Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

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

• other. Nitschke and co-workers reported, that mixing of 2-formylpyridine (3.0 equiv), 6-methyl-2-formylpyridine (3.0 equiv), tris(2-aminoethyl)amine (1.0 equiv) and ethanolamine (3.0 equiv) in aqueous solution afforded a dynamic library of imines which subsequently could be self-sorted into two distinct

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• -aminobutyric acid by high-performance liquid chromatography with molecular fluorescence detection [5]. In addition to the above manipulations, OPA and its derivatives are also valuable reagents [6] in organic chemistry, used to generate phthalimidine [7], imines [8], isoindole [9], 3-hydroxyindanone [10

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

• . Parallel to this, 4CzIPN was also used as an organoredox catalyst for the alkylation of heteroarenes [85], the oxidation of silicates [86], the alkylation of imines [87], the α-arylation/heteroarylation of 2-trifluoroboratochromanones [88]. In these different situations, comparisons with reference

1,8-Bis(dimethylamino)naphthyl-2-ketimines: Inside vs outside protonation

• A. S. Antonov,
• A. F. Pozharskii,
• P. M. Tolstoy,
• A. Filarowski and
• O. V. Khoroshilova

Beilstein J. Org. Chem. 2018, 14, 2940–2948, doi:10.3762/bjoc.14.273

• has been shown that E-isomers of neutral imines can be stabilised by an intramolecular C=N−H···OMe hydrogen bond with a neighbouring methoxy group. Electron-donating OMe groups dramatically increase the basicity of the imino nitrogen, forcing the latter to abstract a proton from the proton sponge

• 4b’ (protonated to the imino group) in the DMSO solution (Scheme 3) [7]. The aim of the present work is to investigate the major factors influencing the effective basicity of the imino functionality. As primary objects for this study, we consider a series of imines 4a–7a (Scheme 4), which differ by

• with good to moderate yields (path b). The monocations 4b–7b and dications 4c–7c were prepared by the treatment of the corresponding imines with one or two equivalents of HBF4 in Et2O (Scheme 5). The so obtained tetrafluoroborates were used for NMR measurements after recrystallisation from EtOH

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

• Soumitra Guin,
• Raman Gupta,
• Debashis Majee and
• Sampak Samanta

Beilstein J. Org. Chem. 2018, 14, 2771–2778, doi:10.3762/bjoc.14.254

• preparation of polyfunctionalized pyridine building blocks involving cyclic sulfamidate imines as carbon nucleophiles [67][68][69][70][71]. In this direction, we recently documented an excellent example of an organobase promoted pot-economical approach to 4,6-disubstituted nicotinates by choosing 5-membered

• cyclic sulfamidate imines and MBH acetates of acrylate as coupling partners [68]. Herein, we further present a DABCO-catalyzed and DBU-promoted sequential one-pot procedure for the access to the interesting class of (2-hydroxyaryl)nicotinates/nicotinonitriles from N-sulfonyl ketimines and MBH adducts as

• on the above experimental results as well as our previous report on DABCO-catalyzed reactions of cyclic sulfamidate imines with MBH carbonates of isatins [75], a plausible mechanism is presented and depicted in Scheme 2. For the first step, the nucleophilic Lewis base DABCO reacts with 2a in an SN2

A challenging redox neutral Cp*Co(III)-catalysed alkylation of acetanilides with 3-buten-2-one: synthesis and key insights into the mechanism through DFT calculations

• Andrew Kenny,
• Alba Pisarello,
• Arron Bird,
• Paula G. Chirila,
• Alex Hamilton and
• Christopher J. Whiteoak

Beilstein J. Org. Chem. 2018, 14, 2366–2374, doi:10.3762/bjoc.14.212

• molecule to the initial metallocycle, the conversion is more challenging and therefore requires harsher reaction conditions. This competitive binding (Int 2substrate vs RS 2) is similar to that proposed by Bergman and Ellman for Cp*Rh(III)-catalysed arylation of imines [27]. Additionally RS 1, resulting

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• activation. In 1941, Kharasch and Fields applied a cobalt salt as the catalyst for the homocoupling of Grignard reagents [28]. After 15 years, Murahashi discovered a cobalt-catalyzed chelation-assisted ortho C–H carbonylation of azobenzene and imines as the preliminary example of directing group assisted C–H

