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

• mediated by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The CNH was then applied as photocatalyst in the photoinduced sulfonation of styrene with p-methylbenzenesulfinic acid. The corresponding β-ketosulfone was obtained in 94% yield. However, the yield

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

• in equilibrium with a spectator bis-nitrene species 19 and proceeded through styrene 20 insertion, followed by ring closure and release of the aziridine. Interestingly, this otherwise classical mechanism is enabled by the accessibility of doublet and quadruplet states close in energy and this

• -closure (Scheme 12). A wide range of substrates including diverse mono-, di-, and trisubstituted styrene derivatives (21a,i,h, 26a–d and 27a–i) substrates as well as unactivated or deactivated tri- and tetrasubstituted scaffolds (21j,n,o, 26e–g and 27j–o) were efficiently converted. Conclusion The use of

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

• addition (e.g., 351, 352). It was shown that the presence of a heteroatom plays a crucial role due to the otherwise non-selective, facile addition of Cu-Bpin to alkenes (Scheme 56) [103]. Based on previous studies on asymmetric 3-component carboboration of styrene derivatives [104] and 1,3-dienes [105

• electrophiles, such as N-cyanosulfonamides, leading to 1,2 or 4,3-borocyanation in a regiospecific fashion from borocuprative intermediates, respectively [111]. Extending earlier efforts from the Montgomery group for Cu-catalyzed cascade diborylation/ortho-cyanations of terminal allenes [112] and styrene

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

• functional group tolerance of the method. Further, the authors carried out an interesting mechanistic study: From their observations, they ruled out a possible radical chain process (path I) because the reaction with styrene cannot be initiated by heating or through a radical initiator. In addition, the

• , and no significant selectivity was observed when nonsymmetrical iodonium salts were reacted under the optimized reaction conditions. Later in 2015, Greaney and co-workers described the copper-photocatalyzed azidation of styrene olefins and the concomitant introduction of a nucleophile (Scheme 9) [26

• irradiation in MeOH to perform the trifluoromethyl methoxylation of styrene derivatives. The methodology was applied to a broad range of styrene derivatives, showing a good functional group tolerance. Noteworthy, α-, β-, and α,β-substituted styrenes were readily functionalized in good to excellent yields. To

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

• traditional reactivity of this compound. Here, we investigated the possibility of applying monochloroacetic acid as a substrate for photoredox catalysis with styrene to directly produce γ-phenyl-γ-butyrolactone. Instead of using nucleophilic substitution, we cleaved the carbon chlorine bond by single-electron

• monochloroacetic acid. Based on these data, we concluded that the visible-light-promoted reductive photoredox C–C bond coupling reaction with monochloroacetic acid should be possible. As such, we chose fac-[Ir(ppy)3] and [Cu(dap)2]Cl for the photoredox reaction between monochloroacetic acid and styrene in

• trapping the radical by replacing styrene with TEMPO (2,2,6,6-tetramethylpiperidin-1-yl)oxyl). However, GC–MS analysis indicated full conversion of TEMPO to the adduct resulting from a radical coupling between a cyanomethanide radical and TEMPO (Scheme 3) for the highly reducing [Ir(ppy)3] (−1.73 V vs SCE

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

• observed in up to 30%. The configuration of the newly formed double bond was determined based on the vicinal coupling constant 3JHH between CH=CH [(E)-isomer: 3JHH = 16.5 Hz, (Z)-isomer: 3JHH = 12.1 Hz]. We also showed that the method is applicable to styrene and phthalylallylamine, although, for these

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

• improvements of these methods have recently been achieved by Moeller et al. who designed a photovoltaic apparatus for the efficient Sharpless dihydroxylation of styrene in up to 94% enantiomeric excess [65]. Tanaka and co-workers explored the catalytic applicability of optically active Mn-salen complex 72

• potentiostatic electrolysis, styrene derivatives 143 could be transformed into their asymmetric epoxides 144 via direct electrochemical regeneration of FADH2. The authors claimed that this method is superior with respect to substitution of the complex native regeneration cycle, which consists of three enzymes

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

• obtained products with stable E-configuration through a SET process. In 2017, Loh and co-workers [141] introduced a Cu(I/II)-catalyzed Cvinyl–H trifluoromethylation of a variety of styrene derivatives. This process was achieved by using 1-methylimidazole (NMI) as ligand and tetrabutylammonium iodide (TBAI

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• a microwave reaction vessel 3a (1.01 g, 5.00 mmol, 1.00 equiv) was mixed with styrene (651 mg, 6.25 mmol, 1.25 equiv), tris(o-tolyl)phosphine (61 mg, 0.20 mmol, 0.04 equiv), Pd2(dba)3 (92 mg, 0.10 mmol, 0.02 equiv) and NEt3 (863 ΜL, 0.63 g, 6.25 mmol, 1.25 equiv) and suspended in anhydrous DMF (6 mL

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• heptafulvenes [18][19][20][21][26][28][227] also participating in such reactions. However, Nair et al. reported that during cycloadditions of 8,8-dicyanoheptafulvene and styrene derivatives (Scheme 16), [8 + 2] and [4 + 2] adducts formed in approximately 1:1 ratio for each styrene variant tested, thus lowering

