Unexpected chiral vicinal tetrasubstituted diamines via borylcopper-mediated homocoupling of isatin imines

• Marco Manenti,
• Leonardo Lo Presti,
• Giorgio Molteni and
• Alessandra Silvani

Beilstein J. Org. Chem. 2022, 18, 303–308, doi:10.3762/bjoc.18.34

• . Interestingly, the molecule does not bear any pseudo-mirror plane, that is, the observed conformer is asymmetric (C1) in itself, regardless the configuration of the two sulfinamide substituents. This peculiarity is likely due to the hindered rotation across the newly formed C–C bond, joining the two oxindole

Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• 18 via a concerted protonation and C–C bond formation. Weakened dispersive interactions caused by a substituent or heteroatom resulted in low yields and reduced regioselectivities. In 2020, Li and Van der Eycken and co-workers reported the synthesis of densely functionalized, polycyclic azepino[5,4,3

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

• emphasis given to green strategies. This is the first review on iron- and cobalt-catalyzed Sonogashira coupling reactions which comprehends literature up to 2020. Keywords: C–C bond formation; cobalt; green reaction; iron; nanoparticles; Sonogashira; Introduction The palladium-catalyzed cross-coupling

• reaction between an aryl/vinyl halide (Cl, Br, I, OTf) and a terminal alkyne in the presence of a Cu(I) co-catalyst under basic conditions to form a Csp2–Csp bond generating an arylalkyne is known as the Sonogashira (Sonogashira–Hagihara) coupling [1] and has become an important C–C bond-forming reaction

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

• hydride, and C–C bond-forming reductive elimination. Computational results indicate the origin of regioselectivity is involved in the reductive elimination step. Keywords: C–H activation; density functional theory; hydroacylation; iridium catalysis; regioselectivity; Introduction Organic synthesis is

• hydroacylation reactions [74][75][76][77][78], we propose a catalytic cycle utilizing iridium that proceeds with three key steps: (1) iridium(I) oxidative addition into the aldehyde C–H bond, (2) insertion of the olefin into the iridium hydride, and (3) C–C bond-forming reductive elimination. The hydroacylation

• last key step in the catalytic cycle involves the C–C bond-forming reductive elimination to form the final ketone intermediate IN3a or IN3b (Figure 1). Two possible transition states, 2aTS3a and 2bTS3b, can be located. The concerning free energy barrier about IN2a to IN3a, via 2aTS3a is 10.8 kcal/mol

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• exhibiting solid-state fluorescence, although the fluorescence partially disappears in solution, and there is a large shift to red and blue [98][99]. Carbon–carbon bond formation The main steps in a synthesis usually involve C–C bond formation, which is usually the main reaction step, or functional group

• transformations. Organometallics are the most commonly used catalysts to promote C–C bond formation. In addition, other so-called classical reactions are also widely used, such as Friedel–Crafts alkylation and acylation, Wittig and Horner–Emmons reactions, carbonyl addition/substitution, α-alkylation, aldol

• )phenyl]ethylene in acetic acid efficiently produced 4-vinyl-1,2-naphthoquinones 55 and 4-aryl-1,2-naphthoquinones 56a,b, respectively, under nickel(II) catalysis, forming a C–C bond (Scheme 16) [103]. When the reaction was carried out in 10% aqueous methanol solution at room temperature for 5 hours, 56b

A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

• Haopei Wang and
• Zachary T. Ball

Beilstein J. Org. Chem. 2021, 17, 2932–2938, doi:10.3762/bjoc.17.202

• contrast, photorelease systems based on C–C or C=C bond photocleavage are quite rare [14][15]. We recently reported a vinylogous analogue of this photo-deprotection process, which allowed photocleavage of alkenyl sp2 C–X bonds, rather than benzylic sp3 C–X cleavage [16][17]. We now report that further

• , which leads to formyl products from formal oxidative cleavage of a C=C bond. Our interest in vinylogous analogues of 2-nitroaryl photoreactive groups stems from studies into alkenylboronic acid reagents for Chan–Lam-type modification of peptide backbone N–H bonds, directed by a proximal histidine

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

• significant development over the past 10 years. First achieved by Li and co-workers in 2007 [44], cross-dehydrogenative-coupling (CDC) reactions offer a highly atom economic approach to carbon–carbon (C–C) and carbon–heteroatom (C–X) bond formation via C–H activation [45][46]. Generally speaking, C–C bond

• forming reactions can be classified into three types (Scheme 1): the reaction of a compound bearing functional group (X), coupling with another compound bearing functional group (Y), producing a new C–C bond through the formation of X–Y (Scheme 1a). Secondly, the reaction of a C–H compound with a C–X