• alkenes, which required a stoichiometric amount of oxidant. Herein, we wish to review the cobalt-catalyzed hydroarylation of alkynes, alkenes, allenes, enynes, imines, and isocyanates. These reactions usually proceed via either an oxidative addition of Ar–H to a low-valent cobalt to form A1 intermediate

• temperature (Scheme 7) [48]. These reactions resemble the Ni(0)-catalyzed hydroheteroarylation reaction [49]. In addition, imines 9 and 11 bearing a p-methoxyphenyl (PMP) group were also treated with internal alkynes in the presence of a cobalt catalyst generated from CoBr2, P(3-ClC6H4)3, and t-BuCH2MgBr at

A general and atom-efficient continuous-flow approach to prepare amines, amides and imines via reactive N-chloramines

• Katherine E. Jolley,
• Michael R. Chapman and
• A. John Blacker

Beilstein J. Org. Chem. 2018, 14, 2220–2228, doi:10.3762/bjoc.14.196

• afford amides. Primary and secondary imines were produced under continuous conditions from the reaction of N-chloramines with base, with one example subsequently reduced under asymmetric conditions to produce a chiral amine in 94% ee. Keywords: continuous flow; CSTR; N-chloramine; synthetic methods

• reagents can be used as electrophilic or radical amination agents in a wide range of reactions [14]. In the present study, we opted to evaluate the addition of N-alkyl-N-chloramines with (a) alkenes to produce amines, (b) aldehydes to give amides, (c) reaction with a base to afford imines. Several alkenes

• upon scale-up makes this a useful reaction to translate to flow. Likewise, imines are an important class of compounds and are increasingly used as precursors to optically active amines [35][36][37][38][39]. Whilst normally prepared via a corresponding carbonyl compound, final dehydration can be

Revisiting ring-degenerate rearrangements of 1-substituted-4-imino-1,2,3-triazoles

• James T. Fletcher,
• Matthew D. Hanson,
• Joseph A. Christensen and
• Eric M. Villa

Beilstein J. Org. Chem. 2018, 14, 2098–2105, doi:10.3762/bjoc.14.184

• susceptibility of unsymmetrical imine analogs towards rearrangement. As summarized in Table 2, under condensation conditions this dynamic system can be expected to produce up to four unique imines and two unique aldehydes through a series of condensation, rearrangement and hydrolysis steps. The initial

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

• . Aliphatic aldehydes gave poor yields, with sterically hindered examples not reacting at all. The author attributed this to the formation of enamines. Under the reported reaction conditions primary aliphatic and aromatic amines all produced imines. The benzamide moiety is somewhat common in biologically

• group described the use of similar – also mild – reaction conditions to synthesise benzoxazoles from 2-substituted phenolic imines (Scheme 24). This implies that the DHPM manipulation was perhaps a preliminary study that served to optimise mild oxidation conditions. Tang et al. reported a procedure for

Cobalt-catalyzed nucleophilic addition of the allylic C(sp³)–H bond of simple alkenes to ketones

• Tsuyoshi Mita,
• Masashi Uchiyama,
• Kenichi Michigami and
• Yoshihiro Sato

Beilstein J. Org. Chem. 2018, 14, 2012–2017, doi:10.3762/bjoc.14.176

• -allylmetal complex that reacts with electrophiles, triggered by allylic C(sp3)–H activation. To this end, Schneider [26], Kanai [27], and we [28][29] reported in 2017 catalytic allylic C(sp3)–H activation of alkenes to react carbonyl electrophiles such as imines, ketones, and CO2 via nucleophilic allylmetal

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

• , arenes and heteroarenes [43][44]. A first solution to value the 2-iodobenzoic moiety released from EBX has arisen from the reaction of derivatives 22 with N-(aryl)imines 23 in the presence of 10 mol % of Pd(OAc)2, which gives access to tri- or tetrasubstituted furans 24 and N-(aryl)formamides 25 (Scheme

•  10a) [45]. The scope of the overall transformation is wide both in terms of imines and EBX reagents. Several isotope-labelling experiments have allowed for proposing a mechanism for this complex transformation (Scheme 10b). The latter would first involve the addition of a Pd(II)-2-iodobenzoate species

