An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• co-workers reported a photoinduced oxidation of allyl alcohols to acrylaldehydes at room temperature, catalyzed by diphenyl disulfide derivatives [18]. In the proposed mechanism, disulfide is split by the photoirradiation to form thiyl radicals. Then, the abstraction of the α-hydrogen atom from allyl

• disulfide-catalyzed isomerization of allyl alcohols to carbonyl compounds under high-pressure mercury lamp irradiation (λ > 300 nm) at room temperature. The yield of the reaction reached up to 91% (Scheme 23) [30]. Using the water-soluble dendrimer disulfide, the photoinduced isomerization in water was also

• successful. For the photoinduced oxidation reaction of allyl alcohols, the dendrimer disulfide is a better mediator than diphenyl disulfide, because dendritic substituents are quite effective in inhibiting side reactions initiated by the addition of sulfanyl radicals to the unsaturated bonds. A plausible

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• thietanes 328 [91] (Scheme 62). One year later, the same group reported the intramolecular photo [2 + 2] cycloadditions of 2-allyl-N-methyldithiosuccinimide (329) with the same irradiation source at room temperature for 1 h, generating another highly strained tricyclic thietane 330. 2-((6,6-Dimethylbicyclo

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• base (Table 1, entries 7 and 8). The second methodology consisted of an inverted sequence of reactions in relation to the previous approach, starting from the treatment of 13a with 15a,b to give 3-(pyrrol-2-yl)acrylates 16a–b (Scheme 2). The latter compounds were alkylated with allyl bromide (14e) and

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• with a C=C double bond was explained by the steric hindrance of the iminoxyl radical. On the other hand, di-tert-butyliminoxyl radical (8) can react with unsaturated hydrocarbons by abstracting the hydrogen atom from the allyl or benzyl position (Scheme 10) [35][45][60][61]. The C-centered radicals

• formed after hydrogen atom abstraction from the allyl or benzyl position couple with the di-tert-butyliminoxyl radical forming the oxime ethers 21 and 22. 1,4-Cyclohexadiene is dehydrogenated to benzene instantly and exothermally at room temperature [45]. The solvent-free reaction of oxime radical 8 and

• cyclohexene takes 1 h at 25 °C [61]. The benzyl hydrogen atoms are abstracted at higher temperatures [35][45]. Reactions of di-tert-butyliminoxyl radical (8) with allylic moieties can theoretically occur by two pathways that give the same final product – the O-allyl derivative of the oxime [35][77]. In the

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

Copper-based fluorinated reagents for the synthesis of CF₂R-containing molecules (R ≠ F)

• Louise Ruyet and
• Tatiana Besset

Beilstein J. Org. Chem. 2020, 16, 1051–1065, doi:10.3762/bjoc.16.92

• -generated copper-based reagent (19 examples, up to 80% yield, Scheme 7e). With a similar method and in the presence of 1,10-phenanthroline as a ligand, the functionalization of alkenyl halides (8 examples, up to 82% yield), allyl halides (7 examples, up to 99% yield) and benzyl bromides (6 examples, up to

Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents

• Yafei Guo and
• Syuzanna R. Harutyunyan

Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90

• intermediate formed upon this ACA could be trapped with acetaldehyde and allyl bromide or allyl acetate to form valuable compounds with high ee and dr values. Later, Harutyunyan’s research group showed that also non-activated lactams with alkyl-protected groups could undergo ACA reactions with EtMgBr, with 93

Diversity-oriented synthesis of 17-spirosteroids

• Benjamin Laroche,
• Thomas Bouvarel,
• Martin Louis-Sylvestre and
• Bastien Nay

Beilstein J. Org. Chem. 2020, 16, 880–887, doi:10.3762/bjoc.16.79

• derivatives of several steroidal skeletons, starting from available 17-ethynyl-17-hydroxysteroid compounds 1–3 (Scheme 2). Alkylation of the alcohol function proceeded well under classical conditions (NaH then RCH2Br in DMF), either in the presence of allyl bromide or of 4-pentenyl bromide. Mestranol (1

