Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• electrocyclization of compounds 1a and b [19][20][21][22]. Interestingly, Baldwin and Moses demonstrated the irradiation or sunlight-promoted cycloisomerization of a similar tetraenyl framework into the bicyclo[3.1.0]hexane core through a 6π-conrotatory stereocontrol [23][24]. To date, the known strategies to

Formal total synthesis of macarpine via a Au(I)-catalyzed 6-endo-dig cycloisomerization strategy

• Jiayue Fu,
• Bingbing Li,
• Zefang Zhou,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2022, 18, 1589–1595, doi:10.3762/bjoc.18.169

• total synthesis of macarpine [12] is proposed via a Au(I)-catalyzed cycloisomerization reaction. Retrosynthetically, the target molecule macarpine (1) could be disconnected into naphthol 12 (Scheme 3), a key intermediate reported by Ishikawa in the total synthesis of macarpine. This intermediate could

• be synthesized from silyl enol ether compound 10 via the Au(I)-catalyzed cycloisomerization reaction developed by our group [15]. The compound 10 could be constructed by the Sonogashira coupling reaction from readily prepared iodoarene 8 [12][16] and ketone 5, which could be synthesized by using

• building blocks 5 and 8 in hand, ketone 9 was prepared via a palladium-catalyzed Sonogashira coupling reaction in a yield of 95%. The precursor 10 for the gold(I)-catalyzed [19][20][21][22][23][24] cycloisomerization was then synthesized by treating ketone 9 with sodium bis(trimethylsilyl)amide (NaHMDS

Supramolecular approaches to mediate chemical reactivity

• Pablo Ballester,
• Qi-Qiang Wang and
• Carmine Gaeta

Beilstein J. Org. Chem. 2022, 18, 1463–1465, doi:10.3762/bjoc.18.152

• whose geometry, in low-polarity solvents, is controlled by the 1,2,3-alternate conformation of the calix[6]arene skeleton. These catalysts can tune the selectivity of the catalytic cycloisomerization of 1,6-enynes in response to the relative orientation of the coordinated gold(I) atom with respect to

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• cycloisomerization of the α-ketoester 22, which can be described as a Friedel–Crafts-type reaction or an aldol reaction of an S,O-ketene acetal (Scheme 4). The required ketoester 22 was synthesized from sulfonylchromenone 20, accessible from dihydroxyacetophenone 19 and thiol 18 derived from known alcohol 17 [11][12

• ]. DMP oxidation of α-hydroxyester 21 and subsequent cycloisomerization led to the desired cyclization product 23 via transition state II in a dr of 5:1. Final deprotection gave preussochromone A (24). (−)-Preussochromone D A similar approach was chosen in the synthesis of the structurally related

• -diketoester. Synthesis of euphorikanin A (16) by intramolecular, nucleophilic addition [6]. Ketoester cycloisomerization for the synthesis of preussochromone A (24) [10]. Diastereoselective, intramolecular aldol reaction of an α-ketoester 28 in the synthesis of (−)-preussochromone D (30) [13][14]. Synthesis

Diametric calix[6]arene-based phosphine gold(I) cavitands

• Gabriele Giovanardi,
• Andrea Secchi,
• Arturo Arduini and
• Gianpiero Cera

Beilstein J. Org. Chem. 2022, 18, 190–196, doi:10.3762/bjoc.18.21

• polarity solvents, of a novel class of diametric phosphine gold(I) cavitands characterized by a 1,2,3-alternate geometry. Preliminary catalytic studies were performed on a model cycloisomerization of 1,6-enynes as a function of the relative orientation of the bonded gold(I) nuclei with respect to the

• catalytic activity was demonstrated in promoting gold(I)-catalyzed cycloisomerization of 1,6-enynes, with ample scope and high regioselectivity. However, preliminary studies suggested that the catalytic event occurs outside the macrocyclic cavity. In order to get more insights on the role of the cavity to

• in controlling the reactivity of gold(I)-catalyzed transformations by means of supramolecular macrocycles, we choose a cycloisomerization of 1,6-enynes as a model reaction [36]. Substrate 1a was reacted in the presence of monomeric gold(I) catalyst A’(AuCl) (2 mol %), using AgSbF6 as the chloride

