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

• precursor, recovery of the target π-CPC is possible via a cheletropic decarbonylation step upon photolysis or thermolysis (Scheme 1, bottom right). This dual activation mode has led to the solid-state formation, on a preparative scale, of higher acenes up to nonacene [28][29][30][31][32][33] and

• % yield. At that stage, the initial ring size of precursor 51 was recovered, and two further steps including a McMurry reaction and a thermolysis were then necessary to obtain endohedral fullerene (H2)n@54. As seen in the two first parts of this review, synthetic strategies involving a late-stage ring

Inductive heating and flow chemistry – a perfect synergy of emerging enabling technologies

• Conrad Kuhwald,
• Sibel Türkhan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2022, 18, 688–706, doi:10.3762/bjoc.18.70

• included a carboxylation and a Parham cyclization and hence a Grignard alkylation of ketone 82 using reagent 81. The resulting alcohol 83 was subjected to thermolysis that led to water elimination. This step proceeded in just 30 s by employing the inductive heating technique. The crude elimination product

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• hole-type conductivity with μh = 1.2⋅10−3 cm2⋅V−1⋅s−1. Therein, the thermolysis of a thin film of the device at 220 °C, accompanied by the elimination of Boc groups, led to a significant decrease of the OFET performance. For the example of the polymers 52 series, the importance of the spatial

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• synthesized (Scheme 10) [83]. As an alternative, a more efficient direct route for synthesizing fullerenylpeptides 23 [83] and 24 [88] by prolonged thermolysis of various diazoamides in the presence of C60 was developed (Scheme 11). For conjugation, some scientists successfully used mono- and

• fullerene based on diazo compounds allows us to state the following: An alternative to the synthesis of methanofullerenes by the Bingel methodology is provided by the thermal [2 + 1] cycloaddition of diazo compounds to the fullerene. Then follows the photolysis or thermolysis of pyrazoline intermediates by

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• hydrogenolysis of benzyl ethers (H2, Pd) [72], DIBAL-H reduction of esters to form alcohols [73], oxidative cleavage of vinyl groups to form carboxylic acids (KMnO4) [74], and the conversion of the acids into amines using the Curtius rearrangement (SOCl2, followed by Me3SiN3, thermolysis, and acid hydrolysis of

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• nitrogen heteroatoms were synthesized in multistep synthetic routes. A Buchwald–Hartwig amination of brominated precursors, thermolysis of azide precursors, and a Cadogan reaction of nitro-substituted precursors were successfully applied to eventually build-up pyrrole rings to stable and soluble fused

• syntheses and characterization of fused S,N-heterotetracenes, SN4 (‘SSNS’), benzannulated SN4' (‘NSSN’), and SN4'' (‘SNNS’) by application of various cyclization methods to build up pyrrole rings in the tetraheterocyclic systems. Among them, a Buchwald–Hartwig amination of brominated precursors, thermolysis

• (Scheme 1). Synthesis of S,N-heterotetracene H-SN4 13 by thermolysis of azide precursors. Smaller parent heterotriacene dithienopyrrole (H-DTP) was first synthesized by Zanirato et al. by thermolysis of 3-azido-2,2’-bithiophene as the key step [9]. We therefore tried to build up tetracyclic H-SN4 13 via

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

• Mysore Bhyrappa Harisha,
• Pandi Dhanalakshmi,
• Rajendran Suresh,
• Raju Ranjith Kumar and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178

• ; potassium persulfate; thiazole; vinyl azide; Introduction Vinyl azide is one of the most versatile and potent building blocks explored in the synthesis of several heterocycles [1][2][3][4][5]. It can undergo photolysis or thermolysis to afford highly strained three-membered 2H-azirine, which can act as the

Microwave-assisted synthesis of 2-substituted 4,5,6,7-tetrahydro-1,3-thiazepines from 4-aminobutanol

• María C. Mollo,
• Natalia B. Kilimciler,
• Juan A. Bisceglia and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2020, 16, 32–38, doi:10.3762/bjoc.16.5

• prepared by a double displacement reaction between 2,6-dichlorothiobenzamide and 1,4-butylene dibromide [29]. In 1970, Mente prepared a dehydro analogue, namely 2-(4-chlorophenyl)-4,7-dihydro-1,3-thiazepine, via thermolysis of N-(4-chlorothiobenzoyl)-2-vinylaziridine [30]. No yields were reported for these