• -trifluoromethylation of dienes. Catalytic benzoyloxy-trifluoromethylation of allylamines. Catalytic benzoyloxy-trifluoromethylation of enynes. Catalytic benzoyloxy-trifluoromethylation of allenes. Alkynylation of N-(aryl)imines with EBX for the formation of furans. Catalytic benzoyloxy-alkynylation of diazo compounds

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

• methyl ester 120 in four steps (Scheme 39) [73]. The organocatalytic properties of this inherently chiral calixarene Brønsted acid was firstly examined in the aza-Diels–Alder reaction of imines bearing electron-withdrawing or electron-donating substituents 122 with Danishefsky’s diene (123, Scheme 40

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• imines published since the beginning of 2015. Keywords: asymmetric synthesis; chiral 3-amino-2-oxindoles; chirality; isatin imines; nucleophilic addition; Introduction Chiral oxindoles represent an important class of products widely present in nature and exhibiting many biological activities. Among

• organocatalyzed methodologies [10][13]. The simplest method to prepare chiral quaternary 3-amino-2-oxindoles is based on enantioselective catalytic nucleophilic additions to isatin imines. This is not only because of the easy access to isatin imines, but also by the possibility of using a wide range of

• additions to isatin imines have been developed, including Mannich reactions, aza-Morita–Baylis–Hillman reactions, Friedel–Crafts reactions, aza-Henry reactions, additions of heteronucleophiles, Strecker reactions, among others. The goal of this review is to update the catalytic asymmetric synthesis of

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• HOMO are possible – due to similar energy gaps – both electron-rich as well as electron-poor dipolarophiles/dipoles react more quickly than parent (unsubstituted) ones. Using semi-empirical quantum calculations (CNDO/2), Houk et al. [58] calculated average HOMO/LUMO energies for azomethine-imines

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• alkenylation reaction of pivalophenone N–H imine with an alkenyl phosphate. The reaction tolerates various substituted pivalophenone N–H imines as well as cyclic and acyclic alkenyl phosphates. Keywords: alkenylation; C–C bond formation; C–H activation; cobalt; imine; Introduction Transition-metal-catalyzed

• catalyst, which is reported herein (Scheme 1c). The present alkenylation features a mild reaction temperature and displays applicability to a variety of substituted pivalophenone N–H imines and alkenyl phosphates. It should be emphasized that pivalophenone N–H imines and related bulky N–H imines can be

• readily prepared from the corresponding aryl nitriles and organolithium or Grignard reagents, while analogous N-substituted imines are nontrivial to synthesize because of sluggish ketone/amine condensation. As such, the present reaction would complement the N-arylimine-directed alkenylation. Results and

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• at 78 °C, [4 + 2] cycloaddition took place between the o-QM generated from the corresponding aminonaphthol as diene component and cyclic imines playing the role of heterodienophiles (Scheme 5). Fülöp and co-workers then extended their studies by applying both 2-aminoalkyl-1-naphthols and 1-aminoalkyl

• -2-naphthols [81]. These bifunctional compounds were reacted with various cyclic imines such as 4,5-dihydrobenzo[c]azepine or 6,7-dihydrothieno[3,2-c]pyridine to have new naphthoxazinobenzazepine 44 and -thienopyridine 45 derivatives [82]. Transformations at 80 °C in 1,4-dioxane as solvent were

• polyheterocycles formed was also described. The [4 + 2] cycloadditions between cyclic imines and o-QMs derived from Mannich bases could also be successfully applied in the syntheses of natural alkaloid-like compounds 47. Osyanin et al. reported the preparation of rutaecarpine and evodiamine, the 14-oxa analogues

Recent developments in the asymmetric Reformatsky-type reaction

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

• fashion leading to cyclic as well as acyclic products, and includes (aza)-versions using imines instead of aldehydes or ketones as electrophilic partners. In addition, the mild reaction conditions usually employed and the use of cheap nontoxic metals has prompted the development of diastereo- and

• -β-(N-tert-butylsulfinyl) amino esters through ZnEt2-mediated aza-Reformatsky reactions of the corresponding chiral α-oxygenated sulfinyl imines 25 with ethyl bromodifluoroacetate (26) performed in the presence of RhCl(PPh3)3 as an additive in THF [27]. Starting from (S)-N-tert-butylsulfinyl imines

• 25, the reaction led to the corresponding (R,S)-products 27 as major diastereomers in low to excellent diastereoselectivities (6–90% de) and moderate yields (46–64%). The lowest diastereoselectivity (6% de) was obtained in the reaction of aliphatic sulfinyl imines (S)-25a,b (R = Et, C11H23) while

