Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• (177), albolic acid (178), and ceroplastol II (179) (Scheme 37). For the synthesis of hypoestin A (177), the side chain was introduced by selective deprotonation of 184, addition of acetaldehyde, dehydration and conjugated addition of Me2CuLi. These three last steps provided the desired product 177 in

• 50% overall yield. For the synthesis of albolic acid (178) and ceroplastol II (179), the side chain was introduced by deprotonation and addition of the corresponding aldehyde. After dehydration of the subsequent alcohol and conjugated addition of Me2CuLi, the regioselective reductive opening of

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• aromatic common intermediate 9 (Scheme 10). Despite the simplicity, the most obvious disconnections, such as an anionic enone conjugated addition and a direct cationic Friedel–Crafts reaction failed. Highlighting the power of radical disconnection, the group thought of utilizing a β-keto carbon-centered

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• reductive strategy through nitrogen loss of sulfonyl hydrazones [13][14]. In addition, a sulfa-1,6-conjugated addition reaction [15][16][17] has also been developed for this purpose. Most of the reported methods are affected by long reaction times and the need for expensive metal catalysts or reagents

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• was described by Sun et al. [46]. In this method, the catalyst (DHQ)2PYR 42 reacts with tert-butyl 2-bromoacetate, and then an ylide is formed by the base Cs2CO3. After a conjugated addition of this intermediate to the coumarin 43 followed by nucleophilic substitution, the corresponding cyclopropa[c

• electron-donating and electron-withdrawing substituents. Additionally, the products were evaluated as acetylcholinesterase (AChE) inhibitors and compound 93d showed a promising activity. Gurubrahaman et al. developed a method for the synthesis of (Z)-2-methylenepyrans 96 through a conjugated addition of 4

• via domino reaction between 4-hydroxycoumarins (1) and substituted methylene malononitriles 92. Conjugated addition of 4-hydroxycoumarins 1 to nitroolefins 95. Michael addition of 4-hydroxycoumarin 1 to α,β-unsaturated ketones 2 promoted by primary amine thiourea bifunctional catalyst 97

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• -mediated conjugated addition of methyllithium to enone 59 in the presence of boron trifluoride ether [34][35] produced desired ketone 60 in 75% yield. The resultant ketone 60 was converted to waihoensene (16) in two steps. Palladium-catalyzed carboxylative trimethylenemethane cycloaddition In 1986, Trost

• ] (Scheme 13B). Exposure of ester 159 to PhSH [75], p-toluidine and a catalytic amount of Ir(dF(CF3)ppy)2(dtbbpy)PF6 under the irradiation of blue LED light [76][77] afforded tricycle 162 in 50% yield. The authors suggested that this process involves an intramolecular 5-exo-conjugated addition of a radical

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• results may suggest that fluoroalkyl groups behave as bulky substituents rather than as electron-withdrawing ones, perhaps due to the purely inductive nature of the latter [71]. In the same work, the authors described the conjugated addition of several nucleophiles to model substrate 59d (Scheme 33). In

• conjugated addition of trimethylaluminum to form 66, followed by Lewis acid-mediated retro Diels–Alder reaction (Scheme 38). In another study by Riera and co-workers, they studied the influence of the olefin counterpart on the regioselectivity of the reaction [79]. Two olefins other than norbornadiene were

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• -ligands [23]. The asymmetric addition of various nucleophiles to unsaturated sulfones is also considered as an effective route to chiral sulfones. The conjugated addition of arylboronic acids to unsaturated sulfones under catalysis of Rh complexes was reported [24][25][26]. It was shown that arylboronic

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• ]. In short, the organocatalytic conjugated addition of benzoylacetonitrile to cinnamaldehyde generates the hemiacetal 30, which next initiates the multicomponent sequence upon condensation with the aniline and formation of the imine, eventually occurring as a stable cyclic aminal. The attack of the

Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

• Leon Buschbeck,
• Aleksandra Markovic,
• Gunther Wittstock and
• Jens Christoffers

Beilstein J. Org. Chem. 2019, 15, 981–991, doi:10.3762/bjoc.15.96

• -free click reactions) [14]. The second functional unit, the maleimide moiety, is a reactive probe for mercaptane, which could be, e.g., a protein holding a cysteine residue on its surface [15][16][17]. The successful ligation by conjugated addition can be followed by the changes of the fluorescence

An efficient and concise access to 2-amino-4H-benzothiopyran-4-one derivatives

• Peng Li,
• Yongqi Wu,
• Tingting Zhang,
• Chen Ma,
• Ziyun Lin,
• Gang Li and
• Haihong Huang

Beilstein J. Org. Chem. 2019, 15, 703–709, doi:10.3762/bjoc.15.65

• Chinese Academy of Medical Sciences, 1 Xian Nong Tan Street, Beijing 100050, P. R. China 10.3762/bjoc.15.65 Abstract A highly efficient and convenient protocol was developed to access 2-amino-4H-benzothiopyran-4-ones through a process of conjugated addition–elimination. The sulfinyl group was proved to

• group to afford the desired 2-amino-4H-benzothiopyran-4-ones through conjugated addition–elimination by nucleophiles. Subsequently, substrates 2a and 3a were reacted with a variety of alkyl/arylamines in the optimized solvent isopropanol (Table 2). Substrate 2a having an ethylsulfinyl group in general

• chromatographical purification that was employed in the milligram-scale synthesis. Overall, this synthetic route is efficient and applicable to scale-up. Conclusion In summary, we have developed a facile and efficient strategy for the synthesis of 2-aminobenzothiopyranones through a conjugated addition–elimination

