Visible-light-induced nickel-catalyzed α-hydroxytrifluoroethylation of alkyl carboxylic acids: Access to trifluoromethyl alkyl acyloins

• Feng Chen,
• Xiu-Hua Xu,
• Zeng-Hao Chen,
• Yue Chen and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2023, 19, 1372–1378, doi:10.3762/bjoc.19.98

• of H2O were added to the reaction mixture [40] (Table 1, entry 6), but the addition of more water did not improve the reaction efficiency further (Table 1, entry 7). The structure of nickel catalysts played a significant role in the reaction efficiency. Switching the Ni catalyst to NiCl2(dtbbpy

• light-induced charge transfer event to give trifluoroethoxyl radical B, followed by a 1,2-hydrogen atom transfer (HAT), producing the stable radical C. For the nickel cycle, it is initiated by oxidative addition of Ni(0) catalyst E to acyl electrophile D formed in situ from carboxylic acid 1 with

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

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

• involves a hydride abstraction from the benzylic site of isochroman to generate a cationic species A, whereas the malonate is activated by the In/Cu catalyst (B). Subsequently, the coupling of the two intermediates yields the desired product and regenerates the catalyst. Alternatively, In(III) may be

• involved in the activation of DDQ by coordinating the carbonyl oxygen atom which leads to an increase in the oxidation activity of DDQ. Subsequently, Li et al. improved the above method, using a mixture of indium and copper salts as a catalyst, NHPI (N-hydroxyphthalimide) as a co-catalyst to achieve the

• triggers the whole coupling reaction. The potential application of NHIP as a catalyst for oxidative coupling reactions with oxygen as a terminal oxidant was explored. In 2011, Garcia-Mancheño et al. developed a Cu-catalyzed CDC of cyclic benzyl ethers 10 with aliphatic or α,β-unsaturated aldehydes 13 or 14

Metal catalyst-free N-allylation/alkylation of imidazole and benzimidazole with Morita–Baylis–Hillman (MBH) alcohols and acetates

• Olfa Mhasni,
• Jalloul Bouajila and
• Farhat Rezgui

Beilstein J. Org. Chem. 2023, 19, 1251–1258, doi:10.3762/bjoc.19.93

• 5a [27] as the model substrate bearing a good leaving group, with imidazole (2a, 2 equiv) as a powerful nucleophilic reagent. The reaction was achieved with no need of a catalyst or any additive in toluene at reflux affording within 24 h the SN2-type product 6a in 82% yield (Table 1, entry 1

• , the use of DABCO, commonly used as a powerful catalyst or a nucleophilic additive in the reaction of acyclic MBH adducts with various nucleophiles [21][34][35][36][37], did not afford the SN2/SN2’ products but provided the 1,4-adduct 8a in 84% yield (Table 2, entry 4). Alternatively, we also

• investigated the reaction of alcohol 1a [38] and imidazole (2a, 2 equiv), without any catalyst or additive in refluxing methanol, a solvent commonly employed in the conversion of MBH adducts using a variety of amines [39][40]. Our study showed that the imidazole (2a) reacted with alcohol 1a, without any

Acetaldehyde in the Enders triple cascade reaction via acetaldehyde dimethyl acetal

• Alessandro Brusa,
• Debora Iapadre,
• Maria Edith Casacchia,
• Alessio Carioscia,
• Giuliana Giorgianni,
• Giandomenico Magagnano,
• Fabio Pesciaioli and
• Armando Carlone

Beilstein J. Org. Chem. 2023, 19, 1243–1250, doi:10.3762/bjoc.19.92

• intercepts the nitroalkene 3 in a Michael-type addition forming intermediate B. Hydrolysis regenerates catalyst 1 that can then selectively condense with the α,β-unsaturated aldehyde 4 to form chiral iminium ion intermediate C. Iminium ion C reacts with intermediate B in a further Michael-type reaction. The

• last step involves the enamine intermediate which drives an intramolecular aldol condensation to form the final product 5. In this elegant cascade process, catalyst 1 promotes three consecutive carbon–carbon bond forming steps generating four stereogenic centers with high diastereoselectivity and

• developed in our previous work [17], we tried to introduce 6 as an acetaldehyde equivalent, adding water in the reaction system and Amberlyst-15 as a catalyst to accelerate the hydrolysis process (Scheme 2). To our delight, 6 as an acetaldehyde surrogate allows a slightly better yield with doubled

