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

• photoinduced cycloaddition of carbon dioxide with epoxides [56]. The synthesis of a 3D supramolecular framework, [{Mn(TCPP)0.5(H2O)}·2H2O]n, where Mn(TCPP) is Mn(II) meso-tetrakis(4-carboxyphenyl)porphyrin, was derived from MnCl2·6H2O and TCPP. The cycloaddition product, a cyclic carbonate, was obtained from

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• (NDA) and naphthalenemonoimide (NMI) moieties. The double C–H bond activation initially used palladium(II) acetate in acetic acid as the coupling system. The subsequent screening revealed, however, that a catalytic coupling could be also achieved in the presence of silver(I) carbonate as the

• that the coupling and α-oxygenation can also be achieved with 1 equiv of Pd(OAc)2 in the presence of 2 equiv of silver carbonate. Nevertheless, Ag2CO3 oxidation provided lower yields and the efficiency of this variant was dramatically diminished when the loading of palladium(II) acetate was decreased

Photocatalytic deaminative benzylation and alkylation of tetrahydroisoquinolines with N-alkylpyrydinium salts

• David Schönbauer,
• Carlo Sambiagio,
• Timothy Noël and
• Michael Schnürch

Beilstein J. Org. Chem. 2020, 16, 809–817, doi:10.3762/bjoc.16.74

• ). Eosin Y was inefficient under these conditions (Table 1, entry 20). Since [Ru(bpy)3]Cl2 is significantly cheaper than the iridium catalyst, the former was used in further reactions. Regarding the addition of different bases, the yield remained unchanged, when lutidine was added. Potassium carbonate and

Reaction of indoles with aromatic fluoromethyl ketones: an efficient synthesis of trifluoromethyl(indolyl)phenylmethanols using K₂CO₃/n-Bu₄PBr in water

• Thanigaimalai Pillaiyar,
• Masoud Sedaghati and
• Gregor Schnakenburg

Beilstein J. Org. Chem. 2020, 16, 778–790, doi:10.3762/bjoc.16.71

• (TMG), also known as Barton's base, in excellent yields (Figure 2A) [24]. Recently, Liu and co-workers reported this reaction in the presence of cesium carbonate in acetonitrile (Figure 2B) [25]. Dinuclear zinc [26], cinchonidine catalysts, and solvent-free conditions [27] have been also utilized for

• of potassium carbonate and tetrabutylphophonium bromide, which mediate the reaction in water through the formation of the interface between organic and aqueous phases. The advantageous of this reaction include high yields, no column chromatography, broad substrate scope, multiscale synthesis, and

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

• ]. 2.1 Formation and reactions of allylic C–B bonds The synthesis of α-stereogenic allylboronates was reported by Ito in 2005 using CuO-t-Bu/Xantphos (CuCl and KO-t-Bu form CuO-t-Bu in situ as the active catalyst precursor), an enantioenriched allyl carbonate, and B2pin2 (310; Scheme 50) [93]. Both (Z

• ] with C(sp2)-containing electrophiles such as tert-butyl allyl carbonate or aldimines using B2pin2, Liao et al. reported the same approach, albeit using more challenging C(sp3) electrophiles (e.g., CH3I) for the enantioselective methylboration. Both aliphatic alkenes and styrenes could be used with

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

• choice in this type of coupling reaction. Potassium carbonate was chosen due to the sensitivity of the amide 3 towards harsh basic conditions. With these conditions we were able to couple (Z)-bromide 4 with amide 3 selectively to yield (Z)-enamide 16. The obtained double bond geometry was confirmed by

• the indicative NMR coupling constants of 9.6 Hz. Moreover, we observed a concentration dependent formation of the undesired desilylated (Z)-enamide 17 (Table 1). The best results were achieved using a 65 mM solution of the amide 3. Using dry potassium carbonate, purified copper(I) iodide provided the

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• solvents, including toluene, EtOH, THF, H2O, CH2Cl2 and dimethyl carbonate (DMC). Among them, DMC afforded the product 3a in an excellent yield and as greener solvent compared to CH3CN, it was selected as the best solvent for this ring-opening N-alkylation (Table 1, entry 11). When replacing KOt-Bu by

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• (R = Me, iPr and Ph) in benzene produced chiral acetal 22. Subsequent palladium-catalyzed C–C coupling of the acetal with 4-fluorophenylboronic acid (FPBA) in the presence of caesium carbonate and tri-tert-butylphosphine afforded aryl fluorides 23. Pure ligands 24 (63–72%) were obtained by

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• using cesium carbonate as base in DMF at 40 °C [42], giving both the enantiomers of 2 in optically pure forms. The remaining fluorine substituents were subsequently replaced by a series of phenols including unsubstituted phenol, p-tert-butylphenol, and m-tert-butylphenol to produce the corresponding

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• tandem formation of C–Se and Se–fluoroalkyl bonds have emerged in the last five years. In 2014, Hor and Weng reported the trifluoromethylselenolation of (hetero)aryl iodides and alkyl bromides with the Ruppert–Prakash reagent, TMSCF3, elemental selenium, potassium fluoride, and silver carbonate under

