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

• of ethers to obtain symmetric and asymmetric 1,1-bis-indolylmethane derivatives (Scheme 23) [84]. The reaction proceeds through the tandem oxidative coupling of the C–O bond and cleavage of the C–H bond. Fe plays a dual role in catalysing the C–C bond coupling and C–O bond cleavage as Lewis acid

• pathway. Initially, a tert-butoxyl radical is generated by thermal decomposition. Then, the tert-butoxyl radical extracts an α-hydrogen atom from tetrahydrofuran to form tetrahydrofuran radical A. Sc(OTf)3 as a Lewis acid activates pyridine forming the pyridine complex B. Then, radical A adds to the more

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

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

• 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

• benzofuran-2(3H)-one derivative 144 having an aza-quaternary stereocenter. The achiral Lewis acid tris(pentafluorophenyl)borane was required as additive in the reaction system to enhance the chemical yield and enantioselectivity. After two additional steps, i.e., demethylation of the phenolic ether and ester

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

• work-up of intermediate H (Scheme 2b). Review Conventional method for the Clauson–Kaas synthesis of N-substituted pyrroles This section describes Clauson–Kaas pyrrole syntheses using traditional methods, such as Brønsted acid or Lewis acid-catalyzed reactions in various organic solvents at higher

• excellent yields. To obtain the best reaction conditions, various Lewis acid catalysts (e.g., FeCl3 CuCl2, InCl3, Cu(OTf)2, Mg(OTf)2, Zn(OTf)2, Yb(OTf)3, Y(OTf)3, Bi(OTf)3, La(OTf)3 and Sc(OTf)3), different solvents (e.g., CH2Cl2, CHCl3, CH3CN, CH3NO2, n-hexane, and dioxane), temperatures (90–110 °C), and

• various substituted anilines, primary arylamides, and sufonylamides 20 and 2,5-DMTHF (2) in the presence of 10 mol % MgI2 etherate in MeCN at 80 °C (Scheme 9a). MgI2 etherate is a main-group Lewis acid catalyst that selectively activates electron-rich aromatic amines. This is a mild, efficient, and highly

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

• example, when esters 1a are subjected to Lewis acid-induced denitration, highly electron-deficient enones (reaction b) [4] are obtained. The latter compounds are highly reactive and undergo reaction with, e.g., mercaptoacetaldehyde affording thiophenes (reaction c) [5] or with activated (hetero)aromatic

• compounds to give diarylated (oxoalkyl)malonates [6]. In the reaction using tin(II) chloride as the Lewis acid, the ring opening and nucleophilic attack of the nitro group occur, to produce functionalized isoxazolines (reaction d) [7]. In contrast, denitration under basic conditions generates highly

Asymmetric tandem conjugate addition and reaction with carbocations on acylimidazole Michael acceptors

• Brigita Mudráková,
• Renata Marcia de Figueiredo,
• Jean-Marc Campagne and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 881–888, doi:10.3762/bjoc.19.65

• of −7.13 eV and an even more negative NBO charge of −0.368 at the C-2 position. We can confer from these data that Zn enolates obtained from acylimidazoles are somewhat less reactive than silyl enol ethers obtained in the Lewis acid-promoted conjugate addition of Grignard reagents [23]. This finding

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 direct selective C4-alkylation of pyridine has been reported by the groups of Hiyama [62] (Scheme 12a) and Zhang [63] (Scheme 12c) in 2010 and 2020, respectively. The Hiyama group developed a C-4-selective alkylation of pyridines using a Ni/Lewis acid cooperative catalytic system in combination

• with a bulky N-heterocyclic carbene ligand and (2,6-t-Bu2-4-Me-C6H2O)2AlMe (MAD) as the Lewis acid which allowed the direct C-4 alkylation of pyridines 1 (Scheme 12a). With the optimized reaction conditions in hand the group also screened the alkene and pyridine substrate scope which resulted C4

