Photoswitches beyond azobenzene: a beginner’s guide

• Michela Marcon,
• Christoph Haag and
• Burkhard König

Beilstein J. Org. Chem. 2025, 21, 1808–1853, doi:10.3762/bjoc.21.143

• aromatic amines. Another strategy for both symmetric and asymmetric targets is the azo coupling of a diazonium salt 15 (Scheme 5A) with a nucleophile, which can be a (hetero)aromatic 16 [29] (B), a lithiated ring 19 [39] (C), or a precursor 20a,b [29][32][40] (D). In case of more than one reactive position

• acylhydrazones are accessible with comparatively low synthetic effort, especially compared to diarylethenes and fulgides. The synthesis of arylhydrazones is usually performed through condensation between a carbonyl 112 and a hydrazine 111 (Scheme 35A) [109]. Alternatively, one can perform an azo-coupling between

Tandem diazotization/cyclization approach for the synthesis of a fused 1,2,3-triazinone-furazan/furoxan heterocyclic system

• Yuri A. Sidunets,
• Valeriya G. Melekhina and
• Leonid L. Fershtat

Beilstein J. Org. Chem. 2024, 20, 2342–2348, doi:10.3762/bjoc.20.200

• Federation 10.3762/bjoc.20.200 Abstract A straightforward protocol for the synthesis of a previously unknown [1,2,5]oxadiazolo[3,4-d][1,2,3]triazin-7(6H)-one heterocyclic system was developed. The described approach is based on tandem diazotization/azo coupling reactions of (1,2,5-oxadiazolyl)carboxamide

• a 1,2,3-triazin-4-one core. The proposed method is based on tandem diazotization/azo coupling reactions of the corresponding amides (Scheme 1). In addition, application perspectives of thus prepared heterocyclic entities as thermally stable components of functional organic materials or NO-donor drug

• of thus generated diazonium salts. In this regard, amide 2a and mesitylene were selected as model objects to optimize the reaction conditions, since azo coupling of (1,2,5-oxadiazolyl)diazonium salts with electron-donating arenes is known to proceed quantitatively [42]. We varied the diazotization

A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• two options for the generation of 4-ethoxy-2,3,6-triaminopyridine (9). One possibility comprised the deprotection of the dicarbamate 5 with potassium hydroxide giving the diamine 6, followed by azo coupling with the diazonium salt obtained from aniline and sodium nitrite to give azo compound 7

• differed from the above path by leaving the hydroxy group of all intermediate 4-hydroxypyridine derivatives 12–15 unprotected [19]. Moreover, instead of azo coupling or nitroso formation, a simple nitration protocol with nitric acid to give the nitro derivative 13 and subsequent reduction with Raney nickel

Synthesis of mono-functionalized S-diazocines via intramolecular Baeyer–Mills reactions

• Miriam Schehr,
• Daniel Hugenbusch,
• Tobias Moje,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2018, 14, 2799–2804, doi:10.3762/bjoc.14.257

• functionalized with a carboxylic acid 4 or a benzyl alcohol 5 could not be obtained using the reductive azo coupling. For the benzyl alcohol 5 a variety of different, unidentified byproducts formed and in case of the carboxylic acid 4 only the starting material was retrieved. We now present a reliable one-pot

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

Nitration of 5,11-dihydroindolo[3,2-b]carbazoles and synthetic applications of their nitro-substituted derivatives

• Roman A. Irgashev,
• Nikita A. Kazin,
• Gennady L. Rusinov and
• Valery N. Charushin

Beilstein J. Org. Chem. 2017, 13, 1396–1406, doi:10.3762/bjoc.13.136

• obtained 2,8-bis(RCO)-substituted derivatives as building blocks for the synthesis of more complicated ICZ-containing compounds [42][43][44]. In addition, other research groups have previously reported convenient methods for C12-formylation, azo-coupling, bromination and chlorination of 6-mono-substituted

The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors

• Faith M. Akwi and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 1987–2004, doi:10.3762/bjoc.12.186

• II azo dye was used as a model reaction for the study. At found optimal azo coupling reaction temperature and pH an investigation of the optimum flow rates of the reactants for the diazotization and azo coupling reactions in Little Things Factory-MS microreactors was performed. A conversion of 98

