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

• a wide range of transformations [7][8]. Moreover, they proposed a plausible mechanism for the aforementioned conversions (Scheme 2). Initially, an NaI/PPh3 complex I was formed through a cation–π interaction. Subsequently, the combination of complex I with N-(cyclohexanecarbonyloxy)phthalimide

Selectivity control towards CO versus H₂ for photo-driven CO₂ reduction with a novel Co(II) catalyst

• Lisa-Lou Gracia,
• Philip Henkel,
• Olaf Fuhr and
• Claudia Bizzarri

Beilstein J. Org. Chem. 2023, 19, 1766–1775, doi:10.3762/bjoc.19.129

• (helping in the deprotonation of the radical cation BIH•+ formed after the reductive quenching of the PS), but also can actively assist the catalysis, by capturing CO2 [50][51][52]. On the other hand, having three hydroxy groups, TEOA is also considered a proton donor and the formation of metal hydrides is

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

• Swagat K. Mohapatra,
• Khaled Al Kurdi,
• Samik Jhulki,
• Georgii Bogdanov,
• John Bacsa,
• Maxwell Conte,
• Tatiana V. Timofeeva,
• Seth R. Marder and
• Stephen Barlow

Beilstein J. Org. Chem. 2023, 19, 1651–1663, doi:10.3762/bjoc.19.121

• and 1,3-dimethyl substituents in pseudo-equatorial positions and the reactive hydridic 2-H-atom pesudo-axial. The cation structures (Figure 5) give some insight into the variety of dopant-ion shapes and sizes that can be afforded by these types of dopants. The angle between the imidazolium ring and

• -membered rather than six-membered aromatic ring, the structure of 1i+PF6− contains a somewhat more planar cation (31.9°). Finally, we note that the new structures reported here mean that the 1b and 1h systems join the 1c (Y = Fc; R = R' = H) system [50] as families for which 1+, 1H, and 12 members are all

• since 4-(dimethylamino)phenyl and metallocenyl groups are π-donors, unlike cyclohexyl, and thus might be expected to be better able to stabilize an adjacent cation. However, aryl and metallocenyl substituents also stabilize adjacent radicals more effectively than alkyl groups and this effect is

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• cation and crown ether pocket, dimerisation of the crown porphyrin molecule would occur. The dimerisation led to interesting changes in the visible, NMR, ESR, and emission spectral features. Further developments by Camilleri, Gunter, Boitrel, and Osuka focused on the exploitation of meso-crowned

• -capped calix[4]pyrrole cavitand 4. The heteroditopic receptor had multiple binding sites, proving efficient in encapsulating a CsF ion pair. The calix[4]arene-crown-6-capped pocket was exploited as an excellent binding site for the Cs+ cation, whereas the calix[4]pyrrole was aligned to trap the fluoride

• separation between the cation and anion. Sessler and co-workers introduced a similar ion-pair receptor, in which the calix[4]arene-strapped calix[4]pyrrole 5 demonstrated an additional binding mode of CsF (Figure 5). The binding constant Ka = 1.3·104 M−1 in CHCl3/MeOH 9:1 was reported [101][102]. This

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• necessary. MF-ROMP, also termed photo-ROMP, is a novel technique to polymerize cyclic olefins. It begins with the reductive quenching of an photoexcited photocatalyst (PC) at an enol ether initiator to produce a radical cation carrier [90]. Then, the carrier undergoes cyclic addition with a cyclic olefin

• monomer to generate a cyclobutene radical cation intermediate. The thermodynamically instable intermediate subsequently forms the propagating radical cation species via a ring-opening process. The reduced PC•− terminates the catalytic loop by reducing the propagating species to provide a polymer chain

Unraveling the role of prenyl side-chain interactions in stabilizing the secondary carbocation in the biosynthesis of variexenol B

• Moe Nakano,
• Rintaro Gemma and
• Hajime Sato

Beilstein J. Org. Chem. 2023, 19, 1503–1510, doi:10.3762/bjoc.19.107

• possibility of through-space interactions with prenyl side chains using DFT calculations. Our calculations show that (i) the unstable secondary carbocation is stabilized by the cation–π interaction from prenyl side chains, thereby lowering the activation energy, (ii) the four-membered ring formation is