• and styrene derivatives to afford [8 + 2] and [4 + 2] cycloadducts in a 1:1 ratio [227]. Reaction of 6-aminofulvene and maleic anhydride, showing observed [6 + 2] cycloaddition; the [4 + 2] cycloaddition is not observed [114]. Schemes for Diels–Alder cycloadditions in dynamic combinatorial chemistry

Friedel–Crafts approach to the one-pot synthesis of methoxy-substituted thioxanthylium salts

• Kenta Tanaka,
• Yuta Tanaka,
• Mami Kishimoto,
• Yujiro Hoshino and
• Kiyoshi Honda

Beilstein J. Org. Chem. 2019, 15, 2105–2112, doi:10.3762/bjoc.15.208

• green light irradiation [24][25]. In the course of this study, we found that these thioxanthylium photocatalysts efficiently oxidized styrene derivatives such as trans-anethole, and promoted radical cation Diels–Alder reactions. Based on the background mentioned above, in order to expand the utility 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

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• ; cross metathesis; Hoveyda–Grubbs catalyst; olefin metathesis; RCM; ring-closing metathesis; ring-opening cross metathesis; ROCM; ruthenium metathesis catalyst; styrene; 2-vinylbenzylamine; Introduction Ruthenium-catalysed olefin metathesis reactions have been playing an important role in various fields

• way in lower yields [32]. The third part of this study was devoted to the demonstration of catalytic properties of metallo-complexes 11 in “standard” metathesis reactions (Scheme 6, Table 3). As a model substrate we chose easily available alkenes and dienes, such as i) styrene (12) and allylbenzene

• (14) for CM reactions, ii) diethyl diallylmalonate (17) and diallyltosylamide (19) for RCM reactions, iii) norbornene (21) and styrene/hex-1-ene for ROCM metathesis reactions. This selection of model subtests for metathesis is also explained by the possibility to control the course of metathesis and

Synthesis of the aglycon of scorzodihydrostilbenes B and D

• Katja Weimann and
• Manfred Braun

Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56

• particularly attractive as it leads in an atom-economic manner directly to the carbon skeleton of scorzodihydrostilbenes, starting from suitably substituted acetophenone and styrene derivatives. Furthermore, Murai’s protocol offers another advantage: the regioselective formation of the anti-Markovnikov product

• acetate. The combined organic layers were washed with brine, dried with sodium sulfate and concentrated under reduced pressure. The crude product was purified by column chromatography (ethyl acetate/n-hexane, 1:9) to give 2.01 g (61%) of styrene 7a as a colorless liquid. The spectroscopic data agree with

• those described in the literature [22]. General procedure for the synthesis of dihydrostilbenes 8: In a glove-box under argon atmosphere, a 20 mL overpressure tube was charged with ketone 6 (4.0 mmol), styrene 7 (8.0 mmol), [Ru(p-cymene)Cl2]2 (62.0 mg, 0.1 mmol), P(4-CF3C6H4)3 (190 mg, 0.6 mmol), and

Low-budget 3D-printed equipment for continuous flow reactions

• Jochen M. Neumaier,
• Amiera Madani,
• Thomas Klein and
• Thomas Ziegler

Beilstein J. Org. Chem. 2019, 15, 558–566, doi:10.3762/bjoc.15.50

• well [29]. Although 3D printing of reaction devices is a growing field in the last years, there are only a few examples of organic reactions with FDM-printed reactors [7]. Reactors made of materials like PLA, ABS (acrylonitrile butadiene styrene) or HIPS (high-impact polystyrene) are described 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

• we have proposed for photocatalytic oxyamination is outlined in Figure 1c. Photoinduced one-electron oxidation of an appropriately electron-rich styrene 1 results in the formation of a radical cation 1•+ that is susceptible to attack by various heteroatomic nucleophiles, including carbamates [21][22

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• -substituted vinylsilanes with Grubbs catalyst of first or second generation (A), the active methylene complex B and the corresponding (E)-1-phenyl-2-(silyl)ethene are formed. The methylene complex B in the presence of styrene undergoes metathetic conversion to benzylidene complex A and ethene. When dichloro

• -substituted vinylsilanes are used, the pathway shown in Scheme 1b is also possible. Metathesis of dichloro-substituted vinylsilanes with Grubbs catalyst A leads to styrene and (silyl)methylidene complex C. Formation of (silyl)methylidene complex C has not been confirmed by spectroscopic methods. The reaction

• allyltrimethoxysilane, ethyl undec-10-enylate, oct-7-enyltrimethoxysilane, 5-bromopentene, pent-4-en-1-ol) and styrene. Moreover, the catalytic activity of the first generation Grubbs’ catalyst (Ru-1) was demonstrated in CM of OVS with pent-4-en-1-ol and 5-bromopentene. It has been found that terminal alkenes undergo

