Complexation of chiral amines by resorcin[4]arene sulfonic acids in polar media – circular dichroism and diffusion studies of chirality transfer and solvent dependence

• Bartosz Setner and
• Agnieszka Szumna

Beilstein J. Org. Chem. 2019, 15, 1913–1924, doi:10.3762/bjoc.15.187

• conclusion comes from a comparison of complexes in methanol and DMSO. One would expect that due to the dual hydrogen bond donor/acceptor character of methanol this solvent should be more destructive to ion-pair complexes based on charged hydrogen bonds than DMSO that can only serve as a hydrogen bond

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

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

• to be 100% stereospecific under dry mortar and pestle grinding [110]. The hydrogen-bond donor 4,6-dichlororesorcinol was used as the supramolecular catalyst for the transformation in the solid-state. From single crystal X-ray analysis the authors have proved the formation of the 2:2 complex 42 from

Study on the regioselectivity of the N-ethylation reaction of N-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxamide

• Pedro N. Batalha,
• Luana da S. M. Forezi,
• Maria Clara R. Freitas,
• Nathalia M. de C. Tolentino,
• Ednilsom Orestes,
• José Walkimar de M. Carneiro,
• Fernanda da C. S. Boechat and
• Maria Cecília B. V. de Souza

Beilstein J. Org. Chem. 2019, 15, 388–400, doi:10.3762/bjoc.15.35

• ), and anticancer activity for three cancer cell lines (Figure 1) [16]. Although it is not a general rule for achieving a bioactive profile, any groups attached to C-3 of the 4-oxoquinoline moiety, especially those containing a hydrogen bond donor group, such as a carboxyl, an acyl hydrazide or a

• , accomplished through temperatures above 200 °C, any derivatization afterwards should maintain the N–H carboxamide group intact, in order to provide the hydrogen bond donor group attached to C-3, which is usually related to the bioactivity of such compounds (Figure 2) [3][23]. In order to obtain an N1-alkylated

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• these studies should facilitate the development of new ligands. In terms of mapping of glutamate receptors hydroxyglutamic acids 2–4 (Figure 2) should be of great interest since an additional hydroxy group is capable of acting as a hydrogen bond donor as well as a hydrogen bond acceptor. In fact (2S,4S

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• )–2.05(2) Å) than with chlorosilanol 8 (OH···2.16(0) Å). Due to its two hydroxy units, the silanediol 9 shows higher catalytic activity as hydrogen bond donor than chlorosilanol 8, e.g., C–C coupling N-acyl Mannich reaction of silyl ketene acetals 11 with N-acylisoquinolinium ions (up to 85% yield and 12

• ]) to the corresponding silanediols. While hydrolyses of dichlorosilanes have been studied extensively [23][24][25], hydrolyses of alkoxy dichlorosilanes are much less explored. Hydrogen bond donor (HBD) catalysis is an emerging field in organic synthesis [26][27][28], employing, e.g., squaramides [29

• ) (Table 5, Figure 17), which is the longest hydrogen bond for BIFOXSiCl(OH) (8) and BIFOXSi(OH)2 (9). In dimeric structures of silanediol 9 (Figure 14) the hydroxy group O4H is a hydrogen bond donor to O3. The hydrogen atom of the O–H group (O3H) is pointing outwards and can form a hydrogen bond to an

Determining the predominant tautomeric structure of iodine-based group-transfer reagents by ¹⁷O NMR spectroscopy

• Nico Santschi,
• Cody Ross Pitts,
• Benson J. Jelier and
• René Verel

Beilstein J. Org. Chem. 2018, 14, 2289–2294, doi:10.3762/bjoc.14.203

• residual value (Table 1). Conceivably, this may be due to intermolecular hydrogen bonding with the solvent or other alcohol molecules in the concentrated solution. In fact, including a methanol solvent molecule as a hydrogen-bond donor in the DFT calculation will shift the δcalc in the right direction for

Synthesis and supramolecular self-assembly of glutamic acid-based squaramides

• Juan V. Alegre-Requena,
• Marleen Häring,
• Isaac G. Sonsona,
• Alex Abramov,
• Eugenia Marqués-López,
• Raquel P. Herrera and
• David Díaz Díaz

Beilstein J. Org. Chem. 2018, 14, 2065–2073, doi:10.3762/bjoc.14.180

• conjugated to an aromatic cyclobutenedione ring, can be easily synthesized from different derivatives of squaric acid and amines [1][2][3][4]. The possibility to fabricate chiral squaramide derivatives and their efficient hydrogen bond donor/acceptor ability has driven the pivotal role of these compounds in

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

Investigations towards the stereoselective organocatalyzed Michael addition of dimethyl malonate to a racemic nitroalkene: possible route to the 4-methylpregabalin core structure

• Denisa Vargová,
• Rastislav Baran and
• Radovan Šebesta

Beilstein J. Org. Chem. 2018, 14, 553–559, doi:10.3762/bjoc.14.42

• an additional hydrogen bond donor group was not tested in too much depth. Therefore, we have synthesized two binaphthol-based diastereomeric squaramide catalysts (Sa,R,R)-C8 and (Sa,S,S)-C8 (Scheme 3). Starting from (S)-BINOL (8), amine 9 was obtained in five steps following literature procedures

