Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• halogenohydroxylation (Hal = I, Br) or addition–elemination of bromine (forming bromobutadienes) with high stereoselectivity [25][26]. Apart from that, reactions of sulfur containing allenes were studied in acidic media [27][28]. Despite promising results, there was no further research in this area. Based on our recent

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

• the catalyst Ru-4 with the short linker, the activity of Ru-4@NB4exp dropped to TON = 3,000, even though the conjugation was almost quantitative [62]. However, this “influence” on the activity could not be transferred to the regio- and stereoselectivity of the polymer microstructure. Apart from ROMP

Synthesis of cis-hydrindan-2,4-diones bearing an all-carbon quaternary center by a Danheiser annulation

• Gisela V. Saborit,
• Carlos Cativiela,
• Ana I. Jiménez,
• Josep Bonjoch and
• Ben Bradshaw

Beilstein J. Org. Chem. 2018, 14, 2597–2601, doi:10.3762/bjoc.14.237

• stereoselectivity of the ring-formation step can be explained by the suprafacial addition of the allene to the double bond of the α,β-unsaturated compound 4, the diastereoselectivity being sterically controlled by the methyl group on the β-face. The transformation of the vinylsilane moiety in 5 into the

Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine

• Piotr Pomarański,
• Piotr Roszkowski,
• Jan K. Maurin,
• Armand Budzianowski and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2018, 14, 2384–2393, doi:10.3762/bjoc.14.214

• transformation [22]. In such cases the stereoselectivity may depend on additional chelation effects [28][29][30][31][32][33][34]. Buchwald and co-workers reported an efficient stereoselective synthesis of axially chiral biarylamides by Pd–O bond formation during the oxidative addition step [28][29]. Also other

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• and co-workers developed a cobalt-catalyzed hydroarylation of 2-vinyloxiranes with indoles 7 to form C2-allylated products 46, albeit in low stereoselectivity (Scheme 29b) [83]. Similarly, Cheng et al. reported a hydroarylation reaction of arenes 7 with a bicyclic alkene to form ring-opening products

Asymmetric Michael addition reactions catalyzed by calix[4]thiourea cyclohexanediamine derivatives

• Zheng-Yi Li,
• Hong-Xiao Tong,
• Yuan Chen,
• Hong-Kui Su,
• Tangxin Xiao,
• Xiao-Qiang Sun and
• Leyong Wang

Beilstein J. Org. Chem. 2018, 14, 1901–1907, doi:10.3762/bjoc.14.164

• convenience and good stereoselectivity [5][6]. Accordingly, different versions of this reaction have been extensively studied. Notably, the Michael addition reaction of 1,3-dicarbonyl compounds to conjugated nitroalkenes is very important for the synthesis of chiral nitro carbonyl compounds, such as bioactive

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• applied in this reaction. A C(sp3)–I(III) intermediate 34, which was trapped by vicinal nitrogen nucleophiles to form the chiral syn-β-fluoroaziridine 33, was proposed. Both fluoroaziridines 33 and β-fluoropyrrolidines 36 were obtained in good yields and high anti-stereoselectivity. However, the reaction

• , the cinnamamide 41i could be transformed to the corresponding difluorination product 42i with excellent enantioselectivity and high stereoselectivity, albeit in moderate yields (Scheme 14, top) [64]. Inspired by the propensity for such anchimeric assistance in these reactions, an enantio- and

DFT calculations on the mechanism of copper-catalysed tandem arylation–cyclisation reactions of alkynes and diaryliodonium salts

• Tamás Károly Stenczel,
• Ádám Sinai,
• Zoltán Novák and
• András Stirling

Beilstein J. Org. Chem. 2018, 14, 1743–1749, doi:10.3762/bjoc.14.148

• the basis of the mechanism the origin of the stereoselectivity is ascribed to the interaction of the Cu ion with the oxazoline oxygen driving the ring-closure step selectively. Keywords: catalysis; DFT calculation; iodonium salts; reaction mechanism; tandem arylation–cyclisation; Introduction

• (Scheme 2, step 1). In the next step we compared the energetics of two different paths (paths A and B), to get insight into the order of the arylation and cyclisation steps. Additionally, the relevance of vinyl cation formation and the stereoselectivity were examined. The energy profiles start with the

• stereoselectivity of the reaction and it also excludes the formation of vinyl-cation intermediates. The obtained results could serve as a useful and more general description of the mechanism of the carboarylation–ring closure strategy based on the utilisation of alkynes and diaryliodonium salts, beyond the selected

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• various aldehydes as shown in Scheme 21 [56]. It involved the reaction of a pre-prepared enantiopure toluene 70 with aromatic as well as aliphatic aldehydes in the presence of LDA. The stereoselectivity was in favor of the anti-diastereoisomer and was found to be dependent on the size of the aldehyde. It

• Fujisawa and co-workers in 1984 as depicted in Scheme 22 [57]. Coincidentally, the presence of the sulfenyl group at the α-position of the carbonyl center was found to be crucial for the stereoselectivity. Despite the sharp advancement in the field of biotechnology in the last decade, the application of

