Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• /arylation of cyclic oxalates 33 with terminal alkyne 34 and aryl bromides 3 (Scheme 20) [73]. As to the scope, aryl bromides 3 containing various electron-withdrawing substituents displayed better efficiency over the electron-rich aryl bromides. The authors proposed a plausible catalytic cycle to account

• ) photocatalyst 10-III. The active iridium(III) photocatalyst 10-I is regenerated by a SET process between 10-III and the nickel(I) species 10-X. The addition of the tertiary radical 10-IV to the terminal alkyne 34 followed by an intramolecular 1,5-HAT results in a nucleophilic secondary alkyl radical species 10

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

• ). Representative examples included indenoanthracenes 61a–c, bearing aryl groups linked to the alkyne, and indenoanthracenes 61d–f, containing tetramethylsilane groups at the terminal alkyne [46]. From commercially available 1,8-dichloroanthraquinone (62) and by using modified Suzuki–Miyaura coupling reaction

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

• complex mixture was observed when an aliphatic terminal alkyne was used, and no annulation product was detected for internal alkynes. Our copper-promoted C−H annulation protocol was not restricted to terminal alkynes. Under identical reaction conditions, commercially available alkynylcarboxylic acid 4

• . Proposed reaction pathway. Optimization of the copper-mediated C−H/N−H functionalization with terminal alkyne 2a.a Supporting Information Supporting Information File 232: Characterization data for 3 and copies of 1H, 13C, and 19F NMR spectra. Funding Generous support by National Natural Science

• Discussion We initiated our investigation by utilizing benzhydrazide 1a and ethynylbenzene (2a) as the standard substrates (Table 1). After preliminary solvent optimization, we discovered that the desired ortho-selective C−H activation occurred efficiently by the treatment of hydrazide 1a with terminal

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

• alkyne 155 was reacted with bromobenzene and sodium azide under microwave heating in an EtOH/H2O mixture in the presence of copper iodide, sodium ascorbate, and N,N-dimethylethylenediamine (156) to afford the double-headed nucleoside 157a. The reaction of the terminal alkyne 155 with benzyl bromide and

• -benzyl-1H-1,2,3-triazol-4-yl)-2′-deoxyuridine (157b), and 5-(1-pivaloyloxymethyl-1H-1,2,3-triazol-4-yl)-2′-deoxyuridine (157c). The synthesis started from 5-ethynyl-2′-deoxyuridine (155) which in turn was synthesized from 5-iodo-2′-deoxyuridine following literature procedures [77][78][79]. The terminal

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

• sulfoxides 2e and 2f (Table 2, entries 5–8). The reaction of (Z)-sulfoxides (Z)-2e and (Z)-2f, in which the methyl group and chloro group were located trans to each other, tended to give alkynes 4 with low efficiency (Table 2, entries 6 and 8). The terminal alkyne 4g was obtained from both geometric isomers

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

• 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

• , reaction 1). On the other hand, reaction 2 in Scheme 4 indicates an example of the phosphinylphosphination of a terminal alkyne. The detailed analysis of the products in this reaction revealed the formation of 8% of the addition product 3n’, which might be formed by the addition of Ph2P• to the alkyne

• addition to 2n. A plausible reaction pathway for the radical addition of Ph2P(O)PPh2 to terminal alkynes. Phosphinylphosphination of terminal alkyne 2a with 1 under different reaction parameters. Supporting Information Supporting Information File 24: Characterization data and copies of NMR spectra

Effective microwave-assisted approach to 1,2,3-triazolobenzodiazepinones via tandem Ugi reaction/catalyst-free intramolecular azide–alkyne cycloaddition

• Maryna O. Mazur,
• Oleksii S. Zhelavskyi,
• Eugene M. Zviagin,
• Svitlana V. Shishkina,
• Vladimir I. Musatov,
• Maksim A. Kolosov,
• Elena H. Shvets,
• Anna Yu. Andryushchenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2021, 17, 678–687, doi:10.3762/bjoc.17.57

• of our study, the Ugi products 6 were involved in IAAC. Compounds such as 6aab, 6abb and 6aeb with terminal alkyne fragment can be easily cyclized under thermal uncatalyzed conditions in various solvents – from nonpolar benzene to polar protic solvents, and even in water, depending on substrate

