Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• study [41][42] in 2017. This metal-catalyzed, photoinduced, and asymmetric radical transformation requires two catalysts, namely, (i) a metal catalyst that promotes electron transfer and (ii) a separate chiral catalyst that facilitates the highly stereoselective bond formation. In 2016, Fu [82

• subsequent stereoselective transformations. In addition, Fimognari’s group [101] utilized copper photoredox catalysts to achieve the N-desulfonylation of benzenesulfonyl-protected N-heterocycles 72 (Scheme 29). In 2019, Xiao’s group [102] observed that under visible light or copper catalysis, cycloketone

• applications of photoinduced copper-catalyzed reactions include alkene/alkyne functionalization, organic halide functionalization, and alkyl C–H functionalization. This review introduced the photoinduced copper-catalyzed stereoselective reactions within these broad reaction categories. Copper salts coordinate

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• reduced in a stereoselective manner adopting Luche conditions to provide diol 24 (dr 97:3), which after masking the primary alcohol moiety as a silyl ether, allowed isolation of the desired product 25 in 86% yield. This intermediate possessed the correct chirality on the free secondary alcohol to

• stereoselective reduction (Scheme 8). Among a selection of reagents, Mohapatra found that lithium tri-tert-butoxyaluminum hydride in ethanol at low temperature furnished 71 as a single diastereoisomer in 94% yield. The allylic alcohol moiety was protected as TBDPS ether 73 (92%) and oxidatively cleaved following

• ). The olefin moieties can be installed via stereoselective allylation and cinnamic acid esterification of 94, which is derived from symmetrical alcohol 95. The right-hand side portion of this molecule can be constructed by epoxidation of the allylic alcohol derived from α,β-unsaturated ester 96 and the

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• with Hg(OAc)2 affording the corresponding cyclized pyanosylmethylmercuric chloride derivatives 12 (Scheme 5). This methodology can be used to synthesize rare C-glycosyl carbohydrates from easily available sugars. In a similar manner, stereoselective cyclization of C-glycosyl amino acid derivative 13

• using mercuric trifluoroacetate Hg(TFA)2 at room temperature was performed. The reaction proceeds primarily through stereoselective cyclization to give α-ᴅ-C-glycopyranosyl amino acid derivative 14 as the major product [43]. Nevertheless, C-mannopyranosyl derivatives cannot be achieved in a similar

• of Hg(OAc)2 [53]. The cyclized products 34A,B formed from starting material 33 were regiospecific and followed Markovnikoff’s type addition in the reaction [54][55][56][57]. It was also reported that the formation of α-phosphorylated pyrrolidines mostly takes place in regio- and stereoselective ways

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• step by chloride abstraction that leads to the formation of an oxocarbenium intermediate, which then undergoes the stereoselective addition of the nucleophile. Mechanistic insights revealed that two thiourea molecules are, in fact, needed and cooperatively participate in the activation of 73. However

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• transformations have become one of the most reliable and basic tools for designing and manufacturing biologically relevant molecules and functional materials [1][2][3][4]. The formation of highly chemo-, regio-, and stereoselective products with excellent yields is the key reason for transition-metal catalysis as

Transition-metal-free intramolecular Friedel–Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives

• Tülay Yıldız,
• İrem Baştaş and
• Hatice Başpınar Küçük

Beilstein J. Org. Chem. 2021, 17, 2203–2208, doi:10.3762/bjoc.17.142

• method using π-activated alcohols has frequently been used for xanthene synthesis. Some of these methods are the stereoselective synthesis of 9-vinyl-substituted unsymmetrical xanthenes and thioxanthenes by intramolecular FCA reaction [39], Lewis acid-catalyzed intramolecular FCA [40], and the synthesis

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

• group on the glycosyl donor and the acceptor for the stereoselective formation of the β(1–3) linkage (Figure 4) [132]. Interestingly, oligomers bearing several 4,6-O-benzylidene groups show anomalously small coupling constants for some of the C-1 hydrogens. NMR [133] and X-ray [134] studies revealed