• completed through bridging from the exomethylene group, and (iii) the annulation from the exomethylene group proceeds in a barrier-free manner. Keywords: biosynthesis; carbocation; cation–π interaction; DFT; terpene; Introduction Terpene/terpenoids are most abundant natural products in nature, more than

• as the C–H–π interaction between the carbocation intermediate and the Phe residue of terpene cyclase in the biosynthesis of sesterfisherol [21], and the intricated rearrangement reaction mechanism promoted by the equilibrium state of the homoallyl cation and the cyclopropylcarbinyl cation in the

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

• sulfur atom to Fe3+ to generate Fe2+ and radical cation I. Subsequent cleavage of the N–S bond led to cation II and radical III. Interaction of III with Fe2+ regenerated the Fe3+ species and IV. At the same time, electrophilic addition of II to alkene 9 yielded intermediate V, which was subjected to the

• (PIDA) and meta-chloroperbenzoic acid (m-CPBA) toward 3-sulfinylated and 3-sulfonylated product, respectively, were performed in this work. A plausible mechanism involves the treatment of 1 with BF3·Et2O toward cation I, which reacted with the C–C triple bond in 12 to give sulfonium intermediate II

• or 14, caused polarization of the S–N bond and produced an electrophilic intermediate I. Through the nucleophilic attack of the alkyne on I, cation II was generated, leaving Al-coordinated phthalimide/succinimide III. Finally, 4-endo-trig spirocyclization of II rendered the unstable intermediate IV

Cyclization of 1-aryl-4,4,4-trichlorobut-2-en-1-ones into 3-trichloromethylindan-1-ones in triflic acid

• Vladislav A. Sokolov,
• Andrei A. Golushko,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2023, 19, 1460–1470, doi:10.3762/bjoc.19.105

• delocalization of the positive charge from the carbonyl group to the aromatic ring. It should be mentioned that cation Bm was generated by two ways in TfOH: either directly by protonation of enone 2m or from hydroxy ketone 1m. The latter was found to undergo fast dehydration into enone 2m in TfOH at room

• analogously to cation Ba. The cyclization of dication Aa into indanone 3a is very favorable (ΔG298 = −101.3 kJ/mol). However, the formation of both enones 2 and indanones 3 from hydroxy ketones 1 is observed in TfOH (Table 1). We assume that, at first, hydroxy ketones 1 undergo dehydration into enones 2

• C1 (0.60 e). This carbon atom gives 14.9% contribution to the LUMO. Contrary to that, the carbon C3 bears no positive charge (−0.13 e) and contributes 12.1% to the LUMO. The intramolecular cyclization of cation Ba takes place between the atom C3 and the ortho-carbons of the phenyl ring. Thus

Functional characterisation of twelve terpene synthases from actinobacteria

• Anuj K. Chhalodia,
• Houchao Xu,
• Georges B. Tabekoueng,
• Binbin Gu,
• Kizerbo A. Taizoumbe,
• Lukas Lauterbach and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 1386–1398, doi:10.3762/bjoc.19.100

• 26 can be well understood from the cyclisation mechanism towards 23 (Scheme 1B). After substrate ionisation to A a 1,10-cyclisation leads to the (E,E)-germacradienyl cation (B) that can either be deprotonated to 24 or captured with water to yield 26. Both compounds are important neutral intermediates

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

• cesium cation with the halogen atom and the activation of the Sn–O bond of the stannylene acetal via a pentacoordinated intermediate with the fluoride anion [110]. The acetylation of the secondary alcohol and the deprotection of the primary alcohol with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• -methylisochroman, 3-methoxyanisole). Mechanism experiments showed that the coupling of aromatic ring radicals with ether oxygen ions produced an intermediate radical cation, which achieves a catalytic cycle through the Cu center. Lee et al. disclosed TBHP as an oxidant and Pd(OAc)2/Cu(OTf)2 as the catalyst to

