Molecular recognition using tetralactam macrocycles with parallel aromatic sidewalls

• Dong-Hao Li and
• Bradley D. Smith

Beilstein J. Org. Chem. 2019, 15, 1086–1095, doi:10.3762/bjoc.15.105

• tetralactams with parallel aromatic sidewalls are well-suited for various practical supramolecular applications such as molecular machines [72], optical imaging [73], organocatalysis [55], detection [74], and separations [24]. X-ray crystal structures of various squaraine rotaxanes show that the macrocycle

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• : asymmetric organocatalysis; axial chirality; biaryls; hydrogen bond; oxo-Diels–Alder reaction; Introduction The Diels–Alder (DA) reaction is a useful and easy-to-perform method for the synthesis of six-membered rings through the direct formation of C–C bonds between a diene and a dienophile (a substituted

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

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

• organocatalysis using PhI (10 mol %)–mCPBA at ambient conditions as well as under neat mixing [115]. The N1,N1-dibenzylbenzene-1,2-diamine (Figure 27) which is an integrated system by the combination of aniline and N,N-dibenzylaniline led to the successful formation of 1-benzyl-2-phenyl-benzo[d]imidazole 48 under

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

• ; metathesis; Michael addition; organocatalysis; terpenes; Introduction The guaiane sesquiterpene (−)-isoguaiene (1) has been isolated from the liverworts Pellia epiphylla [1] and Dumortiera hirsuta [2] as well as from several Pimpinella species [3][4], while the (+)-enantiomer of 1 has been isolated from the

New α- and β-cyclodextrin derivatives with cinchona alkaloids used in asymmetric organocatalytic reactions

• Iveta Chena Tichá,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2019, 15, 830–839, doi:10.3762/bjoc.15.80

• complexes [2]. CD derivatives have been increasingly applied in catalysis and biomimetic reactions [3][4] thanks to host–guest interactions and to the non-toxic, chiral skeleton of CDs. More specifically, CDs applied in reactions involving metal catalysis [5], organocatalysis [6] and artificial enzymes [7

• improve the rate and modulate the regioselectivity and enantioselectivity of reactions [11]. For example, metal-based CD catalytic systems and CD derivatives for organocatalysis have already shown promising results in the studies by Hapiot and Monflier [12], Armspach [13] and others [14][15]. The chemical

• potential of asymmetric organocatalytic reactions using CD derivatives. However, a wide range of catalytic groups, especially cinchona alkaloids (Figure 2), have been used in organocatalysis with excellent results. These naturally occurring compounds and their derivatives are commonly applied in various

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

• Antonella Di Vincenzo,
• Antonio Palumbo Piccionello,
• Alberto Spinella,
• Delia Chillura Martino,
• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2019, 15, 633–641, doi:10.3762/bjoc.15.59

• -sensitive functionalities in the highly hydrophobic nanoporous environment provided by the fully synthetic calixarene-based polymer, might open interesting perspectives for applicative purposes, in particular in the fields of organocatalysis and of hybrid organic-inorganic materials, such as in the emerging

Thiol-free chemoenzymatic synthesis of β-ketosulfides

• Adrián A. Heredia,
• Martín G. López-Vidal,
• Marcela Kurina-Sanz,
• Fabricio R. Bisogno and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2019, 15, 378–387, doi:10.3762/bjoc.15.34

• ][40]. Such a combination has been scarcely exploited as compared to strategies comprising transition metal catalysis and biocatalysis [41] or, in a lesser extent, organocatalysis and enzymes [42]. In this context, a versatile and robust synthesis of β-ketosulfides avoiding the use of thiols under

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

• % ee), reaction of 1-chloroisochroman (18) and silyl ketene acetals 11 (up to 85% yield and 5% ee), reaction of chromen-4-one (20) and silyl ketene acetals 11 (up to 98% yield and 4% ee). Keywords: hydrogen bonds; hydrolysis; ion pairs; organocatalysis; silanediol; Introduction Silanediols are

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• intermediates mimic single steps of the proposed catalytic cycle in the gas phase. Thus, the charge-tagged catalyst proved one more time its superior effectiveness for the detection and study of reactive intermediates at low concentrations. Keywords: charge-tag; electrospray ionization; enamine organocatalysis

• -proline-catalyzed aldol reaction. Organocatalysis has become a major research field with many applications and has proven to be a valuable complementary approach to organometallic or enzymatic catalysis [29][30][31][32][33][34]. The advantages especially in comparison to organometallic catalysis lie in a

