One-pot synthesis of 1,3,5-triazine-2,4-dithione derivatives via three-component reactions

• Gui-Feng Kang and
• Gang Zhang

Beilstein J. Org. Chem. 2020, 16, 1447–1455, doi:10.3762/bjoc.16.120

• being susceptible to nucleophilic attack. The resulting substituted thioureas underwent a cyclization reaction providing the desired triazinethiones (Scheme 1a and 1b). However, this method required the preparation of the starting isothiocyanates, which limited its synthetic applications. In another

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• and co-workers reported an excellent thiyl radical-catalyzed enantioselective cyclization reaction of vinylcyclopropanes with alkenes [7]. For the extension of this concept, in 2018, Miller and co-workers reported a UV-light-promoted disulfide-bridged peptide-catalyzed enantioselective cycloaddition

Microwave-assisted efficient and facile synthesis of tetramic acid derivatives via a one-pot post-Ugi cascade reaction

• Yong Li,
• Zheng Huang,
• Jia Xu,
• Yong Ding,
• Dian-Yong Tang,
• Jie Lei,
• Hong-yu Li,
• Zhong-Zhu Chen and
• Zhi-Gang Xu

Beilstein J. Org. Chem. 2020, 16, 663–669, doi:10.3762/bjoc.16.63

• overnight (Scheme 1). The reaction provided the crude Ugi adduct 5a after the removal of methanol under reduced pressure. The crude residue was then exposed to a series of different cyclization reaction conditions. First, based on the previous works on the Dieckmann cyclization reaction [40][41], we

• /Dieckmann cyclization reaction route to lead to pyrrolopyridinones 7a–l. aYield of the isolated product of the Dieckmann cyclization reaction. bOverall yield over two steps of isolated product. Postulated reaction mechanism. Optimization of the Dieckmann reaction for compound 7a. Supporting Information

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• definition and fails as a real “click” reaction. Although this cyclization reaction requires elevated temperatures and often yields both the 1,4- and 1,5-regioisomers, the Cu or Ru alkyne–azide cycloaddition falls exactly into the above definition [11]. In this respect, the copper-catalyzed cycloaddition

Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

• Svetlana V. Amosova,
• Andrey A. Filippov,
• Nataliya A. Makhaeva,
• Alexander I. Albanov and
• Vladimir A. Potapov

Beilstein J. Org. Chem. 2020, 16, 515–523, doi:10.3762/bjoc.16.47

• compound from selenium dihalides was the preparation of 1,4-selenasilafulvenes by cyclization reaction with diethynyldimethylsilane [15][16]. The creation of new methodologies for the synthesis of new classes of organoselenium compounds and especially selenium heterocycles, with promising biological

Synthesis of 4-amino-5-fluoropyrimidines and 5-amino-4-fluoropyrazoles from a β-fluoroenolate salt

• Tobias Lucas,
• Jule-Philipp Dietz and
• Till Opatz

Beilstein J. Org. Chem. 2020, 16, 445–450, doi:10.3762/bjoc.16.41

• ), emtricitabine (3) and capecitabine (4). Synthesis of potassium (Z)-2-cyano-2-fluoroethenolate (8) by Dietz et al. [36]. Scope of the cyclization reaction. All yields are those of the purified products. aNo further purification was required to obtain analytically pure material. bUse of sodium methoxide. cUsing O

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• relatively good yields. Notably, a low isolated yield was reported when starting from 2-(4-chlorobutyl)pyridine (n = 4) and this was attributed to the competing cyclization reaction affording cyclic pyridinium salts. The prominent 2-(diphenylphosphine)pyridine (4) has proved to be an interesting building

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

• sodorifen [58] biosynthesis for example, require the action of a methyltransferase preceding cyclization. Surprisingly, more and more terpene BGCs are characterized that do not harbor classical TCs, but instead use a variety of different enzyme classes for the cyclization reaction. These atypical terpene

• oxidative [66] and reductive cyclizations [67] have been described. The reductive cyclization reaction is particularly noteworthy, as the reduction and cyclization step are catalyzed by two distinct enzymes [67]. These examples show that the classical division of terpene biosynthesis into a cyclization and

• decoration phase needs to be modified, as it is now known that enzyme families, traditionally regarded as tailoring enzymes, can potentially be involved in the cyclization reaction. The ever-increasing number of alternative terpene cyclization mechanisms suggests that nature has likely evolved additional