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• release of a nitrogen molecule to form the desired product 46. In 2018, Ding and co-workers reported the synthesis of 2-tetrazolyl-substituted 3-acylpyrroles 53 via sequential Ugi-azide/Ag-catalyzed oxidative cycloisomerization reactions in good yield (Scheme 20) [64]. Firstly, The Ugi-azide reaction

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• temperature. It was an example of cycloisomerization of 2-ethynylaniline derivatives utilizing mild reaction conditions (Scheme 50) [110]. Rong et al. had demonstrated the Hg(II)-salt-catalyzed enolate umpolung reaction for the efficient synthesis of various 3-indolinones and 3-coumaranones 174. They had

• difficult for organic chemists. Morimoto and co-workers were the first to disclose the Hg(OTf)2-catalyzed cycloisomerization of amino ynone to produce the azaspiro skeleton. Later, this methodology was successfully used for the synthesis of several spiroskeleton structures. Natural products such as

• -methylenepiperidine. a) Preparation of indole derivatives through cycloisomerization of 2-ethynylaniline and b) its mechanism. a) Hg(OTf)2-catalyzed synthesis of 3-indolinones and 3-coumaranones and b) simplified mechanism. a) Hg(OTf)2-catalyzed one pot cyclization of nitroalkyne and b) its plausible mechanism

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• cycloisomerization of diolefins triggered by the MHAT process. Some challenges associated with the development of these reactions were the reversible nature of the HAT and the competition with linear isomerization and reductive pathways (Scheme 18) [72][73]. In 2014, the Shenvi group developed an olefin

• of this kind of reaction is the catalytic use of the hydride donor, in this case phenylsilane (PhSiH3), due to the regeneration of the active metal hydride species in the cycloisomerization mechanism pathway (Scheme 18). The lower cyclization constant for the six-membered ring formation, in

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• cycloisomerization/Pictet–Spengler cyclization of 2-(4-aminobut-1-yn-1-yl)aniline [16], the Ru and Rh-catalyzed [2 + 2 + 2] cycloadditions of yne-ynamides [17], and the Pd-catalyzed tandem coupling-cyclization [18] are significant works in the area (Scheme 1). However, the use of toxic and expensive metal catalysts

Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

• Renata Kaczmarek,
• Dariusz Korczyński,
• James R. Green and
• Roman Dembinski

Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1

• only provide a biological impact but also create a synthetic handle for further functionalization/modification. Among others, alkynyl uridines undergo cycloisomerization to potent antiviral agents, furopyrimidines [13], related halofuropyrimidines [14], and can be converted into interstrand dimers [15

• , triethylamine, in DMF, and at room temperature – to avoid cycloisomerization to furopyrimidines (Scheme 1). The modified pyrimidine nucleoside scaffolds, propargyl acetate-substituted 2'-deoxyuridine (R = Ac, 2) and propargyl methyl ether-substituted uridine (R = Me, 3), were obtained in 87% and 61% yield

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

• of the two L2·(AgOTf)2 stereoisomers highlighted their different geometry. The catalytic activity of all silver(I) complexes was effective under homogeneous conditions in two tandem addition/cycloisomerization of alkynes using 0.5–1 mol % of catalytic loading. Keywords: coordination macrocycle

• candidates for directional metal coordination. Herein, a new syn-atropisomer of 9,10-DPA ortho-substituted by two thioethers is exploited as a ligand for silver(I) salts. The impact of this bis-thioether ligand on silver(I) homogeneous catalysis is evaluated in two tandem addition/cycloisomerization

• 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

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

• ) complex 64, which on reductive elimination gave the final product 62 (Scheme 22). Also, Irina V. Rassokhina and others have employed Cu(OAc)2 for the synthesis of imidazo[1,2-a]pyridines under aerobic conditions (Scheme 23) [114]. They have performed aminomethylation and cycloisomerization of propiolates

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• protected 3-aminoglycals from non-carbohydrate precursors. Most of them used a common methodology for the construction of the pyranosyl glycal ring which is based on a cycloisomerization reaction of chiral homopropargylic alcohols [7][8][9][10]. In some cases, the strategy used for the preparation of the

Gold-catalyzed post-Ugi alkyne hydroarylation for the synthesis of 2-quinolones

• Xiaochen Du,
• Jianjun Huang,
• Anton A. Nechaev,
• Ruwei Yao,
• Jing Gong,
• Erik V. Van der Eycken,
• Olga P. Pereshivko and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2018, 14, 2572–2579, doi:10.3762/bjoc.14.234