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

• behavior of P450 oxygenases encouraged early work on site-selective C–H functionalization [20]. Throughout their studies, it was found that manganese could perform the same HAT and RLT steps as iron at heme active sites. Groves developed the manganese tetramesitylporphine catalyst V (Scheme 2), which was

• functionalization via the canonical organometallic steps of oxidative addition/reductive elimination was ruled out via catalytic reaction of the macrocyclic Groves-type porphyrin catalyst V, a species that is unable to accommodate the mutual cis-orientation of ligands for metal-centered reductive elimination. The

• molecular iron catalyst II and stoichiometric hydroxyiodinane as a terminal oxidant [38]. It is proposed that an azidoiodinane is generated in situ and serves as the radical initiator, generating an azido radical which adds to the less substituted position on the alkene. The resultant transient radical is

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

• -toluenesulfonic acid (PTSA) as an acidic catalyst in chloroform at 65 °C for three hours, which provided copper(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrin 3 in 40% yield (Table 1, entry 1). To improve the isolated yield of the desired porphyrin 3, various experiments were performed by reacting copper(II) 2,3

• afforded porphyrin 3 in only 32% and 40% yield, respectively (Table 1, entries 1 and 4). Interestingly, when trichloroacetic acid (TCA) was used as an acidic catalyst under identical conditions, the output of the reaction was improved giving the desired porphyrin 3 in 65% isolated yield (Table 1, entry 5

• ). However, the reaction in the presence of comparatively strong trifluoroacetic acid (TFA) afforded an inseparable mixture of products under the same conditions (Table 1, entry 6). Hence, trichloroacetic acid was found to be an efficient acidic catalyst for the formation of the targeted porphyrin 3 in good

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

• couple the reduction to water oxidation or other reactions. Furthermore, the performance of the molecular photosensitizer and catalyst combinations developed are often very dependent on the properties of the sacrificial donors. This review has two aims: 1. Highlight work being done to recycle sacrificial

• quenched by a substrate or catalyst and then reduced by the sacrificial donor (oxidative quenching pathway). In the presence of protons, proton donors, or oxidized donor species with a low pKa, a proton-coupled electron transfer (PCET) can take place [14][15]. PCET reactions are important in artificial

• discharge and charge the donor-containing organic phase (Figure 2A) [34]. The first solution contained an organic lithium salt and a hydrogen-evolution catalyst which could generate hydrogen via a light-driven or dark process. The second solution contained an organic chloride salt and a water oxidation

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

• reported by Hadjiarapoglou, Varvoglis and co-workers [107][108][109][110][111][112] and Moriarty et al. [113][114][115], who observed metal-free cycloadditions between iodonium ylides and olefins in the absence of a transition metal catalyst. These reactions proceeded under mild conditions without catalyst

• produced in 74% yield after six days at room temperature in the absence of catalyst (Scheme 2a) [107]. At that time, the authors did not articulate any theory as to how the reaction might initiate under such mild conditions, though they recognized that the decomposition of 8 into a free carbene would not

• have been feasible. In 1989, Moriarty was investigating the intramolecular cyclopropanation of 10 under copper-catalysis, presuming that the reaction would proceed through a metallocarbene intermediate [113]. However, a control experiment showed the reaction to also be viable without catalyst, from

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

• byproducts, and increased efficiency in industrial processes. As such, this field of research is of great importance and interest to both academia and industry. This work showcases a sustainable and catalyst-free oxidation method for heteroatoms (e.g., S, P, and Se) using only air, water and light. An

• flow using the HANU flow reactor, indicating scalability and improving safety. Keywords: catalyst-free; flow chemistry; oxygen; photochemistry; sustainable oxidation; Introduction Oxidation reactions are widely used in the chemical industry, but are often problematic due to challenges with

• ) [2][3][4]. Additionally, practical implementation of hydrogen peroxide can be challenging due to requirements for precise dosing to avoid issues such as dismutation, overoxidation, and catalyst degradation [5]. In this respect, oxygen, or preferably air, represents a better alternative to traditional

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

• generation of reactive intermediates for both oxidative and reductive processes via photon activation of a catalyst. Although this represents a significant step towards chemoselective and, more generally, sustainable chemistry, its efficacy is limited by the energy of visible light photons. Nowadays

• photoredox catalysts and ii) energy that parallels the energy of UV-driven transformations, but under cheaper, safer conditions and in a more selective manner by indirect substrate activation via a catalyst. These are: a) multi-photon processes that accumulate visible light photon energies for electron

