Pd-catalyzed dehydrogenative arylation of arylhydrazines to access non-symmetric azobenzenes, including tetra-ortho derivatives

• Loris Geminiani,
• Kathrin Junge,
• Matthias Beller and
• Jean-François Soulé

Beilstein J. Org. Chem. 2025, 21, 2234–2242, doi:10.3762/bjoc.21.170

• )–aryl intermediate (B). Subsequently, ligand exchange occurs, generating hydrazido complexes C and C'. When bulky substituents are present on the phosphine ligand and/or (both) coupling partner(s) has ortho-substituent(s), the hydrazido complex C, chelating on the terminal nitrogen, is preferentially

• carbonate, yielding the Pd(II) intermediate G. This intermediate then undergoes β–H elimination to afford the desired azobenzene product, along with a Pd(II) species H. Finally, reductive elimination regenerates Pd(0), completing the catalytic cycle. Then, a general reaction pathway for the formation of

Thiadiazino-indole, thiadiazino-carbazole and benzothiadiazino-carbazole dioxides: synthesis, physicochemical and early ADME characterization of representatives of new tri-, tetra- and pentacyclic ring systems and their intermediates

• Gyöngyvér Pusztai,
• László Poszávácz,
• Anna Vincze,
• András Marton,
• Ahmed Qasim Abdulhussein,
• Judit Halász,
• András Dancsó,
• Gyula Simig,
• György Tibor Balogh and
• Balázs Volk

Beilstein J. Org. Chem. 2025, 21, 2220–2233, doi:10.3762/bjoc.21.169

• compounds 3 [22][23]: A suspension of 5 (100 mg), ketone 6 (1.10 equiv), bismuth(III) nitrate pentahydrate (0.22 equiv) and PPA (2.7 equiv) in MeOH (1 mL) was heated at 110 °C in a glass screw cap vial until the starting material and the hydrazone intermediate 7 were consumed. Then the solids were filtered

Synthesis of triazolo- and tetrazolo-fused 1,4-benzodiazepines via one-pot Ugi–azide and Cu-free click reactions

• Xiaoming Ma,
• Zijie Gao,
• Jiawei Niu,
• Wentao Shao,
• Shenghu Yan,
• Sai Zhang and
• Wei Zhang

Beilstein J. Org. Chem. 2025, 21, 2202–2210, doi:10.3762/bjoc.21.167

• . However, the reaction of 2-azido-5-bromobenzaldehyde (1d) gave only a trace amount of product 8h. Instead, compound 8h', an intermediate without lactamization, was isolated in 59% yield. It is likely that the bromo group on the phenyl ring interfered with the lactamization process. Two control reactions

Electrochemical cyclization of alkynes to construct five-membered nitrogen-heterocyclic rings

• Lifen Peng,
• Ting Wang,
• Zhiwen Yuan,
• Bin Li,
• Zilong Tang,
• Xirong Liu,
• Hui Li,
• Guofang Jiang,
• Chunling Zeng,
• Henry N. C. Wong and
• Xiao-Shui Peng

Beilstein J. Org. Chem. 2025, 21, 2173–2201, doi:10.3762/bjoc.21.166

• reversible C–H activation to give the six-membered intermediate C. Substitution of the acetate ligand in C by 3 caused the generation of complex D. The six-membered ruthenacycle E was then obtained by migratory insertion of acetylene into the Ru–C bond. Finally, reductive elimination of E formed the target

• generation of 12a in Cu rod electrodes, the Cu anode was expected to liberate Cu+ into the reaction mixture. The reaction of this Cu+ with DMSO and I− afforded (DMSO)nCuI, which was coordinated with C≡C to give B. The intermediate C was obtained by cyclization of B and deprotonation. Further protonation of C

• occurred to give a radical cation PhSeSePh•+ at the anode. The subsequent cleavage of Se–Se bond formed a radical PhSe• and a cation PhSe+. Further additional oxidation of PhSe• yielded another PhSe+, which worked as the major reactive species and quickly added to C≡C in 13a to form intermediate A. Finally

C2 to C6 biobased carbonyl platforms for fine chemistry

• Jingjing Jiang,
• Muhammad Noman Haider Tariq,
• Florence Popowycz,
• Yanlong Gu and
• Yves Queneau

