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

• alkali alkoxide as the base (Scheme 6) [15]. In the case of IPr·HX, it was found that the use of CuI afforded a significant amount of [(IPr)2Cu] complexes even when a large excess of the metal salt was used. Furthermore, the combination of KOMe and toluene afforded a higher yield of [(IPr)CuI] [15]. It

• diaminocarbene complex 32 and diamidocarbene (DAC) complex 33. The mononuclear N-heterocyclic carbene (NHC)–copper alkoxide complexes [(6-NHC)CuOt-Bu] (6-NHC = 6-MesDAC (30), 6-Mes (31)) were prepared by the addition of free carbenes to the tetrameric tert-butoxide precursor [Cu(Ot-Bu)]4, or by protonolysis of

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

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

• be envisioned for the carbonannulation of diazabicyclic alkenes with 2-formylphenylboronic acid up to the last step which likely operates through a β-hydride elimination of the Rh(I) alkoxide, furnishing the final carbonyl-containing product. In 2013, Lautens reported the synthesis of oxazolidinone

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

• allene 14, giving a boryl diene 16. A Cope rearrangement of the boryl diene 16 followed by transborylation gave the dienyl boronic ester 18 and regenerated the catalyst (Scheme 5). Chang reported the alkoxide-promoted hydroboration of N-heteroarenes with HBpin, the first explicit example of a B‒N/B‒H

• . Alkoxide-promoted hydroboration of heterocycles and the proposed mechanism. Borane-catalysed reduction of indoles and the proposed mechanism. H-B-9-BBN-catalysed hydrocyanation of enones and the proposed mechanism. Borane-catalysed hydroboration of nitriles and the proposed mechanism. Myrtanylborane

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• -mediated cross-coupling (77% yield for the coupling step, Scheme 4a) [20]. In this cross-coupling, an α,ω-difunctionalized Grignard reagent bearing a magnesium alkoxide moiety at the end of the aliphatic chain is used as a coupling partner. Following in those footsteps, similar syntheses of other insect

• allow the use of alkenyl halides as cross-coupling partners in the absence of NMP. A remarkable feature of the alkyl–dienyl cross-coupling reactions displayed in Scheme 4 is the implication of α,ω-difunctionalized Grignard reagents, bearing a magnesium alkoxide moiety at the end of the chain. Magnesium

• alkoxides exhibit strong σ-donating properties, given the high nucleophilicity of the alkoxide moiety. Moreover, the beneficial effect of molecular σ-donating additives on the yields and selectivities of iron-mediated cross-coupling reactions had already been reported in the literature. Nakamura thus

Modular synthesis of 2-furyl carbinols from 3-benzyldimethylsilylfurfural platforms relying on oxygen-assisted C–Si bond functionalization

• Sebastien Curpanen,
• Per Reichert,
• Gabriele Lupidi,
• Giovanni Poli,
• Julie Oble and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2022, 18, 1256–1263, doi:10.3762/bjoc.18.131

• platforms. Preparation of 3-silylated 2-furyl carbinols. C–Si bond functionalization of 2,3-disubstituted furyl carbinols by 1,4-silyl migration. Attempts of C3–Si bond functionalization promoted by intramolecular activation via alkoxide. Alkoxide-promoted cyclic siloxane formation from 2-[(3

Molecular diversity of the base-promoted reaction of phenacylmalononitriles with dialkyl but-2-ynedioates

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

Beilstein J. Org. Chem. 2022, 18, 991–998, doi:10.3762/bjoc.18.99

• the reaction was carried out in weak basic solution (Supporting Information File 1) and its single crystal structure was determined by X-ray diffraction (Figure 4). When DABCO was used as a base, the further addition of the alkoxide ion to the cyano group in cis-position of the cyclopentyl ring

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

• alkoxide to the carbonyl group in the ester moiety produces the cyclic intermediate (J). Finally, the dispiro compound 8 is formed by elimination of tri(n-butyl)phosphine oxide. Conclusion In summary, we have investigated tri(n-butyl)phosphine-catalyzed annulation reactions of bis-chalcones with