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

Enhanced single-isomer separation and pseudoenantiomer resolution of new primary rim heterobifunctionalized α-cyclodextrin derivatives

• Iveta Tichá,
• Gábor Benkovics,
• Milo Malanga and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2018, 14, 2829–2837, doi:10.3762/bjoc.14.261

• findings indicate, (i) the versatility of selectively modified azido and mesitylene CD skeletons in preparing new types of α-CD derivatives and (ii) the potential of using resolved α-CD pseudoenantiomers in other research fields such as organocatalysis. Keywords: diazido-alpha-cyclodextrin

• resolved for the first time. Ultimately, these results enable the preparation of new types of pure, single isomer, pseudoenantiomer-resolved disubstituted α-CD derivatives, which may be used in a wide range of applications, particularly in organocatalysis. Schematic representation of native α-CD (1) and

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• chemistry is that of Stephenson [34]. Organocatalysis in general offers several advantages over transition metal-mediated catalysis. For example, removal of the catalyst during purification is much more straightforward. Furthermore, the organic molecules employed are typically much less environmentally

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

• During the past decades, asymmetric organocatalysis has played an important role as a tool for the syntheses of chiral molecules under mild conditions [1][2][3][4]. Among these reactions, the asymmetric Michael reaction is a powerful strategy to construct versatile intermediates due to its synthetic

• agrochemicals and drugs [7][8]. Although great progress has been made in this research field, it is still need of further effort to synthesize new efficient chiral organic catalysts for this kind of Michael reactions. The thiourea functional group has played a critical role in organocatalysis due to its ability

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

• rim have been successfully developed and used in chiral recognition. But their use in asymmetric organocatalysis hasn’t been reported. To explore the organocatalytic behaviors of inherently chiral calix[4]arenes modified at the lower rim, Li et al. reported the synthesis of N,O-type enantiomers based

• which the chirality is induced by attaching chiral groups to the calixarene backbone is more common and the obtained results are more promising. In addition, the calix[4]arene backbone is much more preferred beyond other ring sizes both in transition metal catalysis and organocatalysis. It can be argued

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• last 25 years. This review highlights the contribution of different chiral hypervalent iodine reagents in diverse asymmetric conversions. Keywords: alkene functionalization; asymmetric synthesis; hypervalent iodine; organocatalysis; oxidation; Introduction It is more than one century ago since the

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

• of the desired nucleotide. As a consequence, assays involving in situ activation were slow and low yielding. We assumed that the inefficient primer extension with in situ activation could be improved via organocatalysis. We had previously found, when studying extension of aminoterminal primers, that

• dimethylaminopyridine [61]. With aminoterminal primers, in situ activation and organocatalysis with 1-methylimidazole in a magnesium-free buffer had led to encouraging results, even at submillimolar nucleotide concentration [62]. So, starting from a primer extension reaction with an RNA-system that gave less than 1

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

• provide 3-substituted isoindolinones in good yields and diastereomeric excesses. This methodology was applied to the asymmetric synthesis of a new pazinaclone analogue which is of interest in the field of benzodiazepine-receptor agonists. Keywords: asymmetric organocatalysis; Aza-Michael reaction; phase

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

• catalyst. Furthermore, specific organocatalysts can provide respective stereoisomers of the key Michael adduct in up to 99:1 er. Keywords: kinetic resolution; Michael addition; organocatalysis; pregabalin; squaramide; Introduction Asymmetric organocatalysis has considerably broadened possibilities for

• amino acids have also been investigated as treatments for ocular disorders [7]. However, the syntheses of this type of compounds were long and relied on the use of Evans chiral auxiliaries or chiral starting materials. Various GABA derivatives were synthesized using asymmetric organocatalysis

• synthesized binaphthol-squaramide catalysts (Sa,R,R)-C8, and (Sa,S,S)-C8 (Scheme 3). Results of the initial catalyst screening are summarized in Table 1. The binaphthyl structural motif has already been employed in the hydrogen-bond-donating organocatalysis [35][36]. However, the binaphthol moiety possessing

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

• )-GABOB. Keywords: alcoholysis desymmetrization; bifunctional organocatalysis; chloramphenicol base; Introduction Over the past decade, remarkable advances in the utilization of natural products as chiral structural motifs for the design of bifunctional organocatalysts have been achieved. A high

