Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• dual catalytic mode. Ooi et al. reported an enantioselective synthesis of 1,2 diamines 247 from tertiary amines 248 and aldimines 249 (Scheme 39) [100]. The proposed mechanism involves a reductive quenching pathway with 248 to produce radical cations 248•+, which following deprotonation and a [1,2

Synthesis of 1,4-benzothiazinones from acylpyruvic acids or furan-2,3-diones and o-aminothiophenol

• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2020, 16, 2322–2331, doi:10.3762/bjoc.16.193

• tertiary amines and should only be carefully treated with reagents containing tertiary amino groups. Because of this, we were encouraged to examine EDC as a carbodiimide in the developed procedure (Table 1, entry 30). As expected, we found that the utilization of EDC in this reaction resulted in the

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• , first reported in 1834 by Liebig, which he named “melon” [119]. The material consists of two-dimensional sheets of hexatopic, hexagonal sp2-hybridised carbon and nitrogen atoms, linked by bridging tertiary amines (Figure 9) [120]. The material is crystalline as sheets are held together by strong π

The McKenna reaction – avoiding side reactions in phosphonate deprotection

• Katarzyna Justyna,
• Joanna Małolepsza,
• Damian Kusy,
• Waldemar Maniukiewicz and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 1436–1446, doi:10.3762/bjoc.16.119

• step of the McKenna reaction. To this end, we used model compounds from our previous work, analyzed the possible side reactions, and proposed solutions in order to minimize or prevent the unwanted processes. We also showed that tertiary amines, that are commonly used as additives to prevent these side

• allyldimethylamine (pKa 8.72), respectively [44]. This effect was reinforced by the higher nucleophilicity of the nitrogen atom in 12 compared with Et3N, as we deduced by comparison of model tertiary amines: Me3N (in MeCN: N 23.05, sN 0.45) and Et3N (in MeCN: N 17.10, sN 0.52) [45][46]. On the other hand, the lower

Accelerating fragment-based library generation by coupling high-performance photoreactors with benchtop analysis

• Quentin Lefebvre,
• Christophe Salomé and
• Thomas C. Fessard

Beilstein J. Org. Chem. 2020, 16, 982–988, doi:10.3762/bjoc.16.87

• of complex amines: bicyclopentanamines, azetidines, spiroazetidines, spiropyrrolidines and spiropiperidines. Functional group tolerance was probed by using functionalized building blocks bearing esters, carbamates, alcohols, tertiary amines, ethers, sulfones and fluorine atoms (Scheme 2 and Scheme 3

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

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

• ]. Benzaldehyde (8) was tested as an alternative to tertiary amines, which are commonly employed in radical-mediated reactions due to their ability to bind to atmospheric oxygen, which inhibits such reactions. The quinoxalines 32 were used as the prime photoinitiators, and the reaction was placed in a

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

• limitations of this KOt-Bu-promoted ring-opening N-alkylation from alkyl bromides with 2-methyl-2-oxazolines were explored using the optimized conditions. As shown in Scheme 2, various benzyl bromides bearing -Me, -t-Bu, -F, and -Cl groups were applied in the synthesis and afforded the tertiary amines 3a–g in

Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

• Dominika Krištofíková,
• Juraj Filo,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2019, 15, 2948–2957, doi:10.3762/bjoc.15.290

• generated using a strong base, such as LDA or similar amides in combination with trialkylsilyl chlorides as silylating agents at low temperature under strictly anhydrous conditions [3][16][17]. An alternative method employs tertiary amines as bases in combination with more reactive silylating agents, such

• acids improved the diastereoselectivity and the reaction rate of silyl ketene acetals of (E)-allylic esters [21]. Chiral bromoboranes were used to form boranyl ketene acetals from ester enolates generated from allyl esters with tertiary amines. The geometry of the enolates depended strongly on the

• , we studied the Ireland–Claisen rearrangement of ester 1c using various tertiary amines as bases. The ester enolate was trapped with Me3SiOTf at −60 °C and allowing the reaction to proceed at room temperature for 24 h. The best yields of acid 3c were achieved with triethylamine (74%) and N-cyclohexyl

Preparation of anthracene-based tetraperimidine hexafluorophosphate and selective recognition of chromium(III) ions