Beilstein J. Org. Chem. 2025, 21, 2103–2172, doi:10.3762/bjoc.21.165

• conversion of a glycolaldehyde acetal (hydroxy acetal). The first step was the reaction of sodium benzyloxide with bromo acetals giving the hydroxy acetals in 75–82% yield. The intermediate ether was converted to the hydroxy acetal with sodium in liquid ammonia in good yield (70%). The hydroxy acetal then

• –Crafts alkylation products were then converted into an intermediate tryptaldehyde that underwent intramolecular olefination to form the targeted product [34]. Glycolic acid (GA) The growing impact of fossil fuel consumption has heightened the need for advancing renewable energy technologies. One

• ) [71]. The Bobleter and Feather groups investigated the reaction mechanism of the conversion of these C3 compounds. The acid-catalyzed equilibrium between 1,3-dihydroxy-2-propane and 2,3-dihydroxypropanal involves an ene-triol intermediate which leads to methylglyoxal by a dehydration reaction at

The application of desymmetric enantioselective reduction of cyclic 1,3-dicarbonyl compounds in the total synthesis of terpenoid and alkaloid natural products

• Dong-Xing Tan and
• Fu-She Han

Beilstein J. Org. Chem. 2025, 21, 2085–2102, doi:10.3762/bjoc.21.164

• (Scheme 3) [31][32]. Oxidation state adjustment of 48 led to the ketone 49. Starting from this common intermediate, firstly, base-promoted double bond migration and oxidation at the γ-position gave tertiary alcohol 50. Deprotection of acetyl in 50 followed by selective oxidation delivered (−)-cyrneine B

• , by employing the same procedures for the synthesis of (−)-cyrneine A (7), the synthesis of (+)-allocyathin B2 (8) could also be achieved smoothly from 52 by utilizing diketone 53 as the intermediate. The diverse syntheses of these terpenoids enabled by the desymmetric enantioselective reduction of

• of 57 to phenolic intermediate followed by the construction of the B ring generated tricyclic core 59. Subsequently, dihydroxylation of the doubled bond in the central six-membered ring using OsO4/NMO gave diol, which was then subjected to acetylation of the two hydroxy groups and hydrogenation of C5

Multicomponent reactions IV

• Thomas J. J. Müller and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2025, 21, 2082–2084, doi:10.3762/bjoc.21.163

• intermediate purification, work-up, or solvent exchange. Domino processes [3] are characterized by the simultaneous presence of all reactants from the outset, whereas sequential reactions permit the controlled addition of components while maintaining the same reaction conditions. Consecutive processes, in turn

Further elaboration of the stereodivergent approach to chaetominine-type alkaloids: synthesis of the reported structures of aspera chaetominines A and B and revised structure of aspera chaetominine B

• Jin-Fang Lü,
• Jiang-Feng Wu,
• Jian-Liang Ye and
• Pei-Qiang Huang

Beilstein J. Org. Chem. 2025, 21, 2072–2081, doi:10.3762/bjoc.21.162

• cyclization of an intermediate derived from ᴅ-tryptophan [60][61]. Subsequently, we developed a five-step total synthesis of (–)-chaetominine (1) and two diastereomers from ʟ-tryptophan [62]. Taking advantages of the high efficiency and flexibility of our strategy [60], we have synthesized several natural and

• compound 14, an intermediate in our synthesis of (–)-isochaetominine A (4) [63]. Indeed, EDCI/HOBt-mediated lactamization of 14 derived amino acid (not shown) via debenzylation increased the yield of (–)-isochaetominine A (4) from 75% to 91% (Scheme 1). Thus, overall yield of the total synthesis of

• intermediate 17 [65] yielded the thermodynamically stable C2/C11-trans and C3/C14-trans diastereomers 19 and 20 (dr = ca. 1:1) in a combined yield of 75% (Scheme 2). The 1H NMR spectrum of this diastereomeric mixture shows only one set of resonance signals, but two sets of resonance signals were observed on

Discovery of cytotoxic indolo[1,2-c]quinazoline derivatives through scaffold-based design

• Daniil V. Khabarov,
• Valeria A. Litvinova,
• Lyubov G. Dezhenkova,
• Dmitry N. Kaluzhny,
• Alexander S. Tikhomirov and
• Andrey E. Shchekotikhin