• nickel Lewis acid catalyst with amino pendant linked NHC complex (Scheme 21). In addition, the authors were able to isolate the bimetallic intermediate structure η2,η1-pyridine–Ni(0)–Al(III) complex 112, as a support for their mechanism for the para-C–H functionalization. They further investigated the

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

• ) chloride (Scheme 26). Alkyne–carbonyl metathesis is proposed to proceed via [2 + 2] cycloaddition and –reversion steps, catalysed by a Brønsted or Lewis acid, with the catalyst proposed to form a σ-complex with the carbonyl group and/or a π-complex with the alkyne [68]. 3.7 Hydroarylation The construction

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

• Following the seminal work of Feringa in 1997 [21], the tandem asymmetric organozinc conjugate addition followed by subsequent aldol reaction was scarcely applied in the last decade. Welker and Woodward studied the reaction of zinc enolates 2 with chiral acetals 3 (Scheme 2) [22]. The Lewis acid (TiCl4 or

• the transient iminium species 68 to afford the corresponding aminomethylation products 69 (Scheme 18) [50]. As seen from Table 2, the diastereoselectivities were somewhat compromised compared to what one can expect from the reactions of cyclic enolates. This erosion was likely caused by Lewis acid

• developed a Lewis acid-promoted conjugate addition to unreactive Michael acceptors such as amides or vinyl heterocycles [60]. Trimethylsilyl triflate or boron trifluoride-activated unsaturated amides underwent highly efficient and enantioselective addition of Grignard reagents. When this methodology was

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

• final ring-opened adduct 37. Copper-catalyzed reactions In 2009, Pineschi and co-workers explored the Cu-catalyzed rearrangement/allylic alkylation of 2,3-diazabicyclo[2.2.1]heptenes 47 with Grignard reagents 48 (Scheme 8) [41]. The reaction is thought to proceed via the Lewis acid-catalyzed [3,4

• success of the reaction, hypothesizing it inhibited the classical [3,3]-sigmatropic Lewis acid-catalyzed rearrangement often observed. Both alkyl and aryl Grignard reagents were amenable to the reaction; however, heteroaryl Grignard reagents resulted in poor conversion. The Cu-catalyzed borylative

• the Lewis acid cocatalyst AgSbF6 was removed from the reaction mixture, it was noted only ring-opened 1,2-hydroxy adducts were formed, so it is likely the Lewis acid is required for dehydration. In contrast, when N-pyrimidinylbenzimidazole derivatives were used, the 1,2-C–H addition product was

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

• functionalization of other heteroaromatic derivatives (24j, 87% yield). It should be noted that the presence of zinc triflate, a Lewis acid, was used for the activation of the electrophilic source VI. Cobalt catalysis: In 2017, Wang described the Cp*Co(III)-catalyzed trifluoromethylthiolation of 2-phenylpyridine

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• reactivity to be rendered catalytic, and exhibit catalysis outwith Lewis acid-type activation. These exchange reactions have allowed redox-neutral catalysis complementary to and beyond the redox catalysis of the transition metals. Boron, aluminium, gallium, and indium have all been demonstrated in catalytic

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• construction of the 8-membered ring from an appropriate cyclopentane precursor. The proposed strategies include metathesis, Nozaki–Hiyama–Kishi (NHK) cyclization, Pd-mediated cyclization, radical cyclization, Pauson–Khand reaction, Lewis acid-promoted cyclization, rearrangement, cycloaddition and biocatalysis

• precursor. The proposed strategies include metathesis, Nozaki–Hiyama–Kishi (NHK) cyclization, Pd-mediated cyclization, radical cyclization (including SmI2), Pauson–Khand reaction, Lewis acid-promoted cyclization, rearrangement, cycloaddition, and biocatalysis. In particular, the purpose will focus on the

Friedel–Crafts acylation of benzene derivatives in tunable aryl alkyl ionic liquids (TAAILs)