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• methylcobalamin and adenosylcobalamin (coenzyme B12) that serve as organometallic cofactors in B12-dependent enzymes. The photolysis (thermolysis) of alkylcob(III)alamins leads to the formation of the corresponding alkyl radical and cob(II)alamin with homolytic Co(III)–C bond cleavage (Figure 1b). This high

Synthesis of pyrimido[1,6-a]quinoxalines via intermolecular trapping of thermally generated acyl(quinoxalin-2-yl)ketenes by Schiff bases

• Svetlana O. Kasatkina,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Ivan G. Mokrushin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2018, 14, 1734–1742, doi:10.3762/bjoc.14.147

• 3-acylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones react regioselectively with Schiff bases under solvent-free conditions to form pyrimido[1,6-a]quinoxaline derivatives in good yields. Keywords: acyl(quinoxalin-2-yl)ketenes; cycloaddition; pyrimido[1,6-a]quinoxalines; Schiff bases; thermolysis

• the thermal decarbonylation (thermolysis) of five-membered 2,3-dioxoheterocycles having a quinoxaline fragment. Currently, three types of such precursors are known: 5-aryl-4-quinoxalin-2-ylfuran-2,3-diones I [21], 3-aroyl-4-arylpyrrolo[1,2-a]quinoxaline-1,2-diones II [55], and 3-acylpyrrolo[1,2-a

• )ketene. STA plot of thermolysis of PQT 1a. Blue solid curve: DSC; green solid curve: TG; greed dashed curve: DTG; violet solid curve: MID (m/z = 28); brown solid curve: MID (m/z = 44); heating rate: 5 °C/min. Scope of the intermolecular trapping of ketenes generated from PQTs 1a–h by Schiff bases 2a–d

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• ]. Transformation of adduct 31 to 11 starts with the synthesis of the stable cyclopropanoid tricyclic 32 from the reaction of the 7-oxabenzonorbornadiene 31 with dichlorocarbene, generated by the phase-transfer method. The thermolysis of dichloride 32 in nitrobenzene at 165 °C resulted in the formation of ring

• and spectroscopic characterization of this elusive molecule obtained by electrocyclic ring-opening reaction of 230 through irradiation in a rigid medium at low temperature or by thermolysis at high temperature [153]. As shown in Scheme 37, compound 230 was synthesized through the addition of benzyne

• anhydride in benzene at 220 °C was reacted, [π2 + π8] cyclo-adduct 234 as a single product was isolated in 52% yield (Figure 9) [153][154]. The thermolysis of 230 in the presence of ethyl vinyl ether gave three volatile products 235–237 in GLC yields of 10%, 7%, and 15%, respectively (Figure 9) [154]. 5

Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

• Hisato Shimizu,
• Akira Yoshimura,
• Keiichi Noguchi,
• Victor N. Nemykin,
• Viktor V. Zhdankin and
• Akio Saito

Beilstein J. Org. Chem. 2018, 14, 531–536, doi:10.3762/bjoc.14.39

• oxidation methods are inapplicable, a two-step procedure based on the liberation of the acylnitroso species by thermolysis of anthracenyl cycloadducts (route b) is widely used [15][16]. Therefore, there is a need to develop novel oxidation methods of hydroxamic acids for HDA reactions. As part of our

Continuous multistep synthesis of 2-(azidomethyl)oxazoles

• Thaís A. Rossa,
• Nícolas S. Suveges,
• Marcus M. Sá,
• David Cantillo and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2018, 14, 506–514, doi:10.3762/bjoc.14.36

• continuous-flow process. The general synthetic strategy involves a thermolysis of vinyl azides to generate azirines, which react with bromoacetyl bromide to provide 2-(bromomethyl)oxazoles. The latter compounds are versatile building blocks for nucleophilic displacement reactions as demonstrated by their

• from vinyl azides through an azirine intermediate (Scheme 3). The process starts with the generation of the azirine from the vinyl azide by thermolysis. Formation of azirines from vinyl azides by photolysis and thermolysis in continuous flow has been previously described [38][39]. The azirine

