Divergent role of PIDA and PIFA in the AlX₃ (X = Cl, Br) halogenation of 2-naphthol: a mechanistic study

• Kevin A. Juárez-Ornelas,
• Manuel Solís-Hernández,
• Pedro Navarro-Santos,
• J. Oscar C. Jiménez-Halla and
• César R. Solorio-Alvarado

Beilstein J. Org. Chem. 2024, 20, 1580–1589, doi:10.3762/bjoc.20.141

• nonaromatic intermediate I-4–Cl (ΔG = −23.1 kcal/mol). Next, aromatization assisted by TFAO–AlCl2 via TS2–Cl (ΔG‡ = 11.1 kcal/mol) and hydrogen transfer from the nonaromatic intermediate to TFAO–AlCl2 are observed. In TS2–Cl, the energy barrier must be overcome to give rise to the 1-chloro-2-naphthol adduct

• the cis transition state TS4–Br (ΔG‡ = 16.1 kcal/mol), which yields the brominated nonaromatic intermediate I-6–Br in a highly exothermic step (ΔG = −52.3 kcal/mol). Finally, I-6–Br undergoes spontaneous aromatization, converting it into the experimentally observed 1-bromo-2-naphthol (P–Br), which is

Bioinformatic prediction of the stereoselectivity of modular polyketide synthase: an update of the sequence motifs in ketoreductase domain

• Changjun Xiang,
• Shunyu Yao,
• Ruoyu Wang and
• Lihan Zhang

Beilstein J. Org. Chem. 2024, 20, 1476–1485, doi:10.3762/bjoc.20.131

• as M1 to M3 of rifamycin PKS whose product experiences later aromatization. (d) Modules with unconventional module compositions (e.g., modules with two KR domains), modules without KR domains, and loading modules were excluded from the data. After organizing and filtering, the KRS and KRC subdomain

Synthesis of 2-benzyl N-substituted anilines via imine condensation–isoaromatization of (E)-2-arylidene-3-cyclohexenones and primary amines

• Lu Li,
• Na Li,
• Xiao-Tian Mo,
• Ming-Wei Yuan,
• Lin Jiang and
• Ming-Long Yuan

Beilstein J. Org. Chem. 2024, 20, 1468–1475, doi:10.3762/bjoc.20.130

• –dehydrogenative aromatization strategy with amines as nucleophiles [11][12]. For instance, the groups of Deng and Li reported the Pd catalyzed oxidative coupling of 2-cyclohexenones with amines [13]. Later, the same group demonstrated the direct amination of phenols by reductive coupling of in situ generated 2

• -cyclohexenones with nucleophilic nitrogen sources like ammonia, amines and hydrazine [14]. The reactions were regarded as via simple nucleophilic addition along with Pd-catalyzed dehydrogenative aromatization in these elegant works (Scheme 1, (1)). The Semmler–Wolff reaction is often implemented in the synthesis

• anilines [19] (Scheme 1, (3)). To date, although plentiful amination–aromatization approaches for the preparation of anilines have been well-established, to develop novel and efficient synthetic methods still remains highly desirable. In continuation of our recent studies on synthetic applications of

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• photocatalytic mechanism. Photoredox-catalyzed hydroacylation of olefins with aliphatic carboxylic acids. Acylation–aromatization of p-quinone methides using carboxylic acids. Visible-light-induced deoxygenation–defluorination for the synthesis of γ,γ-difluoroallylic ketones. Photochemical hydroacylation of

Domino reactions of chromones with activated carbonyl compounds

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 1256–1269, doi:10.3762/bjoc.20.108

• (Scheme 9) [39]. The formation of the products can be explained by 1,4-addition of the terminal carbon of the diene to the chromone to give intermediate J and subsequent attack of the central carbon atom of the 1,3-dicarbonyl unit (aldol reaction). No aromatization and extrusion of the hydroxy group was

• ) [40]. The formation of the products can be explained by 1,4-addition of the terminal carbon of the diene to the chromone to give intermediate O and subsequent attack of the central carbon atom of the 1,3-dicarbonyl unit (aldol reaction). No aromatization and extrusion of the hydroxy group was observed

• minor products as well (7–20% yields). The formation of biphenyls 44 can be explained by 1,4-addition and ring-cleavage to give intermediate AH, aldol reaction (intermediate AI), migration of the ester group from the quaternary carbon to the phenolic oxygen atom (intermediate AJ) and aromatization. The

Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer

• Mohd Farhan Ansari,
• Atul Kumar Maurya,
• Abhishek Kumar and
• Saravanakumar Elangovan

Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98

• mechanism suggested that dearomatization–aromatization pathways operated for the dehydrogenation of the alcohol and C–C bond formations. After the successful attempt of bidentate N-heterocyclic carbene-manganese complex-catalyzed N-alkylation of amines with alcohols at room temperature [41], Liu and Ke's

Carbonylative synthesis and functionalization of indoles

• Alex De Salvo,
• Raffaella Mancuso and
• Xiao-Feng Wu

Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87

• result with some effort because a dearomatization, followed by aromatization, was necessary to achieve the goal. With [Rh(CO)2Cl]2 or [Rh(COD)2]BF4 as the catalyst under atmospheric pressure of CO (1 bar), good yields of the desired products were obtained (Scheme 24). Carbonylative functionalization of

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• concomitant formation of radical 69. Finally, aromatization of 69 via SET to NHPI ester 3, generates pyridinium 73 as a byproduct, while propagating the radical chain reaction. Aggarwal and co-workers discovered the photoinduced decarboxylative borylation of NHPI esters mediated by bis(catecholato)diboron

• ester 10, regenerating pyridine 137 while forming alkyl radical 12, CO2 and phthalimide–B(pin) adduct 139. Subsequently, radical–radical coupling between 12 and one equivalent of 138 affords dihydropyridine 140, which upon re-aromatization, facilitated by ZnCl2 acting as a Lewis acid, yields product 141

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• pristine acene with a dienophile to transiently form a cycloadduct with increased solubility for processing purposes, and unmasking it afterwards via a retro-Diels–Alder reaction [16][17][18][19]. In parallel to retro-Diels–Alder reactions, another efficient strategy for the in situ aromatization of target

• tetrabromothiophene S,S-dioxide 24 at 120–140 °C to yield the corresponding S- and Se-tribenzo[b,d,f]heteropines, 25b and 25c respectively, after oxidative aromatization mediated by DDQ. In the case of tellurepine 23d, attempts of thermally-activated Diels–Alder reaction resulted in Te-extrusion to afford

• acenes, as described in the introduction. Chalcogen extrusion from bridged precursors: access to acenes Deoxygenation of endoxides belongs to the classical methods used in organic chemistry to generate polycylic aromatic hydrocarbons, through a reductive aromatization relying on a variety of chemical

Chiral phosphoric acid-catalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles

• Yumei Wang,
• Guangzhu Wang,
• Yanping Zhu and
• Kaiwu Dong

Beilstein J. Org. Chem. 2024, 20, 205–211, doi:10.3762/bjoc.20.20

• (2p). However, when using 3,3-difluoro-2-(naphthalen-2-ylethynyl)-3H-indole or 3,3-difluoro-2-phenyl-3H-indole as the substrate, the generated indoles underwent fast HF elimination/aromatization and finally gave indole derivatives (2q and 2r) in almost quantitative yields. To examine the efficiency

Biphenylene-containing polycyclic conjugated compounds

• Cagatay Dengiz

Beilstein J. Org. Chem. 2023, 19, 1895–1911, doi:10.3762/bjoc.19.141

• researchers efficiently conducted palladium-catalyzed C–H activated annulation reactions, involving oxanorbornadiene derivative 26 and aryl bromides including dibromoanthracene 27 [38]. Subsequent aromatization reactions were then carried out, resulting in the successful synthesis of the target POAs with high

• the failure in the formation of the desired target products. Upon comparing the UV–vis absorbance graphs of compounds 28 and 29, POA 29 (λmax = 500 nm), which was obtained through the aromatization of compound 28, exhibited a significant bathochromic shift. These observations further support the

• ranging between 45% and 60%. The last step of the sequential reactions is the aromatization step and the target POAs 34a–c were obtained in yields between 80–84%. UV–vis investigations conducted on compounds 34a–c revealed absorption bands that align well with acene structures. While 34a and 34b displayed

Synthesis and biological evaluation of Argemone mexicana-inspired antimicrobials

• Jessica Villegas,
• Bryce C. Ball,
• Katelyn M. Shouse,
• Caleb W. VanArragon,
• Ashley N. Wasserman,
• Hannah E. Bhakta,
• Allen G. Oliver,
• Danielle A. Orozco-Nunnelly and
• Jeffrey M. Pruet

