1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• against various microorganisms and pharmacological targets, including being used in the preparation of several drugs that are on the pharmaceutical market. Among these naphthoquinones, the series of compounds prepared from 1,2-naphthoquinone-4-sulfonic acid salts (β-NQS) stands out. In addition to being

• naphthoquinones [40][41][42]. β-NQS preparation methods generally employ β-naphthol or 1-amino-β-naphthol as starting materials. The first procedure was developed by Witt [43] in the late 19th century when he prepared 1,2-naphthoquinone-4-sulfonic acid ammonium salt (16) in a 60–75% yield from 1-amino-β-naphthol

• employing two equivalents of isoxazolylamines in aqueous solution under reflux with HCl catalysis, resulting in bis(isoxazolyl)naphthoquinones 29 (Scheme 6). The development of synthetic methodologies for the preparation of many bioactive substances is still a challenge. The main issues in synthetic organic

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• ]. Additionally, halotryptophans were incorporated in pentapeptides as building blocks for macrocyclisation by Suzuki–Miyaura cross-coupling (SMC) aiming at the preparation of bicyclic peptides [71]. Recently, intramolecular SMC has been successfully applied to side chain-to-tail cyclisation between

Efficient N-arylation of 4-chloroquinazolines en route to novel 4-anilinoquinazolines as potential anticancer agents

• Rodolfo H. V. Nishimura,
• Thiago dos Santos,
• Valter E. Murie,
• Luciana C. Furtado,
• Leticia V. Costa-Lotufo and
• Giuliano C. Clososki

Beilstein J. Org. Chem. 2021, 17, 2968–2975, doi:10.3762/bjoc.17.206

• -anilinoquinazolines can be prepared from N-methylanilines under basic [14] or acidic [15][16] (Scheme 1c) conditions. Due to our interest in the functionalization of aromatic and heterocyclic compounds of medicinal relevance [21][22][23][24][25][26], we recently reported the preparation of an iodo-substituted analog

• at C6 as substituents in quinazoline ring has been related to increased antiproliferative action of this class of compounds [28]. Therefore, we wish to report the preparation of a library of novel quinazoline-based antitumor candidates through reaction of 4-chloro-6-halo-2-phenylquinazolines with

Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

• Shun Saito,
• Kanji Indo,
• Naoya Oku,
• Hisayuki Komaki,
• Masashi Kawasaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

• (MeOH) λmax (log ε) 229 (4.59), 282 (4.05) nm; IR (ATR) νmax: 3310, 2916, 1724, 1656, 1627, 1548, 1453, 1223, 806 cm–1; 1H and 13C NMR data, see Table 3; HR–ESI–TOFMS (m/z): [M − H]− calcd for C18H21N2O3, 313.1558; found, 313.1556. Preparation of methyl ester 4' To a solution of 4 (0.5 mg, 2.7 μmol) in

• , H3), 5.66 (t, J = 7.4 Hz, 1H, H5), 2.33 (m, 2H, H6), 3.92 (m, 1H, H7), 1.24 (d, J = 6.4 Hz, 3H, H8), 2.01 (d, J = 2.0 Hz, 3H, H9), 1.87 (s, 3H, H10). Preparation of (R)- and (S)-MPA esters 4'a–d To a solution of 4' (0.2 mg, 1.0 μmol), (R)-MPA (2.0 mg, 12 μmol), and N,N-dimethyl-4-aminopyridine (3.9

• ), 1.68 (s, 3H, H10), 3.396 (s, 3H, MPA-OCH3), 4.71 (s, 1H, MPA-CαH). In the same manner as described for the preparation of 4'a and 4'b, a diastereomeric mixture of (S)-MPA esters 4'c and 4'd was prepared from 4' and (S)-MPA. (S)-MPA ester of 7S enantiomer 4'c: 1H NMR data was identical to those of 4'b