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• preparing telechelics uses a symmetrical difunctional olefin compound as a chain-transfer agent (CTA). This was applied for the synthesis of styrene (S)–isoprene (I)–butadiene (B) multiblock copolymers by combining ROMP with nitroxide-mediated polymerization (NMP) [56]. A perfectly regioregular α,ω

• -telechelic poly(1,4-butadiene) bearing alkoxyamine termini was obtained by ROMP of trans,trans,cis-1,5,9-cyclododecatriene in the presence of a symmetric acyclic olefin CTA (Scheme 2). This telechelic polybutadiene was used as the macroinitiator for the NMP of styrene and diene monomers to yield unimodal SBS

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

• Ered(S/S−·) in the range of −2.2 to −2.3 V [23][24], α- and β-methylstyrene (13a and 13b) have an Ered(S/S−·) of −2.5 to −2.7 V [25], and styrene (14) an Ered(S/S−·) of −2.6 V (Figure 1) [25][26]. For non-aromatic, alkylated olefins, like 1-methylcyclohex-1-ene (15), the reduction potentials are

• reduction of α-methylstyrene (13a) as a less activated styrene that could not be addressed before. After optimization, the photoredox catalytic addition of methanol proceeded in quantitative yield within 20 h without any further additive, like triethylamine as electron shuttle. We could speed up the

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• catalysts 61, 64, 65, 67 and 68 (Figure 16) were also investigated in the model asymmetric ring-opening cross metathesis (AROCM) of cis-5-norbornene-endo-2,3-dicarboxylic anhydride (75) with styrene (Scheme 8, Table 3) [32]. In this reaction complex 68 showed the highest selectivity for the formation of the

• the AROCM of a variety of norbornene derivatives with styrene. While isolated yields were generally excellent, enantiomeric excesses were poor. The effect of a dangling amine tether incorporated into the NHC ligand on the catalytic efficiency of ruthenium benzylidene complexes was examined by Fryzuk

• excellent enantioselectivity and E-selectivity. In the AROCM of 75 with styrene (Scheme 8, reaction performed at −10 °C using 5 equiv styrene and 1 mol % of the catalyst), complex 204 gave the desired product 76 in >98% conversion, 93% ee and E/Z ratio > 30:1. Pursuing on this concept, the same group

Cross metathesis-mediated synthesis of hydroxamic acid derivatives

• Shital Kumar Chattopadhyay,
• Subhankar Ghosh and
• Suman Sil

Beilstein J. Org. Chem. 2018, 14, 3070–3075, doi:10.3762/bjoc.14.285

• 6d–f, respectively. Considerable isomerization (1:1 by 1H NMR) of the CM-product 6d to the corresponding styrene derivative was noticed when HG-II was used in place of G-II. 6e behaved similarly. Reaction with the styrene derivative 4g resulted in low conversion to the CM product 6g (57%). Styrene

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• produced to initiate the polymerization. By formation of radicals, the polymerization of C=C functions such as (meth)acrylates or styrene can be initiated. With cations or acids as initiating species, epoxy monomers can be polymerized. Both types of polymerization are widely used both in academic and

A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts

• Daniel S. Müller,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279

• norbornadiene was also investigated by Hoveyda [16]. A highly syndiotactic polymer was obtained by fine tuning of the steric and electronic characteristics of the catalyst (not depicted in this review) [16]. ROCM reactions of norbornene (1) with styrene (5) could be carried out with only one mole percent of

• styrene 32 the protonation and loss of the catechothiolate ligand by Brønsted acid 34 is a faster process leading to catalyst degradation. It should be noted that stereoretentive CM and RCM with (E)-2-butene (E-25) as capping reagent were also reported, however, these reactions required a significantly

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• modification of the first coordination sphere by adding an N-heterocyclic carbene (NHC) ligand and a chelating styrene to the so-called Grubbs 1st generation catalyst, the relatively air- and moisture-stable Grubbs–Hoveyda type (GH-type) catalysts were obtained [7]. These catalysts do not only show stability

• mutant formed the starting variant for the next iterative round. As screening substrate, the pre-fluorescent styrene derivative 3 was used. Following RCM, the fluorescent molecule umbelliferone (4) was generated. In total, five rounds of directed evolution were performed, yielding the mutant

• [52][53], and hydrogen evolution [54]. Further, Lewis et al. employed the NB scaffold for epoxidation of styrene and other olefins [55]. In all studies, the catalyst incorporated into the NB scaffold showed increased activity as compared to the protein-free catalyst under similar conditions

Synthesis of unnatural α-amino esters using ethyl nitroacetate and condensation or cycloaddition reactions

• Glwadys Gagnot,
• Vincent Hervin,
• Eloi P. Coutant,
• Sarah Desmons,
• Racha Baatallah,
• Victor Monnot and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2846–2852, doi:10.3762/bjoc.14.263

• [21] between two equivalents of ethyl nitroacetate (4) and styrene (15), gave the isoxazoline 16 in a 72% yield as a latent α-amino ester [22][23][24]. From this compound, a reductive cleavage of the isoxazoline ring was initiated using palladium over charcoal and a large excess of ammonium formate in