• functionalized compound (Scheme 1b). Lastly, the reaction between two C–H compounds to form a C–C bond, formally eliminating H2, hence the dehydrogenative reference (Scheme 1c). As this coupling reaction does not require functionalization prior to coupling, it shortens the synthetic route, and lowers the

The PIFA-initiated oxidative cyclization of 2-(3-butenyl)quinazolin-4(3H)-ones – an efficient approach to 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones

• Alla I. Vaskevych,
• Nataliia O. Savinchuk,
• Ruslan I. Vaskevych,
• Eduard B. Rusanov,
• Oleksandr O. Grygorenko and
• Mykhailo V. Vovk

Beilstein J. Org. Chem. 2021, 17, 2787–2794, doi:10.3762/bjoc.17.189

• 13. The formation of the last-mentioned can be achieved by an initial PIFA attack on the homoallyl C=C bond [41][42][57][58] through the possible intermediates 14 and 15 alternatively (pathway b). Finally, alkaline hydrolysis of 13 upon work-up of the reaction mixture leads to the formation of target

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

• I-15 leads to enamine I-16. In the presence of the CPA catalyst, an intramolecular Michael addition of the amino group to the enamine in I-16 leads to I-17. Subsequently, the imines I-15 and I-17 are converted to the intermediate I-18, which through elimination by cleavage of the C–C bond gives the

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• aldehyde (33%) being generated (Table 2, entry 11). Similar results were obtained when adding iodine to promote benzylic oxidation [56] (Table 2, entry 12). Finally, Pd(OAc)2 was added in hopes of improving the mediation of C–C bond formation [38] (Table 2, entry 13). Interestingly, here the yield of

Ligand-dependent stereoselective Suzuki–Miyaura cross-coupling reactions of β-enamido triflates

• Tomáš Chvojka,
• Athanasios Markos,
• Svatava Voltrová,
• Radek Pohl and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 2657–2662, doi:10.3762/bjoc.17.179

• causes the tautomerization of complex 5 [30] to zwitterionic carbene 6 which can now isomerize through the C–C bond rotation to the thermodynamically more stable palladium complex 7, followed by reductive elimination to enamide 3. A possible isomerization of enamides 2 or 3 in the presence of a catalyst

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

• Robin Klintworth,
• Garreth L. Morgans,
• Stefania M. Scalzullo,
• Charles B. de Koning,
• Willem A. L. van Otterlo and
• Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

• prior to acid-promoted cyclization cannot be ruled out, since conjugation in the push–pull system should weaken the C=C bond and lower its rotational barrier [20]. Similar enaminone isomerizations have been detected even at room temperature [48]. If thermal isomerization indeed takes place, then one

• , was reported as recently as 2018 [55]. More interestingly, conventional heating in acetic acid of an enaminone bearing a phenacylsulfanyl substituent adjacent to nitrogen on the C=C bond produced ethyl pyrrolo[2,1-b]thiazole-5-carboxylates in moderate yield, while the corresponding microwave-assisted

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

• oxime esters 73 formed cyclic iminyl radicals, which then formed cyanoalkyl radicals through a selective β-C–C bond scission. This protocol was further applied to the aminocarbonylation of cycloketone oxime esters with CO gas and amines 74. Cycloketone oxime esters are reduced by the photoexcited [LnCuI

• –NHR]* complex C or the ground-state LnCuI–NHR species B to generate a cyclic iminyl radical 73a-A, which oxidizes the LnCuII–NHR complex D (Scheme 30, path a or b). Subsequently, radical 73a-A undergoes a β-C–C bond scission to provide the cyanoalkyl radical 73a-B, which is trapped by complex D and

Efficient synthesis of polyfunctionalized carbazoles and pyrrolo[3,4-c]carbazoles via domino Diels–Alder reaction

• Ren-Jie Fang,
• Chen Yan,
• Jing Sun,
• Ying Han and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2021, 17, 2425–2432, doi:10.3762/bjoc.17.159

• acid. Secondly, the Diels–Alder reaction of indole-chalcone A with the dienophile results in the tetrahydrocarbazole B having an exocyclic C=C bond. Thirdly, a new tetrahydrocarbazole intermediate C is formed by a 1,3-H shifting process. The resulting tetrahydrocarbazole intermediate (C) might be a

Synthesis of 5-arylacetylenyl-1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

• Andrey I. Puzanov,
• Dmitry S. Ryabukhin,
• Anna S. Zalivatskaya,
• Dmitriy N. Zakusilo,
• Darya S. Mikson,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2417–2424, doi:10.3762/bjoc.17.158