Beilstein J. Org. Chem. 2025, 21, 2062–2071, doi:10.3762/bjoc.21.161

• trifluoroacetic acid affords intermediate compound 6, bearing a trifluoroacetyl group on the indole moiety. Treatment of 6 with the base yielded the acid 3 in high yield (Scheme 2). The carboxyl group of 3 was converted to the corresponding amides via coupling with mono-N-Boc-protected C2–C4 diamines using PyBOP

• NH proton in the urea moiety (position N5) of indolo[1,2-c]quinazolin-6(5H)-one (1) enables efficient N-alkylation. Accordingly, alkylation of 1 with 1-bromo-3-chloropropane afforded intermediate 11, bearing a reactive chloropropyl side chain suitable for further derivatization. Nucleophilic

Bioinspired total syntheses of natural products: a personal adventure

• Zhengyi Qin,
• Yuting Yang,
• Nuran Yan,
• Xinyu Liang,
• Zhiyu Zhang,
• Yaxuan Duan,
• Huilin Li and
• Xuegong She

Beilstein J. Org. Chem. 2025, 21, 2048–2061, doi:10.3762/bjoc.21.160

• , derived from phenylthiol and geranyl bromide, coupled with chiral epoxide 6, prepared through Sharpless epoxidation and TBS protection of 2-methylprop-2-en-1-ol, under strong basic conditions to generate intermediate 7 to further reduce the sulfide moiety with sodium, furnishing diol 8 with the loss of

• benzylic oxidation to generate a para-quinone methide (pQM) intermediate. Using fusarentin 6-methyl ether as an example, pQM intermediate 10 would be generated. The C10 alcohol should successively undergo an oxa-Michael addition reaction to close the THF ring, providing 7-O-demethylmonocerin. Similarly

•  4a), Kam proposed that tabertinggine might be biosynthetically generated from an ibogamine precursor keto-ibogamine through an indole oxidation and C21–N bond cleavage process to give intermediate 25, which further undergoes a cyclization to form the C16–N bond and dehydration to generate the enone

α-Ketoglutaric acid in Ugi reactions and Ugi/aza-Wittig tandem reactions

• Vladyslav O. Honcharov,
• Yana I. Sakhno,
• Olena H. Shvets,
• Vyacheslav E. Saraev,
• Svitlana V. Shishkina,
• Tetyana V. Shcherbakova and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2025, 21, 2021–2029, doi:10.3762/bjoc.21.157

• substituted 3-(3-oxo-3,4-dihydroquinoxalin-2-yl)propanoic acids containing a pharmacophore quinoxalinone moiety. The tandem Ugi/aza-Wittig combination was also carried out in a one-pot procedure without isolation of the intermediate. Keywords: α-ketoglutaric acid; aza-Wittig reaction; multicomponent reaction

• in 33–93% yields (Scheme 3; Table 3). According to the literature [31][53], this reaction proceeds through the formation of an iminophosphorane intermediate (Scheme 3), the product of a Staudinger reaction, which, however, was not isolated because it easily undergoes intramolecular cyclization on a

• this case a carboxyl proton. In order to avoid the step of isolation of the intermediate azide derivatives 8, we also studied a one-pot method for the synthesis of compounds 9. For this KGA 1, aldehydes 2a,b, azidoanilines 7b,c, and tert-butyl isocyanide (4) were stirred in methanol at 45 °C for 24

Understanding the origin of stereoselectivity in the photochemical denitrogenation of 2,3-diazabicyclo[2.2.1]heptene and its derivatives with non-adiabatic molecular dynamics

• Leticia A. Gomes and
• Steven A. Lopez

Beilstein J. Org. Chem. 2025, 21, 2007–2020, doi:10.3762/bjoc.21.156

• , and T2, conical intersections, transition structures, and singlet–triplet crossing were computed using CASSCF(10,8)/6-31G(d)//MP2/6-31G(d) [81]. The results suggested a stepwise C–N bond breaking with the formation of the diazenyl diradical intermediate [81]. In 2003, Olivucci and his co-workers

• with experimental observations. They argued that the DZ intermediate reacts before thermal equilibration. The formation of inverted housane occurs via the pseudo-axial-to-equatorial inversion of DZ. From the axial DZ, the puckered-DR (puc-DR in Scheme 3) radical could be formed resulting in retained