• Qing-Xiang Liu,
• Feng Yang,
• Zhi-Xiang Zhao,
• Shao-Cong Yu and
• Yue Ding

Beilstein J. Org. Chem. 2019, 15, 2847–2855, doi:10.3762/bjoc.15.278

• the tertiary amines, and the π systems, were most likely the binding sites for Cr3+ through Cr3+···N and Cr3+···π interactions (Scheme 2). In order to obtain further information on the binding pattern between 3 and Cr3+, 1H NMR titration studies were done in DMSO-d6. The spectra are depicted in Figure

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

• cathodes in the presence of chiral inductors, including tertiary amines, optically active proteins, and alkaloids [19][20], in 1975, Miller’s group reported the first example of the modification of electrodes via covalent binding [21]. They chemically modified air-oxidized graphite electrodes via treatment

• , Luo’s group disclosed another potential application of integrating electrochemical oxidation with chiral amine catalysis [77]. Using chiral primary amine 130 as a catalyst, the authors reported an electricity-driven cross-dehydrogenative coupling of ketones 129 with tertiary amines 128. The

• potentiostatic electrolysis of a mixture of ketones 129 with tertiary amines 128 in an undivided cell under standard conditions furnished C1-alkylated tetrahydroisoquinolines 131 in high yields with excellent enantioselectivity (Scheme 42). Enzyme catalysts: In 1981, Tischer’s group reported the electroenzymatic

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• was selectively reduced with DIBAL-H to benzyl alcohols 23f–h, which were oxidized with Dess–Martin periodinane to the corresponding benzaldehyde 26f–h. Reductive amination of 26f–h with 7 gave the tertiary amines 13f–h. Methylation with iodomethane and subsequent precipitation gave 3f–h as orange

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

Transient and intermediate carbocations in ruthenium tetroxide oxidation of saturated rings

• Manuel Pedrón,
• Laura Legnani,
• Maria-Assunta Chiacchio,
• Pierluigi Caramella,
• Tomás Tejero and
• Pedro Merino

Beilstein J. Org. Chem. 2019, 15, 1552–1562, doi:10.3762/bjoc.15.158

• -mediated oxidation of tertiary amines [26] by trapping them with cyanide anion [27][28]. These results point out the formation of transient carbocations III that can be stabilized by the presence of heteroatoms in the alpha position. The formation of transient carbocations do not contradict, necessarily

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• that the amine could play a role in promoting the [2,3]-sigmatropic rearrangement. After a screening of different tertiary amines, Rubin et al. found that DBU could be used as a base in the phosphinylation reaction but also as an efficient catalyst for the subsequent [2,3]-sigmatropic rearrangement of

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• from the less hindered and more reactive, less substituted position of its two canonical forms. In a similar manner, Rueping et al. demonstrated the functionalisation of C–H bonds α to tertiary amines with various nucleophiles. They also reported the formation of C–C bonds from α-amino C–H bonds using

Nucleophilic fluoroalkylation/cyclization route to fluorinated phthalides

• Masanori Inaba,
• Tatsuya Sakai,
• Shun Shinada,
• Tsuyuka Sugiishi,
• Yuta Nishina,
• Norio Shibata and
• Hideki Amii

Beilstein J. Org. Chem. 2018, 14, 182–186, doi:10.3762/bjoc.14.12

• synthesis of 1, we carried out the nucleophilic trifluoromethylation of 2 employing a small amount of chiral tertiary amines. However, the use of (1R,2R)-(N,N,N’,N’-tetramethyl)-1,2-diaminocyclohexane (8) as a chiral catalyst resulted in the formation of a racemic mixture of 1a (Table 2, entries 1 and 2

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• nanoscale MoS2. The scope of the reaction is quite similar to Li’s report [60]. The photocatalyst nanocomposite was reused in eight consecutive cycles with only slight decrease in activity. Yadav et al. developed a metal-free photoredox-catalyzed α-C(sp3)–H thiocyanation reaction for tertiary amines (Scheme

•  28) [63]. The reaction mechanism is different from the previous examples. The photoexcited state of Eosin Y can be quenched reductively by tertiary amines to form an Eosin Y radical anion and an amine radical cation. Molecular oxygen regenerates Eosin Y and is reduced to its superoxide radical anion

• photooxidized tertiary amines under aerobic conditions to the respective radical cationic species (Scheme 53) [91]. Further steps lead to an enamine intermediate, which can react with the former generated sulfonyl radical. They were able to apply a series of electronically and sterically differing (hetero

Diastereoselective Mannich reactions of pseudo-C₂-symmetric glutarimide with activated imines

