A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

Electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines under mild conditions with a proton-exchange membrane reactor

• Koichi Mitsudo,
• Atsushi Osaki,
• Haruka Inoue,
• Eisuke Sato,
• Naoki Shida,
• Mahito Atobe and
• Seiji Suga

Beilstein J. Org. Chem. 2024, 20, 1560–1571, doi:10.3762/bjoc.20.139

• aryl halides [42]. PEM reactors are also gaining industrial attention. Weber et al. reported a series of large-scale syntheses using PEM reactors [43]. We studied electrochemical transformations [44][45][46][47][48][49] and recently reported the selective reduction of enones using a PEM reactor [50

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• has emerged as an attractive approach for nitroarene reduction [43][44]. In 2021, Huang and colleagues discovered a photoredox system that did not require any transition metal or other photosensitizers [45]. This system employed a combination of NaI and PPh3 to achieve highly selective reduction of

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• . An o-phenolic coupling between two units of tyrosine furnishes the intermediate Int-1, which by deamination, selective reduction of one of the carboxylate groups, macrolactonization, and subsequent structural modifications would lead to the aforementioned combretastatins D (Scheme 1). The second

• carboxylic acid 20, which underwent protection with Troc-Cl and selective reduction in the presence of sodium borohydride to form the alcohol 21. After ester hydrolysis the desired seco-acid 22 was obtained in 82% yield. However, several attempts to achieve the macrolactonization of 22 using PPh3 and DEAD

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• Except for controlled cycloadditions, the site-selective reduction is also difficile to achieve. It mainly depends on the oxidative difference between the potential reactive sites and the careful picking of reductive reagents. Once the oxidative properties of these sites are similar to each other, it is

• mode, the molecular container selectively binds with and shields a certain part of the guest molecule and leaves the remaining part exposed to the reaction medium. This methodology was firstly applied to the site-selective reduction reaction mediated by a cyclodextrin host. In 1991, the Takahashi group

• could be regarded as a protective group by shielding the internal alkenyl site. In 2016, the Rebek group achieved the site-selective reduction of an α,ω-diazide compound by trimethylphosphine (PMe3) in aqueous solution with a cavitand host as the protecting group for one of the azide sites (Figure 5

Total synthesis of ent-pavettamine

• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2021, 17, 1440–1446, doi:10.3762/bjoc.17.99

• yield. The first step involved esterification of malic acid using methanol, followed by selective reduction of the resulting dimethyl ester using borane dimethyl sulfide (BMS) yielding diol 5 (Scheme 2) [1][14][15]. The step achieved chemo-differentiation of the carboxyl groups present in 3 whilst

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

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

• ) via Tu’s protocol [64]. The synthesis of sinensilactam A (20) commenced with a three-step synthesis from ketoeseter 131 to give enone 132 [59] (Scheme 9C). Selective reduction of the ketone moiety of 132 was accomplished under Luche’s conditions [65] in the presence of calcium chloride [63] to produce

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166

• 22 to generate the secondary alcohol 23. The acylation of 23, followed by the treatment with Jones’ reagent effected the THP deprotection as well as an overoxidation to give 13. The syn-selective reduction of 13 was accomplished with a balloon worth of pressure of H2 in the presence of the Lindlar

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

• . The azobenzene building block 8, with an unsubstituted phenyl ring and two orthogonal nitrogen substituents in the 3- and 5-position (Scheme 3), was prepared. The synthesis commenced with the acetylation of 3,5-dinitroaniline (4) in 95% yield, followed by the selective reduction of one nitro group

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• construction of the butenolide (D-ring) and iii) the installation of the three successive epoxides (C-ring). In future syntheses the following issues should be considered: i) avoiding the isomerization of the C-5 chiral center; ii) development of a new method for the β-selective reduction of the C-14 carbonyl

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• aziridine esters 70 which were subjected to a selective reduction of the nitro group to afford the major pyrrolidine-2-one (2R,4'R,1''S)-71 after chromatographic purification [65]. The reduction of the amide bond gave (2R,3'R,1''S)-72 thus providing a cyclic part of (3S,3'R)-68. The transformation of the

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• )-1f. Selective reduction of phosphine oxide (E)-3f. Attempted thermal [2,3]-sigmatropic rearrangement of phosphinite 6a. Computed activation barriers and free enthalpies. [2,3]-Sigmatropic rearrangement of phosphinites 6a–j. Proposed mechanism for the Lewis base-catalyzed rearrangement of phosphinites

Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

• Alex Frichert,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

• conversion to the diastereomer by oxidation and reduction. Conformational analysis of some of the resulting diols obtained under McMurry conditions was complicated by the presence of several conformers of similar energy. The pinacol coupling appears to start at the ketone, as indicated by the selective

• reduction of non-cyclizing cyclohexane systems that were synthesized from limonene oxide. The title compounds and their synthetic precursors are prone to aromatization on contact with air oxygen. Attempted synthesis of cyclohexene-containing eunicellane bicycles by elimination of water from tertiary alkynyl

Stereoselective total synthesis and structural revision of the diacetylenic diol natural products strongylodiols H and I

• Pamarthi Gangadhar,
• Sayini Ramakrishna,
• Ponneri Venkateswarlu and
• Pabbaraja Srihari

Beilstein J. Org. Chem. 2018, 14, 2313–2320, doi:10.3762/bjoc.14.206

• -selective reduction [25] of alkyne 20 was easily achieved with sodium bis(2-methoxyethoxy)aluminum hydride (Red-Al) as a hydride-transfer reagent to furnish the corresponding (E)-allylic alcohol 23. A Swern oxidation of 23 provided the corresponding aldehyde which was subjected to an addition reaction with

Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions

• Nicole C. Neyt and
• Darren L. Riley

Beilstein J. Org. Chem. 2018, 14, 1529–1536, doi:10.3762/bjoc.14.129

• the selective reduction of aldehydes in the presence of ketones and has been demonstrated as a continuous process. Keywords: aldehyde reduction; flow chemistry; selective reduction; sodium dithionite; Introduction Flow chemistry and continuous processing has been acknowledged by the American

• sodium dithionite under basic conditions and the expansion of the approach to allow the selective reduction of aldehydes in the presence of ketones. Results and Discussion Batch-based reduction of aldehydes and ketones The reduction of simple aldehydes and ketones (Table 1, Scheme 1) were envisaged and

• cases the yields were considered to be too low to be of use even though in certain examples (Table 1, entries 1.15 and 1.17) the productivity was arguably moderately better (2.4 and 2.0 times, respectively) than that of the analogous batch processes. Selective reduction of aldehydes in the presence of

A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols

• Anna Czarnecka,
• Emilia Kowalska,
• Agnieszka Bodzioch,
• Joanna Skalik,
• Marek Koprowski,
• Krzysztof Owsianik and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2018, 14, 1229–1237, doi:10.3762/bjoc.14.105

• % yields and is recommended for the substrates containing sulfur atoms, for which transition metal-induced reactions fail. Keywords: diarylmethanes; diarylmethanols; 1,3-dithiane; selective reduction; sodium cyanoborohydride; zinc iodide; Introduction In last decades, diarylmethanes, such as I–IV and

• , and their reduction to the corresponding ortho-1,3-dithianylaryl(aryl)methanes. Attempts of the OH removal in ortho-1,3-dithianyl- 6b and ortho-1,3-dioxanylaryl(aryl)methanols 9 using the Pd-catalyzed hydrogenolysis reaction. A selective reduction of ortho-1,3-dithianylaryl(aryl)methanols to ortho-1,3

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

• literature-known aldehyde (R)-17, which defined the configuration of the C19 stereocenter (mycolactone numbering, see Figure 1). Aldehyde (R)-17 can be easily prepared from commercially available methyl (R)-3-hydroxybutyrate ((R)-47, see Scheme 4) in two steps, namely TBS protection followed by selective

• reduction with DIBAL-H [125]. Aldehyde (R)-17 was submitted to an asymmetric Brown crotylation reaction [126][127] to establish the C16 and C17 stereocenters. Of note, all four possible C16,C17-diastereomers of 18 were prepared (not shown) by using different combinations of (E)- or (Z)-butene and either

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• to handle hazardous components such as hydrazine and molecular oxygen, which represent alternative reagents for selective reduction of C=C double bonds. In fact, combination of hydrazine hydrate (N2H4·H2O) and O2 provide diimide (HN=NH) as reducing agent. Nevertheless, this strategy is rarely used in

• is compatible with sensitive functional groups such as silyl ether, halogenes, and benzyl groups. A very nice application of this approach was the highly selective reduction of artemisinic acid to dihydroartemisinic acid, which are of interest in the synthesis of the antimalarial drug artemisinin

Elongated and substituted triazine-based tricarboxylic acid linkers for MOFs

• Arne Klinkebiel,
• Ole Beyer,
• Barbara Malawko and
• Ulrich Lüning

Beilstein J. Org. Chem. 2016, 12, 2267–2273, doi:10.3762/bjoc.12.219

• monofunctionalized 1,3,5-triazines 16b and 16c carrying methyl ester groups at the end of each „arm“ (Figure 7). The yields of 90% (16b) and 73% (16c) correspond to 97% and 90% yield per coupling step, respectively. By selective reduction, the nitro-substituted triester 16b could be transferred into its amino

Copper-catalyzed aminooxygenation of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives

• Yan Li,
• Xue Zhou,
• Guangfan Zheng and
• Qian Zhang

Beilstein J. Org. Chem. 2015, 11, 2721–2726, doi:10.3762/bjoc.11.293

• investigate the synthetic value of our new aminooxygenation method. Then, the selective reduction of 3g was conducted (Scheme 3). The cleavage of the N–O bond in 3g readily occurred with Mo(CO)6/Et3N at 80 °C to give alcohol 4 [36] in 67% yield. Treatment of 3g with NH2NH2·H2O under mild conditions (25 °C) in

• (1.2 mmol, 4.0 equiv), 2 (0.3 mmol, 1.0 equiv), CuCl2 (10 mol %), DCM (2.0 mL), N2, 70 °C, 10.0 h. Isolated yields. Copper-catalyzed radical aminooxygenation reaction of styrenes. The plausible mechanism. Selective reduction of the aminooxygenation product. The optimization of reaction conditionsa

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• , the proposed strategy offers an efficient construction of all stereocenters of tricyclic core 2, based on the initially established chiral stereocenter, as the configuration at the C1 and C2 positions of 2 would presumably be controlled by face-selective reduction of ketone 3. The Michael precursor 7

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• oxolane bridge between C1 and C7. Hajos–Parrish diketone (107) [39] served as the starting material for the preparation of key intermediate 112. Selective reduction of the ketone and silylation of the resulting alcohol furnished enone 108. α-Carboxylation of the enone with magnesium methyl carbonate and a