• reaction conversions ranging between 66–91% were attained. Keywords: azo coupling; diazotization; microreactor; scale up; Introduction Going green, a familiar catch phrase in the chemical industry, in addition to environment protection laws have influenced and also triggered the development of cleaner

• the procedure of diazotization and azo coupling (using compounds that impart green benefits to the process or make it environment friendly, i.e., short reaction times thus less energy is required for the process, high yield thus low amount of waste generated, etc). Equally, process equipment can also

Synthesis and reactivity of aliphatic sulfur pentafluorides from substituted (pentafluorosulfanyl)benzenes

• Norbert Vida,
• Jiří Václavík and
• Petr Beier

Beilstein J. Org. Chem. 2016, 12, 110–116, doi:10.3762/bjoc.12.12

• toward 4 was prepared independently (Scheme 4). Azo coupling [20] of phenol 11 with a diazonium salt prepared from sulfanilic acid afforded red azo product 13. The regioselectivity is governed by the strong para-directing hydroxy group despite the presence of the bulky SF5 group. Compounds with

Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF₅-substituted phenylboronic esters and iodobenzenes

• George Iakobson,
• Junyi Du,
• Alexandra M. Z. Slawin and
• Petr Beier

Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162

• -coupling reactions with varied degree of success. The most efficient cross-coupling reactions were the Heck reactions with alkenes, a biaryl homocoupling reaction, an azo coupling to electron-rich arenes, and a dediazoniation with TMSN3 in an ionic liquid medium [74][75]. An efficient borylation of

Azobenzene-based inhibitors of human carbonic anhydrase II

• Leander Simon Runtsch,
• David Michael Barber,
• Peter Mayer,
• Michael Groll,
• Dirk Trauner and
• Johannes Broichhagen

Beilstein J. Org. Chem. 2015, 11, 1129–1135, doi:10.3762/bjoc.11.127

• synthesized a small library of nine azobenzene sulfonamides with differing substitution patterns in the 4´-position using either azo coupling reactions or the Mills reaction. We determined the π–π* band and the crystal structures of all nine compounds together with the protein crystal structure of hCAII bound

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

• František Josefík,
• Markéta Svobodová,
• Valerio Bertolasi and
• Petr Šimůnek

Beilstein J. Org. Chem. 2013, 9, 1463–1471, doi:10.3762/bjoc.9.166

• substituents was easily synthesized. A mechanism of the formation of the pyridazinium salts is suggested. A partial drawback is the possibility of the formation of a mixture of products when using a different diazonium salt in each step due to a reversibility of the azo coupling. This can be suppressed by

• using a more reactive diazonium salt before a less reactive one. Keywords: azo coupling; diazonium salt; enaminone; pyridazinium; Introduction As heterocyclic compounds play a very important role in everyday life, e.g., as pharmaceuticals, agrochemicals, dyes, etc. (for many monographies or textbooks

• analysis or HRMS (see Experimental and Supporting Information File 1). Some of them were characterized also by means of X-ray analysis (see below). The mechanism of the azo coupling of primary and secondary enaminones was studied in [29]. The formation of compounds 4 can be assumed to proceed in an

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• were further used for the construction of various charge-transfer chromophores 37–43, in particular by simple diazotation and subsequent azo-coupling of the terminal NH2 group [62][63][64][65][66]. Chromophores 37–43 found wide application as polymer dopants, cross-linkable organic glasses or inorganic

• polyphosphazene backbone and subsequently modified by post-azo coupling with variously substituted benzenediazonium salts to afford systems 125–130 (Figure 22; Table 15; [125][126][127]). These systems possess good optical transparency, high Tg, and large d33 (SHG) and photoinduced birefringence values relative

• solar cells). In 2009, Koszykowska et al. demonstrated facile polymerization of 1-vinylimidazole and subsequent post-azo coupling at imidazole C2 to attach various donor- and acceptor-substituted pendants. Moreover, the poly(N-vinyl-2-(phenylazo)imidazoles 132–134 showed interesting switchable