• linkages is particularly relevant, as α(1–4)-glucans form the backbone of starch, with the linear amylose and the branched amylopectin, and α(1–3)-glucans are related to fungal pathogenicity in plants [168]. Only few options can aid the stereoselective construction of 1,2-cis glycosidic bonds. In general

• -mediated aglycon delivery (BMAD) with the use of a diboron catalyst allowed for regio-, as well as stereoselective glycosylation to achieve an α(1-3)-pentaglucoside [175]. Regioselective 1,2-cis-glycosylation could also be achieved by boron-catalyzed coupling via a SNi-type mechanism [176]. Hydrogen bond

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• acid (4) as catalyst [30]. Based on this pioneer work, our research group described an efficient, highly stereoselective, one-pot process comprising an organocatalytic conjugate addition of dimedone or 4-hydroxycoumarin 1 to α,β-unsaturated aldehydes 2 followed by an intramolecular isocyanide-based

• stereoselective one-pot procedure for the synthesis of five-membered annulated coumarins 28 was described by the group of Enders [40]. Using dual catalysis, with a cinchona primary amine derivative 22 and silver carbonate, a series of functionalized coumarin derivatives 28 were obtained in good yields (up to 91

• synthesis of 3,4-dihydrocoumarins 80 bearing a cyclohexene ring, through [4 + 2] cycloaddition between 2,4-dienals 79 and 3-coumarincarboxylates 43. This stereoselective transformation was performed using a squaramide 81 derivative catalyst, which activates the aldehyde with the formation of an enamine

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• mixture of starting material 6, the conjugate addition product 14, and a trace of the denitration product 15. The structure of both compounds was confirmed by single X-ray crystallography (Figure 4 and Figure 5). The addition of methanol is stereoselective with only a single diastereomer of 14 being

Total synthesis of ent-pavettamine

• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2021, 17, 1440–1446, doi:10.3762/bjoc.17.99

• -pavettamine rather than pavettamine. Chain extension and stereoselective ketone reduction were achieved using the (R)-methyl p-tolyl sulfoxide chiral auxiliary to give the desired 1,3-syn-diol C5 unit. A protecting-group strategy was also developed for the orthogonal protection of the alcohol and amine

• addition of the chiral auxiliary. Our attention then turned to the stereoselective reduction of 8. Chelation-controlled reduction of 8 using ZnCl2 and DIBALH allowed for the successful formation of 16 as a single diastereomer (Scheme 4), as evidenced by 1H NMR spectroscopy [18]. TBS deprotection furnished

• compound 9. Stereoselective reduction of intermediate 8 as key step towards intermediate 4. Reaction conditions: a) i) ZnCl2, rt, 2 h; ii) DIBALH, THF, −78 °C to rt, 2 h, 87%; b) TBAF, THF, 0 °C, 4 h, 87%; c) 5% p-TsOH, 2,2-dimethoxypropane, acetone, rt, 1 h, 86%. Synthesis of the C5 fragments from

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• % from benzyl alcohol (16), alongside 50% of the trifluoroacetate 18. Carrying out the same process via a flow-based protocol allowed for the formation of benzaldehyde (17) in 91% yield with only 8% of the accompanying side product 18 [88]. Similarly, a stereoselective alkylation of an Evans’ type

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• ligands [52][53][54][55] and as chiral auxiliaries [56]. The most widely used synthetic methods to form the aziridine ring [57][58][59][60][61] include intramolecular cyclizations in amines bearing potential leaving groups. Stereoselective syntheses of aziridines have been successfully carried out by

• determined following a single-crystal X-ray analysis (Scheme 11). The stereoselective synthesis of diastereomeric 2-chloro-2-aroylaziridines 36 and 32 was successfully accomplished through a three-component cascade coupling reaction of silyldichloromethanes 33, arylnitriles 34 and chiral N-tert

• through a cyclic transition state to the Si face of the imine (RS)-14. In this way, both cis-aziridines diastereoisomers 36 and 32 were formed from the same chiral imine 14 and arylnitriles 34 (Scheme 12). Chiral sulfinyl imines have been also used in the stereoselective synthesis of aziridines. The

