Recent advances in electrochemical copper catalysis for modern organic synthesis

• Yemin Kim and
• Won Jun Jang

Beilstein J. Org. Chem. 2025, 21, 155–178, doi:10.3762/bjoc.21.9

• group across alkenes 27. This reaction is applicable not only to a wide range of terminal styrenes but also to internal alkenylarenes, enynes, and allenes, providing enantioenriched products in good yields with high enantioselectivities. This reaction involves Co-catalyzed HAT and Cu-catalyzed

Enantioselective regiospecific addition of propargyltrichlorosilane to aldehydes catalyzed by biisoquinoline N,N’-dioxide

• Noble Brako,
• Sreerag Moorkkannur Narayanan,
• Amber Burns,
• Layla Auter,
• Valentino Cesiliano,
• Rajeev Prabhakar and
• Norito Takenaka

Beilstein J. Org. Chem. 2024, 20, 3069–3076, doi:10.3762/bjoc.20.255

• study, Hoveyda and co-workers proposed a similar mechanism for the isomerization of alkynes to allenes catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene [61]. Conclusion In this study, we prepared distilled propargyltrichlorosilane with >99% isomeric purity for the first time, developed its asymmetric

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• annulation of benzamides and allenes [47]. This method demonstrated excellent functional group tolerance, yielding a broad range of C–N axially chiral compounds with good yields and enantioselectivities. The practicality of this strategy was further demonstrated by a decagram-scale synthesis and the LSF of

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

• -Spirofuran steroids Intramolecular cyclization of alcohols with allenes is a common method for obtaining 17-spirodihydro-(2H)-furan-3-ones. In 2006, Jiang et al. utilized a known reaction sequence to construct the 17-spiro heterocycle 27 from the commercially available ethylene deltenone 24 [20][21]. In this

Palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines

• Geng-Xin Liu,
• Xiao-Ting Jie,
• Ge-Jun Niu,
• Li-Sheng Yang,
• Xing-Lin Li,
• Jian Luo and
• Wen-Hao Hu

Beilstein J. Org. Chem. 2024, 20, 661–671, doi:10.3762/bjoc.20.59

• -light-mediated palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines, affording unsaturated γ- and ε-amino acid derivatives with diverse structures. In this methodology, the diazo compound readily transforms into a hybrid α-ester

• process (Scheme 1c). In this process, the hybrid α-ester alkylpalladium radical species from diazo ester adds to the double bond of 1,3-dienes or allenes, followed by the allylpalladium radical-polar crossover path. As with the classical Tsuji–Trost reaction, a subsequent nucleophilic attack of an amine

• allenes that were never used as substrates in interrupted radical Heck/allylic substitution reactions. As summarized in Scheme 3, unsaturated γ-AA derivatives were observed in this reaction albeit with poor stereoselectivity. Linear amines containing alkyl, hydroxy, and terminal alkenyl groups were

Ligand effects, solvent cooperation, and large kinetic solvent deuterium isotope effects in gold(I)-catalyzed intramolecular alkene hydroamination

• Ruichen Lan,
• Brock Yager,
• Yoonsun Jee,
• Cynthia S. Day and
• Amanda C. Jones

Beilstein J. Org. Chem. 2024, 20, 479–496, doi:10.3762/bjoc.20.43

• ) protodeauration (Scheme 1), the depth of experimental mechanistic validation achieved for allenes and alkynes have not been reproduced with alkenes. In an important foundational study by Toste, the expected alkylgold intermediate from intramolecular alkene hydroamination was isolated, however, turnover

• and allenes continues to seek explanation [49]. Some of the observations reported here are not consistent with others while some are consistent and add quantitative detail and each aspect is summarized individually below [6][7]. Although the results may be interpreted within the π-activation

(E,Z)-1,1,1,4,4,4-Hexafluorobut-2-enes: hydrofluoroolefins halogenation/dehydrohalogenation cascade to reach new fluorinated allene

