Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• terminal alkynes at room temperature (Scheme 15a) [67]. The ability to tune the reactivity of the trityl ion rationally improves the approach with excellent regio- and diastereoselectivity for the unsymmetric ethers. In 2018, Ye et al. reported a CDC reaction to form C(sp)–C(sp3) coupling products from

• -catalyzed formation of 1,1-bis-indolylmethane derivatives. Alkylation of coumarins and flavonoids. Direct CDC α-arylation of azoles with ethers. CDC of terminal alkynes with C(sp3)–H bonds adjacent to oxygen, sulfur or nitrogen atoms. Alkylation of terminal alkynes. Co-catalyzed functionalization of glycine

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

• Heck cross-coupling [69][70]. However, researchers have developed various methods for the transition-metal-catalyzed C(sp2)–H olefination using various types of alkenes as coupling partners [71][72][73]. This part of the review covers reports for the alkenylation of pyridine with terminal alkynes

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• recrystallization of the crude product from ethanol. Next, the oxidative dimerization of terminal alkynes 6a–e was carried out in an aerobic medium in the CuI/TMEDA/iPr2NH system at room temperature, which proved to be effective in the synthesis of butadiynes 1–4 [15] (Scheme 3). The desired diarylbutadiynes 5a–e

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• connect a porphyrin with a chromophoric group. Among these, the copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction [1][2] of azides with terminal alkynes is a popular and well established process to link a porphyrin with other moieties via 1,2,3-triazole group [3] (Figure 1). The term “click

• triazoloporphyrins 32a–c and triazole-bridged bisporphyrins 34 in good yields. The “click reaction” of azidoporphyrin 30 with the terminal alkynes 31a–c and 33 in a THF/water (3:1) mixture was investigated by using different catalytic systems. Among these, copper carbene (SIMes)CuBr proved to be a better catalyst

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

• an ambiphilic aluminium precatalyst, (Me2N)C6H4AlMe2, Thomas et al. were able to shut down hydroalumination by the alane and catalyse the C–H borylation of terminal alkynes with HBpin (Scheme 21) [96]. Through kinetic analysis, it was found that the rate of the alkynyl-Bpin product formation was

• mechanistic proposal. Aluminium-catalysed hydroboration of alkenes and the proposed mechanism. Aluminium-catalysed C–H borylation of terminal alkynes and the proposed mechanism. Aluminium-catalysed dehydrocoupling of amines, alcohols, and thiols with H-B-9-BBN or HBpin and the proposed mechanism. Aluminium

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• ester. Finally, this latter was hydrolyzed or reduced to respectively provide albolic acid (178) and ceroplastol II (179). The scope of the reaction was also extended to various products containing the [X-8-5] tricyclic system (Figure 6). Several functionalized terminal alkynes succeeded in the Pauson

Sequential hydrozirconation/Pd-catalyzed cross coupling of acyl chlorides towards conjugated (2E,4E)-dienones

• Benedikt Kolb,
• Daniela Silva dos Santos,
• Sanja Krause,
• Anna Zens and
• Sabine Laschat

Beilstein J. Org. Chem. 2023, 19, 176–185, doi:10.3762/bjoc.19.17

• Crombie’s work on dienamides and prepared dienoates 15 by hydrozirconation of terminal alkynes 16 followed by Pd-catalyzed cross coupling with enoates 17 [55][56]. A repetitive approach gave rise to oligoenoates [57]. Hydrozirconations were also combined with carbonylations to install carbonyl groups. For

• example, the sequential hydrozirconation/carbonylation of propargylic ethers 18 reported by Donato [58] yielded α,β-unsaturated lactones 19. Beside the hydrozirconation/acylation sequence of nitriles utilizing acid chlorides published by Majoral/Floreancig [59][60], Cox revealed that terminal alkynes 16

• enone building blocks 23 for the synthesis of clifednamides [54][62]. The addition of Schwartz's reagent proceeds as a syn-addition affording (E)-alkenylzirconocenes 24 from terminal alkynes [28]. Based on these precedents from the literature, we surmised that it might be possible to establish a related

Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

• Laura Holzhauer,
• Chloé Liagre,
• Olaf Fuhr,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

• , a small library of 1,2,3-triazole-substituted quinoxalines was synthesized applying the method of Chattopadhyay et al. [10] with minor adjustments. Altogether, a series of 21 different aliphatic and aromatic terminal alkynes were reacted with tetrazolo[1,5-a]quinoxaline and Cu(I) triflate as a