A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

• Haopei Wang and
• Zachary T. Ball

Beilstein J. Org. Chem. 2021, 17, 2932–2938, doi:10.3762/bjoc.17.202

• 1 in acetone. Preparation and hydrolysis kinetics (inset) of N-formyl product 11. Dashed line: first-order decay fit used in calculating the rate constant. Proposed mechanism for the formation of aldehyde 3 and N-formyl product 8. Supporting Information Supporting Information File 280: Experimental

Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions

• Qingkai Zeng,
• Qiumeng Long,
• Jihong Lu,
• Li Wang,
• Yuting You,
• Xiaoting Yuan,
• Qianjun Zhang,
• Qingmei Ge,
• Hang Cong and
• Mao Liu

Beilstein J. Org. Chem. 2021, 17, 2840–2847, doi:10.3762/bjoc.17.195

• domains, such as chemosensors [21], drug delivery [22], and nano materials preparation [23]. Although cucurbiturils with their rigid hydrophobic cavities have found broad application in host–guest chemistry, they suffer from insolubility, difficulty in derivatization, and lack of chromophores

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• preparation of highly valuable diarylmethyl sulfones are relatively scarce [24]. In addition, the important link between structural diversity and complexity with bioactivity represented by sulfones has led to the goal of developing strategies to as many these pivotal scaffolds as possible. Isocyanide is an

Biological properties and conformational studies of amphiphilic Pd(II) and Ni(II) complexes bearing functionalized aroylaminocarbo-N-thioylpyrrolinate units

• Samet Poyraz,
• Samet Belveren,
• Sabriye Aydınoğlu,
• Mahmut Ulger,
• Abel de Cózar,
• Maria de Gracia Retamosa,
• Jose M. Sansano and
• H. Ali Döndaş

Beilstein J. Org. Chem. 2021, 17, 2812–2821, doi:10.3762/bjoc.17.192

• from LECO detection system. General procedure for ligands and complexes Synthesis of selected ligands (L1–L3): The known pyrrolidines and aroylaminocarbo-N-thioylpyrrolidine compounds (L1–L3) were synthesized according to published procedures [15]. Preparation of Ni(II) and Pd(II) complexes (L1-M, L2-M

• complexes. Blue and yellow surfaces represent the solvent accessible surface of ligands with a probe radius of 1.4 Å. Hydrogen atoms not involved on hydrogen–bonding interactions are omitted for clarity. Synthetic route for the preparation of L1-M, L2-M and L3-M complexes. Antibacterial and antituberculosis

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• for the preparation of Schiff bases 3aa–af and 3bb–be A mixture of the respective 6-amino-2-alkyl(aryl/heteroaryl)-4-(trifluoromethyl)quinoline (1a–f, 1.0 mmol) and salicylaldehyde (2a–e, 2.0 mmol) in anhydrous acetonitrile (10.0 mL) was heated for 48 h at reflux temperature. After completion of the

The PIFA-initiated oxidative cyclization of 2-(3-butenyl)quinazolin-4(3H)-ones – an efficient approach to 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones

• Alla I. Vaskevych,
• Nataliia O. Savinchuk,
• Ruslan I. Vaskevych,
• Eduard B. Rusanov,
• Oleksandr O. Grygorenko and
• Mykhailo V. Vovk

Beilstein J. Org. Chem. 2021, 17, 2787–2794, doi:10.3762/bjoc.17.189

• key intermediates 7 bearing a homoallyl substituent at the C-2 position. Most of the methods for the preparation of 2-akyl-substitued quinazolin-4(3H)-ones [54] require the use of hardly available starting materials, expensive catalysts, and/or harsh reaction conditions [55], often intolerant to the

Me₃Al-mediated domino nucleophilic addition/intramolecular cyclisation of 2-(2-oxo-2-phenylethyl)benzonitriles with amines; a convenient approach for the synthesis of substituted 1-aminoisoquinolines