Beilstein J. Org. Chem. 2023, 19, 1511–1524, doi:10.3762/bjoc.19.108

• most streamlined method involves a copper-promoted Pictet–Spengler-type cyclization with glyoxal, with oxidative aromatization at the 8-position (Scheme 1) [30][35]. A recent report suggested a mechanistic role of Cu2+ involving C–H activation [36]; however, it is known that this reaction proceeds

• found in the Supporting Information File 1. While unexpected, these oxidative byproducts were still viewed as adding to the structural variability in our berberine series. As the role of Cu2+ was believed to assist in the oxidative aromatization of the expected berberine products, we explored minimizing

• synthesis began with the generation of substituted 2-bromo-1-aminonaphthalenes 9 and 10 (Scheme 6). After α-bromination of tetralones 1 and 2, intermediates 3 and 4 underwent elimination/aromatization with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to afford 2-bromo-1-naphthols 5 and 6 in fairly good yield

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

• , which underwent a ring expansion and 1,2-sulfur migration and subsequent deprotonation/aromatization to deliver product 16. Another work in the use of AlCl3 for cyclization of N‑arylpropynamides 17 with N‑sulfanylsuccinimides 1 was described by Gao and Zhou et al. (Scheme 12) [51]. Annulation in the

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• subsequent removal of MeOH, dehydration and aromatization affords N-substituted pyrroles 21. In 2013, Chatzopoulou [63] and co-workers reported a high-yielding Clauson–Kaas pyrrolyl-phenol synthesis using nicotinamide, which is a cheap and nontoxic catalyst and a vitamin and enzyme cofactor. The authors

• hydrolysis of 2,5-DMTHF (2), which provide intermediate C after the removal of methanol in the presence of CuCl2. In the next steps, nucleophilic addition reaction of amines 34 with intermediate C, dehydration, and intramolecular aromatization affords N-substituted pyrroles 35. In 2018, Patil and Kumar [70

• (2). Further, a nucleophilic attack of amines 40 with intermediate A, MeOH removal, dehydration, and aromatization steps produce N-substituted pyrroles 41 in good to excellent yields. In 2019, Wani et al. [73] used the alkaline-earth metal-based catalyst Ca(NO3)2∙4H2O for a mild, transition metal

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

• elimination of nitrous acid, accompanied by aromatization, yielded furan 13. In addition to the stepwise mechanism, a concerted ring-expansion can be also acceptable [25]. Conclusion Although nitrocyclopropanedicarboxylic acid esters 1a have been used in organic syntheses, nitrocyclopropanes possessing an

Eschenmoser coupling reactions starting from primary thioamides. When do they work and when not?

• Lukáš Marek,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2023, 19, 808–819, doi:10.3762/bjoc.19.61

• , dioxane-Br2 complex, CuBr2) under various conditions always failed or led to oxidative aromatization of the lactam ring – i.e., to 3-hydroxyisoquinoline. Therefore, we decided to prepare [29] an analogous 1,1-dimethyl derivative 2b whose methyl groups (R: Me) prevent such aromatization. The reaction of 2b

Synthesis of substituted 8H-benzo[h]pyrano[2,3-f]quinazolin-8-ones via photochemical 6π-electrocyclization of pyrimidines containing an allomaltol fragment

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Mikhail E. Minyaev and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2023, 19, 778–788, doi:10.3762/bjoc.19.58

• two directions resulting in the formation of a mixture of the corresponding dihydrobenzo[h]pyrano[2,3-f]quinazolines and polyaromatic products. The obtained dihydro derivatives are stable compounds and do not undergo aromatization upon further UV irradiation. The structures of two of the dihydrobenzo

• -electrocyclization under UV irradiation resulting in the formation of unstable intermediate A, starting from which two directions of further transformation are possible. The most obvious pathway is a simple elimination of a methanol molecule with aromatization of the central benzene ring leading to polycyclic

• more preferable process compared to aromatization. The above-mentioned photochemical reaction of pyrimidines 10 allows to synthesize polycyclic products 12 (Scheme 8, method A). In this case, the yields of compounds 12 did not exceed 41%, which is associated with low regioselectivity of the process and