Synthesis and herbicidal activities of aryloxyacetic acid derivatives as HPPD inhibitors

• Man-Man Wang,
• Hao Huang,
• Lei Shu,
• Jian-Min Liu,
• Jian-Qiu Zhang,
• Yi-Le Yan and
• Da-Yong Zhang

Beilstein J. Org. Chem. 2020, 16, 233–247, doi:10.3762/bjoc.16.25

• shown in Scheme 2, Scheme 3 and Scheme 4. The synthesis of compounds I and III was depicted in Scheme 2 and Scheme 3. The commercially available starting materials reacted with methyl chloroacetate in CH3CN and anhydrous potassium carbonate (K2CO3) as the base, and the corresponding products C and K

Allylic cross-coupling using aromatic aldehydes as α-alkoxyalkyl anions

• Akihiro Yuasa,
• Kazunori Nagao and
• Hirohisa Ohmiya

Beilstein J. Org. Chem. 2020, 16, 185–189, doi:10.3762/bjoc.16.21

• rearrangement and then successfully trapped with aryl bromides under palladium catalysis (Scheme 1). This system was extended to an asymmetric version using the chiral α-silyloxybenzylcopper(I) species having a chiral NHC ligand. In the asymmetric system, one example of allylic carbonate was used as the carbon

• homoallylic alcohol derivatives [12][13][14]. Results and Discussion Specifically, the three-component allylic cross-coupling reaction of benzaldehyde (1a, 0.4 mmol), tert-butyl cinnamyl carbonate (2a, 0.2 mmol) and (dimethylphenylsilyl)boronic acid pinacol ester [PhMe2SiB(pin)] (0.4 mmol) occurred in the

• and allylic carbonates 2. Methyl, tert-butyl and fluoro substituents were tolerated at the ortho- or para-positions of the aromatic aldehyde (3ba–da). 2,6-Dimethylphenyl- or 1-naphthyl moieties as the γ-substituent of the primary allylic carbonate were tolerated in the reaction (3ab and 3ac). Cinnamyl

Synthesis and characterization of bis(4-amino-2-bromo-6-methoxy)azobenzene derivatives

• David Martínez-López,
• Amirhossein Babalhavaeji,
• Diego Sampedro and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2019, 15, 3000–3008, doi:10.3762/bjoc.15.296

• cm × 8 mm). Then, morpholine (84 mg, 0.96 mmol), tris(dibenzylideneacetone)dipalladium(0) (29.3 mg, 0.032 mmol), RuPhos (29.8 mg, 0.064 mmol), and cesium carbonate (302.4 mg, 0.96 mmol) were added. The mixture was heated at 100 ºC in the pressure tube for 24 hours. The reaction progress was monitored

• cesium carbonate (302.4 mg, 0.96 mmol) were added. The mixture was heated at 100 ºC in a pressure tube for 36 hours. The reaction progress was monitored by TLC until the starting reagent was consumed. The solvent was evaporated under reduced pressure, and the resulting oil was extracted with DCM three

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

•  1, entries 3 and 4). Using anhydrous sodium carbonate α-pyrone 6a is again formed as the main product in 41% yield, but the yield of 1H-pyridine 5a drops to 3% (Table 1, entry 5). By the addition of water, the yield of 6a could be increased (Table 1, entries 6 and 7). Next we evaluated the use of a

• mixture of two bases, sodium carbonate and sodium acetate, and water (Table 2). With 0.80 equiv of sodium carbonate, 0.60 equiv of sodium acetate and 5.6 equiv of water 1H-pyridine 5a could be isolated in 56% yield. Decreasing the amount of ethyl cyanoacetate (4) the yields drops (Table 2, entry 2

• carbonate (Table 2, entry 10) nor sodium acetate (Table 2, entry 11) caused an increase in yields. Only lowering the reaction temperature to 20 °C α-pyrone 6a was isolated as the main product in 78% yield and 1H-pyridine 5a was obtained in only 7% yield (Scheme 5). Since base(s) and reaction temperature

Unexpected one-pot formation of the 1H-6a,8a-epiminotricyclopenta[a,c,e][8]annulene system from cyclopentanone, ammonia and dimethyl fumarate. Synthesis of highly strained polycyclic nitroxide and EPR study

• Sergey A. Dobrynin,
• Igor A. Kirilyuk,
• Yuri V. Gatilov,
• Andrey A. Kuzhelev,
• Olesya A. Krumkacheva,
• Matvey V. Fedin,
• Michael K. Bowman and
• Elena G. Bagryanskaya

Beilstein J. Org. Chem. 2019, 15, 2664–2670, doi:10.3762/bjoc.15.259

• ), cyclopentanone (1.3 mL, 15 mmol), dimethyl fumarate (576 mg, 4 mmol) and benzene (10 mL) was placed in a Dean–Stark apparatus and stirred under reflux for 48 h. The solvent was distilled off in vacuum and the residue was dissolved in ethyl acetate. The organic layer was washed with 5% sodium hydrogen carbonate