• generation of super-reductants [15] and by Wagenknecht in 2018 for the generation of super-oxidants [16]. Herein, initial excitation of the photocatalyst by a single photon is followed by reduction or oxidation by a sacrificial SET donor (e.g., Et3N [15]) or acceptor (e.g., SF6 [16]) to yield the catalyst

Copper-catalyzed N-arylation of amines with aryliodonium ylides in water

• Kasturi U. Nabar,
• Bhalchandra M. Bhanage and
• Sudam G. Dawande

Beilstein J. Org. Chem. 2023, 19, 1008–1014, doi:10.3762/bjoc.19.76

• types of hypervalent iodine reagents, diaryliodonium salts are commonly used reagents for the N-arylation of nitrogen-containing compounds, particularly for N-arylation of amines under catalyst-free conditions either in the presence of additives or at higher temperatures [26][27][28][29][30][31][32

• , catalyzed by a copper catalyst [39]. Murphy and co-workers reported blue LED-mediated metal-free cyclopropanation of alkenes with iodonium ylides through a diradical intermediate [40]. However, iodonium ylides are relatively unexplored for the arylation of amines. So far only Spyroudis’s group reported N

• -arylation of amines using iodonium ylides obtained from 2-hydroxy-1,4-naphthoquinone in the presence of a Cu(II) catalyst in dichloromethane as a solvent (Scheme 1b) [41]. Albeit useful, this protocol suffers drawbacks such as low yields, formation of byproducts, limited substrate study, and the use of

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

• , increasing the reaction temperature leads to the formation of the desired product 4a with moderate yield (Table 1, entries 3 and 4). Next, we found that TsOH as a catalyst and several studied solvents (toluene, 1,4-dioxane, AcOH) are inefficient (Table 1, entries 5–10). Finally, we settled on the mixture of

The unique reactivity of 5,6-unsubstituted 1,4-dihydropyridine in the Huisgen 1,4-diploar cycloaddition and formal [2 + 2] cycloaddition

• Xiu-Yu Chen,
• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 982–990, doi:10.3762/bjoc.19.73

• acetylenedicarboxylates and 5,6-unsubstituted 1,4-dihydropyridines. The advantages of the reaction include the use of readily available starting materials, simple reaction conditions, without using any catalyst, high molecular diversity and atomic economy. Therefore, this reaction not only successfully developed

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

• reactions include mild reaction conditions and the use of a sole catalyst without the need of other chiral ligands [4][5]. In these reactions, stereoinduction in the products is achieved by the chiral environment present in the catalyst itself. Depending upon the reactivities, organocatalysts can be

• categorized into two major divisions: 1) covalent bonding and 2) noncovalent bonding catalysts. A covalent bonding organocatalyst reacts with a substrate to form an activated chiral intermediate which undergoes a stereoselective reaction with another reagent. A noncovalent bonding catalyst usually assembles

• system. Like the classical Friedel–Crafts reaction, the aza-Friedel–Crafts reaction also requires the presence of a Lewis acid catalyst for rate acceleration. The reaction can be very easily modulated by different Lewis acidic metallic compounds which effectively form a coordinate bond by accepting the

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

• acid catalysts and transition metal catalysts. The goal of this review is to summarize the synthesis of various N-substituted pyrrole derivatives using a modified Clauson–Kaas reaction under diverse conventional and greener reaction conditions. Keywords: catalyst; Clauson–Kaas pyrrole synthesis; 2,5

• -dialkoxytetrahydrofuran. This reaction was originally discovered by N. Clauson–Kaas and Z. Tyle in 1952 [37] (Scheme 2a). Initially, acetic acid was used as a catalyst in this classic reaction; however, diverse modifications have been reported for this procedure using various Brønsted acid catalysts, metal catalysts, and

• (P2O5) as a catalyst for the conversion of various aliphatic amines, aromatic amines, sulfonamides and primary amides into N-substituted pyrroles (Scheme 5). These pyrroles were synthesized in 46–100% yields by the modified Clauson–Kaas reaction between amines 10 and 2,5-DMTHF (2) in the presence of

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

• manner due to their intrinsic mildness and broad substrate compatibility [16][17][18][19][20]. This transformative synthetic tool often utilizes direct single-electron transfer (SET) between an electronically excited photoredox catalyst and an organic substrate, resulting in oxidation or reduction, to

• ground state catalyst [21][22][23][24][25][26]. While early research has focused on methods for the functionalization of relatively simple hydrocarbons [27][28][29][30], developments in photoredox catalysis have gained traction recently as a viable strategy for the total synthesis of natural products [31