• descriptive than in the case with IAAC on terminal alkyne due to the lack of transformation of the alkyne proton into a triazole one that was tracked for compounds 7aab, 7abb and 7aeb previously. However, there is still a significant change of the aromatic signals from the azidobenzene group multiplet (in the

• . Synthesis of Ugi products 6, their structures and yields. Cyclization of Ugi-product 6aab with terminal alkyne fragment. The substrate scope of intermolecular cycloaddition. Optimizing the reaction conditions for IAAC on internal alkynes. Supporting Information Supporting Information File 68: General

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• using a four-step sequence such as Negishi’s (Z) and (E)-stereoselective isomerization of the terminal alkyne followed by iodinolysis [19][70][71], oxidation to the corresponding aldehydes and enantioselective Kiyooka–Mukaiyama aldol reaction followed by TES protection of the resulting alcohols (Scheme

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• (2) was synthesized from terminal alkyne 76 (Scheme 9). This alkyne was prepared from 5-bromopentene, according to the procedure described by Negishi [54]. Zr-catalyzed carboalumination furnished vinylalane, treated with p-menthane-3-carboxaldehyde providing the allylic alcohols (−)-77a and (−)-77b

Ring-closing metathesis of prochiral oxaenediynes to racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans

• Viola Kolaříková,
• Markéta Rybáčková,
• Martin Svoboda and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2020, 16, 2757–2768, doi:10.3762/bjoc.16.226

• (Scheme 9). With the aim to enable the further functionalization of the products of the oxaenediyne metathesis, we also synthesized substrates modified at the terminal alkyne positions with silyl or ester groups. Because these substrates were inaccessible by the above described methods, we obtained the

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• triazoles 33–44. General reaction conditions for CuAAC reactions: Azide (1.00 equiv), terminal alkyne (1.05 equiv), CuSO4·5H2O (0.1 equiv), sodium ascorbate (0.50 equiv), CHCl3, (0.1 M) and water (12.5 mM) at 25 °C for 48 h. b) Methylation reaction of adamantly-substituted triazole 42 with Meerwein′s salt

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• cyclopentenone ring in all cases (Scheme 32). This was expected for terminal alkyne 58a, since this is the substitution pattern always found (see Scheme 4). On the other hand, for alkynes bearing substituents of similar steric bulk, the electron withdrawing group is expected to occupy the β-position. However

Fluorohydration of alkynes via I(I)/I(III) catalysis

• Jessica Neufeld,
• Constantin G. Daniliuc and
• Ryan Gilmour

Beilstein J. Org. Chem. 2020, 16, 1627–1635, doi:10.3762/bjoc.16.135

• these species in inhibiting aconitase [22] must be reconciled with synthetic utility. To that end, catalysis-based strategies to unmask the venerable α-fluorocarbonyl motif [23] from a terminal alkyne were considered (Figure 1). This general strategy was appealing given the commercial availability of

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• proceeded efficiently for a wide range of substrates in moderate to excellent yield, including various alkyl halides 93, carbon tetrachloride, 2-norbornene, cyclic alkenes, a terminal disubstituted olefin, and a terminal alkyne. The reaction mechanism was thought to proceed via energy transfer from the

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

• protecting groups [12]. Later, ruthenium complexes-catalyzed alkyne–azide cycloadditions (RuAACs) regioselectively produced the opposite form of the disubstituted triazoles. Thus, a wide range of azides was reacted with diverse nonactivated terminal alkyne substrates using ruthenium complexes to generate

• . Different ratios of Cu/Au (1:1, 3:1, and 5:1) were studied for the coupling reaction of a nonactivated terminal alkyne with an organic azide. Control measurements showed that 1:1 and 3:1 samples were more efficient than a 5:1 sample. The authors stated that increasing the Cu/Au ratio caused the formation of

Controlling alkyne reactivity by means of a copper-catalyzed radical reaction system for the synthesis of functionalized quaternary carbons

• Goki Hirata,
• Yu Yamane,
• Naoya Tsubaki,
• Reina Hara and
• Takashi Nishikata