Chemistry of polyhalogenated nitrobutadienes, 17: Efficient synthesis of persubstituted chloroquinolinyl-1H-pyrazoles and evaluation of their antimalarial, anti-SARS-CoV-2, antibacterial, and cytotoxic activities

• Viktor A. Zapol’skii,
• Isabell Berneburg,
• Ursula Bilitewski,
• Melissa Dillenberger,
• Katja Becker,
• Stefan Jungwirth,
• Aditya Shekhar,
• Bastian Krueger and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2022, 18, 524–532, doi:10.3762/bjoc.18.54

• poor leaving group quality of the formal alkoxide. A conceivable mechanistic pathway for the reaction cascade to pyrazole 7 is shown in Scheme 6. Initially, a nucleophilic attack of the NH2 group of 7-chloro-4-hydrazinylquinoline on the C2 position of the oxazolidine ring of 6 leads to the formation of

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• enyliridium(III) alkoxide complex which eventually leads to the formation of isomerized 1-naphthol products [61]. Interestingly, the loading of the iridium precatalyst (Table 1, entries 11–13) also had a substantial effect on the isomerization of 13b, with increased loading producing more byproduct. Other

• whereas it is 5.9 kcal/mol to form IN3b, via 2bTS3b. The Ir(I) alkoxide intermediate IN3b (IN3a) is rather thermodynamically stable (Figure 1), 31.5 (30.6) kcal/mol lower in energy than the preceding intermediate IN2b (IN2a) indicating a strongly exergonic process. By comparing all the competing

• an activation energy of 4.8 to 5.6 kcal/mol, respectively, to produce the aforementioned thermodynamically stable Ir(I) alkoxide intermediates INa3 and INb3. Based on the extremely high energy barrier required for acyl migration over hydride migration, we hypothesize iridium-catalyzed hydroacylation

Stepwise PEG synthesis featuring deprotection and coupling in one pot

• Logan Mikesell,
• Dhananjani N. A. M. Eriyagama,
• Yipeng Yin,
• Bao-Yuan Lu and
• Shiyue Fang

Beilstein J. Org. Chem. 2021, 17, 2976–2982, doi:10.3762/bjoc.17.207

• heating was to prevent the removal of the base-labile protecting group in 3 by the excess strong base by allowing the excess base to be consumed selectively via β-elimination of the tosylate in 1. The product of premature removal of the base-labile protecting group – an alkoxide – would complicate the

• convenience of the one-pot PEG elongation approach. The phenethyl group in 8 was removed with KHMDS and the intermediate alkoxide was reacted directly with 2 in one pot to give the (PEG)20 derivative 9. The same procedure was simply repeated to give PEG derivatives Ph(CH2)2O(PEG)28O(CH2)2Ph (10), Ph(CH2)2O

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

• aromatic and cyano groups. The oxidation of species 80 would reduce the Fe catalyst back to its reduced form, while a tert-butyl alkoxide can furnish the final product through acid-base catalysis. In 2019, Li and co-workers investigated a three-component dialkylation of alkenes 82 with common alkanes 83

Allylic alcohols and amines by carbenoid eliminative cross-coupling using epoxides or aziridines

• Matthew J. Fleming and
• David M. Hodgson

Beilstein J. Org. Chem. 2021, 17, 2385–2389, doi:10.3762/bjoc.17.155

• alkoxide. Keywords: alkenes; aziridines; epoxides; lithiation; synthetic methods; Introduction Methods for the convergent generation of alkenes can be of significant utility in organic synthesis [1]. A relatively under-examined approach is through the interaction of two carbenoids [2]. Dimerisation of

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• catalyst-bound alkoxide species (3·OEt) that is then able to attack the benzaldehyde for product 2 formation. However, it took some time until the scientific community started considering and taken cognizance of the potential of this type of activation mode in catalysis. In this regard, Jacobsen and co

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

• catalysts (Scheme 11) [63]. Here, the use of a zinc-based Lewis acid (LA) was found to activate α-hydroxy C‒H bonds by forming alkoxide (O‒LA) and suppressing the C‒O bond formation by inhibiting the formation of a nickel alkoxide species. The authors also claimed that the use of the zinc-based LA also

