Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• wide redox window (E = 3.22 eV, +1.65 V/−1.77 V), can be exploited as photocatalysts for various transformations, including the reductive dehalogenation of benzylic halides (Scheme 7) [52]. In this protocol, the excited state photocatalyst OD18 can generate C(sp3) radicals through the reductive

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• [28]. The authors reported that meso-5,10,15,20-tetraphenyl-21-monothiaporphyrin (STPP), combined with Hantzsch ester (HEH) and N,N-diisopropylethylamine (DIPEA), promoted the dehalogenation of α-functionalized carbonyl-containing compounds under red light (λ > 645 nm) in a reductive quenching. DIPEA

• and TPFPP. Photoarylation of isopropenyl acetate A) Comparison between batch and continuous-flow approaches and B) end-to-end protocol. Dehalogenation induced by red light using thiaporphyrin (STPP). Applications of NiTPP as both photoreductant and photooxidant. Proposed mechanism for obtaining

Towards the total synthesis of chondrochloren A: synthesis of the (Z)-enamide fragment

• Jan Geldsetzer and
• Markus Kalesse

Beilstein J. Org. Chem. 2020, 16, 670–673, doi:10.3762/bjoc.16.64

• provided alcohol 11 in an excellent yield which was subjected to aminolysis to provide amide 3 in seven steps and an overall yield of 16% [16][17][18][19][20]. Synthesis of (Z)-bromide 4 For the synthesis of (Z)-bromide 4 we chose a palladium-catalyzed, stereoselective dehalogenation as the key step

• ][19][20], whereas the (Z)-bromide 4 can be generated in a four-step sequence with a 39% overall yield, including a palladium-catalyzed, stereoselective dehalogenation [21][22][23][24][25]. Retrosynthetic analysis of chondrochlorene A (1). Synthesis of amide 3 [16][17][18][19][20]. TIPDSCl2 = 1,3

• -dichloro-1,1,3,3-tetraisopropyldisiloxane, TBSOTf = tert-butyldimethylsilyl trifluoromethanesulfonate, proton sponge = 1,8-bis(N,N-dimethylamino)naphthalene. Synthesis of (Z)-bromide 4 using a palladium-catalyzed, stereoselective dehalogenation [21][22][23][24]. TBSOTf = tert-butyldimethylsilyl

Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas

• Zhenghui Liu,
• Peng Wang,
• Zhenzhong Yan,
• Suqing Chen,
• Dongkun Yu,
• Xinhui Zhao and
• Tiancheng Mu

Beilstein J. Org. Chem. 2020, 16, 645–656, doi:10.3762/bjoc.16.61

• most suitable Rh salt for the conversion. In addition, in spite of low yields, Rh species with valence states of 0, +1, +2 or +3 all promoted the reaction at least to some extent. It is worth noting that as a good leaving group, I− tends to leave in an alkaline environment, and dehalogenation and

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• nitriles [21], carbonyl or imine species [22], iodonium or diazonium salts [23], or halide species [24]. The formation of radicals from halide species by photoredox catalysis has been widely studied. It has been applied as a mild method for the dehalogenation of several compounds [25][26][27]. In the light

• generation of hydrated electrons and applied that for the dehalogenation of monochloroacetic acid [32][33]. However, to the best of our knowledge, a photoredox catalyzed application of monochloroacetic acid without using a sacrificial electron donor is not known. Interestingly, monochloroacetic acid also

Functionalization of the imidazo[1,2-a]pyridine ring in α-phosphonoacrylates and α-phosphonopropionates via microwave-assisted Mizoroki–Heck reaction

• Damian Kusy,
• Agata Wojciechowska,
• Joanna Małolepsza and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 15–21, doi:10.3762/bjoc.16.3

• analyses. Compound 4 is the product of dehalogenation reaction, which is known to be catalyzed by palladium [1][18]. The second side product, compound 5, is probably the result of the cleavage of the C–CN bond in the solvent (propionitrile or acetonitrile), followed by a palladium-catalyzed cyanation of

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• dehalogenation side-product. Finally, a Knoevenagel condensation in the presence of cyanoacetic acid and piperidine is performed to lead to the targeted compounds BOD-TTPA-alk and BOD-TTPA. 3. Optical properties The optical properties of compounds BOD-TTPA-alk and BOD-TTPA were first evaluated in diluted (≈10−6

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