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• this is important to explain and predict the stereoselectivity of anomeric modifications under Mitsunobu conditions. Though the Mitsunobu reaction is often not the first choice for the anomeric modification of carbohydrates, this review shows the high value of the reaction in many different

• circumstances. Keywords: anomeric stereoselectivity; carbohydrates; glycoside synthesis; Mitsunobu reaction; Introduction Fifty years ago, Oyo Mitsunobu reported a preparation of esters from alcohols and carboxylic acids supported by two auxiliary reagents, diethyl azodicarboxylate (DEAD) and

• dimethylformamide, has been shown to be influential in terms of efficacy and stereoselectivity [19]. Since its infancy, the Mitsunobu reaction has found applications in carbohydrate chemistry, as its broad scope and mild conditions are ideal for the formation of conjugates with sensitive natural products. Standard

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• (OTf)2, Yb(OTf)3) and a Brønsted acid (TfOH) were proven useful as activators, by which the reaction finished in a short time and gave the products with high stereoselectivity [79]. Recently, the reaction was revisited by Kajimoto et al., who sought a glycosylation reaction that could be applied to

• /acetonitrile/isobutyronitrile/pivalonitrile greatly improved both the chemical yields and stereoselectivity, as shown in Scheme 21. The results suggested that both the solvent system and iodonium salt promoter are required for selectivity. Even though glycals have a π-electron-rich enol ether unit, reports

Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119

• in C7 was crucial to guarantee the stereoselectivity. Meanwhile, the good catalysis was maintained with both dihydrocinchonidine-derived C14 and dehydro compound C15. Finally, the quaternary ammonium group from quinine was examined (Table 1, entries 16 and 17), and C16 and C17 gave the result

• stereoselectivity. For the screening of the base, the reduction of volume or concentration of 50% aq NaOH resulted in a decreased yield (Table 2, entries 11 and 12). If NaOH was replaced by K2CO3, no reaction took place (Table 2, entry 13). As far as the reaction temperature was concerned (Table 2, entry 7, 14 and

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• corresponding (S,S)-40 as obtained without further separation of conformational isomers. Both the catalytic activity and the stereoselectivity were changed to different extents depending to the substituents on the calixarene skeleton. Best efficiencies and enantioselectivities were obtained when

• to 90%) but moderate diastereoselectivities (up to 65:35) were obtained (Scheme 26). A general organocatalyzed aldol reaction mechanism in water was suggested by the authors. Accordingly, the observed catalytic activity and stereoselectivity was explained by the formation of a hydrophobic and

• activity and stereoselectivity of catalyst 99. As shown in Figure 11, this catalytic system renders to use the calixarene cavity and in consequence of this both the high diastereoselectivity and enantioselectivity can be explained. Furthermore, when 99 used in 2 mol % can be recycled easily and re-used six

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• -isocupreine as organocatalyst instead of 15 mol % of β-isocupreidine (Scheme 11) in this reaction resulted in the formation of the corresponding (R)-configured products ent-36 with good to high enantioselectivities (83–95% ee) and moderate to good yields (37–79%), as shown in Scheme 12. The stereoselectivity

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• coupled with the alkyne under palladium catalysis. A broad range of TMS-substituted acetylenes 29 was converted efficiently under the optimized reaction conditions, forming the desired arylacetylenes 30 in good yields with high stereoselectivity. The applicable substrate scope is rather broad including

• iodoarenes 32. These species smoothly underwent subsequent Suzuki–Miyaura, Sonogashira and Mirozoki–Heck couplings. The respective arylated, alkynylated and alkenylated products 33a–d were obtained in high yields with excellent stereoselectivity. Due to the intramolecular pathway of the first step, high AE

• , azidobenziodoxolones 36b (ABX), could be utilized for atom-economical reactions. Gillaizeau and co-workers developed an iron-catalysed oxyazidation of enamides 45 using ABX derivatives 36b (Scheme 24) [58]. The reaction proceeds with complete regio- and stereoselectivity introducing the azide group in C2 and the ester

Stereoselective nucleophilic addition reactions to cyclic N-acyliminium ions using the indirect cation pool method: Elucidation of stereoselectivity by spectroscopic conformational analysis and DFT calculations

• Koichi Mitsudo,
• Junya Yamamoto,
• Tomoya Akagi,
• Atsuhiro Yamashita,
• Masahiro Haisa,
• Kazuki Yoshioka,
• Hiroki Mandai,
• Koji Ueoka,
• Christian Hempel,
• Jun-ichi Yoshida and
• Seiji Suga

Beilstein J. Org. Chem. 2018, 14, 1192–1202, doi:10.3762/bjoc.14.100

• presents the diastereoselective synthesis of disubstituted piperidine derivatives by the indirect cation pool method and the elucidation of the stereoselectivity based on both NMR analyses of the cyclic N-acyliminium ions and DFT calculations. Results and Discussion N-Acyliminium ions obtained from N-Boc

Iodine(III)-mediated halogenations of acyclic monoterpenoids

• Laure Peilleron,
• Tatyana D. Grayfer,
• Joëlle Dubois,
• Robert H. Dodd and
• Kevin Cariou