Synthesis of multiply fluorinated N-acetyl-D-glucosamine and D-galactosamine analogs via the corresponding deoxyfluorinated glucosazide and galactosazide phenyl thioglycosides

• Vojtěch Hamala,
• Lucie Červenková Šťastná,
• Martin Kurfiřt,
• Petra Cuřínová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2021, 17, 1086–1095, doi:10.3762/bjoc.17.85

• donors for the installation of a 1,2-cis-linked multifluorinated GlcNAc and GalNAc moiety. Results and Discussion Our approach to the synthesis is summarized in Scheme 1. Challenging regio- and stereoselective introduction of fluorine at C3 and C4 of the pyranose ring, together with azide installation at

Nitroalkene reduction in deep eutectic solvents promoted by BH₃NH₃

• Chiara Faverio,
• Monica Fiorenza Boselli,
• Patricia Camarero Gonzalez,
• Alessandra Puglisi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2021, 17, 1041–1047, doi:10.3762/bjoc.17.83

• also demonstrated. A wide variety of alkyl- and aryl-substituted nitroalkenes were reduced with high chemoselectivity, including β-substituted nitroolefins, and thus paving the way to the study of innovative, sustainable and stereoselective reductive methods to synthesize enantiopure nitroalkanes

Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

• Ákos Bajtel,
• Mounir Raji,
• Matti Haukka,
• Ferenc Fülöp and
• Zsolt Szakonyi

Beilstein J. Org. Chem. 2021, 17, 983–990, doi:10.3762/bjoc.17.80

• synthesised in a stereoselective manner. Isopinocarveol prepared from (−)-α-pinene was converted into condensed oxazolidin-2-one in two steps by carbamate formation followed by a stereoselective aminohydroxylation process. The relative stereochemistry of the pinane-fused oxazolidin-2-one was determined by 2D

• -2-one; stereoselective; tautomerism; Introduction The best known 2-amino-1,3-diol derivative sphingosine (1) plays a crucial role in intracellular signaling as second messenger, and its derivatives called sphingolipids are also critical for cell growth, cell differentiation, cell recognition, and

• the lack of a readily available natural sources and the high biological importance of sphingolipid analogues, their synthesis has been the subject of numerous studies [16]. The key step for the synthesis is the stereoselective construction of the 2-amino-1,3-diol moiety of the molecules. Generally

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• glycoconjugates [1][2][3][4]. Due to the large diversity of glycosyl donors and acceptors there is no general glycosylation method developed so far. To ensure high yielding, as well as regio- and stereoselective glycosidic bond formation, a proper combination of glycosyl donor and acceptor, protecting and leaving

• [27]) and coupling partners [28], great attention has been paid to a stereoselective glycosylation by sterically fixed glycosyl fluorides as glycosyl donors [29][30][31]. The enhanced stability of glycosyl fluorides has also allowed to develop a straightforward protecting-group-free strategy towards

• facilitating for the synthesis of 2-deoxy glucoside 20 from corresponding fluoride α-19 in 91% yield and good α-selectivity at −10 °C (Scheme 5). Due to the absence of a neighboring group at C2 position, the stereoselective synthesis of 2-deoxy glycosides is challenging [72][73][74]. We hypothesize that the

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• important building blocks and ubiquitous scaffolds in many natural products and active pharmaceutical ingredients (API). Among various established methods, the Prins reaction has emerged as a powerful technique in the stereoselective synthesis of the tetrahydropyran skeleton with various substituents, and

• ; Prins cyclization; stereoselective; tetrahydropyran; Introduction 6-Membered saturated oxygen heterocycles, known as tetrahydropyran (THP), are recognized as privileged scaffolds, present in a variety of biologically important natural products, such as polyether antibiotics, marine toxins, pheromones

• , and pharmaceutical agents. These structural motifs are frequently used as synthons and as key intermediates for natural product synthesis. Therefore, the development of stereoselective synthetic methods for the substituted THP subunit has long been the area of fundamental research in organic chemistry