• Stewart–Grubbs catalyst combined with microwave heating at 120 °C (allyl ethers) or 170 °C (4-pentenyl ethers), demonstrating improved yields [77]. These temperatures were needed for the reaction to quickly go to completion. With 17-O-allylmestranol (5a), a rapid screening of the Stewart–Grubbs (SG

• . Synthesis of spirocyclic steroid derivatives by the RCEYM reaction. Conditions: (a) NaH (2 equiv), allyl or 4-pentenyl bromide (2 equiv), DMF, 0 °C→rt; (b) Second-generation Grubbs catalyst (G-II), toluene, under microwave at 120 °C (5a, 6a, 7) or 170 °C (5b, 6b). One-pot RCEYM/Diels–Alder reaction strategy

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• relative to ethylene (0%) and allyl anion (100%) as references on a linear scale. Large values mean a high degree of conjugations, while low values refer to a rather isolated double bond. The calculated olefinicity values (OL%) for 3- and 2-phospholene oxides 1 and 4 are within a narrow range, between 29

Photocatalytic deaminative benzylation and alkylation of tetrahydroisoquinolines with N-alkylpyrydinium salts

• David Schönbauer,
• Carlo Sambiagio,
• Timothy Noël and
• Michael Schnürch

Beilstein J. Org. Chem. 2020, 16, 809–817, doi:10.3762/bjoc.16.74

• alkyl and allyl groups were also successfully introduced via the same method. Additionally, the typically applied N-phenyl group in the THIQ substrate could be replaced by the cleavable p-methoxyphenyl (PMP) group and successful N-deprotection was demonstrated. Keywords: C–H functionalization; C(sp3)–C

• towards desired bioactive compounds. At last, we turned our interest towards non-benzylic Katritzky salts, showcasing that also the reaction with unactivated secondary alkyl and allyl radicals takes place (Scheme 5). For the less reactive secondary alkyls the more expensive catalyst [Ir(dtbbpy)(ppy)2]PF6

• from amino acids gave a complex reaction mixture, and the desired products could not be isolated. Additionally, alkyl salts derived from primary amines were unreactive. For the more stable allyl radicals, our initially optimized conditions with [Ru(bpy)3]Cl2 in DMA/ACN were again applicable and the

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• ]. 2.1 Formation and reactions of allylic C–B bonds The synthesis of α-stereogenic allylboronates was reported by Ito in 2005 using CuO-t-Bu/Xantphos (CuCl and KO-t-Bu form CuO-t-Bu in situ as the active catalyst precursor), an enantioenriched allyl carbonate, and B2pin2 (310; Scheme 50) [93]. Both (Z

• ] with C(sp2)-containing electrophiles such as tert-butyl allyl carbonate or aldimines using B2pin2, Liao et al. reported the same approach, albeit using more challenging C(sp3) electrophiles (e.g., CH3I) for the enantioselective methylboration. Both aliphatic alkenes and styrenes could be used with

• conversion of 2-substituted 1,3-dienes 376 into borocyano products using commercially available phosphine ligands (Scheme 60). Simply switching from a mono to a bidentate ligand resulted in 1,4 to 4,1-borocupration. The formation of allyl–Cu intermediates in the catalytic cycle readily trap available

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• , washed with THF and dichloromethane, and dried. Different organic halides (benzyl bromides, benzyl chloride, allyl bromide, aliphatic epoxides, and aromatic epoxides) were treated with sodium azide and phenylacetylene in the presence of a catalytic amount of the copper catalyst 121 in water at 70 °C

Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

• Svetlana V. Amosova,
• Andrey A. Filippov,
• Nataliya A. Makhaeva,
• Alexander I. Albanov and
• Vladimir A. Potapov