• ) process, the carbocation intermediate B is generated, which is attacked by a nucleophile to afford the target product. Further, C–H bonds in the ortho-position of a heteroatom are activated through a SET pathway generating a radical cation C, which is easily deprotonated by an oxidant to generate a

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• proposed that electron donor–acceptor (EDA) complex 36 was initially formed between 32 and a sacrificial equivalent of 31, and that 36 underwent a SET to give radical anion 37 and radical cation 38 (Figure 8). While one equivalent of the ylide orchestrated a series of proton transfer (PT) and SET events

Selective and scalable oxygenation of heteroatoms using the elements of nature: air, water, and light

• Damiano Diprima,
• Hannes Gemoets,
• Stefano Bonciolini and
• Koen Van Aken

Beilstein J. Org. Chem. 2023, 19, 1146–1154, doi:10.3762/bjoc.19.82

• on the rate than acids and bases and both the anion and cation appear to influence the reaction kinetics. A deliberate choice of salt can either significantly improve the kinetics or quench the reaction. The latter might be exploited e.g., in late-stage functionalization strategies in order to

• originates from water. In this tentative mechanism, the sulfide I forms with water and oxygen a photoactive complex II which is excited at 365 nm towards III. Via single-electron transfer both a radical cation IV and the superoxide V are generated. Subsequently, the sulfide radical cation IV undergoes a

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

• radical anion or radical cation. As a semi-stable, higher energy ground-state entity, this can accumulate in sufficient concentration under the reaction conditions to absorb another photon and thereby generate a super-reducing or super-oxidizing excited state (Figure 2 left). In addition to ‘radical ion

• -BF4 as a suitable conPET catalyst. Following the conPET catalytic cycle, the Mes-Acr+ cation is excited and reductively quenched by DIPEA to yield the acridine radical Mes-Acr• (Figure 10C) [54]. Upon excitation to its twisted intramolecular charge-transfer (TICT) state, Mes-Acr• has an excited-state

• oxidizing this radical to the corresponding cation. In the presence of Et3N, [FeIII(btz)3]3+ is reductively quenched after excitation to its 2LMCT excited state to generate [FeII(btz)3]2+ (equivalent to PC•− in the classical conPET mechanism) (Figure 20C). [FeII(btz)3]2+ is excited again to the more

Synthesis of tetrahydrofuro[3,2-c]pyridines via Pictet–Spengler reaction

• Elena Y. Mendogralo and
• Maxim G. Uchuskin

Beilstein J. Org. Chem. 2023, 19, 991–997, doi:10.3762/bjoc.19.74

• rearrangement to a more stable benzhydryl-type cation resulting in the formation of isomeric products. In an alternative group of methods, more accessible 2-substituted furans are used as starting compounds. For example, a construction of tetrahydrofuro[3,2-c]pyridines based on the Pictet–Spengler reaction [17

• ][18] was described (Scheme 1c). The most studied variation of this cyclization is based on the generation of an acyliminium cation from the corresponding alcohols [19][20][21][22][23] or alkenes [24][25][26][27][28][29], subsequent attack of furan ring and the formation of annulated tetrahydrofuro[3,2

• -c]pyridines. Moreover, multistep cascade processes with the simultaneous construction of several cores were described, where the key step is the generation of an acyliminium cation and the Pictet–Spengler cyclization [30][31][32], including solid-phase synthesis [33][34][35]. Another route for the

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• dehydration to generate isoxazolium cation 80 paired with a phosphate anion. This chiral phosphate is engaged in H-bonding with the free NH of the heteroarene ring to ease the stereoselective 1,2-addition to in situ generate the cationic heterocyclic scaffold 81. The reaction proceeded faster with pyrroles

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• adjacent strong Lewis acid sites, and the acidity of these Lewis acid sites is due to the inductive effect of sulfate on the metallic cation. Therefore, this nano-sulfated titanium dioxide acts as a new type of Lewis acid catalyst. Intermediate A was first formed by reaction of the catalyst with 2,5-DMTHF