• 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

• different alcohols (Table 3). Excellent yields with high enantioselectivities were obtained in all cases. The sterically more bulky 2-propanol worked well in this reaction. Allylic alcohol, benzyl alcohol and cinnamyl alcohol were also well compatible in this bifunctional organocatalysis conditions to

Quinone-catalyzed oxidative deformylation: synthesis of imines from amino alcohols

• Xinyun Liu,
• Johnny H. Phan,
• Benjamin J. Haugeberg,
• Shrikant S. Londhe and
• Michael D. Clift

Beilstein J. Org. Chem. 2017, 13, 2895–2901, doi:10.3762/bjoc.13.282

• synthetic versatility of quinone-catalyzed oxidative C–C bond cleavage. Keywords: catalysis; deformylation; organic synthesis; organocatalysis; Introduction Imines are extremely versatile intermediates in organic chemistry [1][2][3]. Consequently, many synthetic methods have been developed for the

• derivatives [49][50] from 1,2-amino alcohols. Conclusion In conclusion, we have developed a novel method for the synthesis of imines from 1,2-amino alcohols. This chemistry features an unprecedented application of quinone organocatalysis to enable oxidative deformylation under aerobic conditions. Future work

Synthesis of 1,3-cis-disubstituted sterically encumbered imidazolidinone organocatalysts

• Jan Wallbaum and
• Daniel B. Werz

Beilstein J. Org. Chem. 2017, 13, 2577–2583, doi:10.3762/bjoc.13.254

• ; MacMillan catalyst; organocatalysis; Introduction Organocatalytic iminium and enamine activation has attracted organic chemists for more than one century [1]. Until today a wide and constantly increasing number of different organocatalytic transformations with various substrates have been accomplished [2

• ][3][4][5][6][7]. Initially, proline and proline-derived catalysts have been widely used in asymmetric iminium and enamine organocatalysis [8][9][10][11][12]. Since the beginning of the 21th century imidazolidinone-based organocatalysts developed by MacMillan and co-workers, which are easily

Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors

• Mukta Shaw,
• Yogesh Kumar,
• Rima Thakur and
• Amit Kumar

Beilstein J. Org. Chem. 2017, 13, 2385–2395, doi:10.3762/bjoc.13.236

• transformations [14][15][16][17]. One of the major applications of organocatalysis lies in the field of enantioselective synthesis, where organocatalysts are considered as fundamental tools in the catalysis toolbox [18][19][20][21][22]. Moreover, the reactivity and selectivity of organocatalysts can be further

A mechanochemical approach to access the proline–proline diketopiperazine framework

• Nicolas Pétry,
• Hafid Benakki,
• Eric Clot,
• Pascal Retailleau,
• Farhate Guenoun,
• Fatima Asserar,
• Chakib Sekkat,
• Thomas-Xavier Métro,
• Jean Martinez and
• Frédéric Lamaty

Beilstein J. Org. Chem. 2017, 13, 2169–2178, doi:10.3762/bjoc.13.217

• feature, used for the preparation of biologically active peptides and peptidomimetics [7], for applications in organocatalysis [8][9][10], and for the preparation of novel materials [11][12]. An interesting sub-family of these compounds are DKPs derived from the amino acid proline and its analogues, which

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• strategy. Hereby both, approaches relying on either asymmetric metal- or organocatalysis, have been well-investigated already [105][106][107][108][109][110][111][112][113][114][115][116][117][118][119][120][121][122]. In the field of non-covalent asymmetric organocatalysis, chiral H-bonding catalysis [37

• -transfer reactions is hydrogen peroxide (H2O2). Unfortunately, the direct use of this base-chemical under asymmetric organocatalysis turned out to be rather tricky for α-hydroxylation reactions. One recent report by the Ooi group overcame some of the limitations by using H2O2 in combination with

Mechanochemical enzymatic resolution of N-benzylated-β³-amino esters

• Mario Pérez-Venegas,
• Gloria Reyes-Rangel,
• Adrián Neri,
• Jaime Escalante and
• Eusebio Juaristi

Beilstein J. Org. Chem. 2017, 13, 1728–1734, doi:10.3762/bjoc.13.167

• ][18][19][20][21][22] including strategies based on organocatalysis [23][24][25][26] and kinetic resolution using enzymes such as Candida antarctica lipase B, which was shown to be efficient in the resolution of racemic β-amino acids under various conditions [27][28][29][30]. Among recent developments