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

• -type acceptor, by weak hydrogen-bonding interaction between the oxygen atom of the hydroxy group and the indolic proton (Figure 5). Recently, the conjugated addition of indole derivatives to β,γ-unsaturated α-ketoesters was explored [40]. To this end, the catalytic activity of several chiral thioureas

Copper-catalyzed asymmetric conjugate addition of organometallic reagents to extended Michael acceptors

• Thibault E. Schmid,
• Sammy Drissi-Amraoui,
• Christophe Crévisy,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 2418–2434, doi:10.3762/bjoc.11.263

• for enantio- and regioselective 1,6-additions onto dienoates [28], a wide variety of polyconjugated substrates were tested in order to gain a better insight into the reaction mechanism. Amongst the investigated electrophiles, substrates 79 (n = 1 or 2) could potentially undergo 1,8- or 1,10-conjugated

• addition, respectively. As shown in Scheme 24, the addition of the Grignard reagent occurred preferentially at the most remote olefin. To be noted, polyenic esters gave a slight regioselectivity towards the 1,8- and 1,10-products and low enantioselectivities. Remarkably, only a small portion (<10%) of

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

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

• yields amine radical cation 14, which is converted to α-amino radical 17. Conjugated addition of 17 to methyl vinyl ketone produces radical 79, which is reduced by the Ru(I) or Ir(II) complex with concomitant regeneration of the Ru(II) or Ir(III) complex. Protonation of the resulting enolate furnishes

• amides. Intramolecular interception of iminium ions by sulfonamides. Intramolecular interception of iminium ions by alcohols and sulfonamides. Intermolecular interception of iminium ions by phosphites. Photoredox-catalyzed oxidative phosphonylation by Eosin Y. Conjugated addition of α-amino radicals to

• Michael acceptors. Conjugated addition of α-amino radicals to Michael acceptors assisted by a Brønsted acid. Conjugated addition of α-amino radicals derived from anilines to Michael acceptors. Oxygen switch between two pathways involving α-amino radicals. Interception of α-amino radicals by

Bioinspired total synthesis of katsumadain A by organocatalytic enantioselective 1,4-conjugate addition

• Yongguang Wang,
• Ruiyang Bao,
• Shengdian Huang and
• Yefeng Tang

Beilstein J. Org. Chem. 2013, 9, 1601–1606, doi:10.3762/bjoc.9.182

• the electrophile 4. However, all of these reactions failed to provide satisfactory results and only lead to the recovery or the substantial decomposition of the starting material. We then turned our attention to the organocatalytic conjugated addition reaction. Among the various documented conditions

Organocatalytic asymmetric addition of malonates to unsaturated 1,4-diketones

• Sergei Žari,
• Tiiu Kailas,
• Marina Kudrjashova,
• Mario Öeren,
• Ivar Järving,
• Toomas Tamm,
• Margus Lopp and
• Tõnis Kanger

Beilstein J. Org. Chem. 2012, 8, 1452–1457, doi:10.3762/bjoc.8.165

• calculated VCD spectra of the reaction product 3a. Keywords: Michael addition; non-covalent catalysis; organocatalysis; squaramide; thiourea; Introduction The asymmetric 1,4-conjugated addition (Michael reaction) of C-nucleophiles to enones is a powerful tool for obtaining a significant variety of

• yields (up to 99%) and in high enantioselectivities (up to 93%). This enantioselective 1,4-addition to unsaturated 1,4-diketones affords valuable intermediates for further synthetic transformations. The conjugated addition to unsaturated 1,4-diketone 1. Organocatalysts screened. Proposed transition state

• . Calculated (red) and experimental (blue) IR (A) and VCD spectrum (B) of compound (R)-3a. Screening of the catalysts for the asymmetric conjugated-addition reaction. Enantioselective addition of malonates 2a-2f to unsaturated 1,4-diketone 1a. Enantioselective addition of diethylmalonate 2a to substituted 1,4

Gold-catalyzed propargylic substitutions: Scope and synthetic developments

• Olivier Debleds,
• Eric Gayon,
• Emmanuel Vrancken and
• Jean-Marc Campagne

Beilstein J. Org. Chem. 2011, 7, 866–877, doi:10.3762/bjoc.7.99

• catalyst loading to 1 mol %, the substitution product 10 could be isolated in 60% yield (along with 35% of the Meyer–Schuster product 11). This result could be explained by considering that 11 is derived from 10 through the conjugated addition of water (residual or produced during the substitution reaction

Homoallylic amines by reductive inter- and intramolecular coupling of allenes and nitriles

• Peter Wipf and
• Marija D. Manojlovic

Beilstein J. Org. Chem. 2011, 7, 824–830, doi:10.3762/bjoc.7.94

• to achieve the carbalumination of 1-alkynes [10], internal alkynes [11], conjugated enynes [12], and 1-iodoalkynes [13]. Huang and Pi found that allylzirconocenes underwent conjugated addition to enones in the presence of CuBr·SMe2 [14]. Wipf and Pierce demonstrated that, upon the addition of a zinc

A convenient synthesis of γ-functionalized cyclopentenones

• Nour Lahmar,
• Taïcir Ben Ayed,
• Moncef Bellassoued and
• Hassen Amri

Beilstein J. Org. Chem. 2005, 1, No. 11, doi:10.1186/1860-5397-1-11

• 3 in a basic medium, led to the functionalized cyclopentenones 4. Keywords: Nef reaction; conjugated addition; nitroalkanes; 1,4-diketones; functionalized cyclopentenones; Introduction The cyclopentenones are considered as an important class of compounds because they are present in a large variety