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• selectively targeted by photoredox catalysis to enable unprecedented modification of the amino acid. In this context, it is worth mentioning that the single-electron oxidation of the indole moiety in tryptophan provides the radical cation, which enables selective C-radical generation at the weaker benzylic

• proton transfer from the oxidized indole radical cation [75], generated by SET from the activated photocatalyst. The α-amino radical generated by reductive decarboxylation of a DMAT derivative with a redox-active ester (−1.26 V to −1.37 V vs a saturated calomel electrode) would enable turnover of the

• a tentative mechanism (Figure 2). First, the radical cation I was generated via the oxidation of indole 5 by the excited Ir-based photocatalyst, followed by sequential regioselective proton transfer on the benzylic dimethylallyl unit C–H bond of the C4 side-chain, thereby generating II. Here, the

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• reactive allenes (reaction e), which serve as synthetic intermediates for polyfunctionalized enynes [8]. The ring strain of the cyclopropane ring facilitates the cleavage of the C–C bond, and both cation and anion are stabilized by the adjacent phenyl group and ester functions, respectively (reaction f

• proceeded, to produce furan 13 with a 46% yield (Scheme 6). The coordination of two carbonyl groups to the tin species facilitated the ring opening of the cyclopropane ring to afford betaine [7], then the oxygen atom of the enolate attacked the benzyl cation to construct a five-membered ring. The subsequent

A fluorescent probe for detection of Hg²⁺ ions constructed by tetramethyl cucurbit[6]uril and 1,2-bis(4-pyridyl)ethene

• Xiaoqian Chen,
• Naqin Yang,
• Yue Ma,
• Xinan Yang and
• Peihua Ma

Beilstein J. Org. Chem. 2023, 19, 864–872, doi:10.3762/bjoc.19.63

• + ions [34]. Because of the synergistic combination of Q[8], SQ2 and Hg2+ ions, it shows fluorescence quenching. Cong's group found that Q[7] can encapsulate the benzimidazole part of N-(2-benzimidazolylmethyl)-N,N-bis(2-pyridylmethyl)amine cation (BIBPA+) to construct a host–guest fluorescent probe. The

• ability of the probe to detect Hg2+ ions The metal cation interference experiment was used to investigate whether the G@TMeQ[6] fluorescent probe can selectively detect Hg2+ ion in the presence of other metal cations (Figure 6). The fluorescence intensity of the system was determined by adding other metal

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

• Mg enolates generated from cyclic and linear enones 1 and 85 and enoyloxazolidinones 87. Apart from the most robust tropylium and benzodithiolium cations, reactions were also possible with the dianisylmethylium cation. Interestingly, tritylium cations reacted only in the para-position of a phenyl

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• dimerization of the Schiff base complex and the radical cation formed under one-electron electrochemical oxidation will be sufficiently stable, opening a route to further oxidative modification of the amino acid side chain under appropriate conditions. Additionally, this bulky group may significantly alter the

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• signalize complex formation (interaction with a biomolecule, cyclodextrine, metal cation, etc.) or change of receptor conformation [5][6]. Employment of pyrene as a biosensor is complicated due to its large aromatic surface's hydrophobicity and fluorescence sensitivity to oxygen. Therefore, modifications of

• further promoted by favorable cation–π interactions. In other words, in Phen-Py-1+ and Phen-Py-2+, stacked structures account for around 96% and 98% of population, respectively, while in unionized Phen-Py-1 and Phen-Py-2 these cluster around 84% in both cases (Figure 2). This is further supported by

• that a higher degree of aromatic surfaces overlapping and cation–π interactions also yield excimer fluorescence quenching [30][32][33]. This conclusion is strongly in line with experimental insight reported here and helps in explaining the observed excimer fluorescence quenching with a decrease in the

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

• photoexcitation of the photosensitizer 43 to form 44 which can oxidize aniline 36a to give radical cation 46 (Scheme 7). Deprotonation by DBU produces the radical 40. The radical anion photosensitizer 45 can reduce Ni(I) to Ni(0), closing the first catalytic cycle. The Ni(0) complex can undergo oxidative addition