Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

• Yajing Zhang,
• Qingshan Tian,
• Guozhu Zhang and
• Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

• selectflour to generate Ag(III)F. Subsequently, ethyl phosphite is oxidized by Ag(III)F to generate a P-centered radical (INT-I) and Ag(II)F. The electrophilic phosphonyl radical addition to the triple bond of 1a generates the vinyl-free radical INT-II, which is subsequently trapped by AgF(II) to afford the

Amine–borane complex-initiated SF₅Cl radical addition on alkenes and alkynes

• Audrey Gilbert,
• Pauline Langowski,
• Marine Delgado,
• Laurent Chabaud,
• Mathieu Pucheault and
• Jean-François Paquin

Beilstein J. Org. Chem. 2020, 16, 3069–3077, doi:10.3762/bjoc.16.256

• , France 10.3762/bjoc.16.256 Abstract The SF5Cl radical addition on unsaturated compounds was performed using an air-stable amine–borane complex as the radical initiator. This method showed to be complementary to the classic Et3B-mediated SF5Cl addition on alkenes and alkynes. A total of seven alkene and

• three alkyne derivatives were tested in the reaction, with yields ranging from 3% to 85%. Keywords: amine-borane complex; pentafluorosulfanyl chloride; pentafluorosulfanyl substituent; radical addition; radical initiation; Introduction The pentafluorosulfanyl (SF5) substituent has been attracting its

• recently, it has been shown that some of these common amine–borane complexes can also be used as radical initiators for atom transfer radical addition of alkyl halides to alkenes [48]. They were also used in the free-radical polymerization of alkene-containing monomers such as methyl methacrylate or

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• on 160 to the enone and produces 161. The newly formed 161 was subjected to 5-exo radical addition to the allyl sulfane and subsequent loss of a thiyl radical produces 162. A successive hydrolysis/decarboxylation upon heating and cleavage of acetal on 162 afforded aldehyde 163 in 90% yield. Coupling

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• quenching cycle, generating [Ir]•−, which reduces the phthalimide ester 117 to give α-amino radicals 117• after decarboxylation. The CPA then activates the azaarene 118 through protonation and brings the two reactive species together in a hydrogen bonded complex 119, which facilitates radical addition

• reaction to proceed. Jiang et al. developed a similar system for the enantioselective radical addition into 2-vinylazaarenes 122 using DPZ and either α-amino radicals [60] or ketyl radicals [61], with pyridines being well tolerated as substrates in this latter case (Scheme 17a). The same group also

• chiral environment, producing 247 in excellent yields and enantioselectivities (17 examples, up to 99:1 er). The authors noted that they cannot rule out the alternative mechanism whereby a radical addition of 248• to an acid coordinated 249 is followed by a single electron reduction of the resulting N

A complementary approach to conjugated N-acyliminium formation through photoredox-catalyzed intermolecular radical addition to allenamides and allencarbamates

• Olusesan K. Koleoso,
• Matthew Turner,
• Felix Plasser and
• Marc C. Kimber

Beilstein J. Org. Chem. 2020, 16, 1983–1990, doi:10.3762/bjoc.16.165

• radical addition, using photoredox catalysis, to allenamides and allencarbamates is reported. This transformation synthesizes N-acyl-N’-aryl-N,N’-allylaminals, and proceeds by a conjugated N-acyliminium intermediate that previously has principally been generated by electrophilic activation methods. The

• examining the full mechanism of this transformation, expanding the scope of substrates that can be used in the radical addition step, and alternative fates for the α-N-acyl radical 13 [58][59][60]. Electrophilic activation of allenamides. The planned intramolecular radical addition to allenamides generating

Photoredox-catalyzed silyldifluoromethylation of silyl enol ethers

• Vyacheslav I. Supranovich,
• Vitalij V. Levin and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 1550–1553, doi:10.3762/bjoc.16.126

• carbon–bromine bond. Keywords: difluoroalkylation; organofluorine compounds; photocatalysis; radical addition; silicon reagents; Findings Fluorinated silicon reagents have found widespread use for the introduction of fluorinated fragments [1][2][3][4][5]. Typically, these reagents work under strongly

• of the alkyl group compared to that of an aryl group, which either makes radical addition reversible or attenuates the reactivity of the starting enol ether. Similarly, an aromatic substrate bearing an ortho substituent gave lower yields, which may be associated with the ability of the ortho group to

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• alkyl radicals were easily accessed by the photocatalyzed reduction of the corresponding bromides, in turn promoting an efficient radical addition onto isonitriles. In one instance, the dimeric gold complex [Au2(dppm)2]Cl2 (dppm = bis(diphenylphosphino)methane) acted as the photocatalyst and activated

• intermediate onto the C–C double bond of 16.1 gave radical 16.2·a upon nitrogen loss, which underwent an intramolecular cyclization and finally afforded the substituted phenanthridine 16.3a in a satisfactory yield (Scheme 16, path a) [81]. The same azide 16.1 underwent trifluoromethyl radical addition to give

