Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• )aniline preparation; we also took into account its convenient price. Using G-0 dendron 2a, we synthesised G-1 dendrons in two (→ D-Cl) or three (→ D-N

  NH) orthogonal transformations, with excellent overall yields (90% and 84% from 2a, respectively). The complete chemoselectivity observed during the

Thiocarbonyl-enabled ferrocene C–H nitrogenation by cobalt(III) catalysis: thermal and mechanochemical

• Santhivardhana Reddy Yetra,
• Zhigao Shen,
• Hui Wang and
• Lutz Ackermann

Beilstein J. Org. Chem. 2018, 14, 1546–1553, doi:10.3762/bjoc.14.131

• robustness of the cobalt-catalyzed ferrocene C–H amidation with a variety of 1,4,2-dioxazol-5-ones 2 (Scheme 1). Hence, the chemoselectivity of the cobalt catalyst was reflected by fully tolerating sensitive electrophilic functional groups, including amido, chloro, bromo and nitro substituents in the para

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• auto-amination process enables to address the issue of chemoselectivity in some cases. For example, the Suzuki–Miyaura coupling allows for introducing a pyridinyl or a furyl ring that are not compatible with the rhodium-catalyzed oxidizing amination reactions. In a similar manner, the group of

Metal-free formal synthesis of phenoxazine

• Gabriella Kervefors,
• Antonia Becker,
• Chandan Dey and
• Berit Olofsson

Beilstein J. Org. Chem. 2018, 14, 1491–1497, doi:10.3762/bjoc.14.126

• of the desired aryl moiety, and the ortho-effect exerted by the 2-amido substituent was expected to improve the chemoselectivity further. Salt 5a was synthesized in good yield using our reported arylboronic acid methodology [33] (Scheme 3). Attempts to form the corresponding tosylate salt, either

• , entry 1). This was initially believed to be 2-iodophenyl 4-anisyl ether, i.e., the diaryl ether that would form upon transfer of the anisyl moiety to the nucleophile. The reaction was thus further investigated to find conditions that would allow high yield of 3 with complete chemoselectivity. The amount

• . ammonium chloride solution (Table 1, entry 11). Due to the successful outcome of route A, pathway B was only briefly explored. Several dummy groups were considered for the iodonium salt 7. A phenyl dummy might give sufficient chemoselectivity due to the ortho-effect, and the synthesis of salt 7a was

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

• suitable halide salt. In particular, the chemoselectivity of the reaction can be finely tuned by adjusting several parameters, such as the nature of the halide as well as of the iodine(III) ligands and the halide counterion [15][16]. In the case of polyprenoids, we mostly devoted our efforts to achieve the

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• substituents than in other previously described compounds, showing higher reactivity and chemoselectivity of the benzylic position (see ref. [51]). The reactions of substrates 1h–j proceeded without the use of zinc(II) acetate (see Table 2, entries 7–9 versus entry 2). The installation of other carboxylic

• chemoselectivity of our reaction system towards different classes of benzyl carbon atoms. To this end, the clear direction to the secondary benzylic position in substrates 1a–j [51], and the lack of benzylic acetoxylation of the tertiary carbon in substrate 1k (see Table 2) are noteworthy. As bromo radicals are

The first Pd-catalyzed Buchwald–Hartwig aminations at C-2 or C-4 in the estrone series

• Ildikó Bacsa,
• Dávid Szemerédi,
• János Wölfling,
• Gyula Schneider,
• Lilla Fekete and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 998–1003, doi:10.3762/bjoc.14.85

• reported remarkable advantages of microwave-assisted syntheses, including shorter reaction times, higher yields and chemoselectivity [14][15][16]. Concerning the aromatic ring A of estrone, the Pd-catalyzed Buchwald–Hartwig amination was carried out exclusively at position C-3, starting from the 3-triflate

Chlorination of phenylallene derivatives with 1-chloro-1,2-benziodoxol-3-one: synthesis of vicinal-dichlorides and chlorodienes