Beilstein J. Org. Chem. 2020, 16, 515–523, doi:10.3762/bjoc.16.47

• rearrangements occurred by a nucleophilic attack of the selenocyanate anion at two different carbon atoms of the seleniranium intermediate. The efficient regioselective synthesis of alkyl, allyl, 2-propynyl, benzyl, 4-fluorobenzyl, and 2-pyridinylmethyl 1,3-thiaselenol-2-ylmethyl selenides was developed based on

• with organyl halides. Various substrates were involved in the reaction, providing the introduction of alkyl, benzyl, allyl, and 2-propynyl moieties as well as pharmacophores as 2-pyridylmethyl and 4-fluorobenzyl. A possibility for the synthesis of compounds containing two 1,3-thiaselenol-2

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• 70–85% yield, respectively. Notably, the steric and inductive effects of the substituents did not hamper this ring-opening N-alkylation. Allyl bromide (1h) successfully reacted with 2-methyl-2-oxazoline and produced the corresponding product 3h in good yield (69%). More importantly, bromide

• new and simple transition-metal-free selective ring-opening N-alkylation of 2-methyl-2-oxazoline or 2-(methylthio)-4,5-dihydrothiazole with benzyl halides and allyl halides under mild conditions. Various 2-aminoethyl acetates and N-substituted thiazolidinone derivatives were successfully isolated in

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• ) [25]. This copper-catalyzed photocatalytic reduction generated an aryl radical that was trapped with various allylating reagents. First, the phenyl radical generated from the corresponding diphenyliodonium salt was added to various allyl sulfones substituted in the 2-position. The products were

• isolated in moderate to good yields. Using the more reactive allyl sulfone, a panel of symmetrical diaryliodonium salts was reacted, giving the products in good yields. The authors conducted some mechanistic studies and suggested a plausible catalytic cycle involving [Cu(I)]/[Cu(I)]*/[Cu(II)] species. The

• allylation reaction using the [Cu(I)(dpp)(binc)]BF4 complex (Scheme 16) [32]. The reaction of α-bromomalonates with allyl- and crotylsilanes afforded the allylated products in good yields. To explain the reaction outcome, the authors suggested a reduction of the α-bromomalonate by the excited Cu(I) complex

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• [45][46]. The complimentary effect of P and N can help stabilizing different catalytic species that are produced during catalytic transformations [11][47]. P,N-phosphine ligands can effect regioselective control, due to the trans-effect as exhibited in π-allyl metal complexes, where substitution

Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• different compounds, such as (−)-kainic acid [51][52]. Previous similar approaches reported only planar pyrrolocyclopentenones starting from propargyl alcohol–cobalt complexes and allyl amides [50], or carbohydrate-derived allylpropargylamine [49] (Scheme 1a). Results and Discussion Cyclohexanone (1) and

Functionalization of the imidazo[1,2-a]pyridine ring in α-phosphonoacrylates and α-phosphonopropionates via microwave-assisted Mizoroki–Heck reaction

• Damian Kusy,
• Agata Wojciechowska,
• Joanna Małolepsza and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 15–21, doi:10.3762/bjoc.16.3

• substrates, a mixture of regioisomers, resulting from α- and β-arylation, was formed (see Supporting Information File 1, Figures S16 and S17, S32 and S33) [21]. In case of the reaction with allyl alcohol, the generated products isomerized in situ to give the saturated aldehydes, compounds 12, 21, and 22, a

Synthesis of C-glycosyl phosphonate derivatives of 4-amino-4-deoxy-α-ʟ-arabinose

• Lukáš Kerner and
• Paul Kosma

Beilstein J. Org. Chem. 2020, 16, 9–14, doi:10.3762/bjoc.16.2

• preliminary experiments, Lewis acid cleavage using BBr3, BCl3, and TiCl4, respectively, was not successful, although the latter reagent had previously been used to deprotect two benzyl groups from an allyl glycoside containing a 4-amino-4-deoxy-ʟ-arabinose residue [36]. Cleavage of the benzyl protecting

Regioselectivity of glycosylation reactions of galactose acceptors: an experimental and theoretical study