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• , 26, and 28. The materials were prepared by the Pd(0)-mediated coupling of lithium N-arylindole-3-alkoxide 21 with 3-bromo-N-arylindole 22, followed by a further C-2 bromination (24) and subsequent Suzuki reaction with boronic acids 27 or 25 (Scheme 4) [42]. A similar class of molecules have found

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

• -bifunctional organomagnesium alkoxide reagent 107, which converted esters into di- and monofunctionalized anthracenes (Scheme 25) [59]. They prepared this reagent by deprotonation–magnesiation of compound 106. Then, the treatment of aromatic esters with 107 produced dialkoxide 108, which could be easily

• anthracenes from a bifunctional organomagnesium alkoxide. Palladium-catalyzed tandem C–H activation/bis-cyclization of propargylic carbonates. Ruthenium-catalyzed C–H arylation of acetophenone derivatives with arenediboronates. Pd-catalyzed intramolecular cyclization of (Z,Z)-p-styrylstilbene derivatives

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

• Ryan M. Alam and
• John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

• ) positively influenced the regioselectivity, albeit with poor conversion (59–72%) when compared with other inorganic carbonate bases (vide supra). Despite poor conversion (30%), the use of the strong alkoxide base, potassium tert-butoxide, in tetrahydrofuran (THF) gave an appreciably higher degree of N-1

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• mixing the (n-Bu4N)2CeIVCl6 complex with BnOH under basic conditions. The UV–vis spectra of the CeIV(OBn)Cln complex displayed a band resembling the LMCT band of known cerium–alkoxide complexes, showing considerable overlap with the blue LED region, thus suggesting that the CeIV(OBn)Cln species could be

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• formed by the conjugate addition of the phosphine to the Michael acceptor, is believed to be protonated by the alcohol forming the actual catalytically active species namely ion pair ii, consisting of a phosphonium cation and an alkoxide. The alkoxide in ii then reacts with another electrophile

• alkoxide to yield the product iv and the phosphine. Our results disclosed in the following contribute to the rational selection of proper (pre-)catalysts for this and similar reactions also considering the oxygen sensitivity of the nucleophiles. Results and Discussion To compare the activity of the

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

• could be conducted in an air atmosphere, and the reaction times were shorter using a combination of Fe(acac)3 and PhSiH3 as the reductor (Mukaiyama-like conditions) in the presence of an alkoxide source (Scheme 21) [79]. Under these conditions, the radical formed after the HAT with unactivated olefins

Synthesis of functionalized imidazo[4,5-e]thiazolo[3,2-b]triazines by condensation of imidazo[4,5-e]triazinethiones with DMAD or DEAD and rearrangement to imidazo[4,5-e]thiazolo[2,3-c]triazines

• Alexei N. Izmest’ev,
• Dmitry B. Vinogradov,
• Natalya G. Kolotyrkina,
• Angelina N. Kravchenko and
• Galina A. Gazieva

Beilstein J. Org. Chem. 2021, 17, 1141–1148, doi:10.3762/bjoc.17.87

• is, probably, a result of a transamidation reaction upon the treatment with a base, for example, alkoxide anion. The nucleophilic attack of the alkoxide anion leads to the cleavage of the C(7)–N(8) bond to form intermediates B and C followed by the recyclization of the thiazolidine ring involving the

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

•  18). A sequence of reactions involving elimination of a proton from 83, treatment of 84 with an alkoxide, and protonation of the resulting enolate delivered thermodynamically favored equatorial ester 80 and 81. The highly diastereoselective Brønsted superacid-catalyzed Prins cyclization of

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• -allylic 2-silylacetamides would provide an intermediate alkoxide from which the Brook rearrangement and subsequent oxygenation could proceed (Scheme 1C). This represents in the event a geminal C–C/C–O difunctionalization of amide 8 and results in the α,γ-dioxygenated N-allylic amides 9. Thermal radical

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• and cleaning agents [272][273]. It should be finally mentioned that during the alcoholysis reaction of PLA using alkoxide catalysts, alkaline earth metal adducts (typically of Ca2+) were isolated, and thus suggesting a potential involvement of the metal centre in the depolymerisation mechanism [274