• Tatsuya Ishikawa,
• Tomoko Kawasaki-Takasuka,
• Toshio Kubota and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2017, 13, 2473–2477, doi:10.3762/bjoc.13.244

• lactones in good to excellent yields [4][5]. One of the most intriguing features of this protocol is the fact that the enantiomers at the lactone part were readily obtained only by the selection of the tertiary amines employed in the reaction. It is quite apparent that this success is, at least in part

Regiodivergent condensation of 5-alkoxycarbonyl-1H-pyrrol-2,3-diones with cyclic ketazinones en route to spirocyclic scaffolds

• Alexey Yu. Dubovtsev,
• Maksim V. Dmitriev,
• Аndrey N. Maslivets and
• Michael Rubin

Beilstein J. Org. Chem. 2017, 13, 2179–2185, doi:10.3762/bjoc.13.218

• tertiary amines), while the use of stronger bases (hydroxides or alkoxides) caused decomposition of the base-sensitive 1H-pyrrole-2,3-dione moiety 9. An attempt to perform the reaction in the presence of catalytic amounts of Brønsted acid (TsOH) also did not provide the spirocyclic products. Instead

Sustainable synthesis of 3-substituted phthalides via a catalytic one-pot cascade strategy from 2-formylbenzoic acid with β-keto acids in glycerol

• Lina Jia and
• Fuzhong Han

Beilstein J. Org. Chem. 2017, 13, 1425–1429, doi:10.3762/bjoc.13.139

• efficiency of the reaction, a detailed optimization study was performed with various bases, such as tertiary, secondary and primary amines. When tertiary amines were used as the catalyst, very low yields of 3a were obtained (Table 1, entries 3–5). Unfortunately, a sluggish reaction was observed in the

Construction of highly enantioenriched spirocyclopentaneoxindoles containing four consecutive stereocenters via thiourea-catalyzed asymmetric Michael–Henry cascade reactions

• Yonglei Du,
• Jian Li,
• Kerong Chen,
• Chenglin Wu,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2017, 13, 1342–1349, doi:10.3762/bjoc.13.131

• strategies with chiral transition metals [27][28][29][30][31][32][33], organocatalysts such as secondary amines [34][35][36], nucleophilic phosphines [26][37][38][39][40][41][42][43][44], tertiary amines [45], N-heterocyclic carbenes (NHCs) [46][47][48], and cinchona alkaloid derivatives [25][28][49][50

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

• Maximilian Maier,
• Magnus S. Schmidt,
• Markus Ringwald and
• Christoph P. Fik

Beilstein J. Org. Chem. 2017, 13, 372–383, doi:10.3762/bjoc.13.40

• could isolate crude diamines 8 and 9, containing significant amounts (10–15%) of the tertiary amines 8a and 9a (Scheme 3) or diamine 16, respectively; each could be used without further purification. Classical acylation with acetyl chloride or acryloyl chloride in the presence of triethylamine led to

• responsible for this effect, we decided to use 1,4-diaminobutane (13) and allyl chloride for the synthesis of diamine 11. This also resulted in the positive side effect, that a formation of tertiary amines, comparable to compounds 8a and 9a, is not possible in this case. Interestingly, during the addition of

Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations

• Serena Traboni,
• Emiliano Bedini and
• Alfonso Iadonisi

Beilstein J. Org. Chem. 2016, 12, 2748–2756, doi:10.3762/bjoc.12.271

• excess of several bases (Table 1). In all cases 6-O-silylated derivative 2 was obtained as the main product, but yields and rates were strongly dependent on the adopted base: pyridine (Table 1, entries 6–9) gave much better results than tertiary amines (Table 1, entries 1–5) that, on the other hand, had

Construction of bis-, tris- and tetrahydrazones by addition of azoalkenes to amines and ammonia

• Artem N. Semakin,
• Aleksandr O. Kokuev,
• Yulia V. Nelyubina,
• Alexey Yu. Sukhorukov,
• Petr A. Zhmurov,
• Sema L. Ioffe and
• Vladimir A. Tartakovsky

Beilstein J. Org. Chem. 2016, 12, 2471–2477, doi:10.3762/bjoc.12.241

• ][21][22][23][24][25][26][27][28][29][30][31][32][33][34], have not been prepared so far. In the present work, we focused on the development of a general approach to tertiary amines and polyamines bearing several hydrazonomethyl arms at the nitrogen atom(s). To achieve this goal, we suggested a