• Enrique A. Del Vigo,
• Carlos A. Stortz and
• Carla Marino

Beilstein J. Org. Chem. 2019, 15, 2982–2989, doi:10.3762/bjoc.15.294

• ]. The observation that 13β was formed (Table 1, entry 4) helped to understand the reaction performance and the relative reactivity of hydroxy groups. With the 2,3,4,6-tetra-O-benzyl-β-ᴅ-Galp trichloroacetimidate donor, regioselectivity in favor of the OH-3 group of 1α [32] or allyl 2,6-di-O-benzyl-α- or

Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

• Dominika Krištofíková,
• Juraj Filo,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2019, 15, 2948–2957, doi:10.3762/bjoc.15.290

• rearrangement; silyl ketene acetals; Introduction The Ireland–Claisen rearrangement is a reaction converting allyl esters to γ,δ-unsaturated carboxylic acids. Its key step is a [3,3]-sigmatropic rearrangement of a silyl ketene acetal, which is generated in situ by deprotonation of an allyl ester using a strong

• stereospecificity make this transformation synthetically appealing [12][13]. Allyl esters of various carboxylic acids undergo rearrangement as their lithium enolates or silyl ketene acetals and the corresponding acids were isolated in 75–80% yields. Accordingly, the Ireland–Claisen rearrangement of lithium enolates

• generated from allyl fluoroacetates gave the corresponding α-fluoro-γ,δ-unsaturated acids [14]. The Ireland–Claisen rearrangement of Et3N-solvated enolates showed higher reactivity as well as diastereoselectivity when compared with analogous reactions in THF [15]. The required ester enolates are typically

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• stereocenters 88 were obtained in good yields and enatioselectivities [69]. In 2002, Dunach’s group explored an electroreductive method for the cleavage of the allyl group of β-keto ester 89 followed by the transfer of the same to the carbonyl group to afford a mixture of 91 (major), 92 and 93 (Scheme 33

Unexpected one-pot formation of the 1H-6a,8a-epiminotricyclopenta[a,c,e][8]annulene system from cyclopentanone, ammonia and dimethyl fumarate. Synthesis of highly strained polycyclic nitroxide and EPR study

• Sergey A. Dobrynin,
• Igor A. Kirilyuk,
• Yuri V. Gatilov,
• Andrey A. Kuzhelev,
• Olesya A. Krumkacheva,
• Matvey V. Fedin,
• Michael K. Bowman and
• Elena G. Bagryanskaya

Beilstein J. Org. Chem. 2019, 15, 2664–2670, doi:10.3762/bjoc.15.259

• assignment was based on the single-crystal X-ray analysis (Figure 4) and a possible mechanism for this hydroxylation is shown in Scheme 4. Oxidation of amines with peracids is known to proceed through oxoammonium cation formation [12]. The close proximity of this reactive group to the allyl hydrogen results

Indium-mediated C-allylation of melibiose

• Christian Denner,
• Manuel Gintner,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

• )-2,3,4,5,6-penta-O-acetyl-7,8,9-trideoxy-ᴅ-glycero-ʟ-gulo-8,9-nonenitol (2-syn) and 2’,3’,4’,6’-tetra-O-acetyl-α-ᴅ-galactopyranosyl-(1’→1)-2,3,4,5,6-penta-O-acetyl-7,8,9-trideoxy-ʟ-glycero-ʟ-gulo-8,9-nonenitol (2-anti): Indium (263 mg, 2.29 mmol, 4 equiv) and allyl bromide (420 mg, 3.47 mmol, 6 equiv) were

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

• Ronja Driller,
• Daniel Garbe,
• Norbert Mehlmer,
• Monika Fuchs,
• Keren Raz,
• Dan Thomas Major,
• Thomas Brück and
• Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

• ) [12] to the acyclic terpene synthase substrate geranylgeranyl diphosphate 3 (GGDP) [1][13][14][15][16]. Following initial substrate binding and folding in a product-like conformation, the cyclization reaction can be subdivided into three steps: (1) generation of a reactive allyl carbocation as a