Electrochemical radical cation aza-Wacker cyclizations

• Sota Adachi and
• Yohei Okada

Beilstein J. Org. Chem. 2024, 20, 1900–1905, doi:10.3762/bjoc.20.165

• reactions rather than ionic ones, since five-membered pyrrolidine formation is preferred over six-membered piperidine formation. Further mechanistic studies of the electrochemical radical cation aza-Wacker cyclizations are underway in our laboratory. Experimental Electrochemical aza-Wacker cyclizations: The

• mmol), Bu4NOTf (0.1 M), TFA (1 equiv), CH3CN (0.4 mL), and 1,2-DCE (3.6 mL). Yields reported here are isolated yields. Mechanistic studies of aza-Wacker cyclization. A: Electrochemical (Bu4NOTf in CH3CN/1,2-DCE), B: non-electrochemical (LiClO4 in CH3NO2). Control studies for electrochemical aza-Wacker

Electrophotochemical metal-catalyzed synthesis of alkylnitriles from simple aliphatic carboxylic acids

• Yukang Wang,
• Yan Yao and
• Niankai Fu

Beilstein J. Org. Chem. 2024, 20, 1497–1503, doi:10.3762/bjoc.20.133

• , in an undivided cell, at 2.3 V cell potential, 400 nm LEDs, for 12 hours. a2,4,6-Collidine (1.0 equiv) was used instead of BTMG. bPhen was used instead of BPhen. cDMF/CH3CN (1:15 v/v) was used as solvent. dReactions were run with 0.4 mmol LiClO4 instead of TBABF4. Mechanistic studies and proposed

• catalytic cycles. Reaction discovery and optimization.a Supporting Information Supporting Information File 18: Experimental procedures, mechanistic studies, analytical data and copies of NMR spectra. Funding We thank the National Natural Science Foundation of China (No. 22071252) and the Chinese Academy

Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer

• Mohd Farhan Ansari,
• Atul Kumar Maurya,
• Abhishek Kumar and
• Saravanakumar Elangovan

Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98

• 110 °C for 16 h), moderate to good yields of N-methylamines were produced (Scheme 15). The mechanistic studies suggested that the base activates the complex Mn3. The active catalyst dehydrogenates methanol into formaldehyde and converts nitroarenes to anilines via transfer hydrogenation. The latter

Direct synthesis of acyl fluorides from carboxylic acids using benzothiazolium reagents

• Lilian M. Maas,
• Alex Haswell,
• Rory Hughes and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2024, 20, 921–930, doi:10.3762/bjoc.20.82

• different amides, including dipeptides, under mild and operationally simple conditions in high yields. Mechanistic studies suggest that BT-SCF3 can generate acyl fluorides from carboxylic acids via two distinct pathways, which allows the deoxyfluorinating reagent to be employed in sub-stoichiometric amounts

• under mild and operationally simple conditions while peptide coupling between two amino acids could be efficiently conducted using the longer-chain perfluoroalkyl reagent BT-SC5F11. Mechanistic studies revealed that each equivalent of the benzothiazolium reagent can feasibly generate two equivalents of

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• radical D which is then trapped by TsCl to produce the corresponding alkyl chloride E. Detailed mechanistic studies on a related reaction were recently reported by Shenvi and co-workes [84]. These studies alternatively suggest that intermediate C could also be the result not of a non-simultaneous addition

Palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines

• Geng-Xin Liu,
• Xiao-Ting Jie,
• Ge-Jun Niu,
• Li-Sheng Yang,
• Xing-Lin Li,
• Jian Luo and
• Wen-Hao Hu

Beilstein J. Org. Chem. 2024, 20, 661–671, doi:10.3762/bjoc.20.59

• amine and the traces amount of water in this reaction system may serve as proton sources for the formation of hybrid α-ester alkylpalladium radical. On the basis of above mechanistic studies and previous reports [47][48][49][50][52][58], the following plausible mechanisms are proposed for the palladium

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• and unsymmetrical N,N'-substituted alkyl- and arylindigos with tunable thermal half-lives (follow-up mechanistic studies in 2022) 2018: first report on photochromic monoarylated indigos Synthesis of indigo derivatives Indigo (Ind) is one of the oldest organic molecules, which has been used as a dye

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

• photoredox radical reactions are relatively scarce [52], representing an unexplored area that requires further investigation. Developing asymmetric methodologies in this domain holds great promise for future exploration. Last but not the least, conducting detailed mechanistic studies on iodide/phosphine

Morpholine-mediated defluorinative cycloaddition of gem-difluoroalkenes and organic azides