• -dimethoxyaniline (6a). Next, the cycloisomerization of 7a was investigated in order to identify the optimal conditions. At first, we attempted two reactions using 5 mol % of the standard AuPPh3Cl/AgOTf precatalytic combination in conventional chlorinated solvents such as deuterated chloroform and dichloromethane

Cobalt bis(acetylacetonate)–tert-butyl hydroperoxide–triethylsilane: a general reagent combination for the Markovnikov-selective hydrofunctionalization of alkenes by hydrogen atom transfer

• Xiaoshen Ma and
• Seth B. Herzon

Beilstein J. Org. Chem. 2018, 14, 2259–2265, doi:10.3762/bjoc.14.201

• developed (e.g., reductive coupling [22][23][24][25][26][27][28], formal hydromethylation [29], cycloisomerization [8][30][31], hydrooximation [32], hydroheteroarylation [28][33][34][35], hydroarylation [36][37][38], and cross-coupling [37]). Many of these transformations have found applications in

Is the tungsten(IV) complex (NEt₄)₂[WO(mnt)₂] a functional analogue of acetylene hydratase?

• Matthias Schreyer and
• Lukas Hintermann

Beilstein J. Org. Chem. 2017, 13, 2332–2339, doi:10.3762/bjoc.13.230

• cycloisomerization of alkynols, in which the alcohol adds to the alkyne [19]. The reaction of [W(CO)5(THF)] with ortho-ethynylacetophenone and excess water gives 1,2-diacetylbenzene via neighboring group attack to complexed alkyne, and hydrolysis [20]. The latter pathway represents the π-activation pathway of alkyne

• hydration (Scheme 2a), whereas alkynol cycloisomerization proceeds via rearrangement to a tungsten vinylidene complex and addition of the alcohol hydroxy group to the vinylidene α-carbon [18]. The vinylidene mechanism is related to that of ruthenium-catalyzed anti-Markovnikov hydration of terminal alkynes

Unpredictable cycloisomerization of 1,11-dien-6-ynes by a common cobalt catalyst

• Abdusalom A. Suleymanov,
• Dmitry V. Vasilyev,
• Valentin V. Novikov,
• Yulia V. Nelyubina and
• Dmitry S. Perekalin

Beilstein J. Org. Chem. 2017, 13, 639–643, doi:10.3762/bjoc.13.62

• cycloisomerization in the presence of the cobalt catalytic system CoBr2/phosphine ligand/Zn/ZnI2 giving cyclohexene, diene or cyclopropane structures depending on the type of the phosphine ligand. This unpredictable behaviour suggests that, although the availability of the cobalt catalytic system is appealing, the

• ]. In particular, cycloisomerization of enynes allows one to prepare compounds with exocyclic double bonds and cyclopropanes in a highly selective manner [5][6][7]. While catalytic transformations of enynes have been investigated in detail, there are only a few examples of similar reactions of dienynes

• catalytic system with other phosphine ligands, such as dppm, dppf, or BINAP, did not catalyze cycloisomerization of 1 into any products. In order to explain the formation of products 2–5 we proposed a possible mechanism (Scheme 3) in accordance with the generally accepted concepts [15][18]. The crucial step

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• alcohols revealed a matched/mismatched effect that was strongly dependent on the nature of the solvent. Keywords: asymmetric catalysis; [3.1.0] bicycles; [4.1.0] bicycles; cycloisomerization; 1,6-enyne; 1,7-enyne; ruthenium catalysis; sulfoxide; Introduction Due to their prevalence in natural products [1

• an atom- [5], step- [6], and redox-economical [7] class of reactions that are able to stitch together cyclic molecules quickly and efficiently. The very first enyne cycloisomerization reactions were reported by the Trost group while they were synthesizing substrates intended for thermal Alder–ene

• molecular architectures hold a particular interest to the chemical community, especially in the fields of natural product synthesis and drug design, researchers have made a significant effort to discover asymmetric variations of enyne cycloisomerization reactions [11][12]. Researchers have used a variety of

Recent advances in metathesis-derived polymers containing transition metals in the side chain

• Ileana Dragutan,
• Valerian Dragutan,
• Bogdan C. Simionescu,
• Albert Demonceau and
• Helmut Fischer