• Nataliia V. Kirij,
• Andrey A. Filatov,
• Yurii L. Yagupolskii,
• Sheng Peng and
• Lee Sprague

Beilstein J. Org. Chem. 2024, 20, 452–459, doi:10.3762/bjoc.20.40

• -1,1,1,4,4,4-hexafluorobut-2-enes have been investigated. A simple, one-pot procedure for the preparation of a new allene (1,1,4,4,4-pentafluorobuta-1,2-diene) and some of its transformations is presented. Keywords: allenes; dehydrohalogenation; halogenation; 1,1,1,4,4,4-hexafluorobut-2-enes; isomerization

• agreement with the published data [23]. The most interesting outcome from our point of view was the formation of 1,1,4,4,4-pentafluorobuta-1,2-diene (11). 1,1-Difluoroallenes are building blocks for a great number of valuable transformations [28]. Therefore, the synthesis of new fluorinated allenes

• continues to be relevant. One of the methods for the synthesis of allenes was based on the interaction of bromoolefins with organolithium compounds, followed by the elimination of lithium fluoride [29][30][31]. It was logical to assume that in our case a similar reaction of the Grignard reagent 12 with

Aldiminium and 1,2,3-triazolium dithiocarboxylate zwitterions derived from cyclic (alkyl)(amino) and mesoionic carbenes

• Nedra Touj,
• François Mazars,
• Guillermo Zaragoza and
• Lionel Delaude

Beilstein J. Org. Chem. 2023, 19, 1947–1956, doi:10.3762/bjoc.19.145

• applications [24][25][26][27][28]. N-Heterocyclic carbenes and their enetetramine dimers readily add to the central carbon atom of allenes and heteroallenes X=C=Y (X, Y = CR2, NR, O, S) to afford zwitterionic adducts [29]. In particular, their reaction with carbon disulfide affords stable azolium-2

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• ]. Combination of CSA/TBAC formed an efficient activator system for this sulfenylation/intramolecular cyclization. In the same year, Zhao and co-workers reported the thiocarbocyclization of allenes 136 with N-(organothio)succinimides 1 as electrophilic aryl/alkylthio reagents for the assembly of indene-based

• thiocarbocyclization of allenes with N-thiosuccinimides. Suggested mechanism for electrophilic thiocarbocyclization of allenes with N-thiosuccinimides. Chiral chalcogenide-catalyzed enantioselective hydrothiolation of alkenes. Proposed mechanism for chalcogenide-catalyzed enantioselective hydrothiolation of alkenes

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• site-selective NHC–Cu-catalyzed hydroboration of enantiomerically enriched allenes and conversion to the corresponding β-vinyl ketones demonstrates the importance of the strategy. An example is shown below (Scheme 44). 2.2.4 Reaction with organozinc reagents: Organozinc reagents, such as diethylzinc

• (I)–alkyne complex becomes much smaller than in the uncomplexed alkyne. 2.5 Boration and hydroboration NHC–Cu(I) complexes have also been successfully applied to catalyze the boration and hydroboration of carbonyl compounds, allenes, and similar substrates to obtain boronated products [80]. Clark and

• diastereoselectivity (dr > 99:1) was observed in the reaction of chiral ketones. Hoveyda and co-workers [82] employed two types of NHC–Cu(I) complexes to catalyze the protoboration of terminal allenes to obtain vinylboranes (Scheme 60). A set of alkyl- and aryl-substituted allenes was used as substrates. The

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• reactive allenes (reaction e), which serve as synthetic intermediates for polyfunctionalized enynes [8]. The ring strain of the cyclopropane ring facilitates the cleavage of the C–C bond, and both cation and anion are stabilized by the adjacent phenyl group and ester functions, respectively (reaction f

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• , acrylates, allenes, and alkynes as coupling partners achieving the functionalized C(sp2)–H-olefinated pyridine frameworks via metal catalysis. ortho-C–H Alkenylation In 2012, Huang and co-workers [74] disclosed a ligand-free oxidative cross-coupling reaction of pyridine with acrylates, acrylamides, and