• fully continuous process are described in detail. Results and Discussion Thermolysis of the vinyl azide and oxazole formation. Batch optimization The reaction conditions for the thermolysis of the vinyl azide and the subsequent ring expansion of the intermediate azirine to form the oxazole ring were

Nucleophilic dearomatization of 4-aza-6-nitrobenzofuroxan by CH acids in the synthesis of pharmacology-oriented compounds

• Alexey M. Starosotnikov,
• Dmitry V. Shkaev,
• Maxim A. Bastrakov,
• Ivan V. Fedyanin,
• Svyatoslav A. Shevelev and
• Igor L. Dalinger

Beilstein J. Org. Chem. 2017, 13, 2854–2861, doi:10.3762/bjoc.13.277

• Discussion The only method for the synthesis of 1 described so far deals with the reaction of commercially available 2-chloro-3,5-dinitropyridine (4) with NaN3 followed by thermolysis of the intermediate azide [25][26]. We developed an alternative safe and efficient method for the synthesis of 1 starting

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• surface passivation and inorganic dehydration method. The groups of Yang and Teo et al. demonstrated that the synthesis of excitation-independent green emissive CDs could be achieved through the reaction of β-cyclodextrin in the presence of oligoethyleneimine (OEI) and phosphoric acid under thermolysis

Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products

• Valerij A. Nikolaev,
• Jury J. Medvedev,
• Olesia S. Galkina,
• Ksenia V. Azarova and
• Christoph Schneider

Beilstein J. Org. Chem. 2016, 12, 1904–1910, doi:10.3762/bjoc.12.180

• corresponding amides, are known in the literature [17][18][19][20][21][22][23][24][25]. It is believed that these reactions follow a usual scheme of thermolysis (or photolysis) of diazocarbonyl compounds with intermediate formation of ketenes, which further acylate N-nucleophiles presented in the reaction

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• spectrum of W(CO)5(E-2) (Supporting Information File 1) is similar to that of Cr(CO)5(E-2) [27] and to those of carbene(pentacarbonyl)metal complexes (Cr, W) [60][61]. Thermolysis of W(CO)5(E-2) in refluxing toluene gives imine E-3 [43] after ca. 24 h in almost quantitative yield, as monitored by 1H NMR

• –S24). The appearance of a resonance at δ = 9.68 ppm is assigned to a trace amount of W(CO)5(Z-2). A dark precipitate (possibly tungsten nanoparticles [81][82]) forms during the thermolysis. The half-lives at 60, 70, 80, 90 and 100 °C amount to 145.9, 39.4, 28.9, 16.2 and 12.2 h. The time traces fit to

• of ΔG‡298K = 112 kJ mol−1. The 1H NMR spectra during thermolysis provide no hint for a long-lived intermediate and the reaction cleanly proceeds from the starting material W(CO)5(E-2) to the product E-3. No hydride resonances have been detected up to δ = −30 ppm in the 1H NMR spectra. This suggests

Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene

• Rudolf Knorr,
• David S. Stephenson,
• Ernst Lattke,
• Petra Böhrer and
• Jakob Ruhdorfer

Beilstein J. Org. Chem. 2016, 12, 1178–1184, doi:10.3762/bjoc.12.113

• -Tribromo-1,1-dimethylindane (5): This thermolabile adduct of 3-bromo-1,1-dimethylindene (3) and elemental bromine (see 7) was not purified but recognized through its 1H NMR chemical shifts and its thermolysis product 7. 1H NMR (CDCl3, 200 MHz) δ 1.36 (s, 3H, 1-CH3), 1.39 (s, 3H, 1-CH3), 4.78 (s, 1H, 2-H

Synthesis of 2,1-benzisoxazole-3(1H)-ones by base-mediated photochemical N–O bond-forming cyclization of 2-azidobenzoic acids

• Daria Yu. Dzhons and
• Andrei V. Budruev

Beilstein J. Org. Chem. 2016, 12, 874–881, doi:10.3762/bjoc.12.86

• -azepines 3 as products of the photolysis or thermolysis of aromatic azides [34][35]. The proposed mechanism for their formation was confirmed by identification of the reaction intermediates using low-temperature and time-resolved spectroscopy [36][37][38][39][40][41][42][43]. It is currently believed that