• Zhensheng Zhao and
• Graham K. Murphy

Beilstein J. Org. Chem. 2018, 14, 796–802, doi:10.3762/bjoc.14.67

• reflux, and upon consumption of the allene an inseparable mixture of chlorination products 3a and 3a’ were obtained. While the overall yield of the chlorinated products increased when under reflux conditions, very little change in chemoselectivity was observed (Scheme 2) [31]. As these results were

Enzyme-free genetic copying of DNA and RNA sequences

• Marilyne Sosson and
• Clemens Richert

Beilstein J. Org. Chem. 2018, 14, 603–617, doi:10.3762/bjoc.14.47

• (kcov/khydr), when reacting with an RNA primer. It will not be trivial to find such a leaving group, as the nucleophilicity of alcohols is quite similar to that of water, so that it is difficult to utilize the chemoselectivity toward reaction partners with different softness, pKa, or other structural

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• Aggarwal et al. [80][89] under aqueous conditions. The reaction exhibited a high level of chemoselectivity and regiospecificity yielding 2-(3-methylpyrazol-1-yl)-5-methylpyrazolo[1,5-a]pyrimidines 120 out of the four possible isomers (Scheme 33). In the case of arylbutadiones, formation of two more

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• concentration, obtained by increasing the amount of copper catalyst, was beneficial to the chemoselectivity. Both styrene derivatives and terminal unactivated alkenes were suitable substrates in this transformation but not internal alkenes [55]. Csp2–CF3 bond-forming reactions Direct trifluoromethylation of

A novel synthetic approach to hydroimidazo[1,5-b]pyridazines by the recyclization of itaconimides and HPLC–HRMS monitoring of the reaction pathway

• Dmitry Yu. Vandyshev,
• Khidmet S. Shikhaliev,
• Andrey Yu. Potapov,
• Michael Yu. Krysin,
• Fedor I. Zubkov and
• Lyudmila V. Sapronova

Beilstein J. Org. Chem. 2017, 13, 2561–2568, doi:10.3762/bjoc.13.252

• problem of chemoselectivity and regioselectivity of the reactions under study is associated with the polynucleophilicity of 1,2-diamino-4-phenylimidazole (4), whose structure contains several dinucleophilic centers, namely: 1,3-C,N (C5-N1-NH2), 1,3-N,N (HN3-C2=NH in the other tautomeric form 4-I), 1,4-N,N

Fluorination of some highly functionalized cycloalkanes: chemoselectivity and substrate dependence

• Attila Márió Remete,
• Melinda Nonn,
• Santos Fustero,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2017, 13, 2364–2371, doi:10.3762/bjoc.13.233

• dependence, neighboring group assistance and chemodifferentiation. Keywords: amino acids; chemoselectivity; fluorine; functionalization; stereoisomers; Introduction Fluorinated molecules exert an ever-increasing impact in medicinal chemistry thanks to their valuable biological properties. Numerous drugs

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• , Oppolzer, Gilchrist and others. However, at that time, researchers faced substantial problems associated with low chemoselectivity of reactions with nitrosoalkenes generated in situ from the corresponding α-halooxime precursors as well as with the need of a large access of the nucleophile. In the recent

Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• as sulfate esters and deoxy glycosides have been successfully synthesized. The preactivation-based chemoselective glycosylation is a powerful strategy for oligosaccharide assembly complementing the more traditional premixed method. Keywords: chemoselectivity; glycosides; preactivation; synthesis

• nucleophilically attacks the intermediate forming the desired glycosidic product [22][23][24]. With the preactivation protocol, the donor activation and acceptor glycosylation occur in two distinctive steps. As a result, a unique chemoselectivity can be achieved with preactivation. Glycosyl donors and acceptors

Mechanically induced oxidation of alcohols to aldehydes and ketones in ambient air: Revisiting TEMPO-assisted oxidations

• Andrea Porcheddu,
• Evelina Colacino,
• Giancarlo Cravotto,
• Francesco Delogu and
• Lidia De Luca