• pathways following the S1 to S0 crossing: the reversal to reactant, the inversion product, the retention product, and a diradical intermediate, as shown in Figure 5. Each pathway is shown in a different color, with the products shown at the bottom in their corresponding colors along with the quantum yields

Measuring the stereogenic remoteness in non-central chirality: a stereocontrol connectivity index for asymmetric reactions

• Ivan Keng Wee On,
• Yu Kun Choo,
• Sambhav Baid and
• Ye Zhu

Beilstein J. Org. Chem. 2025, 21, 1995–2006, doi:10.3762/bjoc.21.155

• intermediate, respectively) are neglected to simplify the assignment, considering such information is inexplicit based on the chemical transformations alone and is not available in commonly used chemical databases. Therefore, the index is a denotation of the overall transformation, which is not always

• and restored in the course of the transformations (e.g., Scheme 4A and 4C). Such limitations become obvious in the cases of multistep, multi-intermediate reactions [32][33], particularly in the case of helical chirality where chirality transfer of intermediates is common [34][35][36][37][38][39]. In

Aryl iodane-induced cascade arylation–1,2-silyl shift–heterocyclization of propargylsilanes under copper catalysis

• Rasma Kroņkalne,
• Rūdolfs Beļaunieks,
• Armands Sebris,
• Anatoly Mishnev and
• Māris Turks

Beilstein J. Org. Chem. 2025, 21, 1984–1994, doi:10.3762/bjoc.21.154

• alkynes undergo 1,2-carbofunctionalization, where the highly electrophilic Ar–M species adds to the alkyne, generating a vinyl cation intermediate [7], which typically reacts with an internal nucleophile to form five- [8][9] or six-membered rings [7][9][10] (Scheme 1A). Thus far the internal nucleophilic

• on intermediate allyl cation (Scheme 1C). The obtained tetrahydrofuran and pyrrolidine derivatives with highly substituted vinyl side-chains are regarded as privileged structures in medical chemistry [23][24]. Moreover, the resulting styryl functionality (Ph-C=C-) is often found in drug molecules as

• likely formed via the allylic cation intermediate Int-1 (Scheme 2), from where on two competing mechanistic pathways are possible. Deprotonation of the β-H and reductive elimination affords diene 10. Alternatively, an intramolecular cyclization leads to silylindenes 11. We were interested to see whether

Photochemical reduction of acylimidazolium salts

• Michael Jakob,
• Nick Bechler,
• Hassan Abdelwahab,
• Fabian Weber,
• Janos Wasternack,
• Leonardo Kleebauer,
• Jan P. Götze and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2025, 21, 1973–1983, doi:10.3762/bjoc.21.153

• intermediate A (Figure 1a), in which the formerly electrophilic carbonyl carbon reacts as a nucleophilic center. In this way, the traditional reactivity profile of the carbonyl group is transiently inverted, and unconventional product classes are generated. Alternatively, addition/elimination of the NHC to a

• acid derivative substrates [16]. Over the last few years, a wide range of valuable NHC-catalyzed transformations have also been developed that incorporate redox steps. As an enamine species, single-electron oxidation of a Breslow intermediate is comparatively favored with the resulting open shell

• two reduction steps with an initial reaction with the acylazolium starting material being followed by a presumably more challenging second reduction of a less-activated intermediate species. Using CH2Br2 as an internal reference, a 1H NMR yield of 39% was calculated with further analysis of the crude

Asymmetric total synthesis of tricyclic prostaglandin D2 metabolite methyl ester via oxidative radical cyclization

• Miao Xiao,
• Liuyang Pu,
• Qiaoli Shang,
• Lei Zhu and
• Jun Huang

Beilstein J. Org. Chem. 2025, 21, 1964–1972, doi:10.3762/bjoc.21.152

• intermediate 22 (see Supporting Information File 1 for the details). Reasoning that the preferential coordination of the palladium catalyst with the hydroxy group at C15 and the carbonyl group at C18 in compound 22 may have deactivated the palladium catalyst [34], we protected the hydroxy group. Compound 22

• synthesis of 4 was unsatisfactory because it required nine steps to prepare bicyclic intermediate 25 with an overall yield of just 2.0%. This low efficiency prompted us to develop a more streamlined synthetic route for target compound 4. Second generation asymmetric total synthesis of tricyclic-PGDM methyl