• , according to the Baldwin rules [92]. We began our investigation of the proposed decarboxylative cyclization by exposing the N-Boc derivative 8, Ir catalyst, and K2HPO4 in DMF to a 34 W blue LED lamp at room temperature (Table 1) [93][94][95][96][97]. To our delight, cyclization was observed under these

Synthesis of aliphatic nitriles from cyclobutanone oxime mediated by sulfuryl fluoride (SO₂F₂)

• Xian-Lin Chen and
• Hua-Li Qin

Beilstein J. Org. Chem. 2023, 19, 901–908, doi:10.3762/bjoc.19.68

• 1,4-dioxane the transformations performed the best (Table 1, entries 3–5). A series of copper catalysts such as CuI, CuCN, and Cu2O was screened, in which some showed good catalytic activity (Table 1, entries 6–9), and Cu2O was identified as the most effective catalyst for the desired transformation

• . Accordingly, the catalyst loading of Cu2O was studied next and increasing the loading of Cu2O to 1.0 equivalent, gave the desired product 3aa in a good yield of 72% (Table 1, entry 10). Furthermore, the examination of the effect of base revealed CH3COOK being the most suitable choice (Table 1, entry 11

• Scheme 5. Under the promotion of the base, cyclobutanone oxime preliminarily reacts with SO2F2, generating the activated precursor fluorosulfonate, which further reacts with the alkene 2a in the presence of the copper catalyst under Ar atmosphere for 9 h (Scheme 5a). The corresponding product was

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• a wide substrate scope of both pyridines and olefins including α-olefins, styrenes, and conjugated dienes. The yttrium complex was found to be superior as compared to the scandium complex for the alkylation reaction of bulkier 2-tert-butylpyridine with ethylene. In addition, the yttrium catalyst was

• mechanism involves the coordination of pyridine to the metal center of the cationic catalyst and B(C6F5)3 promotes the ortho-C–H activation (deprotonation) of pyridine to afford pyridyl species 6. Next, the 2,1-migratory insertion of alkene 2 into the metal–pyridyl bond in 6 gives the intermediate 7, which

• pyridine N-oxides 9 with nonactivated secondary (2°) alkyl bromides 10 required 5 mol % of the Pd(OAc)2dppf catalyst, Cs2CO3 (2.0 equiv) as base in toluene at 100 °C as shown in Scheme 3. Under these conditions, the reaction provided diverse 2-alkylpyridine derivatives 11 in moderate to good yields

Honeycomb reactor: a promising device for streamlining aerobic oxidation under continuous-flow conditions

• Masahiro Hosoya,
• Yusuke Saito and
• Yousuke Horiuchi

Beilstein J. Org. Chem. 2023, 19, 752–763, doi:10.3762/bjoc.19.55

• closed system. Keywords: aerobic oxidation; benzaldehydes; benzyl alcohols; homogeneous catalyst; honeycomb reactor; Introduction Oxidation plays a key role in synthesizing highly functionalized molecules [1][2]. While Jones oxidation [3] and oxidation using KMnO4 [4] are classical and powerful methods

• ) were screened (Table 1). The oxidized product p-anisaldehyde (2a) is a valuable substance in food chemistry [34][35] and a valuable intermediate for synthesizing active pharmaceutical ingredients [36]. This oxidation has been often applied for evaluating catalyst activity for aerobic oxidation [37

• at room temperature (Table 1, entry 1). However, four kinds of catalysts were used, and a simpler catalytic system would be preferable. The highly reactive catalyst, 9-azanoradamantane N-oxyl (nor-AZADO), was tried with NaNO2 as a cocatalyst, which resulted in completion of the reaction in 60 min

Synthesis of imidazo[1,2-a]pyridine-containing peptidomimetics by tandem of Groebke–Blackburn–Bienaymé and Ugi reactions

• Oleksandr V. Kolomiiets,
• Alexander V. Tsygankov,
• Maryna N. Kornet,
• Aleksander A. Brazhko,
• Vladimir I. Musatov and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2023, 19, 727–735, doi:10.3762/bjoc.19.53

• proved to be inefficient. In addition, we also tested the one-pot method for the synthesis of similar structures [32]. Aminopyridine, aldehyde and Sc(OTf)3 as catalyst were stirred in MeOH/DCM for 45 min at room temperature, then the isocyanide was added and the mixture was stirred for another 8 h

Palladium-catalyzed enantioselective three-component synthesis of α-arylglycine derivatives from glyoxylic acid, sulfonamides and aryltrifluoroborates