Beilstein J. Org. Chem. 2020, 16, 502–508, doi:10.3762/bjoc.16.45

• Goki Hirata Yu Yamane Naoya Tsubaki Reina Hara Takashi Nishikata Graduate School of Science and Engineering, Yamaguchi University 2-16-1 Tokiwadai, Ube, Yamaguchi, 755-8611, Japan 10.3762/bjoc.16.45 Abstract A terminal alkyne is one of the most useful reactants for the synthesis of alkyne and

• reaction of 3 equivalents of terminal alkyne 1 (aryl substituted alkyne) and an α-bromocarbonyl compound 2 (tertiary alkyl radical precursor) undergoes tandem alkyl radical addition/Sonogashira coupling to produce 1,3-enyne compound 3 possessing a quaternary carbon in the presence of a copper catalyst

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

• warranted, which at the same time may provide biologically active compounds. Results and Discussion Preparation of 5-alkynyluridines was carried out from acyl-protected 5-iodouridines (1a,b) [8][63] and the appropriate terminal alkyne in the presence of catalytic amounts of Pd(PPh3)4, copper(I) iodide

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• to α-pyrones through a consecutive alkynylation–Michael addition–cyclocondensation (AMAC) multicomponent synthesis [23]. The reaction can be rationalized by a Sonogashira coupling between an acid chloride and a terminal alkyne furnishing an alkynone, which is transformed without isolation by addition

Formation of alkyne-bridged ferrocenophanes using ring-closing alkyne metathesis on 1,1’-diacetylenic ferrocenes

• Celine Bittner,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2019, 15, 2534–2543, doi:10.3762/bjoc.15.246

• shown for complex I as well [13][16][46]. Beforehand, the promotion of terminal alkyne metathesis (TAM) proved to be difficult due to several deactivation pathways [47][48][49][50][51][52][53]. Regarding the metathesis of organometallic substrates, numerous examples of a conversion via olefin metathesis

• acetylenic sidechains show the characteristic triplet with a small coupling constant for the terminal alkyne proton at chemical shifts of 2.05 ppm and 2.01 ppm, respectively. The NMR data for the butynyl compound 1a fit the results of Suitor et al. that were published only recently [93]. From saturated DCM

• is in the same range as for the free ligand 2a. Conclusion The present paper reports a new application of terminal alkyne metathesis (TAM) using the highly active molybdenum pre-catalyst MoF6. For the first time, acetylenic ferrocenophanes were accessed using ring-closing alkyne metathesis

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

• century, Sharpless and co-workers proposed the concept of “click chemistry” [14], which stands for the secure, quick, selective, general and facile reaction between two organic functional groups. In click chemistry, the Huisgen cyclization, which occurs between an organic azide and a terminal alkyne

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

• react with aldehydes 1 in the presence of NaHSO4·SiO2 and the product obtained was refluxed with phenylacetylene (as terminal alkyne, 2) in the presence of CuI to obtain the product, however, in the second pathway, 1 and 2 were taken together in the presence of CuI and the product obtained was treated

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

• , leading to final lactams 20. This mechanism is partially corroborated by the following multicomponent synthesis where benzamide 21, ortho-functionalized with a terminal alkyne group (Scheme 5), a secondary amine 22 and carbon monoxide (23) react to produce 3-methyleneisoindolinones 24 [80]. A palladium

• conjugate addition of benzamide nitrogen onto the 2-ynamide generates the final cyclization product 24 through allene intermediate 28. Taking into account that the reaction does not take place with internal alkynes, the authors conclude that a terminal alkyne is necessary for the formation of the first

• through an addition of copper acetylide, generated from terminal alkyne and copper, to the imine formed by the reaction between the amine and the formyl group. Then, the secondary propargylamine intermediate would act as a nucleophile in a cyclization process to form the lactam ring. The same

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• applied a Diels–Alder reaction of 1,2,4,5-tetrazine with a terminal alkyne unit in a 21-crown-7-based [2]pseudorotaxane 14. The [2]rotaxane 15 was produced in 81% yield having pyridazine groups as stoppers (Figure 7). Very recently, Nierengarten and co-workers reported a solvent-free mechanochemical

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• approach to complex heterocycles. The aldehyde PM69 was further converted into the terminal alkyne PM73 by employing the Bestmann–Ohira protocol (Scheme 21). After its Sonogashira reaction with iodobenzene to the intermediate disubstituted alkyne PM74 this compound was converted into furopyrimidine