Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• 40 has been proven to be the most efficient photocatalyst, promoting key transformations such as the aza-Henry reaction with 44 to give 45 under NIR light irradiation (Figure 6b). The reaction was found to critically depend on the presence of oxygen in the air for it to proceed. Through optimization

• and mechanistic investigations of the near-IR-photocatalyzed aza-Henry reaction, the authors have proposed either a single-electron transfer or an energy transfer mechanism. Additionally, the reaction displayed an unexpected sensitivity to the light wavelength used. Employing a higher-energy light

• findings suggest that cyanins, specifically tailored to absorb in the NIR region, exhibit promising redox properties for applications in organic synthesis. A recent work by Goddard et al. has demonstrated that compound 46 is highly effective in various photoredox transformations, such as aza-Henry

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• activation of both substrates via hydrogen-bonding interactions. Additionally, these macrocycles showed excellent activity for sulfa-Michael additions, as well as a moderate activity for Henry and aza-Henry reactions. These results are consistent with the observation reported by Senge and co-workers

A novel recyclable organocatalyst for the gram-scale enantioselective synthesis of (S)-baclofen

• Gyula Dargó,
• Dóra Erdélyi,
• Balázs Molnár,
• Péter Kisszékelyi,
• Zsófia Garádi and
• József Kupai

Beilstein J. Org. Chem. 2023, 19, 1811–1824, doi:10.3762/bjoc.19.133

• organocatalysts is well-established in several organic reactions, including but not limited to aldol reactions [6], Michael additions [9], Mannich reactions [10], aza-Henry reactions [11], and Diels–Alder cycloadditions [12][13]. Although the benefits of organocatalysts are undoubted, their synthesis is often a

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• -Butanesulfinamide is highly useful in stereoselective synthesis as a stereoinducing group [21]. Thus, N-sulfinylureas and thioureas are a new class of organocatalysts, with the sulfinyl group acting both as an acidifying and a chiral controlling moiety. A variety of N-sulfinylureas catalyzed aza-Henry reaction

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• . In 2011, König and co-workers [150] demonstrated that eosin Y (OD13) was an efficient dye for an aza-Henry reaction [151], affording the tetrahydroquinolines 34.2 (Scheme 34). Simultaneously, the Tan group described the use of rose bengal (OD15) in the same transformation [152]. Regarding the strain

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• additions to isatin imines have been developed, including Mannich reactions, aza-Morita–Baylis–Hillman reactions, Friedel–Crafts reactions, aza-Henry reactions, additions of heteronucleophiles, Strecker reactions, among others. The goal of this review is to update the catalytic asymmetric synthesis of

• –Hillman reactions, Friedel–Crafts reactions, aza-Henry reactions, domino reactions initiated by nucleophilic additions to isatin imines, and miscellaneous reactions. Most of the reactions depicted in this review have been promoted by a wide variety of chiral organocatalysts but chiral metal catalysts have

• -Henry reactions The catalytic asymmetric Henry reaction, also known as catalytic asymmetric nitroaldol reaction, constitutes a useful synthetic methodology towards chiral β-nitro alcohols [69][70]. This reaction and related aza-Henry reactions involving imines have been promoted by both metal catalysts

Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions

• José M. Andrés,
• Miriam Ceballos,
• Alicia Maestro,
• Isabel Sanz and
• Rafael Pedrosa

Beilstein J. Org. Chem. 2016, 12, 628–635, doi:10.3762/bjoc.12.61

• organocatalysts in the stereoselective aza-Henry reaction [31]. Now we describe the results obtained in different stereoselective nitro-Michael additions promoted by these materials. Results and Discussion The ability of the supported catalysts (II–V) to promote the stereoselective nitro-Michael reaction was

The aminoindanol core as a key scaffold in bifunctional organocatalysts

• Isaac G. Sonsona,
• Eugenia Marqués-López and
• Raquel P. Herrera

Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50

• organocatalysts ((thio)ureas, squaramides, quinolinium thioamide, etc.) in the literature containing this favored structural core. They have been successfully employed in reactions such as Friedel–Crafts alkylation, Michael addition, Diels–Alder and aza-Henry reactions. However, the 1,2-aminoindanol core

• acting through hydrogen bonding, such as thiourea, urea, squaramide, and thioamide frameworks. These have been efficiently employed in a few organocatalytic processes such as Friedel–Crafts alkylations, Michael additions, Diels–Alder reactions and aza-Henry reactions, as discussed below. Friedel–Crafts

• activate the 1,3-dicarbonyl compound 36 (Scheme 15). We would like to remark that although the authors indicated that the S enantiomer is obtained in their final products, they depicted the R configuration, as is drawn in the Scheme 15. Aza-Henry reaction Ellman’s group designed a set of pioneering (thio

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• coworkers reported a visible light-mediated aza-Henry reaction that harnesses the synthetic potential of iminium ions. Using only 1 mol % of [Ir(ppy)2(dtbbpy)](PF6) and visible light, a variety of N-aryltetrahydroisoquinolines were oxidatively coupled with nitroalkanes to provide the aza-Henry products in

• nitromethane or oxygen to a radical anion that may abstract a hydrogen atom from amine radical cation 14 to form the iminium ion 15. Interception of the iminium ion by the anion of nitromethane affords the aza-Henry product 16. Oxygen has been the most often used stoichiometric oxidant in the formation of

• . König and coworkers showed that the same aza-Henry reaction can be catalyzed by the organic dye Eosin Y to afford the aza-Henry product 18 (Scheme 5) [67]. In addition to nitroalkanes, dialkyl malonates and malononitrile can be used as pronucleophiles to provide β-diester amine 19 and α-aminonitrile 20

Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step

• James C. Anderson,
• Andreas S. Kalogirou,
• Michael J. Porter and
• Graham J. Tizzard

Beilstein J. Org. Chem. 2013, 9, 1737–1744, doi:10.3762/bjoc.9.200

• unambiguously assigned by single crystal X-ray diffraction but the spectroscopic data did not match those reported for the natural product. The structure of the natural product must therefore be revised. Keywords: alkaloid; aza-Henry; natural products; nitro-Mannich; piperazinone; stereoselective synthesis

• ; Introduction The nitro-Mannich reaction (or aza-Henry reaction) has been developed to a standard where the product β-nitroamines 1 are now privileged building blocks. In part this is due to the complementary synthetic flexibility available from the two different nitrogen atom oxidation states (Scheme 1) [1

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• chlorides and bromides. Again, lower reaction times were reported for the microflow than for the batch reaction, and in this case the productivity of the microflow reactor was shown to be significantly higher than that of the batch reactor (2.5 mmol/h versus 0.4 mmol/h) [54][55]. Aza-Henry reactions can

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• good enantioselectivities. A broad range of substituted nitrostyrenes was studied for these tandem oxa-Michel-aza-Henry-desulfonamidation processes to afford the corresponding 2-aryl-3-nitro-2H-chromenes by a kinetically controlled desulfonamidation step (Scheme 17). 2. Organocatalytic thio-Michael