• Krishna M. S. Adusumalli,
• Lakshmi N. S. Konidena,
• Hima B. Gandham,
• Krishnaiah Kumari,
• Krishna R. Valluru,
• Satya K. R. Nidasanametla,
• Venkateswara R. Battula and
• Hari K. Namballa

Beilstein J. Org. Chem. 2021, 17, 2765–2772, doi:10.3762/bjoc.17.186

• catalyst [36][37][38][39][40]. However, pre-functionalization of isoquinolines to the corresponding halogenated isoquinolines is the main limitation associated with these protocols as they require noxious halogenated acids for their starting materials preparation. Alternative strategies include, amination

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• central chirality information to the axial chirality to give the chiral biaryldiols (Scheme 3) [14]. In 2013, Akiyama and co-workers described the enantioselective preparation of multisubstituted biaryls by the desymmetrization strategy, which was further enhanced by the subsequent asymmetric reaction

• scaffold for a variety of natural products, bioactive compounds and pharmacological agents [79] as well as for a variety of chiral phosphine ligands [80]. As a result, the preparation of axially chiral arylpyrroles has been one of the most important areas of investigation in synthetic chemistry. In the

• chiral arylpyrroles in 2017 [82], a complicated catalytic system and narrow substrate range limited its application. Therefore, the use of chiral phosphoric acids to modulate axial chirality enables the preparation of highly enantioenriched axially chiral arylpyrroles. In this context, Tan and co-workers

The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet–Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids

• Marco Keller,
• Karl Sauvageot-Witzku,
• Franz Geisslinger,
• Nicole Urban,
• Michael Schaefer,
• Karin Bartel and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2716–2725, doi:10.3762/bjoc.17.183

• group following routes A or B, thus reducing the required number of steps for alkaloid total syntheses significantly. In this way we worked out convenient racemic total syntheses of ten 1-benzyltetrahydroisoquinoline alkaloids. Formally, this approach also opens the option for the preparation of

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• sulfur atom instead of C-3', and an unnatural ʟ-configured sugar [20]. The presence of oxygen as a second heteroatom in the sugar ring was also found to result in anti-HIV activity in 1,3-dioxolane nucleosides [21]. A good example for the preparation of 2’,3’-dideoxy-3’-oxacytidine in a stereospecific

• to establish synthetic approaches toward single desired isomers. The methodologies for modified nucleosides are also known as linear approach and convergent approach [3]. We recognized that there are three major obstacles that have to be cleared: i) efficient preparation of the oxathiolane sugar ring

• temperature, and oxidation with a mild oxidizing agent, PDC, provided 28. Using the reaction of lead tetraacetate with 28 via oxidative decarboxylation afforded oxathiolane acetate derivative 20a. The synthesis of a 1,3-oxathiolane precursor required for the preparation of 3TC (1) in four steps was reported

AlBr₃-Promoted stereoselective anti-hydroarylation of the acetylene bond in 3-arylpropynenitriles by electron-rich arenes: synthesis of 3,3-diarylpropenenitriles

• Yelizaveta Gorbunova,
• Dmitry S. Ryabukhin and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2663–2667, doi:10.3762/bjoc.17.180

• –C≡N) are versatile building blocks in organic synthesis for the preparation of a plethora of functionalized compounds and heterocycles. The presence of conjugated acetylene and nitrile bonds in these compounds leads to an enhancement of reactivity of both functional groups. Thus, propynenitriles

Solvent-free synthesis of enantioenriched β-silyl nitroalkanes under organocatalytic conditions

• Akhil K. Dubey and
• Raghunath Chowdhury

Beilstein J. Org. Chem. 2021, 17, 2642–2649, doi:10.3762/bjoc.17.177

• ][35][36]. In this context, Huang, Fu and co-workers reported carbene-catalyzed enantioselective formal [4 + 2] annulation reactions of β-silyl enones with enals and with active acetic esters (Scheme 1g) for the preparation of chiral organosilanes [34][35][36]. Very recently, during the final stage of