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

• -system. According to EPR data, the authors suggested that iminoxyl radicals 101 generated from oximes 100 by photolysis with the addition of the di-tert-butyl peroxide gave nitroxides 102 [123]. The widespread use of iminoxyl radicals in organic synthesis involving a radical addition to a C=C bond

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

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• α-hydroxybenzyl radical 90, which then coupled, forming the 1,2-diol 92 (Scheme 23). In 2014, Melchiorre and co-workers found that 4-anisaldehyde (52) could efficiently catalyze the intermolecular atom transfer radical addition (ATRA) of the haloalkanes 93 to the olefins 94 under irradiation with a

• chiral cyclobutene 180, providing highly functionalized cyclobutanes 182 and an access to the enantioenriched cyanosulfones 183, resulting from cyclobutane ring opening, or the new tetrasubstituted cyclobutanes 184 (Scheme 42). The cyclobutenes 180 were subjected to a photocatalyzed radical addition, and

Controlling alkyne reactivity by means of a copper-catalyzed radical reaction system for the synthesis of functionalized quaternary carbons

• Goki Hirata,
• Yu Yamane,
• Naoya Tsubaki,
• Reina Hara and
• Takashi Nishikata

Beilstein J. Org. Chem. 2020, 16, 502–508, doi:10.3762/bjoc.16.45

• reaction of 3 equivalents of terminal alkyne 1 (aryl substituted alkyne) and an α-bromocarbonyl compound 2 (tertiary alkyl radical precursor) undergoes tandem alkyl radical addition/Sonogashira coupling to produce 1,3-enyne compound 3 possessing a quaternary carbon in the presence of a copper catalyst

• . Moreover, the reaction of α-bromocarbonyl compound 2 and an alkyne 4 possessing a carboxamide moiety undergoes tandem alkyl radical addition/C–H coupling to produce indolinone derivative 5. Keywords: copper catalyst; 1,3-enyne; functionalized quaternary carbon; indolinone; tandem alkyl radical addition

• the reaction of 2a and electron-deficient alkyne 4a was performed under the conditions shown in Table 1, entry 9, the C–H cyclized product 5a was obtained instead of 3k. In this case, an alkyl radical addition followed by C–H cyclization via an alkenyl radical intermediate could be occur (Scheme 4). A

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

• . The use of either homoleptic or heteroleptic complexes in atom transfer radical addition (ATRA) reactions, reductions, oxidations, proton-coupled electron transfer (PCET) reactions, and reactions based on energy transfer will be discussed. 1 Homoleptic Cu(I) complexes Homoleptic complexes based on

• witnessed. 1.1 ATRA reactions Atom transfer radical addition reactions are linchpin transformations in organic synthesis as they allow an easy difunctionalization of alkenes. Usually, these reactions require the use of a radical initiator or thermal activation to initiate the radical chain. Recently

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• of photoredox catalytic C–C bond formation, its application in the field of atom transfer radical addition (ATRA) reactions is very important. Remarkably, this type of C–C bond formation became only popular in 2011, while the first example was already published by Barton in 1994 [28]. Recently

• -trifluoromethylated styrenes no lactone formation took place in these reactions, and only the Kharasch-addition product was observed. The benzylic radical resulting from radical addition to these styrene derivatives seems to be too electron poor for efficient oxidation induced cyclization, thus resulting in a

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• /Cvinyl–CF2H bonds followed a radical addition–elimination process (Scheme 73). Subsequently, Bouyssi and co-workers [135][136][137] used Togni’s reagent to conduct the trifluoromethylation of (hetero)aromatic aldehydes or corresponding N,N-dialkylhydrazones with CuCl as the catalyst at room temperature

Towards the preparation of synthetic outer membrane vesicle models with micromolar affinity to wheat germ agglutinin using a dialkyl thioglycoside

• Dimitri Fayolle,
• Nathalie Berthet,
• Bastien Doumeche,
• Olivier Renaudet,
• Peter Strazewski and
• Michele Fiore

Beilstein J. Org. Chem. 2019, 15, 937–946, doi:10.3762/bjoc.15.90

• glycosides cannot be carried out with unprotected thio-glycosides, implying orthogonal protection and deprotection steps in order to obtain unprotected glycolipids. We decided to investigate the formation of artificial OMV composed of long chain alkyl thioglycosides synthesized by the photoinduced radical

• addition of thiols to alkenes – known as thiol–ene coupling, TEC – a very efficient metal-free click reaction [18][19]. We prepared n-alkyl 1-thio-β--glycosides from unprotected sugar anomeric thiols, commercial n-alkenes and one synthetic lipophilic scaffold presenting two reactive alkenyl ends. Although

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• Supporting Information File 2). These four examples demonstrate the principal possibility of application of catalysts 11 in ROCM reactions. It is known that metathesis reactions carried out in chloroform medium under similar conditions (see Table 3) can give products of the Kharasch radical addition of CHCl3

Dirhodium(II)-catalyzed [3 + 2] cycloaddition of N-arylaminocyclopropane with alkyne derivatives