Construction of hexabenzocoronene-based chiral nanographenes

• Ranran Li,
• Di Wang,
• Shengtao Li and
• Peng An

Beilstein J. Org. Chem. 2023, 19, 736–751, doi:10.3762/bjoc.19.54

• ]azepine and tetrabromothiophene-S,S-dioxide, followed by oxidative aromatization in the presence DDQ to afford compound 25 in an overall 75% yield. Suzuki−Miyaura cross-coupling reaction of compound 25 with (4-ethylphenyl)boronic acid in the presence of Pd(CH3CN)2Cl2, SPhos, and K3PO4 then furnished the

• benzo[b]naphtho[2,3-f]oxepine 66 with tetrabromothiophene-S,S-dioxide in toluene followed by oxidative aromatization in the presence of DDQ afforded tetrabrominated aromatics 67 in an 81% yield. Subsequently, fourfold Suzuki–Miyaura cross-coupling of polybrominated compound 67 was performed, affording

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

• amides was quite wide, including different EWGs and EDGs, as well as heterocycles, ortho-substitution was not tolerated. The authors applied the methodology for the synthesis of biologically important benzo[c]phenanthridine derivatives 117. Through methylation and subsequent aromatization of the

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• ether moiety. The best result was obtained when phenol 101 was subjected to anodic oxidation, leading to the formation of spiro-dimer 102 in 61% yield. Protection of the alcohol using TBSOTf followed by cyclic ether cleavage and re-aromatization gave compound 104. Subsequent dehalogenation followed by

A novel bis-triazole scaffold accessed via two tandem [3 + 2] cycloaddition events including an uncatalyzed, room temperature azide–alkyne click reaction

• Ksenia Malkova,
• Andrey Bubyrev,
• Vasilisa Krivovicheva,
• Dmitry Dar’in,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1636–1641, doi:10.3762/bjoc.18.175

• ] which underwent aromatization with the loss of sulfur dioxide and N-Boc-aniline. The multicomponent character and the fairly large scope of this reaction allows to place pairwise reactive groups in the aldehyde and the amine components, which would set a scene for further elaboration of the product’s

One-pot synthesis of 2-arylated and 2-alkylated benzoxazoles and benzimidazoles based on triphenylbismuth dichloride-promoted desulfurization of thioamides

• Arisu Koyanagi,
• Yuki Murata,
• Shiori Hayakawa,
• Mio Matsumura and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 1479–1487, doi:10.3762/bjoc.18.155

• isomerization with the elimination of the sulfur-and-bismuth moiety. Aminophenol then reacts with D to generate intermediate F via E, which is converted to the benzoxazole 8, accompanied by the elimination of 19 by aromatization. The generation of hydrochloric acid was important in this reaction, and the

On Reuben G. Jones synthesis of 2-hydroxypyrazines

• Pierre Legrand and
• Yves L. Janin

Beilstein J. Org. Chem. 2022, 18, 935–943, doi:10.3762/bjoc.18.93

• {1,1} (0.08 g, 3%) and then compound 3{1,1} (1.86 g, 76%) both as white powders. 3-Methyl-5-phenylpyrazin-2-ol (3{1,1}): NMR data were identical with those observed for the substance obtained via aromatization of 3-methyl-6-phenylpiperazin-2-one [34]. 1H NMR (DMSO-d6) δ 12.28 (br s, 1H), 7.85 (m, 3H

Direct C–H amination reactions of arenes with N-hydroxyphthalimides catalyzed by cuprous bromide

• Dongming Zhang,
• Bin Lv,
• Pan Gao,
• Xiaodong Jia and
• Yu Yuan

Beilstein J. Org. Chem. 2022, 18, 647–652, doi:10.3762/bjoc.18.65

• addition to generate the intermediate 9, which is oxidized by Cu(II) to give 10, which undergoes aromatization and deprotonation to afford the product 3a. At this stage, Cu(I) is regenerated to complete the catalytic cycle. Conclusion In summary, we have developed a convenient copper-catalyzed method for

A study of the photochemical behavior of terarylenes containing allomaltol and pyrazole fragments

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2022, 18, 588–596, doi:10.3762/bjoc.18.61

• two stages: 6π-electrocyclization of 1,3,5-hexatriene systems and subsequent aromatization of the central benzene ring. Among the significant diversity of terarylenes, compounds containing a 5-hydroxy-2-methyl-4H-pyran-4-one (allomaltol) fragment are of particular interest. For such systems two types