• Bastian Jakob,
• Nico Schneider,
• Luca Gengenbach and
• Georg Manolikakes

Beilstein J. Org. Chem. 2023, 19, 719–726, doi:10.3762/bjoc.19.52

• modular access to arylglycines from three readily available building blocks [10][11][12]. The Petasis borono-Mannich reaction usually proceeds in the absence of any external catalyst via zwitterionic intermediates and an intramolecular transfer of the aryl residue form the activated boronate to the

• increase in enantioselectivity. Decreasing the arylboronic acid to active catalyst ratio could be one possible opportunity to decrease the rate of the background reaction. Thus, we envisioned that this could be achieved by the slow generation of small amounts of the boronic acid from a suitable precursor

• phenyltrifluoroborate with 2,2,4,6,7-pentamethyl-2,3-dihydrobenzofuran-5-sulfonylamide and glyoxylic acid in nitromethane at 40 °C in the presence and absence of our previously established Pd(TFA)2-S,S-iPrBox catalyst system (Scheme 3). To our delight, the palladium-catalyzed transformation afforded the desired α

Strategies in the synthesis of dibenzo[b,f]heteropines

• David I. H. Maier,
• Barend C. B. Bezuidenhoudt and
• Charlene Marais

Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51

• 1a in poor yield (20–50%) [39]. The starting material 2a was distilled through a heated (≈150 °C) column packed with Pd/C and glass wool. Crude 1a was collected as a solid and purified. Further research has been conducted on the effect of catalyst choice and composition for large scale synthesis

• . Knell et al. [40][41] reported a comparison of several catalysts, which included potassium-promoted iron, cobalt and manganese oxide catalysts, for the synthesis of 1a. Industrially, 1a is produced by the vapour phase dehydration of 2a over an iron/potassium/chromium catalyst system (Scheme 4) [42]. 2

• the synthesis of intermediate stilbenes 61 by Wittig coupling. The authors elected to use a Pd2dba3/DPEphos (L4)/Cs2CO3 system (dba = dibenzylideneacetone; DPEphos = bis[(2-diphenylphosphino)phenyl] ether) in toluene after catalyst and ligand screening. Cyclisation of several substituted 2,2

Synthesis of medium and large phostams, phostones, and phostines

• Jiaxi Xu

Beilstein J. Org. Chem. 2023, 19, 687–699, doi:10.3762/bjoc.19.50

• -azaphosphocin-1(4H)-yl)acetate (4), respectively, in the presence of the Grubbs first generation catalyst via ring closing metathesis. The products 3 and 4 were further transformed to antitumor agents 5, 6, 9 and 10 through aminolysis with O-TMS hydroxylamine or hydrogenolysis followed by aminolysis with O-TMS

• synthesis of 1,2-oxaphosphaheterocycle 2-oxides. tert-Butyl 2-(bis(allyloxy)phosphoryl)pent-4-enoate (11) generated tert-butyl 2-(allyloxy)-3,4,7-trihydro-1,2-oxaphosphepine-3-carboxylate 2-oxide (12) in excellent 94% yield in the presence of the Grubbs catalyst in DCM. After further allylation with allyl

• bromide, its allylated product 13 further cyclized into bis(1,2-oxaphosphepine 2-oxide) derivative tert-butyl 2,5,5a,6,9-pentahydro-[1,2]oxaphosphepino[2,3-b][1,2]oxaphosphepine-5a-carboxylate 11-oxide (14) in 97% yield under the same conditions (Scheme 2) [27]. The Grubbs 1st generation catalyst-promoted

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

• photocatalyst 10-phenylphenothiazine (PTH) under violet LEDs which uplifted the yield up to 52% (Table 1, entry 7). Now with the optimal catalyst in hand, we screened some common solvents, out of which 1,2-DCE positively impacted the yield (Table 1, entries 8–11). However, the best result was obtained when 3.0

• equiv of Zn(OAc)2 was used as an additive (Table 1, entry 12). To check the viability of other acetylating agents, Zn(OAc)2 was replaced with AcOH, generating the desired product in a comparatively lower yield (Table 1, entry 13). Finally, control experiments without a catalyst (Table 1, entry 14

• functionalization at the newly incorporated active methylene center. Cycle-1 is initiated with the reduction of bromomalonate 2a by the photoexcited catalyst PC* to malonyl radical I. This is followed by the Minisci-type addition of radical I to the imidazopyridine, preactivated by Lewis acidic Zn(OAc)2 [29]. PC