Synthesis of novel alkynyl imidazopyridinyl selenides: copper-catalyzed tandem selenation of selenium with 2-arylimidazo[1,2-a]pyridines and terminal alkynes

• Mio Matsumura,
• Kaho Tsukada,
• Kiwa Sugimoto,
• Yuki Murata and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 863–871, doi:10.3762/bjoc.18.87

• reaction between terminal alkynes and diimidazopyridinyl diselenides, generated from imidazo[1,2-a]pyridines and Se powder, using 10 mol % of CuI and 1,10-phenanthroline as the catalytic system under aerobic conditions. The C(sp2)–Se and C(sp)–Se bond-formation reaction can be performed in one-pot by using

• inexpensive and easy to handle Se powder as the Se source. The reaction proceeded with terminal alkynes having various substitutions, such as aryl, vinyl, and alkyl groups. The obtained alkynyl imidazopyridinyl selenide was found to undergo nucleophilic substitution reaction on Se atom using organolithium

• with an imidazo[1,2-a]pyridine ring, this study focused on the Cu-catalyzed one-pot C(sp2)–Se and C(sp)–Se bond formation for the synthesis of novel alkynyl imidazopyridinyl selenides using Se powder, 2-arylimidazo[1,2-a]pyridines, and terminal alkynes. Results and Discussion Synthesis of alkynyl

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• treated with copper iodide to obtain the phenanthroline–Cu(I) complex (R)-8. A Glaser-type coupling with the terminal alkynes 9, followed by demetalation, proceeds smoothly in 78% yield. This furnishes the desired chiral rotaxane (R)-10, consisting of a BINOL-based macrocycle and a diyne thread. The CD

Synthesis of 3,4,5-trisubstituted isoxazoles in water via a [3 + 2]-cycloaddition of nitrile oxides and 1,3-diketones, β-ketoesters, or β-ketoamides

• Md Imran Hossain,
• Md Imdadul H. Khan,
• Seong Jong Kim and
• Hoang V. Le

Beilstein J. Org. Chem. 2022, 18, 446–458, doi:10.3762/bjoc.18.47

• cycloaddition of alkynes and nitrile oxides performed in organic solvents at elevated temperatures (Figure 1) [11][12][13][14][15][16]. In this method, while 3,5-disubstituted isoxazoles can be accessed from terminal alkynes, 3,4,5-trisubstituted isoxazoles require a high degree of substitution on non-terminal

• reaction proceed at room temperature and improve both the regioselectivity and yields of the isoxazoles. However, these catalysts only work for the reaction with terminal alkynes and only produce 3,5-disubstituted isoxazole products (Figure 1) [19][20]. The synthesis of 3,4,5-trisubstituted isoxazoles from

• highly substituted non-terminal alkynes does not proceed with copper catalysts at room temperature. As an alternative, the usage of ruthenium(II) catalysts enables the reaction to proceed smoothly at room temperature and produces high yields and regioselectivity for both, 3,5-disubstituted and 3,4,5

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• -LED light [111]. Under these conditions, menadione (10) and terminal alkynes 66 underwent a [2 + 2] cycloaddition reaction generating compounds containing cyclobutene rings (67a–c), that are important precursors in natural products syntheses. It is important to note that the choice of the blue-LED

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• steric effects. Anilkumar and co-workers reported an iron-catalyzed Sonogashira coupling of aryl iodides with terminal alkynes in the presence of a catalytic system made up of the greenest solvent, water, in the presence of 10 mol % FeCl3·6H2O and 20 mol % 1,10-phenanthroline as ligand under aerobic

• and co-workers reported a novel Fe-catalyzed cross-coupling for the arylation of terminal alkynes by using a combination of FeCl3 and N,N’-dimethylethylenediamine (dmeda) in catalytic amount [25]. A sample reaction in the absence of catalyst/ligand was also conducted, which yielded no desired product

• /hydroalkoxylation of alkynes was also reported (Scheme 8). Vogel and co-workers demonstrated the Sonogashira cross-coupling reaction of aryl iodides with terminal alkynes by utilizing cheap, non-toxic iron salts and copper iodide (Scheme 9) [26]. The reaction of 4-iodotoluene with phenylacetylene was chosen as the