Beilstein J. Org. Chem. 2015, 11, 2747–2762, doi:10.3762/bjoc.11.296

• allowed the intramolecular cycloisomerization of enynes with high yields and turnover numbers. Copper-containing polymers A copper(I) complex containing a norbornene substituted with the 2-(pyridin-2-yl)-1H-benzimidazole ligand, 44, developed by Il'icheva et al. [64], came to the attention of the

Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

• Andrzej Tracz,
• Mateusz Matczak,
• Katarzyna Urbaniak and
• Krzysztof Skowerski

Beilstein J. Org. Chem. 2015, 11, 1823–1832, doi:10.3762/bjoc.11.198

• to test a range of commercially available, classical ruthenium initiators in ACS grade solvents under air [31]. For this study we choose substrate 1, which is highly prone to non-metathesis reactions, namely isomerization and cycloisomerization. The result we found is that esters constitute

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• RCM and a minor amount of the cycloisomerization product, the unmodified congener, which preferentially exists as its cis-dichloro isomer, shows a switched reactivity. The position of the equilibrium between the cis- and the trans-dichloro species was found to be the crucial factor governing the

• interesting observation is that reactions catalyzed with 14 and 15 gave predominantly the RCM product (compound 17) accompanied by a minor amount of a cycloisomerization-derived compound 19. It is worth noting, that even after heating at 80 °C for 100 h the catalysts were still active, as can be assessed from

• the time/conversion plots (cf. Figure 5a and b). In contrast, the precatalyst 5a promoted predominantly cycloisomerization albeit conversion was poor (cf. Figure 5c). Because all transformations were very slow at 80 °C the next series of test reactions was conducted at 140 °C in xylenes as the solvent

Pd(OAc)₂-catalyzed dehydrogenative C–H activation: An expedient synthesis of uracil-annulated β-carbolinones

• Biplab Mondal,
• Somjit Hazra,
• Tarun K. Panda and
• Brindaban Roy

Beilstein J. Org. Chem. 2015, 11, 1360–1366, doi:10.3762/bjoc.11.146

• -carbolinones have been developed [32][33][34][35][36], such as an intramolecular Heck reaction strategy of 2- and 3-iodoindoles for the synthesis of β- or γ-carbolinones by Beccalli et al. [32], AuCl3 and Pd-catalyzed cycloisomerization of indole-2-carboxamides to β-carbolinones [33][34][35], Pd-catalyzed

Building complex carbon skeletons with ethynyl[2.2]paracyclophanes

• Ina Dix,
• Lidija Bondarenko,
• Peter G. Jones,
• Thomas Oeser and
• Henning Hopf

Beilstein J. Org. Chem. 2014, 10, 2013–2020, doi:10.3762/bjoc.10.209

• and the planar building block 1,2-diethynylbenzene (1) yielded the chiral hetero dimer 22 as the main product. An attempt to prepare the biphenylenophane 27 from the triacetylene 24 by CpCo(CO)2-catalyzed cycloisomerization resulted in the formation of the cyclobutadiene Co-complex 26. Besides by

• in Scheme 5, offers itself for another coupling/cycloisomerization sequence which, in principle, could provide a hybrid molecule consisting of a [2.2]paracyclophane core and a biphenylene bridge, hydrocarbon 27 (Scheme 8). To prepare this new (and also chiral) cyclophane system we applied the

• which a planar triacetylene was subjected to CpCo(CO)2-mediated cycloisomerization [13]. Conclusion In conclusion, we have considerably extended the range of highly unsaturated carbon scaffolds by using ethynyl[2.2]paracyclophanes as substrates for the generation of new layered frameworks. The above

Visible-light photoredox catalyzed synthesis of pyrroloisoquinolines via organocatalytic oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade with Rose Bengal

• Carlos Vila,
• Jonathan Lau and
• Magnus Rueping

Beilstein J. Org. Chem. 2014, 10, 1233–1238, doi:10.3762/bjoc.10.122

• type of compounds [22][23][24][25][26]. Recently, several metal mediated syntheses using a [3 + 2] cycloaddition reaction have been described in the literature. Porco Jr. et al. [27] described a silver-catalyzed cycloisomerization/dipolar cycloaddition for the synthesis of the pyrrolo[2,1-a