Highly regio- and stereoselective phosphinylphosphination of terminal alkynes with tetraphenyldiphosphine monoxide under radical conditions

• Dat Phuc Tran,
• Yuki Sato,
• Yuki Yamamoto,
• Shin-ichi Kawaguchi,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 866–872, doi:10.3762/bjoc.17.72

• reactivities. The method using V-40 as an initiator is successfully investigated for the regio- and stereoselective phosphinylphosphination of terminal alkynes giving the corresponding trans-isomers of 1-diphenylphosphinyl-2-diphenylthiophosphinyl-1-alkenes in good yields. The protocol can be applied to a wide

• variety of terminal alkynes including both alkyl- and arylalkynes. Keywords: (E)-1,2-bis(diphenylphosphino)ethylene derivative; radical addition; stereoselective phosphinylphosphination; terminal alkyne; tetraphenyldiphosphine monoxide; Introduction Organophosphorus compounds are an essential class of

• A1. Radical A1 is captured by Ph2P(O)PPh2 to provide A2, regio- and stereoselectively [62]. Conclusion In conclusion, a highly regio- and stereoselective phosphinylphosphination of alkynes with Ph2P(O)PPh2 has been successfully developed. The radical initiator V-40 can be used to selectively generate

Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols

• Emine Salamci and
• Yunus Zozik

Beilstein J. Org. Chem. 2021, 17, 705–710, doi:10.3762/bjoc.17.59

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

• Deniz Tözendemir and
• Cihangir Tanyeli

Beilstein J. Org. Chem. 2021, 17, 494–503, doi:10.3762/bjoc.17.43

• naturally occurring cinchona alkaloids have shown remarkable performance as organocatalysts for stereoselective synthesis in the past decade [1][2][3][4][5][6]. Among them, quinine-derived organocatalysts make a noteworthy appearance in the formation of new stereogenic centres, which can serve as valuable

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• phosphonodepsipeptides in the future. However, highly stereoselective asymmetric synthetic methods of phosphonodepsipeptides are of high demand and need to be developed in the near future. Phosphonopeptides, phosphonodepsipeptides, peptides, and depsipeptides. The diverse strategies for phosphonodepsipeptide synthesis

Synthesis of legonmycins A and B, C(7a)-hydroxylated bacterial pyrrolizidines

• Wilfred J. M. Lewis,
• David M. Shaw and
• Jeremy Robertson

Beilstein J. Org. Chem. 2021, 17, 334–342, doi:10.3762/bjoc.17.31

• might be thought to be theoretically possible [18][19], via a late-stage addition to an intact pyrrolizidine core. The molecules are isolated as their racemates and, by analogy to the clazamycins, even if the LgnC-mediated hydroxylation is fully stereoselective, the C(7a) center is expected to be

Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclic dienes

• Savva A. Ponomarev,
• Roman V. Larkovich,
• Alexander S. Aldoshin,
• Andrey A. Tabolin,
• Sema L. Ioffe,
• Jonathan Groß,
• Till Opatz and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2021, 17, 283–292, doi:10.3762/bjoc.17.27

• one of the most widely used fluorine-containing building blocks [48][49]. Recently, we have developed an efficient stereoselective synthesis of β-fluoro-β-nitrostyrenes 1 based on the radical nitration of 2-bromo-2-fluorostyrenes [50]. This process takes place with simultaneous elimination of bromine

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• stereoselective methods for the synthesis and transformations of cyclopropane derivatives. These investigations gained a significant interest, because cyclopropane and cyclopropene fragments are present in the structures of many biologically active substances, such as antibiotics, anticancer, and antimycotic

• intermediate allylic cation which was the electrophile in a Friedel–Crafts reaction with 159. The subsequent desilylation of the Friedel–Crafts product gave an α-fluorinated ketone intermediate which then reacted with a second equivalent of 159 in a (Z)-stereoselective, chelation-controlled process. Fu et al