• Tzu-Yu Huang,
• Mario Djugovski,
• Sweta Adhikari,
• Destinee L. Manning and
• Sudeshna Roy

Beilstein J. Org. Chem. 2023, 19, 1545–1554, doi:10.3762/bjoc.19.111

• gem-difluoroalkenes with organic azides in morpholine as a solvent to construct fully decorated morpholine-substituted 1,2,3-triazoles. Mechanistic studies revealed the formation of an addition–elimination intermediate of morpholine and gem-difluoroalkenes prior to the triazolization reaction via two

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• pyrrolines 62 were obtained by changing the reaction solvent to MeCN. Also, organic fluorophore compounds such as benzothienopyrrole and bis-thiolated boron dipyrromethene can be achieved from 3-thiolated pyrroles. Mechanistic studies showed that the oxidative species HNO and HCHO were generated through a

• conversion of 1-I to 2-II was confirmed by mechanistic studies due to the stability of the benzyl carbocation, followed by 6-endo-dig cyclization. In this method, toxic transition metal catalysts, oxidants, or bases are not used, which made it economically and environmentally reliable. In 2023, Gao et al

• is no need to use a metal catalyst, base, or additive. N-(Sulfenyl)succinimide/phthalimide acted as an active electrophilic sulfur source, acted in the reaction mechanisms. However, mechanistic studies need further exploration to define a valid reaction pathway. Therefore, we believe that the use of

Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• form new C–Cl bonds in the presence of transient alkyl radicals, with mechanistic studies implicating homolytic abstraction of a chlorine ligand from the intermediate copper complex. Outside of the substitution products which could be generated from the RLT pathway, alkyl radicals could also undergo an

• simplified manganese salen complex I, allowing for the identity of the carbon–heteroatom bond to be controlled based on added nucleophile and enabling C–Cl, C–N, and C–S bonds to be formed directly while completely suppressing traditional ATRA products [9]. In mechanistic studies, rearrangement products

• adventitious discovery of nitrate functioning as a mild and selective oxidant in RLT catalytic systems presents many opportunities for future method development and are avidly pursuing this area of research. Outlook After scant exploration following its elucidation in early mechanistic studies of bioinorganic

Unravelling a trichloroacetic acid-catalyzed cascade access to benzo[f]chromeno[2,3-h]quinoxalinoporphyrins

• Chandra Sekhar Tekuri,
• Pargat Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2023, 19, 1216–1224, doi:10.3762/bjoc.19.89

• , copper(II) benzo[f]quinoxalinoporphyrin 17 for the mechanistic studies. On photophysical evaluation, the newly synthesized porphyrins displayed significant red-shifted absorption and emission as compared to simple meso-tetraarylporphyrins due to the extended π-electronic conjugation. Hence, the present

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• quenching study (Scheme 3F), expressed that the photoredox reaction started with the reductive generation of a malonyl radical from bromomalonate by interaction with the photocatalyst. Analyzing all the observations from the above mechanistic studies, we propose a plausible mechanism involving sequential

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• their control experiments and literature mechanistic studies (Chegondi et al.) [84], the role of the base (LiOt-Bu) was considered. Following the Cu-catalyzed conjugate addition of B2pin2, the Michael cyclization is facilitated by the transmetalation of stoichiometric Li base with the Cu enolate (Scheme

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• -trifluoromethyl substituent forming the ketone product in <10% yield. While substitution of the norbornene was tolerated, both EWGs and EDGs hindered the reaction. Upon several mechanistic studies, the authors proposed the catalytic cycle begins with the oxidative addition of the active Ni(0) catalyst to imide 27

• typically problematic in C–H activation reactions. Through mechanistic studies, the authors proposed the rate limiting step for this reaction is the C–H cleavage. In 2015, Miura and co-workers reported the Rh-catalyzed domino dehydrative naphthylation of oxabenzonorbornadienes 30 with arylphosphine

Transition-metal-catalyzed C–H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

• Louis Monsigny,
• Floriane Doche and
• Tatiana Besset

Beilstein J. Org. Chem. 2023, 19, 448–473, doi:10.3762/bjoc.19.35

• isolated in 70% yield. Mechanistic studies indicated that the C–H bond activation event was the rate-limiting step and the authors suggested a similar mechanism to the one depicted in Scheme 20: formation of a palladacycle thanks to a concerted metalation deprotonation (CMD) process followed by oxidation