Beilstein J. Org. Chem. 2018, 14, 1103–1111, doi:10.3762/bjoc.14.96

• various functional groups (protected and free alcohols, amine, E and Z olefins, diene moiety) aimed at probing potential chemo-, regio- and stereoselectivity issues – were selected: geranyl acetate (1a), neryl acetate (1b), geraniol (1c), N-tosylgeranylamine (1d) and myrcene (1e, Figure 2). Results and

Synthetic avenues towards a tetrasaccharide related to Streptococcus pneumonia of serotype 6A

• Aritra Chaudhury,
• Mana Mohan Mukherjee and
• Rina Ghosh

Beilstein J. Org. Chem. 2018, 14, 1095–1102, doi:10.3762/bjoc.14.95

• ; oligosaccharides; stereoselectivity; total synthesis; Introduction Complex glycans serve as attractive targets for carbohydrate-based vaccines and therapeutics [1][2][3]. Streptococcus pneumonia (SPn) has been posing a serious threat in recent times. It is a major cause of pneumonia, bacteraemia, and meningitis

Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides

• Kartik Temburnikar and
• Katherine L. Seley-Radtke

Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65

• stereochemical inversion at C3' [75]. The desired stereoselectivity for 2'-deoxy analogues was obtained when BF3·OEt2 was used. Furthermore, another route to the synthesis of C-nucleosides was demonstrated by direct addition of aryl lithium reagents to the 2'-OMe ribonolactone (Figure 11B). While the expected

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• substrates were subsequently tested using 10 mol % of this catalyst in water at room temperature. The achievement of this study was not only on the stereoselectivity of the catalysts, but also on the substrate selectivity (Table 4): the preferred substrates are water-insoluble, suggesting that the reaction

Stepwise radical cation Diels–Alder reaction via multiple pathways

• Ryo Shimizu,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 704–708, doi:10.3762/bjoc.14.59

• material is lost. Indeed, the anodic oxidation of either the Z- (1Z) or the E-form (1E) in the absence of 2,3-dimethyl-1,3-butadiene (2) led to isomerization. In other words, inversion of the configuration of the radical cation 1·+ proceeds readily, leading to a loss in stereoselectivity. The radical

• adduct 3 as an approximately cis/trans = 1:4 mixture, this should proceed via a different intermediate from the acyclic radical cation intermediate (A·+). Here, we propose the cyclic radical cation intermediate B·+ for the rearrangement, imparting stereoselectivity for the six-membered ring closure. The

Liquid-assisted grinding and ion pairing regulates percentage conversion and diastereoselectivity of the Wittig reaction under mechanochemical conditions

• Kendra Leahy Denlinger,
• Lianna Ortiz-Trankina,
• Preston Carr,
• Kingsley Benson,
• Daniel C. Waddell and
• James Mack

Beilstein J. Org. Chem. 2018, 14, 688–696, doi:10.3762/bjoc.14.57

• -assisted grinding conditions, we did not truly understand the influence of the reaction medium on the reaction. Therefore, we were interested in better understanding these observations, with the goal of increasing the overall conversion and having better control over the stereoselectivity of the product

Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue

• Romain Sallio,
• Stéphane Lebrun,
• Frédéric Capet,
• Francine Agbossou-Niedercorn,
• Christophe Michon and
• Eric Deniau

Beilstein J. Org. Chem. 2018, 14, 593–602, doi:10.3762/bjoc.14.46

• previously observed in other Michael-additions involving chiral auxiliaries on the nucleophile and on the Michael acceptor [62]. As for (S)-6a, catalyst 18c bearing a bulky tert-butyl group at the benzyl para-position gave the best results in term of stereoselectivity (80% de, Table 2, entry 7). However, the

Copper-catalyzed asymmetric methylation of fluoroalkylated pyruvates with dimethylzinc

• Kohsuke Aikawa,
• Kohei Yabuuchi,
• Kota Torii and
• Koichi Mikami

Beilstein J. Org. Chem. 2018, 14, 576–582, doi:10.3762/bjoc.14.44

• applicable to this catalytic transformation under the optimized reaction conditions (Scheme 2). Alkyl substituents on the ester moiety of the trifluoropyruvate were found to influence the stereoselectivity drastically. The reaction of trifluoropyruvates (1c–e) bearing sterically demanding substituents such

Recent developments in the asymmetric Reformatsky-type reaction

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

• high stereoselectivity of the process could be explained by to the exclusive formation of the pentacoordinated transition states A and B (Scheme 5). Indeed, steric repulsion between the auxiliary and the bulky dimethyl group prevented a Re attack through transition state B, thus forcing the system to

• diastereoselectivity (>90% de), as shown in Scheme 11. To explain the stereoselectivity of the process, the authors have proposed the six-membered transition state D (Scheme 11). Product 30 was further converted into expected chiral diamine 28 through three supplementary steps. Later in 2015, Liu et al. developed Zn

• reaction could not be extended to aliphatic imines since they led to complex mixtures. To explain the stereoselectivity of the reaction providing (3S,4R)-62a, the authors proposed transition state K arisen from coordination between zinc ions and imine nitrogen, ligand 59, and the Reformatsky reagent