Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• chemoselective carbonyl reduction to obtain the corresponding allylic alcohol derivative 36 was achieved in 92% under Luche reduction conditions employing NaBH4/CeCl3 in MeOH/DCM, resulting in the selective synthesis of the syn-alcohol, as a consequence of the formation of the equatorial alcohol favored by

Microwave-assisted synthesis of 2-substituted 4,5,6,7-tetrahydro-1,3-thiazepines from 4-aminobutanol

• María C. Mollo,
• Natalia B. Kilimciler,
• Juan A. Bisceglia and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2020, 16, 32–38, doi:10.3762/bjoc.16.5

• excess, (LR/substrate 2.5:1, toluene, reflux) the reaction was chemoselective toward the amide group, and compound 2a was obtained in high yield (93%), although the unreacted LR complicated the isolation and purification of the product. Lowering the molar ratio of the starting materials to strictly

Chemical synthesis of the pentasaccharide repeating unit of the O-specific polysaccharide from Escherichia coli O132 in the form of its 2-aminoethyl glycoside

• Debasish Pal and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2019, 15, 2563–2568, doi:10.3762/bjoc.15.249

• stereochemistry of the reducing end sugar. The challenging stereoselective glycosylation with the galactofuranosyl unit was achieved through a chemoselective glycosylation approach depending on the higher reactivity of the furanose derivative over the pyranose system. Structure of the target pentasaccharide

Synthesis of acremines A, B and F and studies on the bisacremines

• Nils Winter and
• Dirk Trauner

Beilstein J. Org. Chem. 2019, 15, 2271–2276, doi:10.3762/bjoc.15.219

• isolated from fungi of the genus Acremonium. Here, we present the asymmetric total synthesis of acremine F which hinges on a modestly enantioselective dihydroxylation and a subsequent kinetic resolution via a highly selective asymmetric reduction. Chemoselective oxidation of acremine F gave access to

Attempted synthesis of a meta-metalated calix[4]arene

• Christopher D. Jurisch and
• Gareth E. Arnott

Beilstein J. Org. Chem. 2019, 15, 1996–2002, doi:10.3762/bjoc.15.195

• ) and rhodium(III) complexes underwent spontaneous, chemoselective cyclometalation via C–H bond activation of the N-bound phenyl group (see Figure 2) [19]. Incorporation of a mesoionic carbene directing group onto the upper rim of a calix[4]arene therefore offered potential for a new route to calix[4

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

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• was chemoselective, furnishing in good yields the products resulting from the transfer of the less hindered arene. However, this methodology exhibits two main limitations. First, arenes 86 with electron-withdrawing groups did not react under the optimized conditions and on the other hand, the atom

An efficient synthesis of the guaiane sesquiterpene (−)-isoguaiene by domino metathesis

• Yuzhou Wang,
• Ahmed F. Darweesh,
• Patrick Zimdars and
• Peter Metz

Beilstein J. Org. Chem. 2019, 15, 858–862, doi:10.3762/bjoc.15.83

• stereoselective Michael addition of aldehyde 4 to methyl vinyl ketone [7][8][10] followed by chemoselective elaboration of the two carbonyl functions. Finally, aldehyde 4 was traced back to the commercially available starting material (S)-citronellal (5). On the other hand, a more rarely used enediyne metathesis

• [11][12][13][14] of compound 7 or its relay surrogate 8 might give rise to the conjugated triene 6, chemoselective hydrogenation [15] of which would generate the target molecule 1. Similar to the disconnection of trienyne 3, the metathesis substrates 7 and 8 can be derived from aldehyde 9, which is

• keto aldehyde 18. Chemoselective dibromoolefination with ylide 19 prepared from dibromomethyltriphenylphosphonium bromide and sodium tert-butoxide [22] led to ketone 20 virtually without erosion of the relative configuration (dr = 22:1). After subjecting 20 to carbonyl olefination with unsaturated

Gold-catalyzed ethylene cyclopropanation

• Silvia G. Rull,
• Andrea Olmos and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7

• diazo reagent must be added in one portion before pressurizing the system. This fact constitutes the main drawback when working with this alkene, and a highly chemoselective catalyst toward cyclopropanation over carbene dimerization is needed to enhance the former transformation. In a first array of

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• -trifluoromethyl benzimidazolidene NHCs With the goal to develop chemoselective catalysts, ruthenium complexes containing unsymmetrical N-trifluoromethyl NHCs were introduced by Togni et al. (150–152, Figure 29) [49]. The presence of one N-trifluoromethyl substituent was supposed to impart positive effects on the

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• traditionally carried out in the presence of transition metal complexes. In this field, 4CzIPN (Scheme 4) that was reported in the first work of Adachi et al. as a green emitter for OLEDs [69][83][84] was revisited numerous times in organocatalysis. In 2017, it was notably used for the chemoselective and

Synthesis of pyrrolidine-based hamamelitannin analogues as quorum sensing inhibitors in Staphylococcus aureus

• Jakob Bouton,
• Kristof Van Hecke,
• Reuven Rasooly and
• Serge Van Calenbergh

Beilstein J. Org. Chem. 2018, 14, 2822–2828, doi:10.3762/bjoc.14.260

• developed and delivered the pyrrolidine analogue in 17 steps in high yield. Chemoselective derivatization of the pyrrolidine nitrogen atom resulted in 6 more compounds. The synthesized compounds were evaluated in a biofilm model, but were all inactive. Keywords: hamamelitannin; iminosugar; pyrrolidine

• pyrrolidine-based hamamelitannin analogues is depicted in Scheme 1. The synthesis of 4 as a key intermediate allows to gain access to a diverse set of analogues by chemoselective late-stage derivatization of the pyrrolidine nitrogen. Previously, we used the iminosugar 5 to prepare a series of 2