• Swantje Lerch,
• Stefan Fritsch and
• Thomas Strassner

Beilstein J. Org. Chem. 2023, 19, 212–216, doi:10.3762/bjoc.19.20

• compounds, acylation is possible by an organic acid chloride/acid anhydride and a Lewis acid [6][7]. In the course of the development of ionic liquids (ILs) as a reaction medium for chemical reactions [8][9], the Friedel–Crafts reaction was also examined [10][11][12][13][14][15][16]. First protocols were

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• analog 26 should also be a reactive dienophile [51], but is a less useful building block, as it reacts twice and the adducts will not be as easily desulfonylated. The dienophile 7 reacts with a wide range of dienes at room temperature, without the need for a Lewis acid catalyst. This is particularly

• give difficulties (Scheme 11a) [42]. The reactivity of the oxy-electrophiles can be enhanced by adding a Lewis acid catalyst such as titanium(IV) isopropoxide [59]. In this way, also epoxides can be smoothly reacted with lithiated dithiins, and both allyl and homoallyl alcohols can thus be prepared in

• alcohol 66 can be lithitated and reacted with a range of electrophiles, even without the need for a Lewis acid catalyst, and good levels of stereoinduction can be achieved. The method was used for the synthesis of a range of hexose sugars, as well as iminosugars (viz 66 → 67 → 68), wherein the piperidine

Organophosphorus chemistry: from model to application

• György Keglevich

Beilstein J. Org. Chem. 2023, 19, 89–90, doi:10.3762/bjoc.19.8

• . elaborated a Lewis acid-catalyzed one-pot synthesis of phosphinates and phosphonates staring from pyridinecarboxaldehydes and diarylphosphine oxides [2]. This protocol is the analogy of the Pudovik reaction, followed by the phospha-Brook rearrangement applied mainly for the synthesis of phosphoric ester

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

• using acyl chloride 6b with an isobutyl side chain is its low volatility in contrast to the highly volatile compound 6a. The aza-Nazarov product 7b was isolated in 61% yield with 20 mol % of AgOTf at 80 °C (Table 1, entry 5). The use of TMSOTf as a Si-based Lewis acid catalyst with 20 mol % loading

• of catalyzing the reaction via anion binding, AgOTf stands out as the optimal Lewis acid for this transformation. The aza-Nazarov cyclization of 3,4-dihydroisoquinolines with TMS-substituted α,β-unsaturated acyl chlorides proceeds efficiently in the presence of AgOTf (20 mol %) in CH3CN at 80 °C to

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• , as illustrated by Baldwin in the synthesis of 9,10-deoxytridachione [18]. In a further demonstration of the versatility of tetraenes connected to α’-methoxy-γ-pyrone, the synthesis of both crispatene and photodeoxytridachione was accomplished by Trauner through the Lewis acid-catalyzed 6π-disrotatory

Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene

• Konstantin Lebedinskiy,
• Volodymyr Lobaz and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170

• somewhat, giving us a 41% yield after 12 h of the reaction. Testing the same conditions for dimer 5, we also noticed a speed up in the reaction rate, but a presence of the trimer with an extra CD moiety connected by carbamate group (Mr ≈ 4000) was spotted, giving us lower yields. We assume the Lewis acid

• methylated primary rim based on the remarkable methylation ability of methyl tosylate with relatively mild bases at solvent-free conditions has been developed. It has been proved that using Lewis acid in the phosphine imide reactions with CDs can increase the reactivity of some low-reactive compounds, giving

Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells

• Merve Karaman,
• Abhishek Kumar Gupta,
• Subeesh Madayanad Suresh,
• Tomas Matulaitis,
• Lorenzo Mardegan,
• Daniel Tordera,
• Henk J. Bolink,
• Sen Wu,
• Stuart Warriner,
• Ifor D. Samuel and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2022, 18, 1311–1321, doi:10.3762/bjoc.18.136

• 23% overall yield. First, hydrolysis of 1, in situ conversion to the acyl chloride and subsequent Lewis acid-promoted Friedel–Crafts acylation reaction produced compound 2 (Scheme 1), where the AlCl3 was also responsible for the demethylation. Compound 2 was then subjected to monoalkylation with 1,4