• and pharmaceutical compounds [78]. Allenes have been applied as useful substrates for the alkenylation of organic molecules [79]. There are various reports for the C–H alkenylation of aromatic C–H bonds using allenes [80]. To this end, Hou and group in 2015 [81] demonstrated the C–H allenylation of

• pyridines with excellent substrate scope using a scandium catalyst (Scheme 16). A vast number of pyridines and allenes were studied as substrates to provide the C2-alkenylated pyridines in good to high yields. Based on the mechanistic experiments a possible catalytic cycle has been proposed (Scheme 16b

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• of allenes, using various boronates as the terminal reductant (Scheme 5) [68]. Experimental and computational studies suggested the reaction proceeded by hydroboration of the allene 14 by bis(pentafluorophenyl)borane to give an allylborane 15, which underwent allylation of a second equivalent of the

• to give aldol-type products 61. Thomas reported the borane-catalysed diastereo- and enantioselective allylation of ketones with allenes and HBpin to give diastereo- and enantioenriched allylic alcohols, after workup (Scheme 15) [78]. The mechanism was investigated by single-turnover experiments and

• transborylation with HBpin, to give the thioBpin 77 product and regenerate the amine-borane catalyst 73 (Scheme 17). Yamamoto reported the borane-catalysed hydroalumination of alkenes and allenes (Scheme 18) [80][81][82][83] in which the organoaluminium products were reacted in situ with various electrophiles to

Tri(n-butyl)phosphine-promoted domino reaction for the efficient construction of spiro[cyclohexane-1,3'-indolines] and spiro[indoline-3,2'-furan-3',3''-indolines]

• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 669–679, doi:10.3762/bjoc.18.68

• the construction of diverse carbocyclic systems [17][18][19][20][21][22][23][24]. In these reactions, the tertiary phosphine firstly adds to electron-deficient alkenes, alkynes, and allenes to give active ionic intermediates. Then, the in situ-generated ionic intermediates further react with various

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

• of a wide range of axially chiral biaryls, heterobiaryls, vinylarenes, N-arylamines, spiranes, and allenes with high efficiency and excellent stereoselectivity. Keywords: allenes; atropisomerism; axial chirality; chiral phosphoric acid; heterobiaryls; spiranes; Introduction Axial chirality is one

• of the most important properties of nature, resulting from the nonplanar arrangement of four groups in pairs about a chirality axis. These include atropisomerism [1], chiral allenes, spiranes, spiroindanes, and so on [2][3]. Recently, there emerged an enormous demand for enantiopure compounds, not

• , axially chiral allenes and spiranes [25] are well-known scaffolds widely used in natural products, ligands, organocatalysts, and functional materials as well as versatile chiral building blocks in organic synthesis [14][26][27]. Chiral phosphoric acids represent an important and widely used class of

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

• synthesis [47]. Further, the Liu group reviewed the synthesis of allenes via transition metal-catalyzed 1,4-functionalizations of unactivated 1,3-enynes [48]. In this review, we will highlight the recent advances in the tandem annulation reactions of 1,3-enyne structural motifs for the construction of

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

• ‘path b' was followed. Cyclization involving allenes (>C=C=C<) Apart from alkenes/alkynes, there are also examples where cyclization takes place involving allene functionalities. Some of the examples are discussed below. Balasubramanian et al. reported the cyclization of aryl allenic ethers 113 on

• insertion and then oxidation (Scheme 54). This methodology was later successfully utilized for the total synthesis of raloxifene and benzo[b]thiophene derivatives [115]. Cyclization involving allenes (>C=C=C<) Hg(II) triflate salts had also been successfully employed for the arylallene 181 cyclization by

• Yamamoto et al [116]. The catalytic pathway was proved to involve the direct H-transfer to the vinylmercury complex from the aromatic ring. It involved Hg(OTf)2-catalyzed cyclization of aryl 1,1-disubstituted allenes with the formation of a quaternary carbon center followed by the formation of a cationic