• to moisture and air. Therefore, this method offers an attractive and robust option for the preparation of chiral β-silyl nitroalkanes. In sharp contrast to the aforesaid reaction, organocatalytic conjugate addition reactions of nitroalkanes to enones have been well studied [39][40][41][42][43]. To

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• after each step prompted us to apply a Mitsunobu and Staudinger reaction for the preparation of amine 2 (Scheme 1) [33]. This one-pot reaction gave the desired amine 2 in 56% yield. Then, the corresponding isothiocyanate 3a was prepared by reaction of amine 2 with CS2 and DCC according to the reported

• solvent was removed in vacuo and the residue was dissolved in DCM (60 mL) and washed with 0.1 M HCl (2 × 30 mL). The organic phase was dried over Na2SO4 and the crude reaction mixture was used in the next reaction step without further purification. General procedure for preparation of N-sulfinylthiourea

• , 2973, 1653, 1159, 1237, 1058 cm−1; HRMS (m/z): [M + Na]+ calcd for C15H29N3O3S2, 386.1543; found, 386.1543; [M + H]+ calcd, 364.1729; found, 364.1722. General procedure for the preparation of N-sulfinylurea pre-catalysts (S,R)-5b and ((S,S)-5b) A stirred solution of (R)-tert-butanesulfinamide or (S

Adjusting the length of supramolecular polymer bottlebrushes by top-down approaches

• Tobias Klein,
• Franka V. Gruschwitz,
• Maren T. Kuchenbrod,
• Ivo Nischang,
• Stephanie Hoeppener and
• Johannes C. Brendel

Beilstein J. Org. Chem. 2021, 17, 2621–2628, doi:10.3762/bjoc.17.175

• the spherical analogues with regard to blood circulation time, drug loading, and tumor penetration abilities [1][2][3]. However, the straightforward preparation of cylindrical polymer aggregates with defined and reproducible length still remains challenging but represents a prerequisite for the

• interest. While ultrasonication (US) represents a standard but rather harsh fragmentation technique, we additionally introduced dual asymmetric centrifugation (DAC) as an excellent alternative top-down method for effective, more controlled, and adaptable preparation of polymer nanostructures [24][25][26

Synthesis of new bile acid-fused tetrazoles using the Schmidt reaction

• Dušan Đ. Škorić,
• Olivera R. Klisurić,
• Dimitar S. Jakimov,
• Marija N. Sakač and
• János J. Csanádi

Beilstein J. Org. Chem. 2021, 17, 2611–2620, doi:10.3762/bjoc.17.174

• , modified and optimized reaction conditions for the Schmidt synthesis were established for the preparation of bile acid-fused tetrazoles using TMSN3. It was shown that depending on the starting compound, ACN was optimal for ketones and DCM was optimal for enones. Among the tested Lewis acid catalysts

• for the preparation of tetrazoles with hydrazoic acid Caution: Hydrazoic acid should be handled with care in an efficient fume hood since it is toxic and explosive. In a two-neck round-bottom flask equipped with an addition funnel and argon inlet, a benzene solution of hydrazoic acid (18 mL) and boron

• products were obtained and were purified by column chromatography. General procedure for preparation of tetrazoles with TMSN3 In a flame-dried two-neck round-bottom flask equipped with an argon inlet, 0.10 mmol of the carbonyl compound was dissolved in 4 mL of dry solvent, and 6–12 equiv of TMSN3 and 3–6

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• as an important synthetic strategy for the preparation of a large variety of β-amino carbonyl and similar motifs which are present in many bioactive natural products [8][9], antibiotics [10][11][12] and chiral auxiliaries [13][14][15]. However, the reaction of many nitrogen-nucleophiles, such as

• to good yield of 53–99% with an ee of 74–93% [54]. Liu et al. accomplished a catalytic cascade aza-Michael–Henry-dehydration protocol for the preparation of chiral 3-nitro-1,2-dihydroquinolines 83 from the reaction of N-protected aminobenzaldehydes 80 with substituted nitroolefins 81 by using