Novel amide-functionalized chloramphenicol base bifunctional organocatalysts for enantioselective alcoholysis of meso-cyclic anhydrides

• Lingjun Xu,
• Shuwen Han,
• Linjie Yan,
• Haifeng Wang,
• Haihui Peng and
• Fener Chen

Beilstein J. Org. Chem. 2018, 14, 309–317, doi:10.3762/bjoc.14.19

• moiety as monodentate hydrogen bond donor to activate the electrophile (anhydride), whilst retaining the tertiary amine functionality to activate the nucleophile (alcohol, Figure 2). As part of our ongoing research program on chloramphenicol base organocatalysis, herein, we report a new class of

• bond donor were developed and evaluated for enantioselective organocatalytic alcoholysis of meso-cyclic anhydrides. These structural diversified organocatalysts were found to induce high enantioselectivity in alcoholysis of anhydrides and was successfully applied to the asymmetric synthesis of (S

• Lingjun Xu Shuwen Han Linjie Yan Haifeng Wang Haihui Peng Fener Chen Department of Chemistry, Fudan University, Shanghai 200433, PR China 10.3762/bjoc.14.19 Abstract A family of novel chloramphenicol base-amide organocatalysts possessing a NH functionality at C-1 position as monodentate hydrogen

Stereochemical outcomes of C–F activation reactions of benzyl fluoride

• Neil S. Keddie,
• Pier Alexandre Champagne,
• Justine Desroches,
• Jean-François Paquin and
• David O'Hagan

Beilstein J. Org. Chem. 2018, 14, 106–113, doi:10.3762/bjoc.14.6

• demonstrated that both associative and dissociative pathways operate to varying degrees, according to the nature of the nucleophile and the hydrogen bond donor. Keywords: benzylic fluorides; C–F activation; chiral liquid crystal; 2H NMR; PBLG; stereochemistry; Introduction The C–F bond is the strongest

• C–F amination reactions employing water/isopropanol [3] and triols [4][5] as hydrogen-bond donor activators. Through these studies, the authors suggested that multiple donors (even when using a triol) surround the fluorine atom of the benzyl fluoride, thus stabilising the transition state through

• donors, namely HFIP, in the presence or absence of trifluoroacetic acid (TFA). For both of these activators, Paquin et al. proposed a dissociative unimolecular (SN1) mechanism, whereby the strong hydrogen bond donor associates with the benzyl fluoride, leading to ionisation of the molecule, generating a

Ring-size-selective construction of fluorine-containing carbocycles via intramolecular iodoarylation of 1,1-difluoro-1-alkenes

• Takeshi Fujita,
• Ryo Kinoshita,
• Tsuyoshi Takanohashi,
• Naoto Suzuki and
• Junji Ichikawa

Beilstein J. Org. Chem. 2017, 13, 2682–2689, doi:10.3762/bjoc.13.266

• afford difluoromethylated dihydrophenanthrene derivative 4a in almost quantitative yield [29][30]. A difluoromethyl group functions as a hydrogen-bond donor and a bioisostere of a hydroxy group, as a result of which difluoromethyl-bearing compounds attract much attention as bioactive materials [31][32

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• located on the oxygen atom and the dipole moment of the amide bond is 3.6 D [7]. The amide bond can also perform hydrogen bonds, with the oxygen atom as the hydrogen bond acceptor and N–H as hydrogen bond donor. This characteristic is important for the formation of secondary structures and folding into

Synthesis and metal binding properties of N-alkylcarboxyspiropyrans

• Alexis Perry and
• Christina J. Kousseff

Beilstein J. Org. Chem. 2017, 13, 1542–1550, doi:10.3762/bjoc.13.154

• similar tether do not. To probe involvement of the carboxylate/carboxylic acid moiety (e.g., in forming inter- or intramolecular hydrogen bonds) we prepared C6 ester derivative 10 (Figure 7) as a direct point of comparison with C6SP. In the absence of a hydrogen bond donor group, the concentration of 10MC

Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides

• Ryota Miyaji,
• Yuuki Wada,
• Akira Matsumoto,
• Keisuke Asano and
• Seijiro Matsubara

Beilstein J. Org. Chem. 2017, 13, 1518–1523, doi:10.3762/bjoc.13.151

• -hydroxybenzamide substrates comprise both amide and phenolic moieties. These can interact with a hydrogen-bond donor and a hydrogen-bond acceptor, respectively. Such interactions are expected to recognize a specific conformation of the substrate molecule to realize the enantioselective construction of axially

Syntheses of 3,4- and 1,4-dihydroquinazolines from 2-aminobenzylamine

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

Beilstein J. Org. Chem. 2017, 13, 1470–1477, doi:10.3762/bjoc.13.145

• different nucleophilicity of both amino groups, the predictable formation of a hydrogen bond between the aromatic amino group (hydrogen bond donor) and the aliphatic NHR (hydrogen bond acceptor) could increase the nucleophilicity of the former and decrease the reactivity of the latter, favoring the chance