Anomeric 1,2,3-triazole-linked sialic acid derivatives show selective inhibition towards a bacterial neuraminidase over a trypanosome trans-sialidase

• Peterson de Andrade,
• Sanaz Ahmadipour and
• Robert A. Field

Beilstein J. Org. Chem. 2022, 18, 208–216, doi:10.3762/bjoc.18.24

• (CuAAC, click chemistry), from α-azidosialic acid 1 and commercially available terminal alkynes (Figure 2B), and assessed their inhibitory activity towards TcTS and bacterial neuraminidase. Results and Discussion Synthesis of sialic acid derivatives A small series of anomeric 1,2,3-triazole-linked sialic

• 13C NMR experiment, where the α-anomer is a doublet and the β-anomer is a singlet [28]. The key intermediate 1 was further used in CuAAC reaction [29][30][31][32] with eleven (hetero)aromatic and non-aromatic terminal alkynes readily available in our lab [23]. Although CuAAC is reputedly tolerant of a

• 20 mol % excess of the terminal alkynes in a mixture of solvents (DMF/H2O 4:1) at 60 °C and Cu(I) generated in situ [33], but in catalytic amount. This approach resulted in the synthesis of eight 1,4-disubstituted 1,2,3-triazole derivatives (2a–h) in good yields (45–78%) and high purity. Other two

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

Electrocatalytic C(sp³)–H/C(sp)–H cross-coupling in continuous flow through TEMPO/copper relay catalysis

• Bin Guo and
• Hai-Chao Xu

Beilstein J. Org. Chem. 2021, 17, 2650–2656, doi:10.3762/bjoc.17.178

• terminal alkynes has been achieved in a continuous-flow microreactor through 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)/copper relay catalysis. The reaction is easily scalable and requires low concentration of supporting electrolyte and no external chemical oxidants or ligands, providing straightforward

• ]. In this context, few methods have been developed for the dehydrogenative cross-coupling of tetrahydroisoquinolines with terminal alkynes because of the prevalence of the tetrahydroisoquinoline moiety in natural products and bioactive molecules [3][4][5][6][7][8][9][10]. These methods proceed through

• reaction of tetrahydroisoquinolines with terminal alkynes (Scheme 1C) [10]. The chiral ligand was found to be critical for the stereoinduction as well as product formation for these electrochemical reactions that are conducted in batch. Continuous-flow electrochemical microreactors offer several advantages

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• -catalyzed coupling reactions of terminal alkynes was published by Hwang and co-worker. In 2012, they [65] achieved a photoinitiated Sonogashira reaction using aryl halides (bromides and iodides) 20 and aryl- or alkylacetylenes 19. In control experiments, the replacement of the copper salt with palladium

• -forming reaction [74]. As a notable exception, in 2016, Hwang’s group [75] reported the novel synthesis of unsymmetrical 1,3-conjugated diynes 31 from terminal alkynes under LED irradiation. The reaction mechanism involved a bipolar heterodimeric copper phenylacetylide species that showed similar

• photophysical properties (Scheme 16). In 2019, Vlla’s group [76] explored the copper-catalyzed alkynylation of dihydroquinoxalin-2-ones 34 with terminal alkynes under irradiation. 4-Benzyl-3,4-dihydroquinoxalin-2(1H)-one 35 was subjected to an oxidation process with a CuII salt to generate a nitrogen radical

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

• ]. Then, they also reported another CuH-catalyzed coupling reaction of 1,3-enynes 54 and nitrile to prepare polysubstituted pyrroles 55 (Scheme 21) [66]. The substrates 54 could be easily prepared by Sonogashira coupling of terminal alkynes and vinyl halides. It is worth mentioning that the addition of

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• propargylic carbonates 113 with terminal alkynes 114. The scope of this reaction consisted of 12 examples that were synthesized in moderate to good yields (40–87%). The authors obtained the best yields by using electron-deficient aryl alkynes or secondary carbonates with electron-rich arene substituents (115a

• + 2 + 2] cycloaddition of 1,2-bis(propiolyl)benzene derivative 178 and terminal/internal alkynes 177 (Scheme 41) [75]. The authors performed the reactions with terminal alkynes in toluene, and reactions with internal alkynes in dichloromethane (DCM). They noted that the use of 1,2-bis

