Substituted nitrogen-bridged diazocines

• Pascal Lentes,
• Jeremy Rudtke,
• Thomas Griebenow and
• Rainer Herges

Beilstein J. Org. Chem. 2021, 17, 1503–1508, doi:10.3762/bjoc.17.107

• Fmoc chloride to accomplish an orthogonal protective group strategy. The removal of the Boc groups from compounds 5 with TFA gave the mixed aniline and nitro precursors 6. In previous approaches, the nitro groups were reduced to hydroxylamines with zinc and oxidized to the corresponding nitroso

• compounds with iron(III) to perform an intramolecular Baeyer–Mills reaction [15][21]. We found that a complete reduction of the nitro group to aniline 7 and oxidation with mCPBA is increasing the yield of the intramolecular cyclization from 39% to 62% (over two steps) for the unsubstituted diazocine 8c as

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• , 14, 16–18, 20, and 21 For the synthesis of the azopyridines, Baeyer–Mills reactions [18] with 4-substituted 3-aminopyridines were applied [4]. The nitroso compounds 3 and 6 were synthesized by two different methods. 1-Bromo-3-nitrosobenzene (3) was obtained by oxidation of 3-bromoaniline (2) using

• of 1e (top), 1h (left) and 1j (right) in acetone water (1:9) (solid line) and after deprotonation using cesium carbonate (dashed line) in the PSS at 505 nm (green) and 435 nm (blue). Synthesis of the nitroso compounds 3 and 6 using the two different methods described by Wegner et al. [19][20][21] and

Starazo triple switches – synthesis of unsymmetrical 1,3,5-tris(arylazo)benzenes

• Andreas H. Heindl and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2020, 16, 22–31, doi:10.3762/bjoc.16.4

• evaluated for the preparation of tris(arylazo)benzenes 3. The first one relied on the consecutive condensation of anilines with nitroso compounds, Baeyer–Mills reactions [13]. With a suitable protecting group strategy, the selective construction of the individual AB branches should be achievable (Scheme 1

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• -nitrobenzaldehyde (8a) to give the corresponding tertiary amine 9a in high yield. The nitro group of 9a was subsequently reduced by SnCl2 in high yield. The resulting aniline 10a was used to obtain the azo compounds 12a–e in varying yields through a Mills reaction with the corresponding nitroso compounds 11a–e

• performed following the strategies shown in Scheme 1 as disclosed for compounds 2a–e. Briefly, a reductive amination of 7 and 8b gave nitro compound 9b, which after reduction to 10b, coupling with nitroso compounds 11a–e to 13a–e and methylation gave iodide salts 3a–e with purities of trans-isomers ≥99% and

• compound 9c which was reduced to aniline 10c and used to obtain the azo compounds 14a–d,f–i in variable yields through a Mills reaction with the corresponding nitroso compounds 11a-b,e–j. Methylation of 14a–d,f–i with MeI yielded compounds 4a–d,f–g,i as orange powders with ≥99% trans-isomer in moderate to

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

• sulfur bridge is oxidized to the sulfoxide or sulfone. Hence, neither reductive nor oxidative conditions are compatible with the –CH2-S– bridge. An alternative strategy, that applies weakly acidic conditions is the condensation of aryl nitroso compounds with anilines. This Baeyer–Mills reaction was

Electrochemical Corey–Winter reaction. Reduction of thiocarbonates in aqueous methanol media and application to the synthesis of a naturally occurring α-pyrone

• Ernesto Emmanuel López-López,
• José Alvano Pérez-Bautista,
• Fernando Sartillo-Piscil and
• Bernardo A. Frontana-Uribe

Beilstein J. Org. Chem. 2018, 14, 547–552, doi:10.3762/bjoc.14.41

• ]. With thiocarbonates 4 and 6 in our hands, their electrochemical behavior was studied in the MeOH/H2O media previously described (Figure 1). This mixture of solvents has been used for the electrochemical preparation of anilines, hydroxylamines and nitroso compounds via the reduction of aromatic nitro