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• the desired α-carbonyl group. (−)-Preussochromone A In 2020, the Koert group disclosed the synthesis of (−)-preussochromone A (24), a fungal metabolite with a highly substituted tetrahydrothiopyrane core annulated to a chromenone [10]. The tetrahydrothiopyrane ring was closed by a Lewis-acid-promoted

• 27. Subsequent oxidation gave α-ketoester 28 which was used in an intramolecular, Lewis acid-mediated aldol reaction, presumably via tridentate complex transition state III, to give diol 29 as a single diastereomer. Inversion of the secondary alcohol and deprotection gave preussochromone D (30

Dienophilic reactivity of 2-phosphaindolizines: a conceptual DFT investigation

• Nosheen Beig,
• Aarti Peswani and
• Raj Kumar Bansal

Beilstein J. Org. Chem. 2022, 18, 1217–1224, doi:10.3762/bjoc.18.127

• -phosphaindolizines having an EWG at the 3-position only, namely 3-ethoxycarbonyl-1-methyl-2-phosphaindolizine (1: R1 = Me, R2 = COOEt) did not undergo the DA reaction with DMB alone or in the presence of sulfur even when refluxing in toluene [12]. The reaction could be accomplished only in the presence of a Lewis

• acid catalyst, namely ethylaluminum dichloride [13]. Furthermore, when carrying out the reaction of compounds 1 (R1 = Me, R2 = COOMe, COOEt, COOCMe3) with DMB in the presence of the catalyst O-menthoxyaluminium dichloride, generated in situ, complete diastereoselectivity was observed. The DA reactions

Lewis acid-catalyzed Pudovik reaction–phospha-Brook rearrangement sequence to access phosphoric esters

• Jin Yang,
• Dang-Wei Qian and
• Shang-Dong Yang

Beilstein J. Org. Chem. 2022, 18, 1188–1194, doi:10.3762/bjoc.18.123

• Herein, we report a Lewis acid-catalyzed Pudovik reaction–phospha-Brook rearrangement sequence between diarylphosphonates or -phosphinates and α-pyridinealdehydes to access valuable phosphoric ester compounds. This transformation provides an extended substrate scope that is complementary to similar

• previously reported base-catalyzed transformations. Keywords: Lewis acid; phospha-Brook rearrangement; phosphoric esters; Pudovik reaction; Introduction Phosphoric esters are widely used in agrochemistry, biological sciences, clinical treatments, as well as in general organic transformations [1][2][3][4][5

• [46][47][48][49]. Thus, searching for an alternative catalytic system, for example, a mild Lewis acid-catalyzed system, to achieve a wide applicability and provide a substrate scope complementary to previously reported base-catalyzed reactions, is a highly desirable task. However, such a process is

Reductive opening of a cyclopropane ring in the Ni(II) coordination environment: a route to functionalized dehydroalanine and cysteine derivatives

• Oleg A. Levitskiy,
• Olga I. Aglamazova,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2022, 18, 1166–1176, doi:10.3762/bjoc.18.121

• thermodynamic stability (1.3:1, see Supporting Information File 1). Notably, the coordination to the Lewis acid increases the regioselectivity of protonation in the allylic anions formed in the electrolysis. Thus, using LiCl as a supporting electrolyte increases the ratio to 5:1. An even more pronounced effect

• can be achieved if the electrolysis is performed in the undivided cell equipped with a Zn or Mg anode. In this case, the anodically generated Zn2+ or Mg2+ worked as Lewis acid and the isomeric α-β and β-γ alkene complexes are formed in 54:1 ratio (though the total yield is decreased to 50%). In case

Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

• Laura Holzhauer,
• Chloé Liagre,
• Olaf Fuhr,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

• reaction to take place. The increase of the amount of catalyst did not significantly improve the yield, while the addition of a base (DIPEA) or Lewis acid (AlCl3) resulted in suppression of imidazole formation and almost complete conversion to the amine 17. Addition of Zn(OTf)2 reduced the yield of the