• proposed mechanism to 21 involved the formation of an electron-deficient, resonance-stabilized radical species, followed by intramolecular alkylation of the unactivated alkene to generate radical 29 via a diastereoselective 5-exo-trig cyclization step. Radical intermediate 29 was trapped by 2,4,6

Enantioselective desymmetrization strategy of prochiral 1,3-diols in natural product synthesis

• Lihua Wei,
• Rui Yang,
• Zhifeng Shi and
• Zhiqiang Ma

Beilstein J. Org. Chem. 2025, 21, 1932–1963, doi:10.3762/bjoc.21.151

• intramolecular cyclization of 16 generated benzofuran 17 in 83% yield. After protecting the phenolic hydroxy group of 17, cross-metathesis (CM) with allylic alcohol 18 catalyzed by 13 furnished intermediate 19. Desilylation of 19 produced heliannuol G (20) and heliannuol H (21), with the structure of 21

• transformation involving acyl-group migration, [4 + 2] cycloaddition and aromatic Pummerer-type reaction, provided chiral spiro compound 59 with the 6/6/5/5/6/6 scaffold, and this intermediate was further elaborated to 60 in six additional steps. Lipases from Pseudomonas genus Pseudomonas is a genus of Gram

• Takabe and co-workers in their synthesis of (E)-3,7-dimethyl-2-octene-1,8-diol (isolated from Danaus chrysippus) (Scheme 10) [42]. Prepared from geraniol (61) in eight steps, diol 62 was converted to enantioenriched compound 63 in 75% yield with 90% ee in the presence of PSA. This intermediate was

Stereoselective electrochemical intramolecular imino-pinacol reaction: a straightforward entry to enantiopure piperazines

• Margherita Gazzotti,
• Fabrizio Medici,
• Valerio Chiroli,
• Laura Raimondi,
• Sergio Rossi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2025, 21, 1897–1908, doi:10.3762/bjoc.21.147

• methanesulfonic acid, which acts as a strong Brønsted acid to selectively protonate the imine nitrogen atoms. This protonation step increases the electrophilicity of the adjacent imine carbons by inductive effect, leading to the formation of a highly reactive diiminium intermediate 4a. When formed, compound 4a is

• electrochemically reduced to give the carbon-centered diradical intermediate 5a and the spatial proximity of these two radical centers allows a rapid intramolecular radical–radical coupling resulting in the formation of the desired piperazine 2a. The feasibility of this mechanism is supported by literature

• initiation of the SET reduction process, which leads to the consumption of the diiminium salt 4a and to the formation of the diradical intermediate 5a. Conclusion In conclusion, we have successfully developed a simple and mild electroreductive, stereoselective intramolecular coupling of aromatic diimines

Preparation of spirocyclic oxindoles by cyclisation of an oxime to a nitrone and dipolar cycloaddition

• Beth L. Ritchie,
• Alexandra Longcake and
• Iain Coldham

Beilstein J. Org. Chem. 2025, 21, 1890–1896, doi:10.3762/bjoc.21.146

• possibility to access the core of this ring system with the nitrone intermediate shown in Scheme 1A. As a model study, we describe here efforts towards an intermolecular variant with the oxindole shown in Scheme 1B; in this case a leaving group X will be displaced by the oxime to give an intermediate nitrone

Chiral phosphoric acid-catalyzed asymmetric synthesis of helically chiral, planarly chiral and inherently chiral molecules

• Wei Liu and
• Xiaoyu Yang

Beilstein J. Org. Chem. 2025, 21, 1864–1889, doi:10.3762/bjoc.21.145

• interactions with the enehydrazine intermediate, which is essential for achieving high levels of stereocontrol. Using the optimal catalyst CPA 1, a series of aza[6]helicenes 3a,b was synthesized with excellent enantioselectivity and high yield. However, this method demonstrated notably reduced efficiency and

• acid substrates 43 which, upon treatment with ynamide 44, yielded the vinyl acetate intermediate INT-A (Scheme 13). Subsequently, the one-pot CPA-catalyzed intramolecular esterification of this intermediate afforded the planarly chiral macrocycles 45 with good yield and high enantioselectivity

• 71 yielded the cyclic intermediate INT-B, which then underwent addition with aniline co-catalyst 73 to form INT-C. The CPA-enabled release of CO2 from INT-C yielded the imine-containing intermediate INT-D, which underwent iterative addition with INT-B, followed by release of CO2 to afford INT-E. The