• ], it was shown by means of NMR spectroscopy and DFT calculation that the protonation of these oxadiazoles in Brønsted superacids TfOH and FSO3H gave reactive N,C-diprotonated species. The protonation of oxadiazoles 1 takes place at the nitrogen N4 and the α-carbon of the side chain C=C bond. One would

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

• Songeziwe Ntsimango,
• Kennedy J. Ngwira,
• Moira L. Bode and
• Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

• furnishing the central ring through C–C bond formation. Indeed, this strategy has been employed for decades in reactions such as dehydrative cyclization of acyl-O-aminobiphenyls at very high temperatures (the Pictet–Hubert reaction and Morgan–Walls reaction) [5][6], which is also reflected in modern methods

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

• adduct 23-IV. The radical adduct 23-IV is captured by nickel(0) species 23-V followed by oxidative addition to aryl bromide 3 to give the nickel(III)(alkyl)(aryl) intermediate 23-VII. Facile C–C-bond forming reductive elimination of 23-VII delivers the desired product 95 and nickel(I) species 23-VIII. A

Transition-metal-free intramolecular Friedel–Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives

• Tülay Yıldız,
• İrem Baştaş and
• Hatice Başpınar Küçük

Beilstein J. Org. Chem. 2021, 17, 2203–2208, doi:10.3762/bjoc.17.142

• synthesized using the combination of hexafluoroisopropanol and triflimide as a catalyst [29]. One of the most effective C–C bond establishing reactions, which ensures an efficient synthetic way to a plenty of functionalized aryl compounds, is the Friedel–Crafts cyclization reaction [30][31][32][33][34

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF₃·OEt₂ catalysis

• Karthikeyan Soundararajan,
• Helen Ratna Monica Jeyarajan,
• Raju Subimol Kamarajapurathu and
• Karthik Krishna Kumar Ayyanoth

Beilstein J. Org. Chem. 2021, 17, 2186–2193, doi:10.3762/bjoc.17.140

• Reactions associated with carbon–carbon bond formations are explored for their synthetic utility in extending the carbon framework in organic molecules [1][2][3]. Among the known C–C bond forming methodologies the Friedel–Crafts reaction is the most utilized methodology. As a result of its broad scope of

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• norbornadiene C=C bond, followed by ROM of the resulting cyclopentane-fused isoxazolines. In the final step, selective CM by chemodifferentiation of the newly created olefin bonds on the resulting alkenylated derivatives took place. As coupling olefin partners in CM reactions, several commercial fluorine

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

• anthracene derivatives 33. The strategy involved a palladium(II)-catalyzed tandem transformation with diphenyl carboxylic acids 31 and acrylates 32 (Scheme 7) [41]. This new methodology involved a carboxyl-directed C–H alkenylation, a carboxyl-directed secondary C–H activation, an intramolecular C–C-bond

• fumaronitrile to produce the Wittig reagents. Despite the limitations, the authors noted that DBU was no longer required in these reactions. The scope of these reactions included five examples of substituted anthracene-2,3-dicarbonitriles 96 (40–62% yield) [57]. BN arenes include analogs in which a C=C bond has

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

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

• catalyst in the reductive dimerization of aryl olefins 32 reported by van der Donk in 2002 [71]. This group showed the formation of a new C–C bond between benzylic carbons, affording compounds 33 with two vicinal quaternary carbon centers (Scheme 17). The occurrence of a radical pathway was proposed based

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• -quinones, competitive reaction courses involving either ethylenic C=C or carbonyl C=O bonds were observed. For example, the more polar arylnitrile oxides and 1,4-benzoquinones reacted via addition to the C=C bond to give fused isoxazole derivatives [10][11][12] as well as with the C=O bond yielding

• spirocyclic 1,4,2-dioxazole derivatives [13][14]. Furthermore, for photochemically generated benzonitrile isopropanide, competitive C=O and C=C additions with 1,4-quinones were observed [15]. On the other hand, the slightly less polar benzonitrile benzylide underwent [3 + 2]-cycloaddition to the C=C bond

• reported by Huisgen [17], who in the reaction of nitrile imine 2 with the same dipolarophile obtained the expected [3 + 2]-cycloadduct to the C=C bond as a single regioisomer, which was isolated in 33% yield. The observed outcome suggests that the thermally generated nitrile imine 2 undergoes [3 + 2

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

• standard sp2-hybridized carbon atom, suggesting that magnesium alkylidene carbenoids (E)-3e have partial vinylidene characteristics [19]. In the transition state structure (E)-3e‡, the ipso carbon atom (C3) of the phenyl group was located at the middle between the C=C bond (C2–C3: 1.72 Å, C1–C3: 1.70 Å