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• be an effective catalyst for the synthesis of rhodamine and rosamine dyes as well as for their selenium or tellurium analogous [29], the usage of that Pd(0) catalyst showed yields comparable with those obtained with PdCl2(PPh3)2 (Table 1, entry 4). The exchange of sodium carbonate with cesium

• carbonate resulted in no reaction at all (Table 1, entry 5). Whereby usage of potassium phenyltrifluoroborate (19) resulted in a yield comparable to boroxine 18b (Table 1, entry 6), usage of pinacol ester 20 showed no reaction in the cross-coupling reaction (Table 1, entry 7). Although described

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

• sodium carbonate to give (+)-3-methyleneverbanone (5) in 57% yield from 3. α,β-Unsaturated ketone 5 was exclusively reduced to allylic alcohol (1R,2R,4S,5R)-3-methyleneneoisoverbanol (6), using the Luche method [24]. 1,2-Reduction of enone 5 was achieved with sodium borohydride in the presence of cerium

• sodium hydroxide (2.7 mL, 8.1 mmol) were carefully added. After cooling to 0 °C, a 30% solution of hydrogen peroxide (1.2 mL, 12 mmol) was added dropwise to the reaction mixture. The solution was stirred for 30 minutes at rt and 1 h at 50 °C. After this time, potassium carbonate was added to saturate the

Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

• Benedikt C. Melzer,
• Alois Plodek and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222

• cross-coupling reactions, 4-bromo-5 iodobenzo[c][2,7]naphthyridine (13) is regarded as an interesting building block for synthetic chemists. Another interesting building block is ester 14, which was obtained in 37% yield by quenching 5-metalated 9d with diethyl carbonate. The quenching of 9d after

Regioselective Pd-catalyzed direct C1- and C2-arylations of lilolidine for the access to 5,6-dihydropyrrolo[3,2,1-ij]quinoline derivatives

• Hai-Yun Huang,
• Haoran Li,
• Thierry Roisnel,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2019, 15, 2069–2075, doi:10.3762/bjoc.15.204

• % affording 1a in 83% yield. The use of KOAc associated to PdCl(C3H5)(dppb) catalyst also afforded the regioisomer 1a in a quite good regioselectivity and yield (Table 1, entry 11). The higher conversions observed in the presence of acetate bases compared to carbonate bases (Table 1, entries 4–6 and 8–11

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• was stirred at reflux for 48 h. After cooling, the excess of acetic anhydride was evaporated under reduced pressure. The residue was triturated with dichloromethane (20 mL) and H2O (20 mL). The aqueous layer was neutralized by adding solid sodium carbonate and extracted with dichloromethane (2 × 20 mL

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

• . Keywords: benzimidazole; cesium carbonate; cyclization; selenium; selenoazole; Introduction Selenium-containing heterocyclic ring systems have attracted attention not only because of their chemical properties and reactivities, but also for their wide biological activities [1][2][3][4]. For example

• . Experimental General procedure for the synthesis of benzoimidazo[2,1-b]benzoselenoazoles: 1-(2-Bromoaryl)benzimidazoles 1 (0.5 mmol), selenium powder (79 mg, 1.0 mmol, 2 equiv), and cesium carbonate (326 mg, 1.0 mmol, 2 equiv) were dissolved in DMF (1 mL) under Ar atmosphere. The mixture was stirred at 150 °C

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

• Rosana Ribić,
• Ranko Stojković,
• Lidija Milković,
• Mariastefania Antica,
• Marko Cigler and
• Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

• substitution of bromine from tert-butyl bromoacetate with 2,3,4,6-tetra-O-acetyl-α-ᴅ-mannopyranose (9) in the presence of potassium carbonate followed. Chemoselective removal of the tert-butyl ester group from compound 10 resulted with O-mannoside 11 with a free carboxy group available for coupling of the

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• hydrogenation followed by saponification converted 178 into (2S,3S)-N-Boc-3-hydroxy-2-hydroxymethylpyrrolidine (2S,3S)-179, one of the simplest members of the iminosugar family. Reaction of aziridine 4-methoxyphenyl esters either (2R,1′S)-5e or (2S,1′S)-5e with vinylene carbonate at 280 °C gave a mixture 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

• carbonate as a base under aerobic conditions. Along with the synthesis of pyrido[1,2-a]benzimidazoles 78, they have reported the synthesis of benzimidazo[1,2-a]quinoline 79 and benzimidazo[1,2-a]isoquinoline 80 in good to excellent yields. They have used differently substituted arylboronic acids 77 as one

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

• Aleksandr S. Krylov,
• Artem A. Petrosian,
• Julia L. Piterskaya,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2019, 15, 1563–1568, doi:10.3762/bjoc.15.159

• ring of the starting 2-hydrazinylpyridines 1i and 1j significantly violates the reaction selectivity, leading to a rapid resinification of the reaction mixture. However, the exclusion of potassium carbonate allows the reaction to proceed selectively within 150 hours at a temperature of 60 °C. The

• . The ease of the formation of isomers 11 in this case and 12 in other similar synthesis, is caused not only by the presence of a nitro group in the pyridine ring, but also by the presence of hydrogen chloride, which is eliminated by potassium carbonate in the former experiments (Scheme 2). The acid