Pathway economy in cyclization of 1,n-enynes

• Hezhen Han,
• Wenjie Mao,
• Bin Lin,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2025, 21, 2260–2282, doi:10.3762/bjoc.21.173

• and co-workers achieved an innovative gold-catalyzed cascade cycloisomerization of 3-allyloxy-1,6-diynes to access cyclopropane- and cyclobutane-fused benzofurans/chromanols (Scheme 5) [12]. In this study, solvent polarity and trace water were identified as key parameters governing the reaction

• synthetic intermediates, and used to successfully modify diverse bioactive scaffolds via late-stage functionalization, collectively demonstrating the method’s synthetic utility. In 2025, the Das group developed a palladium-catalyzed cycloisomerization of 2-alkynylbenzoate-cyclohexadienone that enables

• derivatives 31 (Scheme 7, path b). This work provided a novel approach for constructing substituted naphthalene and indene frameworks via gold-catalyzed cycloisomerization of 1,5-enynes. In 2016, Liu et al. achieved the stereoselective syntheses of furofuran and furopyran scaffolds from propargyl vinyl ethers

Asymmetric total synthesis of tricyclic prostaglandin D2 metabolite methyl ester via oxidative radical cyclization

• Miao Xiao,
• Liuyang Pu,
• Qiaoli Shang,
• Lei Zhu and
• Jun Huang

Beilstein J. Org. Chem. 2025, 21, 1964–1972, doi:10.3762/bjoc.21.152

• the total syntheses of PGs via organocatalysis, and enyne cycloisomerization, respectively. Thus, from a strategic viewpoint, developing alternative synthetic approaches for the stereoselective construction of the highly substituted cyclopentanol core framework in compound 4 may advance the efficient

Enantioselective desymmetrization strategy of prochiral 1,3-diols in natural product synthesis

• Lihua Wei,
• Rui Yang,
• Zhifeng Shi and
• Zhiqiang Ma

Beilstein J. Org. Chem. 2025, 21, 1932–1963, doi:10.3762/bjoc.21.151

• 25 with vinyl butanoate and PPL delivered monoester 26 in 92% yield (99% ee). The axial chirality was transferred to the C7’ stereocenter through a Ag(I)-catalyzed cycloisomerization of the allenol, constructing the dihydrofuran ring. Lipase-catalyzed ester hydrolysis provided allylic alcohol 27

Transition-state aromaticity and its relationship with reactivity in pericyclic reactions

• Israel Fernández

Beilstein J. Org. Chem. 2025, 21, 1613–1626, doi:10.3762/bjoc.21.125

• corresponding transition states is comparable). Thermal cycloisomerization of 1,3-hexadien-5-ynes (Hopf cyclization) Since the original report by Hopf and Musso in 1969 [80], the thermal cycloisomerization reactions of 1,3-haxedien-5-ynes have been widely applied to the synthesis of aromatic six-membered rings

• cycloisomerization reaction of 1,3-hexadien-5-yne. 1,3-Dipolar cycloaddition reactions between t-BuN3 and cyaphide complexes. LA-catalyzed Diels–Alder reactions between isoprene and methyl acrylate. Computed free activation energies (ΔG≠, in kcal/mol), synchronicity (Sy), and NICS(3, +1) values in the corresponding

Recent total synthesis of natural products leveraging a strategy of enamide cyclization

• Chun-Yu Mi,
• Jia-Yuan Zhai and
• Xiao-Ming Zhang

Beilstein J. Org. Chem. 2025, 21, 999–1009, doi:10.3762/bjoc.21.81

• cyclization modes that provide entries to various N-heterocycles, some of which serve as key structural motifs in natural alkaloids. This review highlights recent advancements in enamide-based cyclization reactions, including enamide–alkyne cycloisomerization, [3 + 2] annulation, and polycyclization, with a

• have attracted considerable attention due to their promise in the total synthesis of alkaloids [16]. Notably, these valuable compounds can be employed as efficient synthons in enamide–alkyne cycloisomerization, [n + m] cycloadditions, pericyclic reactions, and radical cyclizations. A comprehensive

• review of these advancements up until 2015 has already been documented [16]. In this review, recent breakthroughs of these enamide cyclizations will be surveyed from the viewpoint of natural product synthesis. Leveraging the enamide–alkyne cycloisomerization cyclizations, Lycopodium alkaloids

Formaldehyde surrogates in multicomponent reactions

• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Bernhard Westermann

Beilstein J. Org. Chem. 2025, 21, 564–595, doi:10.3762/bjoc.21.45

• ). The alkyne reacts with the in situ-generated carbanion through a 5-endo-dig-cycloisomerization process to yield a nitrogen-containing five-membered heterocycle (Scheme 44). Examples in which the propargyl group is incorporated into the amine [106] or the carboxylic acid components [107] are known

Solvent-dependent chemoselective synthesis of different isoquinolinones mediated by the hypervalent iodine(III) reagent PISA

• Ze-Nan Hu,
• Yan-Hui Wang,
• Jia-Bing Wu,
• Ze Chen,
• Dou Hong and
• Chi Zhang

Beilstein J. Org. Chem. 2024, 20, 1914–1921, doi:10.3762/bjoc.20.167

• ) diacetate (PIDA) [22][23]. And more recently, Du and our group have developed a method for the chemoselective cycloisomerization of o-alkenylbenzamides to 3-arylisoquinolinones, using PhIO as oxidant in combination with a catalytic amount of trimethylsilyl trifluoromethanesulfonate [24]. Although

• , isopropyl, cyclopropyl, phenyl, or hydrogen, respectively, the intramolecular amination smoothly gave the corresponding 4-substituted isoquinolinone products 2b,c,d–f in 51–94% yield. Notably, when 1c was used as the substrate, the cycloisomerization product 2c' was observed in 31% yield besides 2c in 51

One-pot Ugi-azide and Heck reactions for the synthesis of heterocyclic systems containing tetrazole and 1,2,3,4-tetrahydroisoquinoline

• Jiawei Niu,
• Yuhui Wang,
• Shenghu Yan,
• Yue Zhang,
• Xiaoming Ma,
• Qiang Zhang and
• Wei Zhang

Beilstein J. Org. Chem. 2024, 20, 912–920, doi:10.3762/bjoc.20.81

• oxidative cycloisomerization reactions for the synthesis of 2-tetrazolyl-substituted 3-acylpyrroles (Scheme 2C) [42]. The Ding group also reported sequential Ugi-azide/Staudinger/aza-Wittig/addition/Ag-catalyzed cyclization reactions for obtaining 12-tetrazolyl-substituted (E)-5H-quinazolino[3,2-a

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