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

• cyclization reaction yielding the corresponding azobenzene 1f was performed using a Cu(I) catalyst generated in situ [36]. Finally, the esters were hydrolyzed under mild conditions resulting in the azobenzene-BAPTA macrocycle 1. To gain some insight into the possible structures of the 1E and 1Z chelators and

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• complexes 1a–d were evaluated as homogeneous catalysts in two tandem addition/cycloisomerization reactions using alkynes 2 and 3. 2-Alkynylbenzaldehyde 2 [58][59] was chosen as the first model substrate for a cyclization reaction in the presence of methanol as a second nucleophile. This tandem addition

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

• Ronja Driller,
• Daniel Garbe,
• Norbert Mehlmer,
• Monika Fuchs,
• Keren Raz,
• Dan Thomas Major,
• Thomas Brück and
• Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

• ) [12] to the acyclic terpene synthase substrate geranylgeranyl diphosphate 3 (GGDP) [1][13][14][15][16]. Following initial substrate binding and folding in a product-like conformation, the cyclization reaction can be subdivided into three steps: (1) generation of a reactive allyl carbocation as a

• stereochemical reaction. The cyclization mechanism of CotB2 has been investigated extensively in recent years. By isotope labeling and NMR spectroscopic investigations [35], it has been shown that CotB2 catalyzes the complex regio- and stereospecific cyclization reaction with an unusual carbon–carbon bond

• of taxadiene synthase (PDB-ID 3P5R; [53]), co-crystallized with FGGDP, where the substrate is bound but the cyclization reaction has not been initialized and consequently the substrate is not yet cleaved. Identical observations have been made for the crystal structure of aristolochene synthase co

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• (A) and emission (B) spectra of SyTh2 in acetonitrile in the course of the cyclization reaction (irradiation at 365 nm). Emission was not fully depleted due to incomplete conversion in the photostationary state (PSS, α = 71%). Absorption spectra of the OFs (A) and CFs (B) of AsTh1 (a), SyTh1 (b

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

• to a pentacyclic ketone. A similar cyclization reaction was developed by our group some years ago for ester substrates [18], and an analogous cyclization of nitriles was described by Kristensen in ring-closing cascade reactions [34]. The new cyclization method was first tested with ester 20a

Click chemistry towards thermally reversible photochromic 4,5-bisthiazolyl-1,2,3-triazoles

• Chenxia Zhang,
• Kaori Morinaka,
• Mahmut Kose,
• Takashi Ubukata and
• Yasushi Yokoyama

Beilstein J. Org. Chem. 2019, 15, 2161–2169, doi:10.3762/bjoc.15.213

• phenyl groups. The Ru(I)-catalyzed Huisgen cyclization reaction proceeded rather smoothly to give 1o, 2o and 3o in moderate chemical yields of 36%, 53% and 20%, respectively. Since the reported chemical yield of the reaction of tolan, the simplest bisarylethyne, and 2-phenylethyl azide was 63% [19], it

Analysis of sesquiterpene hydrocarbons in grape berry exocarp (Vitis vinifera L.) using in vivo-labeling and comprehensive two-dimensional gas chromatography–mass spectrometry (GC×GC–MS)

• Philipp P. Könen and
• Matthias Wüst

Beilstein J. Org. Chem. 2019, 15, 1945–1961, doi:10.3762/bjoc.15.190

• [5][32]. In 1999 Schmidt et al. were able to show that the enantiomers of germacrene D are formed via two different H-transfer pathways in Solidago canadensis. (S)-(−)-Germacrene D is generated by a cyclization reaction, that includes a 1,3-hydride shift as opposed to the cyclization reaction of (R

Inherent atomic mobility changes in carbocation intermediates during the sesterterpene cyclization cascade

• Hajime Sato,
• Takaaki Mitsuhashi,
• Mami Yamazaki,
• Ikuro Abe and
• Masanobu Uchiyama

Beilstein J. Org. Chem. 2019, 15, 1890–1897, doi:10.3762/bjoc.15.184

• ], and it appears that inherent reactivity [17] is in good accordance with the experimental outcome. This may mean that terpene cyclases do not tightly regulate the cyclization reaction steps once the carbocation is generated. Therefore, we considered that key regions of GFPP that control the fit of the

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

• (III) intermediate 144 which underwent reductive elimination to give the desired product 137 and Cu(I) species (Scheme 49). The mechanism has shown that molecular iodine (I2) used in the reaction was the source of iodine in the final product rather than CuI. A condensation–cyclization reaction between

Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• DTT 1 in 91% yield (Scheme 1). Triacene dithieno[3,2-b:2’,3’-d]selenophene (DTS, 2) was successfully prepared as well from diiodinated bithiophene 5 in 51% yield after purification in a C–Se cross-coupling/cyclization reaction with selenourea as selenium source, copper oxide nanoparticles as catalyst

One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines in a consecutive three-component fashion

• Christina Görgen,
• Katharina Boden,
• Guido J. Reiss,
• Walter Frank and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1360–1370, doi:10.3762/bjoc.15.136

• Chemie und Makromolekulare Chemie, Universitätsstraße 1, D-40225 Düsseldorf, Germany 10.3762/bjoc.15.136 Abstract A consecutive three-component activation–alkynylation–cyclization reaction of (hetero)aryl glyoxylic acids, oxalyl chloride, arylacetylenes, and hydrazides efficiently forms 1,5-diacyl-5

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

• previously proposed by Marcaccini and co-workers [17]. Here, the route included the Ugi-4CR reaction of varied amines and isocyanides with the androstanic aldehyde 4 and chloroacetic acid followed by a post-cyclization reaction by treating the Ugi products 5 with ethanolic KOH under ultrasonication. This

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

• Heck cyclization reaction between the substituted alkyne and aryl bromide in 133 takes place to form a cyclic palladium intermediate 134 with E-configuration, resulting from a syn-addition mechanism of this step. The addition of a silver salt reduces the probability of isomerization of the double bond

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

• stereogenic centers in a one-step [4 + 2] cycloaddition or cyclization reaction [6][7][8] and it has become hugely popular in preparing vital intermediates for the syntheses of key structural subunits of natural products with biological activities (e.g., carbohydrates, antibiotics, toxins etc.) [9][10

Efficient synthesis of pyrazolopyridines containing a chromane backbone through domino reaction

• Razieh Navari,
• Saeed Balalaie,
• Saber Mehrparvar,
• Fatemeh Darvish,
• Frank Rominger,
• Fatima Hamdan and
• Sattar Mirzaie

Beilstein J. Org. Chem. 2019, 15, 874–880, doi:10.3762/bjoc.15.85

• base-catalyzed cyclization reaction is reported. The synthesis was carried out through a three-component reaction of (arylhydrazono)methyl-4H-chromen-4-one, malononitrile, primary amines in the presence of Et3N at room temperature. However, carrying out the reaction under the same conditions without

• products 5a–d were not formed. The reaction mechanism is shown in Scheme 2. The chemical structures of the products 5a–d are shown in Figure 4. Usually, to activate the nitrile group for cyclization reaction, the existence of Lewis acid, the addition of organolithium reagents or metal

• fused heterocyclic backbones with high selectivity. Conclusion In conclusion, we have successfully established an efficient route toward the synthesis of a diverse array of fused heterocyclic skeletons through a domino reaction. We showed an interesting behavior of the base for the cyclization reaction

Synthesis of functionalized diazocines for application as building blocks in photo- and mechanoresponsive materials

• Widukind Moormann,
• Daniel Langbehn and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 727–732, doi:10.3762/bjoc.15.68

• using oxygen and the yields are increased from 65% to 95% in the parent system [30]. In a recent work we observed that the reduction of 2,2′-dinitrodibenzyl is difficult to stop at the azo stage because further reduction to the hydrazine is faster than the preceding cyclization reaction [27]. The

Synthesis of 2H-furo[2,3-c]pyrazole ring systems through silver(I) ion-mediated ring-closure reaction

• Vaida Milišiūnaitė,
• Rūta Paulavičiūtė,
• Eglė Arbačiauskienė,
• Vytas Martynaitis,
• Wolfgang Holzer and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2019, 15, 679–684, doi:10.3762/bjoc.15.62

• alkynylation/cyclization reaction between 2-iodophenol and (triethoxysilyl)alkynes [20]. In recent years silver and gold salts have found application as versatile and mild catalysts to access the benzo[b]furan ring system through intramolecular cyclization of 2-alkynylphenol substrates [21], including

• substrates 3a–j, the optimal conditions for the subsequent cyclization reaction were next investigated using 3a as the model compound (Table 1). First, we attempted the desired cyclization of 3a to 2H-furo[2,3-c]pyrazole 4a using the synthetic protocol involving Cs2CO3 in dry DMF at 60 °C, which has been

• Cs2CO3/AgOTf system does not offer any advantages for this cyclization compared to the K2CO3/AgOTf system (Table 1, entry 8). With the optimized conditions for the 5-endo-dig cyclization reaction identified, the scope of this transformation for the preparation of several 2,5-disubstituted 2H-furo[2,3-c