• -phenylanthranil) by thermolysis of 2-azidobenzophenone. In another work [55], the photochemical formation of 3-amino-6-nitro-2,1-benzisoxazole starting from 2-azido-4-nitrobenzamide was observed. The authors subsequently investigated the multiplicity of the involved nitrene by repeating the reaction in the

Solving the puzzling competition of the thermal C²–C⁶ vs Myers–Saito cyclization of enyne-carbodiimides

• Anup Rana,
• Mehmet Emin Cinar,
• Debabrata Samanta and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 43–49, doi:10.3762/bjoc.12.6

• (Scheme 1) can be switched between C2–C6 and Myers–Saito reaction channels depending on the substitution at the alkyne terminus, as disclosed by Schmittel [18] and Wang [19]. In 1998, Schmittel et al. [18] reported that the thermolysis of enyne-carbodiimide 1a in toluene/1,4-cyclohexadiene yielded the

• Myers–Saito product 3a, whereas the thermolysis of enyne-carbodiimide 1b produced the C2–C6 product 6b. In 1999 Wang et al. [19] stated that the thermal cyclization of enyne-carbodiimides 1c furnished C2–C6 (Schmittel) products 6c in p-xylene under reflux conditions. Based on the experimental findings

• study, we chose first to interrogate enyne-carbodiimides 7a–c (Scheme 2), the synthesis and thermolysis of which have been reported by Wang and coworkers [19]. The methyl (7a) and tert-butyl groups (7b) at the alkyne terminus are ideal to vary the steric influence and the n-propyl group in 7c offers a

Efficient synthetic protocols for the preparation of common N-heterocyclic carbene precursors

• Morgan Hans,
• Jan Lorkowski,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2015, 11, 2318–2325, doi:10.3762/bjoc.11.252

• serves de facto as a carbene source for most catalytic and synthetic purposes. Alternative methods to generate NHCs without the intervention of a base, which might lead to unwanted side-reactions, include the facile cleavage of NHC·CO2 zwitterions (Scheme 1, path B) [31][32][33][34][35], the thermolysis

Investigation on the reactivity of α-azidochalcones with carboxylic acids: Formation of α-amido-1,3-diketones and highly substituted 2-(trifluoromethyl)oxazoles

• Kandasamy Rajaguru,
• Arumugam Mariappan,
• Rajendran Suresh,
• Periasamy Manivannan and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2015, 11, 2021–2028, doi:10.3762/bjoc.11.219

• various substituted benzoic acids 2d–g as well and the resultant α-amido-1,3-diketones 3k–o are obtained in moderate to good yields (Figure 3). The mechanism for the formation of α-amido-1,3-diketone 3 is given in Scheme 2. Initially, by thermolysis, α-azidochalcone undergoes denitrogenative decomposition

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• acetylenedicarboxylate (DMAD) to deliver compounds 332a,b (77%). These DA adducts were irradiated in diethyl ether/dichloromethane (5:1) to offer the corresponding bioxaquadricyclane 333, subsequent thermolysis gave the bioxepine 334 (81%). Finally, aromatization of bioxepine 334 with trifluoroacetic acid (TFA

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

• Nikolai V. Rostovskii,
• Mikhail S. Novikov,
• Alexander F. Khlebnikov,
• Galina L. Starova and
• Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

• generated by thermolysis of 2-diazo-1,3-diketones [12] or 5-arylfuran-2,3-diones [13]. Therefore, the presence of compounds 8f,g among the reaction products provides evidence for the formation of some amounts of acetyl(methyl)ketene (12) under the reaction conditions, which, in turn, gives us insight to the

Organic chemistry on surfaces: Direct cyclopropanation by dihalocarbene addition to vinyl terminated self-assembled monolayers (SAMs)

• Malgorzata Adamkiewicz,
• David O’Hagan and
• Georg Hähner

Beilstein J. Org. Chem. 2014, 10, 2897–2902, doi:10.3762/bjoc.10.307

• of vinyl-terminated SAMs has been demonstrated, e.g., through surface modification of radicals generated by C–O bond thermolysis [17] and in a more controlled sense via olefin cross metathesis/enyne metathesis [18] of mixed vinyl and acetylenyl-terminated SAMs followed by Diels–Alder modifications of