Beilstein J. Org. Chem. 2017, 13, 2049–2055, doi:10.3762/bjoc.13.202

• catalyst for the selective oxidation of primary alcohols to aldehydes under ambient aerobic conditions (Scheme 1) [25][26]. The procedure is operationally simple and extremely effective in terms of both chemoselectivity and reaction yield [27][28]. Gao (2016) further improved this methodology by replacing

Chemoselective synthesis of diaryl disulfides via a visible light-mediated coupling of arenediazonium tetrafluoroborates and CS₂

• Jing Leng,
• Shi-Meng Wang and
• Hua-Li Qin

Beilstein J. Org. Chem. 2017, 13, 903–909, doi:10.3762/bjoc.13.91

• tetrafluoroborates; carbon disulfide; chemoselectivity; diaryl disulfides; photocatalyst; Findings The development of methods for the functionalization of peptides and proteins under mild conditions is a current frontier in the fields of chemistry, biology and drug discovery [1][2][3][4]. Most of the

• pharmaceutically relevant proteins contain disulfide bonds, furthermore, the disulfide ligation and its established chemoselectivity is of great advantage for proteins’ functionalization [5]. In addition, disulfides also play valuable roles as versatile building blocks for industrial applications [6][7][8]. Thus

• (Table 1, entries 7 and 8). Unfortunately, under the applied conditions, the chemoselectivity of the reaction was poor, affording a mixture of unexpected diphenyl sulfide (4a) and diphenyl polysulfides (5a) as byproducts. Thus, a study to optimize the reaction conditions with regard to chemoselectivity

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

• Carmen Moreno-Marrodan,
• Francesca Liguori and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73

• issues owing to many potential side reactions, particularly in relation to chemoselectivity, i.e., over-hydrogenation of alkenes to alkanes [44][45], resistance of other functional groups (ketones [46][47], amines [48][49], azides [50]), regioselectivity [51][52] , isomerization [53][54] and

• in the absence of theoretical or mechanistic studies. Phenylacetylene (7), 1-bromo-4-ethynyl benzene (8) and 1-ethynyl-4-nitrobenzene (9) were hydrogenated using a Pd@C catalyst with trimodal pore-size distribution [152]. The chemoselectivity to the corresponding alkene product showed to follow the

Continuous N-alkylation reactions of amino alcohols using γ-Al₂O₃ and supercritical CO₂: unexpected formation of cyclic ureas and urethanes by reaction with CO₂

• Emilia S. Streng,
• Darren S. Lee,
• Michael W. George and
• Martyn Poliakoff

Beilstein J. Org. Chem. 2017, 13, 329–337, doi:10.3762/bjoc.13.36

• ., boron salts from reductive amination [4]. Hydrogenation offers a greener approach but is often only applicable to simple substrates due to chemoselectivity issues. An approach that has received much attention recently is the concept of hydrogen borrowing catalysis [5][6][7][8][9][10][11][12][13][14][15

A chemoselective and continuous synthesis of m-sulfamoylbenzamide analogues

• Arno Verlee,
• Thomas Heugebaert,
• Tom van der Meer,
• Pavel I. Kerchev,
• Frank Van Breusegem and
• Christian V. Stevens

Beilstein J. Org. Chem. 2017, 13, 303–312, doi:10.3762/bjoc.13.33

• one single step. Furthermore, acid chlorides show a high reactivity [21] making m-(chlorosulfonyl)benzoyl chloride an ideal starting material as was shown by Yang et al. [18]. By transferring this reaction to a multistep flow set-up, we envisioned an improved chemoselectivity. This phenomenon is not

• ][24][25][26], resulting in an improved chemoselectivity. Furthermore, the use of an automated process leads to the possibility to produce libraries of compounds in a fast manner. In addition, an alternate biocompatible and water miscible solvent would result in a flexible and automated chemoselective