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

• preparation of imines (Scheme 1). The condensation of an amine with an aldehyde or ketone is the oldest and most commonly employed method for imine synthesis [4]. More recently, the catalytic dehydrogenation of amines mediated by metal and organic catalysts has begun to emerge as an alternative approach for

• the preparation of imines [5][6]. The majority of these methods involve cleavage of a C−H bond at the α-position of an amine substrate [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Methods that deliver imines through amine α-C−C bond cleavage are far less

Regioselective decarboxylative addition of malonic acid and its mono(thio)esters to 4-trifluoromethylpyrimidin-2(1H)-ones

• Sergii V. Melnykov,
• Andrii S. Pataman,
• Yurii V. Dmytriv,
• Svitlana V. Shishkina,
• Mykhailo V. Vovk and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2017, 13, 2617–2625, doi:10.3762/bjoc.13.259

• decarboxylative addition of malonic acid mono(thio)esters to aldehydes and imines has become an increasingly popular synthetic strategy [28][30][31][32][33][34][35][36]. However, the utility of trifluoromethylketimines as electrophilic substrates in this reaction remains underinvestigated. The only published work

Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes

• Jury J. Medvedev,
• Ilya V. Efimov,
• Yuri M. Shafran,
• Vitaliy V. Suslonov,
• Vasiliy A. Bakulev and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2017, 13, 2569–2576, doi:10.3762/bjoc.13.253

• domino reactions of diazo compounds with intermediate formation of ylides [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Thus, it was for example shown that ammonium or oxonium ylides generated in the course of intermolecular processes can be easily trapped by ketones, imines, α,β-unsaturated

Diastereoselective Mannich reactions of pseudo-C₂-symmetric glutarimide with activated imines

• Tatsuya Ishikawa,
• Tomoko Kawasaki-Takasuka,
• Toshio Kubota and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2017, 13, 2473–2477, doi:10.3762/bjoc.13.244

• , Nakanarusawa 4-12-1, Hitachi 316-8511, Japan 10.3762/bjoc.13.244 Abstract As an extension of the boron enolate-based aldol reactions, the oxazolidinone-installed bisimide 1a from 3-(trifluoromethyl)glutaric acid was employed for Mannich reactions with tosylated imines 2 as electrophiles to successfully obtain

• article. Results and Discussion On the basis of our previous study [4], the chiral glutarimide 1a was employed as the starting material and optimization of reaction conditions with benzaldehyde-based imines 2 was performed (Table 1). Lithium enolate by the action of LDA to 1a was found to be ineffective

• as long as the imines with benzyl (2aa) or Boc (2ab) as substituents R were employed (Table 1, entries 1 and 2). However, the attachment of the stronger electron-withdrawing 4-toluenesulfonyl (Ts) moiety attained efficient activation of the imine 2ac to afford the desired Mannich product 3a in 85

Asymmetric synthesis of propargylamines as amino acid surrogates in peptidomimetics

• Matthias Wünsch,
• David Schröder,
• Tanja Fröhr,
• Lisa Teichmann,
• Sebastian Hedwig,
• Nils Janson,
• Clara Belu,
• Jasmin Simon,
• Shari Heidemeyer,
• Philipp Holtkamp,
• Jens Rudlof,
• Lennard Klemme,
• Alessa Hinzmann,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2017, 13, 2428–2441, doi:10.3762/bjoc.13.240

• substituents in the Cα-position facilitate a base induced rearrangement to α,β-unsaturated imines, while azide-substituted propargylamines form triazoles under surprisingly mild conditions. A panel of propargylamines bearing fluoro or chloro substituents, polar functional groups, or basic and acidic functional

• groups is accessible for the use as precursors of peptidomimetics. Keywords: amino acid analogous side chains; desilylation; Ellman’s chiral sulfinamide; intramolecular Huisgen reaction; peptidomimetics; propargylamines; rearrangement to α,β-unsaturated imines; Introduction Terminal alkynes display an

• structure of fluorinated propargylamines occurs in important drugs, like HIV protease inhibitor DPC 961 and its analogues [78][79][80][81][82][83], particular effort was put on the synthesis of N-sulfinyl propargylamine 7k. Because of the poor electrophilicity of imines 5, the nucleophilic addition of