Spectral and DFT studies of anion bound organic receptors: Time dependent studies and logic gate applications

• Srikala Pangannaya,
• Neethu Padinchare Purayil,
• Shweta Dabhi,
• Venu Mankad,
• Prafulla K. Jha,
• Satyam Shinde and
• Darshak R. Trivedi

Beilstein J. Org. Chem. 2017, 13, 222–238, doi:10.3762/bjoc.13.25

• and R2 with varied positional substitution of a cyano and nitro signaling unit having a hydroxy functionality as the hydrogen bond donor site have been designed, synthesized and characterized by FTIR, 1H NMR spectroscopy and mass spectrometry. The receptors R1 and R2 exhibit prominent visual response

• aromatic ring and possess hydrogen-bond donor functionality, namely a hydroxy group in the naphthyl part, which can act as an active binding site for anions. Additionally, both receptors R1 and R2 encompass an electron-withdrawing substituent, a CN group (R1) or a NO2 functionality (R2), in the para

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• Pavel Nagorny Zhankui Sun Chemistry Department, University of Michigan, Ann Arbor, MI 48109, USA School of Pharmacy, Shanghai Jiao Tong University, No. 800 Dongchuan Rd., Shanghai 200240, P. R. China 10.3762/bjoc.12.283 Abstract Hydrogen bond donor catalysis represents a rapidly growing subfield

• organic catalysts for electrophile activation through the formation of C–H hydrogen bonds and C–X halogen bonds. Keywords: C–H hydrogen bond; counteranion activation; electrophile activation; halogen bond donor; hydrogen bond donor; organocatalysis; Review Introduction Over the past century chemists

• these efforts. The use of synthetic hydrogen bond donors for the activation of neutral or ionic electrophiles has been one of the major focuses of these research efforts in the past two decades (Figure 1) [1]. Many privileged hydrogen bond donor scaffolds capable of forming single or double hydrogen

Bifunctional catalysis

• Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1079–1080, doi:10.3762/bjoc.12.102

• , stereochemically defined products through the action of the bifunctional catalyst system. Many bifunctional catalysts possess either Lewis or Brønsted basic functionality and a hydrogen-bond donor group suitably positioned over a chiral scaffold. Compared to single functional group catalysts, the cooperative

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• amine of the catalyst and ketone substrate and protonation of the tertiary amino group. The protonated amine then served as hydrogen bond donor to activate the carbonyl group of isatin substrates, thereby facilitating the aldol addition. Interestingly, the authors obtained the R-/S-enantiomer by using

The aminoindanol core as a key scaffold in bifunctional organocatalysts

• Isaac G. Sonsona,
• Eugenia Marqués-López and
• Raquel P. Herrera

Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50

• formation of catalytically active oxazaborolidines using cis-1,2-aminoindanol derivatives [9][10] and (b) the synthesis of more active cooperative thiourea-urea-based organocatalysts, which employ the aminoindanol framework as structural linker between two hydrogen-bond-donor moieties [11]. The latter ones

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• depicted in the left, in Scheme 2, seems to be operative, when the R group of the organocatalyst possesses a moiety, that is able to form hydrogen bonds, being the hydrogen bond donor. Employing this logic, many organocatalysts have been developed, possessing various groups, that are able to form hydrogen

Effective in silico prediction of new oxazolidinone antibiotics: force field simulations of the antibiotic–ribosome complex supervised by experiment and electronic structure methods

• Jörg Grunenberg and
• Giuseppe Licari

Beilstein J. Org. Chem. 2016, 12, 415–428, doi:10.3762/bjoc.12.45

• side chain, keeping neverthelss the NH group as a hydrogen bond donor. Finally, we added a second CH3CONH group to the side chain (candidates 27 and 28). A further H-bond donor could improve the enthalpic affinity between the drug and the receptor by increasing the chance for a second H-bond between

Organocatalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones with bifunctional amine-thiourea catalysts bearing multiple hydrogen-bond donors

• Ming-Liang Zhang,
• Deng-Feng Yue,
• Zhen-Hua Wang,
• Yuan Luo,
• Xiao-Ying Xu,
• Xiao-Mei Zhang and
• Wei-Cheng Yuan

Beilstein J. Org. Chem. 2016, 12, 295–300, doi:10.3762/bjoc.12.31

• enantioselectivity (up to 73% ee). A possible transition-state model, characterized by the bifunctional catalyst acting as a multiple hydrogen-bond donor, is also proposed. The application of 1H-pyrrole-2,3-diones in the catalytic asymmetric reactions for the preparation of biologically relevant compounds is

A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

• Steven C. Zimmerman

Beilstein J. Org. Chem. 2016, 12, 125–138, doi:10.3762/bjoc.12.14

• acid group making it a better hydrogen bond donor. However, titrations in a mixed aqueous–organic solvent suggest that the carboxylic acid within the molecular tweezer is actually less acidic and likely a less effective hydrogen bonding unit [22]. Preorganization and cost of freezing single bond