Efficient method for propargylation of aldehydes promoted by allenylboron compounds under microwave irradiation

• Jucleiton J. R. Freitas,
• Queila P. S. B. Freitas,
• Silvia R. C. P. Andrade,
• Juliano C. R. Freitas,
• Roberta A. Oliveira and
• Paulo H. Menezes

Beilstein J. Org. Chem. 2020, 16, 168–174, doi:10.3762/bjoc.16.19

• -560, Brazil Universidade Federal de Campina Grande, Centro de Educação e Saúde: Cuité, Paraíba, Brazil 10.3762/bjoc.16.19 Abstract The propargylation of aldehydes promoted by microwave irradiation using allenylboron compounds in a chemo- and regioselective way is described. The corresponding products

• conversion of aldehydes into the corresponding homopropargylic alcohols 2 in moderate to high yields and in a very regioselective way, while the propargylated product was obtained as the major product in all cases. Aromatic aldehydes such as benzaldehyde, 2-methylbenzaldehyde and 3,5-dimethylbenzaldehyde

• gave the corresponding products 2b–d in good yields in a regioselective way regardless of the position of the substituent on the aromatic ring. When aldehydes containing electron-donating groups such as 2-, 3- or 4-methoxybenzaldehyde or 3,4,5-trimethoxybenzaldehyde were used, the corresponding

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

• Abhijit Paul,
• Debnath Chatterjee,
• Srirupa Banerjee and
• Somnath Yadav

Beilstein J. Org. Chem. 2020, 16, 140–148, doi:10.3762/bjoc.16.16

• are biologically and medicinally very important compounds, and their syntheses have received considerable attention. Herein, we report the synthesis of 3-alkenylindoles via a regioselective alkenylation of indoles, catalysed by a ruthenium nanocatalyst (RuNC). The reaction tolerates several electron

• Pd-catalysed Fujiwara–Moritani or oxidative dehydrogenative Heck reaction via dual C–H activation [21][22][23][24]. One of the early examples of this reaction, reported by Gaunt and co-workers, involved the regioselective, solvent-controlled C3 alkenylation of indoles with alkenes containing electron

• reaction of aza compounds [43][44]. Again, a Ru nanoparticle-catalysed C–H selenylation of indoles was reported by Lin et al. [45]. Herein, we report the Ru-catalysed regioselective synthesis of C3 alkenylindoles using a near-naked, surfactant-free, and recyclable Ru nanocatalyst in a heterogeneous manner

SnCl₄-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

• Kesatebrhan Haile Asressu and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2019, 15, 2990–2999, doi:10.3762/bjoc.15.295

• in the presence of acetic anhydride. Among the various Lewis acids tested, the desired acetolysis products were obtained in moderate yields under tin(IV) chloride catalysis. Our methodology could be extended to regioselective protecting group installations and manipulations towards a number of

• as catalyst under neat conditions, which provided the expected β-ring-opened product 12 in a moderate yield (Table 1, entry 5). This acetolysis reaction resulted in regioselective acetylation of positions O-7 and O-2 in line with the principles of green chemistry. It is known that anomeric acetates

Regioselectivity of glycosylation reactions of galactose acceptors: an experimental and theoretical study

• Enrique A. Del Vigo,
• Carlos A. Stortz and
• Carla Marino

Beilstein J. Org. Chem. 2019, 15, 2982–2989, doi:10.3762/bjoc.15.294

• Universitaria, 1428 Buenos Aires, Argentina 10.3762/bjoc.15.294 Abstract Regioselective glycosylations allow planning simpler strategies for the synthesis of oligosaccharides, and thus reducing the need of using protecting groups. With the idea of gaining further understanding of such regioselectivity, we

• , whose relative reactivity is still rather poorly understood [6]. Regioselective approaches for the glycosylation of acceptors with more than one free hydroxy group have been developed, and in some of the cases they were successfully rationalized [7][8][9]. In other cases, the results could not be

• molecular modeling approach. Results and Discussion For this study, ᴅ-Galp derivatives with both their OH-2 and OH-6 group blocked were required. The regioselective functionalization of carbohydrates is usually a difficult task due to the similar reactivity of secondary hydroxy groups [13]. We synthesized

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• challenging introduction of functional groups (mostly hydroxy groups) into nonactivated C–H bonds [46][105][106][107][108][109][110][111][112]. The absence of directing functional groups, however, renders these regioselective oxidations of nonactivated carbon atoms highly challenging, as the chemical

Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

• Hoang Huy Do,
• Saif Ullah,
• Alexander Villinger,
• Joanna Lecka,
• Jean Sévigny,
• Peter Ehlers,
• Jamshed Iqbal and
• Peter Langer

Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276

• diindolofurans by regioselective Suzuki–Miyaura couplings of tetrabromofuran and subsequent cyclization by tetrafold Buchwald–Hartwig reaction [31]. We also studied the synthesis of benzo[4,5]furo[3,2-b]indoles by a similar concept. However, while performing our studies, Truong et al. reported the synthesis of

• ten benzo[4,5]furo[3,2-b]indole derivatives based on regioselective Suzuki–Miyaura reaction of 2,3-dibromobenzofuran with 2-bromophenylboronic acid and subsequent cyclization. The difference between the work of Truong and our approach mainly lies in the synthesis of the cyclization precursor. The

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• then underwent a regioselective monodeprotection to generate a lone phenol group. The phenolate was reacted with 1,2-dibromoethane and the nitrobenzene groups were reduced to the corresponding anilines giving 1a. The double aniline 1a was alkylated using ethyl bromoacetate under basic conditions in

Synthetic terpenoids in the world of fragrances: Iso E Super^® is the showcase

• Alexey Stepanyuk and
• Andreas Kirschning

Beilstein J. Org. Chem. 2019, 15, 2590–2602, doi:10.3762/bjoc.15.252

• isomers but rather as varying mixtures because none of the industrial syntheses is very stereo- and regioselective as shown by GC analysis in Figure 4. So far efforts in industrial production have been directed towards product mixtures that are dominated by one isomer with favourable olfactory properties

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• synthesis of isoquinolones using an N-methoxyamide as directing group for the ortho-position and alkynyl bromide to achieve the regioselective cyclization (Scheme 1B) [31]. In parallel, our group has developed Ru(II) and Rh(III)-catalyzed inter- and intramolecular annulations of aromatic rings with alkynes

Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

• Benedikt C. Melzer,
• Alois Plodek and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222

• Benedikt C. Melzer Alois Plodek Franz Bracher Department of Pharmacy – Center for Drug Research, Ludwig-Maximilians University Munich, Butenandtstr. 5–13, 81377 Munich, Germany 10.3762/bjoc.15.222 Abstract Readily available 4-bromobenzo[c][2,7]naphthyridine undergoes regioselective direct ring

• readily available 4-bromobenzo[c][2,7]naphthyridine (9d) undergoes regioselective direct ring metalation at C-5 with TMPMgCl∙LiCl at −40 °C. Quenching with various electrophiles gives a broad range of 5-substituted products, which should be valuable building blocks for the synthesis of heterocyclic

• benzo[c][2,7]naphthyridine alkaloids perlolidine (6) and subarine (7) with the common benzo[c][2,7]naphthyridine moiety highlighted in bold. A–C): Published methods for the synthesis of 4,5-disubstituted benzo[c][2,7]naphthyridines; D) New approach. Regioselective metalation of 4-bromobenzo[c][2,7

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• amide (Scheme 19). With this method, both mono- and difluorinated benzoic acid derivatives can be selectively obtained in high yields. In 2014, Pu and co-workers [58] devised the regioselective Pd(PPh3)4-catalyzed electrophilic ortho-fluorination of 2-arylbenzothiazoles with NFSI and ʟ-proline as the

• the corresponding products with wide substrate tolerance in moderate to good yields (Scheme 82). After one year, the group of Cai [147] presented a Cu(II)-catalyzed 8-amido chelation-induced regioselective C5-trifluoromethylation of quinolines (Scheme 83a). With CuBr2 as a catalyst and

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• EWG stabilise heptafulvenes (6b’) [9][67]. In many cases, the reactions of fulvenes are peri- [17][22][28][73][74][75][76][77][78][79][80], enantio- [81][82][83][84][85][86][87], diastereo- [17][21][26][28][81][88][89][90][91][92], and regioselective [17][28][74][75][76][81][82][93][94], and result

Regioselective Pd-catalyzed direct C1- and C2-arylations of lilolidine for the access to 5,6-dihydropyrrolo[3,2,1-ij]quinoline derivatives

• Hai-Yun Huang,
• Haoran Li,
• Thierry Roisnel,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2019, 15, 2069–2075, doi:10.3762/bjoc.15.204

• acetate bases in DMA was found to promote the regioselective arylation at α-position of the nitrogen atom of lilolidine with a wide variety of aryl bromides. From these α-arylated lilolidines, a second arylation at the β-position gives the access to α,β-diarylated lilolidines containing two different aryl