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• successful coupling with a particular nucleophile and for prevention of side reactions. There are several sources of α-nitrosoalkenes as shown in Scheme 1. Conventional precursors of α-nitrosoalkenes are α-halooximes 1 (or halo-substituted nitroso compounds [11][12]), which undergo deprotonation/halide

• the first two routes. Tanimoto et al. [22] recently suggested N-siloxysulfonamides 4 as stable sources of unsaturated nitroso compounds (Scheme 1, reaction (4)). However, this approach was used only for the generation of nitrosoallenes so far. Addition of C–H acids anions to conjugated nitrosoalkenes

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• stereo- and regioselectivity for the synthesis of 1,2-oxazine scaffolds. Keywords: diene; hetero-Diels–Alder; nitroso compounds; regioselectivity; stereoselectivity; Review Introduction The hetero-Diels–Alder reaction represents one of the most important methods in organic synthesis, providing various

• regio- and stereoselectivity of the hetero-Diels–Alder reaction as well as the possibility of controlling the regio- and stereoselectivity of 3,6-dihydro-2H-1,2-oxazine formation. Nitroso compounds and dienes Nitroso compounds: Nitroso compounds are highly reactive dienophiles often used for the hetero

• hypochlorite [58] or related electrophilic halogen precursors [59][60] may be used. However, most of these methods result in the formation of nitro derivatives along with the desired nitroso compounds. Relatively new methods for the conversion of nitroalkanes into geminal chloronitroso compounds involving

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

• nitro compounds [17][18][19][20][21], two other routes are available: the annulation of nitroso compounds [22][23] and the thermal [24], catalytic [25][26][27] or photochemical cyclization of aryl azides [28][29][30][31]. However, the presence of electron-withdrawing substituents in the 3-, 5- and 7

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• aldehydes react with an aza electrophile. Imines possessing an electron-withdrawing N-substituent constitute the most commonly used aza electrophile and the reaction affords an α-aminocarbonyl compound as the product. The NHC-mediated addition of aldehyde-derived acyl anions to nitroso compounds leading to

• electrophiles (nitroso compounds) are some of the developments that revamped the synthetically unattractive, monotonous image of benzoin condensations. The driving force behind this remarkable evolution of benzoin reaction is NHC-catalysis. Benzoin chemistry is well-set to benefit, in the near future, from new

Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

• David Porter,
• Belinda M.-L. Poon and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 2549–2556, doi:10.3762/bjoc.11.275

• regioisomers in the hetero-Diels–Alder reaction with nitroso compounds, yet Cenini et al. only detected one isomer. From this observation they concluded that their Ru-catalysed amination reaction and the Diels–Alder reactions were occurring ‘on metal’ without generation of a free nitroso species [57]. In

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

• ). Another commonly used method is the condensation between anilines and aryl nitroso compounds, known as the Mills reaction. According to these transformations, nine sulfonamide containing azobenzenes 1a–i with different moieties in the 4´-position were synthesized. The substitution in the 4´-position will

• % yield over two steps. Additionally, several in situ generated nitroso compounds bearing a nitro and a carboxylic acid ester were reacted with sulfanilamide to obtain nitro azobenzene 1g and ethyl ester azobenzene 1i, respectively. Commercially available nitrosobenzene gave rise to the unsubstituted

• -pot reaction over three steps in 25%. By diazotization of 1d and trapping the salt with TMS-azide, we obtained azido azobenzene 1e in 63% yield through a [3 + 2] and retro-[3 + 2] cycloaddition (Scheme 1b) according to the procedure of Barral et al [10]. For the Mills reaction, different nitroso

Synthesis of SF₅-containing benzisoxazoles, quinolines, and quinazolines by the Davis reaction of nitro-(pentafluorosulfanyl)benzenes

• Petr Beier and
• Tereza Pastýříková

Beilstein J. Org. Chem. 2013, 9, 411–416, doi:10.3762/bjoc.9.43

• Davis and Pizzini [7] and probably proceeds through the formation of σH adducts that give nitroso compounds, which upon deprotonation enter an intramolecular addition–elimination process as shown in Scheme 1. Typical reaction conditions are an excess of alkali metal hydroxide in a low-boiling-point