Systematic pore lipophilization to enhance the efficiency of an amine-based MOF catalyst in the solvent-free Knoevenagel reaction

• Pricilla Matseketsa,
• Margret Kumbirayi Ruwimbo Pagare and
• Tendai Gadzikwa

Beilstein J. Org. Chem. 2025, 21, 1854–1863, doi:10.3762/bjoc.21.144

• and the amine catalyst (Scheme 1A) [47][48]. However, there is another possible mechanism where malononitrile is deprotonated by the amine catalyst. Here, the resulting carbanion would attack benzaldehyde to form 2-(hydroxy(phenyl)methyl)malononitrile (HPMM) as an intermediate that then loses a water

• intermediate depending on the lipophilicity of the pores. Under solvent-free conditions, we observed the formation of 2-(hydroxy(phenyl)methyl)malononitrile (HPMM, Figure 5), an intermediate which is subsequently dehydrated to yield the main product (BMN) as the reaction progresses [53]. Looking at the ratio

• of final product to intermediate (BMN:HPMM), we observed that relatively more of the hydroxy intermediate was observed with the unfunctionalized KSU-1 catalyst (Figure 5) when compared to the lipophilicized catalysts, with the amount of HPMM decreasing with increasing aliphatic chain surface area

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

• -nitrobenzyl bromide (47) with 50 or with 52, after its reduction with NaBH4. The intermediate products are then treated with lead in a buffered basic environment to get the final product in low yield accompanied by two by-products, 54a,b. For the O-heterodiazocine, reduction with triphenylphosphine and a

Fe-catalyzed efficient synthesis of 2,4- and 4-substituted quinolines via C(sp²)–C(sp²) bond scission of styrenes

• Prafull A. Jagtap,
• Manish M. Petkar,
• Vaishnavi R. Sawant and
• Bhalchandra M. Bhanage

Beilstein J. Org. Chem. 2025, 21, 1799–1807, doi:10.3762/bjoc.21.142

• the FeIII species. An alternative mechanism involving a concerted [4 + 2] cycloaddition between the aza-butadiene moiety in II and the alkene, leading to intermediate IV, cannot be ruled out. Conclusion In summary, we have successfully developed a highly efficient method for the oxidative C–C bond

Synthesis of chiral cyclohexane-linked bisimidazolines

• Changmeng Xi,
• Qingshan Sun and
• Jiaxi Xu

Beilstein J. Org. Chem. 2025, 21, 1786–1790, doi:10.3762/bjoc.21.140

• nucleophilically attacks the phosphonium in A to generate intermediate B by loss of triphenylphosphine oxide and triflic acid. The nucleophilic sulfonamide in B intramolecularily attacks the generated imine moiety in B to form intermediate C, in which triflic acid may protonate the imine moiety in B to assist the

• nucleophilic attack. Intermediate C further transforms to imidazoline product 5 by loss of triphenylphosphine oxide and triflic acid. Conclusion Both chiral bisoxazolines and bisimidazolines are efficient and widely applied chiral ligands in metal-catalyzed asymmetric organic reactions. Several chiral

Preparation of a furfural-derived enantioenriched vinyloxazoline building block and exploring its reactivity

• Madara Darzina,
• Anna Lielpetere and
• Aigars Jirgensons

Beilstein J. Org. Chem. 2025, 21, 1737–1741, doi:10.3762/bjoc.21.136

• ][24] (Scheme 1). The proposed strategy relied on the N-deprotection of the intermediate ester 3d inducing O-to-N rearrangement to form amide 5 as a precursor of vinyloxazoline 6. For this purpose, Alloc (allyloxycarbonyl) turned out to be a suitable N-protecting group as it was compatible with the

• oxidation in methanol in batch electrolysis conditions, providing unsaturated esters S-3d and R-3d, respectively (Scheme 2). The previously used one-reactor two-step conditions were found to be productive for the electrosynthesis of S-3d, requiring the addition of acetic acid for the intermediate spiroketal

• -wise process [22]. The first step involves addition of the oxazoline nitrogen to TsNCO leading to a zwitterionic intermediate A, which undergoes 1,4-conjugate addition forming a cyclic intermediate B. Subsequently, the electron-rich double bond in intermediate B reacts with a second equivalent of TsNCO