• Wentong Liu,
• Yi Kuang,
• Zhifan Wang,
• Jin Zhu and
• Yuanhua Wang

Beilstein J. Org. Chem. 2019, 15, 542–550, doi:10.3762/bjoc.15.48

• radical cation C resulting from cyclopropane ring opening reacts with alkyne substrate 2a generating radical D. The intermediate radical D yielded E through intramolecular radical addition. After hydrogen atom transfer (HAT) from complex A, the desired product is obtained with regeneration of the N

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• to generate intermediate 38 which is oxidized by Cu(II) to provide the CF3-substituted dihydronaphthalenes derivatives 31 along with releasing a proton [65][66]. The trifluoromethylthiolation of MCPs 1 with AgSCF3 was achieved by Shi et al. which proceeds through a sequence of radical addition, ring

• and aldehydes 48 to provide 2-acyl-3,4-dihydronaphthalenes 49 in moderate to excellent yields via a series of radical addition, ring-opening and cyclization in the presence of DTBP (di-tert-butyl peroxide) and Lewis acids (Scheme 12) [73]. Moreover, the experimental results showed MCPs 1 with electron

• radical addition of intermediate 66 to the C–C double bond in MCPs moiety furnishes the more stable benzyl radical intermediate 67, which is ring-opened to give alkyl radical 68. Finally, intermediate 68 goes through SET with the Rh(III) species and intramolecular cyclization with the 2-position of the

N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• well as the first pentafluorosulfanylation method starting from sulfur hexafluoride [2]. We are convinced that the value of phenothiazine derivatives in photoredox catalysis is still underestimated. While these compounds found widespread use in ATRA (atom transfer radical addition) polymerization [15

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• ). Conclusion We have established a protocol for a photoinduced radical addition of xanthates to olefins using an iridium-based photocatalyst under blue LED irradiation, leading to diverse xanthate adducts. This reaction proceeds through a radical-chain propagation mechanism via an initiation involving a

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• (III) form of 1 has recently been found to catalyze atom transfer radical addition of alkyl halides to olefins (phenyl vinyl sulfone and acrylates) in the presence of NaBH4 [115]. In addition, a new light-driven method for generating acyl radicals from 2-S-pyridyl thioesters was developed through the

Hypervalent iodine compounds for anti-Markovnikov-type iodo-oxyimidation of vinylarenes

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Mikhail A. Syroeshkin,
• Alexander A. Korlyukov,
• Pavel V. Dorovatovskii,
• Yan V. Zubavichus,
• Gennady I. Nikishin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2018, 14, 2146–2155, doi:10.3762/bjoc.14.188

• target products (yields up to 91%). In contrast to previous studies in which oxidants promote the electrophilic addition of iodine to the C=C bond, radical addition predominates in the discovered process. Radical pathway starts from the attack of imide-N-oxyl radicals on the double C=C bond, which allows

Functionalization of graphene: does the organic chemistry matter?

• Artur Kasprzak,
• Agnieszka Zuchowska and
• Magdalena Poplawska

Beilstein J. Org. Chem. 2018, 14, 2018–2026, doi:10.3762/bjoc.14.177

• ) radical addition, (d) formation of phenol, (e) adsorption of phenol onto the graphene sheet. Acknowledgements This work was financially supported by the National Science Centre (Poland) through the grant OPUS No. 2016/21/B/ST5/01774. Artur Kasprzak acknowledges Foundation for Polish Science (FNP) for the

Visible light-mediated difluoroalkylation of electron-deficient alkenes

• Vyacheslav I. Supranovich,
• Vitalij V. Levin,
• Marina I. Struchkova,
• Jinbo Hu and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2018, 14, 1637–1641, doi:10.3762/bjoc.14.139

• with blue light is described. The reaction involves radical addition of 1,1-difluorinated radicals at the double bond followed by hydrogen atom transfer from sodium cyanoborohydride. Keywords: difluoroalkylation; organofluorine compounds; radical addition; visible light; Introduction Applications of

• boron-centered radical anion 5. After the initiation event, the reaction proceeds via a chain mechanism. Thus, radical addition at the double bond gives radical 6, which abstracts a hydrogen atom from cyanoborohydride to generate boryl radical anion 5. The latter species can readily abstract the iodine

Investigations of alkynylbenziodoxole derivatives for radical alkynylations in photoredox catalysis

• Yue Pan,
• Kunfang Jia,
• Yali Chen and
• Yiyun Chen

Beilstein J. Org. Chem. 2018, 14, 1215–1221, doi:10.3762/bjoc.14.103

• NMR spectra of BI-alkynes 3a–f were studied with the focus on the α-carbon, which position directly underwent α-radical addition [19]. The electron density of the α-carbon was decreased in 3a with electron-deficient 3,4-difluoro groups on the benziodoxole, and was increased for 3f with electron

• to optimal 80% yield. Based on mechanistic investigations above, we propose that the electronic effect on benziodoxoles affected both the radical acceptor and oxidative quencher reactivity of BI-alkyne derivatives (Scheme 7). In the alkyl or acyl radical addition step to BI’-alkyne (step 1) and the