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• . also investigated the reactivity of a variety of CF3-substituted propargyl alcohols (Scheme 33) [87]. The reactivity of the benzylic (trifluoromethyl)propargyl alcohol 126 strongly depends on the reaction conditions, as allenes 127 or indenes 128 were both obtained under FeCl3 activation. Indeed, with

• a longer reaction time, allenes 127 undergo a subsequent intramolecular hydroarylation reaction leading to indenes 128. The authors suggested the formation of FeCl3–HFIP complexes being involved in a Lewis acid-assisted Brønsted acid catalysis. The CF3-substituted propargyl alcohol 129 was found to

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• rearrangement product 99 in 85% yield. The synthesis of daphenylline (11) was completed by a seven-step synthesis from benzofuran 99. Phosphine-catalyzed enantioselective [3 + 2] annulation In 2019, Lu and co-workers disclosed a novel chiral-phosphine-catalyzed enantioselective [3 + 2] annulation of allenes and

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• to allenes 80 to give complex bicyclic products 81 in moderate yields and good enantioselectivities (20 examples, up to 92:8 er) (Scheme 9b) [47]. The Bach group recently developed an enantioselective synthesis of cyclobutane 82 from enal 83 and diene 84 (Scheme 11a) [48]. Most of the examples

• by Bach to the deracemisation of allenes rac-194 (Scheme 29) [85]. The proposed mechanism proceeds through configurationally isomeric hydrogen bonding complexes 195 and 195’, with subsequent photoexcitation of the thioxanthone chromophore leading to racemisation of the allene through a triplet state

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• -iminium triflates R‒C≡C‒C(CF3)=N+Me2 TfO− [27]. As a first synthetic application, we have reported the phospha-Michael addition providing 3-(triphenylphosphonio)-1-(trifluoromethyl)-1-(dimethylamino)allenes, which were subsequently transformed into α-(trifluoromethyl)pyrroles. In the present paper, we

A complementary approach to conjugated N-acyliminium formation through photoredox-catalyzed intermolecular radical addition to allenamides and allencarbamates

• Olusesan K. Koleoso,
• Matthew Turner,
• Felix Plasser and
• Marc C. Kimber

Beilstein J. Org. Chem. 2020, 16, 1983–1990, doi:10.3762/bjoc.16.165

• subsequently formed radical (Scheme 3) [41]. The thought process behind this approach is based on three observations; (i) Akita and co-workers disclosure on the photoredox-catalyzed oxytrifluoromethylation of allenes 6 to give 2-trifluoromethylated allyl acetates 7 [42][43][44]; (ii) that intramolecular

• product was observed when ethanol was used as the nucleophile giving product 39 in 52% isolated yield. In contrast, isopropanol gave an inseparable mixture of the α- and γ-addition products, 40a/b in 33% isolated yield. As with the case for the formation of 19, all of the starting allenes were consumed in

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• mechanistic studies. The reactivity of the substituted allenes towards triplet aromatic thiones was investigated. The product analysis revealed the formation of thietanes and occasionally of [4 + 2] cycloadducts (thiopyrans) generally in high overall yields. Steady-state measurements showed that electron

• -donating substituents present in the allenes enhanced the overall reaction rate. There was little effect of the solvent polarity on the reaction rate. The formation of thietanes involved the excited triplet thiones and the π-bond of allenes [66]. In 1984, Bos and co-workers realized the photocycloaddition

• reaction of the first stable thiobenzaldehyde, 2,4,6-tri(tert-butyl)thiobenzaldehyde (211) with substituted allenes 212. Irradiation of thiobenzaldehyde 211 with RCR1=C=CH2 (212) gave diastereospecific [2 + 2] cycloadducts, thietanes 213 in 75–95% yields [67] (Scheme 41). In 1984, Coyle and Rapley