• potential of a chemoselective synthesis as a continuous process. As bench mark, aniline and azepane were used as first and second reagent, respectively. After addition of the first reactant and completion of the reaction (followed by TLC) the second reactant was added. The chemoselectivity was determined by

Silyl-protective groups influencing the reactivity and selectivity in glycosylations

• Mikael Bols and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2017, 13, 93–105, doi:10.3762/bjoc.13.12

• benzoylated thioglycosides with high chemoselectivity and was therefore used in a range of high yielding oligosaccharide syntheses [38]. The bifunctional silicon protective group DTBS (Figure 1) has been used both to increase and decrease the reactivity of glycosyl donors. The 4,6-O-DTBS-protected

Poly(ethylene glycol)s as grinding additives in the mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins

• Andrea Mascitti,
• Massimiliano Lupacchini,
• Ruben Guerra,
• Ilya Taydakov,
• Lucia Tonucci,
• Nicola d’Alessandro,
• Frederic Lamaty,
• Jean Martinez and
• Evelina Colacino

Beilstein J. Org. Chem. 2017, 13, 19–25, doi:10.3762/bjoc.13.3

• activated by mechanochemical energy [12]. The yields, reaction rates and chemoselectivity obtained in the presence of melted PEGs were compared with the results obtained in dry-grinding conditions. Results and Discussion H-Leu-OMe was used as benchmark for the mechanochemical preparation of 3-ethyl-5

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

• Anna Zaghi,
• Daniele Ragno,
• Graziano Di Carmine,
• Carmela De Risi,
• Olga Bortolini,
• Pier Paolo Giovannini,
• Giancarlo Fantin and
• Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

• . Moreover, the disclosed flow procedure constituted an equally effective (complete chemoselectivity) and environmentally benign alternative to the analogous batch process towards benzoin- and Stetter-type products mediated by toxic cyanide anions [29][30]. Results and Discussion The possibility of

Continuous-flow synthesis of primary amines: Metal-free reduction of aliphatic and aromatic nitro derivatives with trichlorosilane

• Riccardo Porta,
• Alessandra Puglisi,
• Giacomo Colombo,
• Sergio Rossi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2016, 12, 2614–2619, doi:10.3762/bjoc.12.257

• synthetically relevant intermediates (precursors of baclofen and boscalid). Keywords: chemoselectivity; continuous processes; flow synthesis; nitro reduction; trichlorosilane; Introduction The reduction of nitro compounds to amines is a fundamental transformation in organic synthesis. The nitration of

• demonstrated. The use of extremely inexpensive and non-hazardous chemicals, the very high chemoselectivity and the possibility to realize a completely automated reduction/work-up/isolation process are distinctive features that make the protocol suitable for the reduction of a large variety of products and

Highly chemo-, enantio-, and diastereoselective [4 + 2] cycloaddition of 5H-thiazol-4-ones with N-itaconimides

• Shuai Qiu,
• Choon-Hong Tan and
• Zhiyong Jiang

Beilstein J. Org. Chem. 2016, 12, 2293–2297, doi:10.3762/bjoc.12.222

• chemoselectivity and thus the moderate yield. When the H-bond donor was changed from thiourea to urea (catalyst II), it did not provide better results (Table 1, entry 2) [17][19]. In the [4 + 2] annulation of 5H-thiazol-4-ones with nitroalkenes, dipeptide-based thiourea−amide−tertiary amine III (DP-TAA) was

• ). To improve the chemoselectivity, we synthesized a series of DP-UAAs through tuning of the substituent groups of the urea. We were pleased to find that the reaction rate could be tremendously increased by utilizing DP-UAA V as the catalyst, and 3a was obtainable with high enantioselectivity, high

• chemoselectivity and excellent yield of 98% (Table 1, entry 10). With the optimal reaction conditions in hand, we examined the substrate scope of the enantioselective [4 + 2] cycloaddition between 5H-thiazol-4-ones 1 and N-itaconimides 2, catalyzed by DP-UAA V (Scheme 1). Firstly, with 1a as the model 5H-thiazol-4