• (diphenylphosphino)ethane (DPPE) as ligand improved the yield of the anthraquinones. Representative examples included anthraquinones 179a and 179b obtained from terminal alkynes and 179c and 179d from internal alkynes [75]. Multicomponent reactions In 2009, Singh and co-workers reported a solvent-free methodology to

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• , and a wide variety of aliphatic moieties, (hetero)aromatic units with electron-donating and electron-withdrawing groups, respectively, and ferrocenyl-substituted terminal alkynes was screened. Diverse triazoles disulfides 98 were achieved in good to high yield. Several aliphatic and aromatic azides

Copper-mediated oxidative C−H/N−H activations with alkynes by removable hydrazides

• Feng Xiong,
• Bo Li,
• Chenrui Yang,
• Liang Zou,
• Wenbo Ma,
• Linghui Gu,
• Ruhuai Mei and
• Lutz Ackermann

Beilstein J. Org. Chem. 2021, 17, 1591–1599, doi:10.3762/bjoc.17.113

• Institute for Sustainable Chemistry (WISCh), Georg-August-Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany 10.3762/bjoc.17.113 Abstract The efficient copper-mediated oxidative C–H alkynylation of benzhydrazides was accomplished with terminal alkynes. Thus, a heteroaromatic removable N-2

• context, You [25], Huang [26], Liu [27], Li [28], and co-workers elegantly disclosed copper-mediated/catalyzed cascade C−H alkynylation and annulation with terminal alkynes to afford 3-methyleneisoindolinone derivatives, through the assistance of 8-aminoquinoline [29] or 2-aminophenyl-1H-pyrazole [30

• -catalyzed C−H activations with the MHP auxiliary [41][42][43][44]. In continuation of studies on sustainable 3d transition metal-catalyzed C−H activation [41][42][43][44][45][46][47][48][49], we have now discovered a robust copper-promoted oxidative C−H/N−H functionalization with terminal alkynes (Figure 1d

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• 148 was then 5′-O-dimethoxytritylated in the presence of DMTrCl (4,4′-dimethoxytrityl chloride) and pyridine. The 5′-O-dimethoxytritylated nucleoside 149 was further coupled with terminal alkynes 150a–d under Sonogashira conditions to afford the double-headed nucleosides 151a–d (Scheme 38) [24

Fritsch–Buttenberg–Wiechell rearrangement of magnesium alkylidene carbenoids leading to the formation of alkynes

• Tsutomu Kimura,
• Koto Sekiguchi,
• Akane Ando and
• Aki Imafuji

Beilstein J. Org. Chem. 2021, 17, 1352–1359, doi:10.3762/bjoc.17.94

• synthesis [1]. Electrophilic additions of alkynes give functionalized compounds, and cycloadditions such as the Huisgen reaction afford cyclic compounds. Weakly acidic terminal alkynes can be deprotonated, and the resulting acetylides are used as carbon nucleophiles. Terminal alkynes are also used for the

Highly regio- and stereoselective phosphinylphosphination of terminal alkynes with tetraphenyldiphosphine monoxide under radical conditions

• Dat Phuc Tran,
• Yuki Sato,
• Yuki Yamamoto,
• Shin-ichi Kawaguchi,
• Shintaro Kodama,
• Akihiro Nomoto and
• Akiya Ogawa

Beilstein J. Org. Chem. 2021, 17, 866–872, doi:10.3762/bjoc.17.72

• reactivities. The method using V-40 as an initiator is successfully investigated for the regio- and stereoselective phosphinylphosphination of terminal alkynes giving the corresponding trans-isomers of 1-diphenylphosphinyl-2-diphenylthiophosphinyl-1-alkenes in good yields. The protocol can be applied to a wide

• variety of terminal alkynes including both alkyl- and arylalkynes. Keywords: (E)-1,2-bis(diphenylphosphino)ethylene derivative; radical addition; stereoselective phosphinylphosphination; terminal alkyne; tetraphenyldiphosphine monoxide; Introduction Organophosphorus compounds are an essential class of

• ]. The phosphinylphosphination of various terminal alkynes 2 with Ph2P(O)PPh2 1 was conducted under the optimization conditions (Scheme 3). Terminal alkylalkynes 2a, 2b, and 2c reacted efficiently with 1 to give the corresponding adducts 3a, 3b, and 3c in moderate to good yields (67%, 71%, and 83