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• -depth mechanistic studies were so far reported regarding the reactivity of the enol phosphate electrophiles (Scheme 3 and Scheme 4, and Table 2, entry 4). Phosphate free anions released at each catalytic cycle could act either as NMP or alkoxides, that is, as ligands to the magnesium cations, or as

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• analysis of lactam 19l. In order to shed light on the details of the reaction mechanism, we have performed carefully designed mechanistic studies which consist of experiments on the effect of β-silicon stabilization, the alkene geometry of the α,β-unsaturated acyl chloride reactants, and adventitious water

• catalytic aza-Nazarov reaction starting from cyclic and acyclic imines and TMS-substituted α,β-unsaturated acyl chlorides to yield α-methylene-γ-lactam heterocycles with high diastereoselectivities. We also report the results of our detailed mechanistic studies along with the necessary control experiments

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

• intermediate radical reduction. The observed diastereoselectivity can be rationalized by referring to earlier mechanistic studies [79]. The same (−)-configured intermediate 147 was utilized in a HAT-initiated oxidation to access (−)-minovincinine (150) in 38% yield after deprotection (Scheme 12). Interestingly

Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• products that can be purified by SiO2 column chromatography, other noteworthy advantages are the possibility of isolating side products that may aid in mechanistic studies, and the recyclability and robustness of the SiO2 columns. One of the main issues that can be found with this purification technique is

Characterization of a new fusicoccane-type diterpene synthase and an associated P450 enzyme

• Jia-Hua Huang,
• Jian-Ming Lv,
• Liang-Yan Xiao,
• Qian Xu,
• Fu-Long Lin,
• Gao-Qian Wang,
• Guo-Dong Chen,
• Sheng-Ying Qin,
• Dan Hu and
• Hao Gao

Beilstein J. Org. Chem. 2022, 18, 1396–1402, doi:10.3762/bjoc.18.144

• ]. Conclusion We have identified a new fungal FC-type DTS, which is responsible for the biosynthesis of talaro-7,13-diene (1). Further mechanistic studies revealed that 2,6-cyclization in the formation of 1 is likely to be triggered by protonation of the neutral intermediate 3, and Tyr91 in TadA plays a

B–N/B–H Transborylation: borane-catalysed nitrile hydroboration

• Filip Meger,
• Alexander C. W. Kwok,
• Franziska Gilch,
• Dominic R. Willcox,
• Alex J. Hendy,
• Kieran Nicholson,
• Andrew D. Bage,
• Thomas Langer,
• Thomas A. Hunt and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2022, 18, 1332–1337, doi:10.3762/bjoc.18.138

• relies upon stoichiometric reagents or transition-metal catalysis. Herein, a borane-catalysed hydroboration of nitriles to give primary amines is reported. Good yields (48–95%) and chemoselectivity (e.g., ester, nitro, sulfone) were observed. DFT calculations and mechanistic studies support the proposal

• is proposed to serve as the key turnover step in catalysis, supported by computational mechanistic studies. This approach uses both a commercially-available catalyst and turnover reagent, providing good user accessibility, and displays comparable chemoselectivity to current state-of-the-art catalysed

A one-pot electrochemical synthesis of 2-aminothiazoles from active methylene ketones and thioureas mediated by NH₄I

• Shang-Feng Yang,
• Pei Li,
• Zi-Lin Fang,
• Sen Liang,
• Hong-Yu Tian,
• Bao-Guo Sun,
• Kun Xu and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2022, 18, 1249–1255, doi:10.3762/bjoc.18.130

• ) should be a key intermediate for this tandem reaction. On the basis of the above mechanistic studies and the previous works on iodide-mediated electrochemical transformation [37][38][39][40], a possible mechanism for this electrochemical reaction was proposed (Scheme 5). It is well known that amino acid

Electrochemical hydrogenation of enones using a proton-exchange membrane reactor: selectivity and utility

• Koichi Mitsudo,
• Haruka Inoue,
• Yuta Niki,
• Eisuke Sato and
• Seiji Suga

Beilstein J. Org. Chem. 2022, 18, 1055–1061, doi:10.3762/bjoc.18.107

• 72% yield with good selectivity (89%). Both 1f and 1g could be used in this reactions, and the corresponding alcohols 3f and 3g were obtained as major products. Mechanistic studies To gain further insight into the reaction mechanism of the chemoselectivity of a Pd/C cathode system, some additional

• . Charge was passed to the circulated solution until 1 was consumed. The yield was determined by GC analysis using n-dodecane as an internal standard. Values in parentheses show the chemoselectivity of 3, which was calculated as yield of 3 / yield of (2 + 3). Mechanistic studies. Electroreduction of 1a