenation reaction, all proceeded smoothly. The catalysts could be used for a long time, with high activity being retained for at least 8 h under neat conditions. It is noted that in all cases no Pd

A two step synthesis of a key unit B precursor of cryptophycins by asymmetric hydrogenation

• Benedikt Sammet,
• Mathilde Brax and
• Norbert Sewald

Beilstein J. Org. Chem. 2011, 7, 243–245, doi:10.3762/bjoc.7.32

• reductive dehalogenation was observed to give rac-Boc-Tyr(Me)-OMe (rac-11) as reported for a similar case [16]. Therefore, ent-4 was synthesized analogously also using the commercially available enantiomeric catalyst ([(COD)Rh-(S,S)-Et-DuPhos]BF4). Conclusion A novel two step synthesis of the important

Reciprocal polyhedra and the Euler relationship: cage hydrocarbons, C_nH_n and closo-boranes [B_xH_x]²⁻

• Michael J. McGlinchey and
• Henning Hopf

Beilstein J. Org. Chem. 2011, 7, 222–233, doi:10.3762/bjoc.7.30

• by sodium- or magnesium-mediated dehalogenation of the appropriate REX3 precursor, where R is a very bulky alkyl or aryl group, and X is chlorine or bromine [38][39]. The hexatellurium cation, [Te6]4+, is also trigonal prismatic [40][41]. Similarly, the inorganic cubane analogues R8E8, where E = Si