• to prepare either α- [22][23][24][25][26][27][28][29][30][31] or β-arylated [32][33][34][35][36][37] indoles, depending on the reaction conditions. However, to the best of our knowledge, no example of regioselective α- or β-arylations via the C–H bond functionalization of lilolidine has been reported

Naphthalene diimides with improved solubility for visible light photoredox catalysis

• Barbara Reiß and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201

• oleum in good yields [55][56][57]. The regioselective introduction of just two substituents can be controlled by stoichiometry. Accordingly, the 2,6-dibromo derivative 8 was prepared by 1.5 equivalents DBH and further used as crude product because it cannot be purified due to its very poor solubility

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

• Ullmann-type coupling to give aryl azide 2, which readily reacted with phenylacetylene in a copper-catalyzed Huisgen 1,3-dipolar cycloaddition to give 1,2,3-triazole 3 (Scheme 1). The formation of the ruthenacycle was then achieved using Albrecht’s method involving regioselective methylation of triazole 3

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• include the regioselective dihydroxylation and etherification to introduce the C-14 hydroxy group and the construction of the butenolide moiety. Particularly, the characteristics of Li’s route are low cost, high yield (9 steps, 44% yield) and easy handling (all intermediates could be scaled up to 100

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• corresponding dipyrromethenium chloride, which was then converted into its BODIPY analogue 2 through complexation by BF3·OEt2 in basic media. Regioselective introduction of distyryl substituents is achieved via Knoevenagel-type condensation in the presence of piperidine using aldehyde derivatives 3 and 4 whose

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• )-13 prepared from the respective esters (Scheme 4) 5b appeared moderately active as immunostimulants [18]. Amines and amino alcohols By functionalization at C2: Synthesis of enantiomerically pure amines from 2-substituted N-(1-phenylethyl)aziridines 5–7 requires a regioselective reductive aziridine

• to supply (R)-16 [42]. To synthesize (R)-17 the aminosulfonyl group was introduced in a standard way before hydrogenation [43]. The synthesis of amino alcohols of general formula 11 (Scheme 3) from 2-substituted N-(1-phenylethyl)aziridines 5 and 6 can be achieved by a regioselective reductive

• aziridine ring opening combined with functionalization of the C2 substituent and optional alkylation or arylation of the nitrogen atom [44]. Following a similar regioselective aziridine opening, a mixture of epimeric amino alcohols (2R/S,1'R)-23 was prepared in two steps from the aziridine alcohol (2R/S,1'R

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

• not formed. Atmospheric oxygen has oxidized Cu(I) to Cu(II). This Cu(II) acts as an initiator for a single electron transfer (SET) process, to proceed the reaction with benzylamine. A regioselective synthesis of imidazo[1,2-a]pyridines was reported by the group of Kamal and Reddy [123]. They have

Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction

• Xiujun Liu,
• Xiang Ma and
• Yaqing Feng

Beilstein J. Org. Chem. 2019, 15, 1434–1440, doi:10.3762/bjoc.15.143

• Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China 10.3762/bjoc.15.143 Abstract Isoxazoline-linked porphyrins have been synthesized by a regioselective 1,3-dipolar cycloaddition reaction between vinylporphyrin 2 and nitrile oxides. The steric interaction directed the

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• presence of I2 as catalyst. The mechanism follows the initial formation of the imine compound between the aldehyde and the arylamine, followed by an imino-Diels–Alder reaction with the enolate generated from the ketosteroid. The reaction is highly regioselective for the enolization of the ketone, thus

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

• involving a sequential enamine formation-Michael addition to produce intermediate 139, followed by intramolecular cyclization to 141 and aromatization through species 142 and 143 (Scheme 40). The cyclization step takes place in a regioselective manner, leading to five-membered heterocycle 141 rather than to

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• azobenzene [58]. The cyclopalladation process was proved to be a highly regioselective process and the observed palladation rate was faster compared to the conventional solution-phase method. An equimolar amount of 4'-(N,N-dimethylamino)-4-nitroazobenzene and Pd(OAc)2 in the presence of 25 μL of glacial

• acetic acid (for liquid-assisted grinding, LAG) led to the regioselective C–H activation (Figure 5) [58]. In 2008, the mechanochemical synthesis of both [2]- and [4]rotaxanes was reported by Chiu and co-workers. The reactions led to high yields of the products 12 and 13 under solvent-free conditions at a

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• drastically alter its structural properties and reactivities. Prominent examples are the cis-bromination of α,β-unsaturated carboxylato ligands [2], regioselective Diels–Alder reactions of encapsulated dienoate ligands [3], and the stabilization of unusual co-ligand conformations, respectively [4]. The