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• precursors containing simpler decalin systems (identical to 32 and 33 but with an additional conjugated double bond) and found the α-ketol rearranged product superior to periconianone A. Another example of an α-ketol rearrangement in a total synthesis is in the preparation of silvestrol (34) and

• biosynthesis of delitschiapyrone A could occur non-enzymatically in nature by a similar process. The final example of a tandem reaction involving an α-ketol rearrangement in a total synthesis was employed by Chen et al. in the preparation of (±)-securinine (54) and (±)-allosecurinine (55), biological alkaloids

Cryogels: recent applications in 3D-bioprinting, injectable cryogels, drug delivery, and wound healing

• Luke O. Jones,
• Leah Williams,
• Tasmin Boam,
• Martin Kalmet,
• Chidubem Oguike and
• Fiona L. Hatton

Beilstein J. Org. Chem. 2021, 17, 2553–2569, doi:10.3762/bjoc.17.171

• solvent below freezing temperature. Due to their inherent interconnected macroporosity, ease of preparation, and biocompatibility, they are increasingly being investigated for use in biomedical applications such as 3D-bioprinting, drug delivery, wound healing, and as injectable therapeutics. This review

• highlights the fundamentals of macroporous cryogel preparation, cryogel properties that can be useful in the highlighted biomedical applications, followed by a comprehensive review of recent studies in these areas. Research evaluated includes the use of cryogels to combat various types of cancer, for

• ][6]. Here we discuss the preparation of cryogels, their properties and applications, focussing on recent reports of cryogels in emerging applications, including bioprinting, injectable cryogels, drug delivery, and wound healing, as investigations in these key areas have intensified in recent years

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

• Robin Klintworth,
• Garreth L. Morgans,
• Stefania M. Scalzullo,
• Charles B. de Koning,
• Willem A. L. van Otterlo and
• Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

• , 100 °C), 1–3 h. Further functionalization of dihydropyrrolizine 19a. Reagents and conditions: (i) NBS, DMF, 0 °C, 1 h, then rt, 18 h; (ii) PhB(OH)2, Pd(PPh3)4 (cat.), Na2CO3, DMF, reflux, 20 h. Optimization of the cyclization of enaminone 15a to pyrrolizine 19a. Preparation of enaminones 15a–ya, and

Synthesis of new substituted 7,12-dihydro-6,12-methanodibenzo[c,f]azocine-5-carboxylic acids containing a tetracyclic tetrahydroisoquinoline core structure

• Agnieszka Grajewska,
• Maria Chrzanowska and
• Wiktoria Adamska

Beilstein J. Org. Chem. 2021, 17, 2511–2519, doi:10.3762/bjoc.17.168

• ]. Recently, a methodology for the synthesis of dihydromethanodibenzoazocines based on a combination of Friedel–Crafts and Pictet–Spengler reactions was proposed by Moshkin et al. [18]. We have developed a convenient method for the preparation of C-1-substituted tetrahydroisoquinoline derivatives by using the

• -functionalized tetrahydroisoquinoline rings, are presented in Scheme 1. In the Petasis reaction we applied aminoacetaldehyde acetals as the amine component which enabled the preparation of the substrates for the Pomeranz–Fritsch–Bobbitt cyclization in one simple step. The Petasis reaction products were further

In-depth characterization of self-healing polymers based on π–π interactions

• Josefine Meurer,
• Julian Hniopek,
• Johannes Ahner,
• Michael Schmitt,
• Jürgen Popp,
• Stefan Zechel,
• Kalina Peneva and
• Martin D. Hager

Beilstein J. Org. Chem. 2021, 17, 2496–2504, doi:10.3762/bjoc.17.166

• minutes. Afterwards, a sample spectrum with 32 scans was recorded. All graphics were generated with GNU R (version 4.0.2) [33] without further preprocessing of the spectra. The preparation of the samples and the self-healing experiments (including evaluation of the data) were performed according to