• , but modification of one of the coupling partners solved this issue. The desired pyrrolidine-based analogue was synthesized in 17 steps and chemoselective modification of the nitrogen atom provided 6 analogues. Unfortunately, these analogues were inactive in inhibiting S. aureus biofilm formation

Dispersion-mediated steering of organic adsorbates on a precovered silicon surface

• Lisa Pecher,
• Sebastian Schmidt and
• Ralf Tonner

Beilstein J. Org. Chem. 2018, 14, 2715–2721, doi:10.3762/bjoc.14.249

• organic molecules on bare silicon surfaces and subsequent reaction with a second molecule with both reactions being chemoselective (layer-by-layer, LbL, approach) [3][4][5]. To achieve an interface structure with predictable properties, it is important that the molecules used for the first layer show well

Synthesis of dihydroquinazolines from 2-aminobenzylamine: N³-aryl derivatives with electron-withdrawing groups

• Nadia Gruber,
• Jimena E. Díaz and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2018, 14, 2510–2519, doi:10.3762/bjoc.14.227

• others, and involve a reduction step which would be incompatible with the presence of nitro or cyano groups [5][13][14][39][68][69][70][71]. The synthetic sequence towards compounds 1 requires the chemoselective arylation of the benzylic amino group of the precursor with active haloaryl derivatives. SNAr

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

• [10][11][12][13]. In recent years, many successful attempts to regioselective [14][15][16][17], chemoselective [18][19][20][21] or atropselective [1][22][23][24][25][26] synthesis of biaryls were presented, often taking advantage of the popular and useful Suzuki–Miyaura cross-coupling reaction

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

• from 4-(n-octyloxy)aniline, seven G-2 melamine-based dendrimers were obtained in 29–79% overall yields. Their iterative convergent- and chemoselective synthesis consisted of SN2-Ar aminations of cyanuric chloride and final triple N-acylations and Williamson etherifications (→ G-2 covalent trimers) or

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

• sequence, proceeding via arylation of phenols with diaryliodonium salts using our reported methodology [23][24][25]. In reactions with unsymmetrical iodonium salts, this type of O-arylation is known to have an ortho-effect, i.e., chemoselective transfer of the ortho-substituted aryl moiety [29][30]. The

• use of unsymmetrical iodonium salts facilitates the synthesis of the reagents and avoids waste of an expensive iodoarene, and we hence envisioned chemoselective transfer of the desired aryl moiety from an unsymmetrical salt with a suitable “dummy” aryl group. Two different approaches to reach 3 are

• illustrated, either employing 2-iodophenol (4) and 2-acetamido-substituted salt 5 (route A) or N-functionalized phenol 6 with 2-iodophenyl salt 7 (route B). In route A, the chemoselective transfer of the 2-amido aryl group over the other aryl group would require a quite electron-rich dummy group or the use of

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• either TrCl or DMTrCl, the products were recovered in 44% and 43% yields, respectively. Under solvent-free Corey conditions, rapid and chemoselective persilylation of ribonucleoside hydroxy functions was effected in a mixer ball mill (Scheme 2) [41]. Complete consumption of starting materials was

• nucleoside analogues with photoreactive materials. Thus, liquid-assisted grinding of the N-hydroxysuccinimidyl esters of o-, m- or p-phenylazobenzoic acids with excess D-threoninol or of the para isomer with an aminonucleoside in the presence of DMAP and ethyl acetate engendered chemoselective N-acylation

• and carboxylic acid Boc protection using an improvised attritor-type mill. Nucleobase Boc protection via transient silylation using an improvised attritor-type mill. Chemoselective N-acylation of an aminonucleoside using LAG in a MBM. Azide–alkyne cycloaddition reactions performed in a copper vessel

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

• Zhensheng Zhao Graham K. Murphy Department of Chemistry, University of Waterloo, 200 University Ave. W., Waterloo, N2L3G1, ON, Canada 10.3762/bjoc.14.67 Abstract Allyl and vinyl chlorides represent important structural motifs in organic chemistry. Herein is described the chemoselective and

Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66

• , PR China 10.3762/bjoc.14.66 Abstract A mechanically-activated chemoselective Heck coupling for the synthesis of 3-vinylindazoles has been developed with the aid of catalytic amounts of TBAB and NaBr as both dehalogenation restrainer and grinding auxiliary. After tuning of the chemical conditions and

• TBAB [24][25][26][27]. However, for inert and liable to dehalogenation bromo-heteroarenes, no desired response had been obtained yet. Thus, this work was going to establish a mild and chemoselective olefination of 3-bromoindazoles under ball-milling conditions (Scheme 2). Results and Discussion

• procedures [35][36], this mechanochemical protocol provided a solvent-free, highly efficient and tractable alternative, and the residual Pd content in the axitinib was determined to be no more than 2 ppm by ICP analysis. Conclusion In conclusion, a solvent-free, chemoselective Heck cross-coupling for the

Synthetic and semi-synthetic approaches to unprotected N-glycan oxazolines

• Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 416–429, doi:10.3762/bjoc.14.30

• other approaches to the Manβ(1–4)GlcNAc (or equivalent) disaccharide. Elegant protecting group manipulations, involving the formation of a dibenzylidene derivative on the mannose ring, benzylation of the remaining free hydroxy groups on the glucosamine ring, and then regio- and chemoselective reductive

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

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• aryl halides in the past years. In contrast, successful examples of copper-catalyzed trifluoromethylation of alkyl halides are quite limited. In 2011, the group of Shibata [25] firstly reported the copper-mediated chemoselective trifluoromethylation at the benzylic position with shelf-stable

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

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