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

• place in the presence of an excess (3 equiv) of a sacrificial donor, such as iPr2NEt [79]. Later, it was discovered that phenanthridines could be formed starting again from O-2,4-dinitrophenyloximes under photocatalyst-free conditions, by exploiting the capability of these oximes to form visible light

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

• -oxyl radicals, oxime radicals (or iminoxyl radicals) have been underestimated for a long time as useful intermediates for organic synthesis, despite the fact that their precursors, oximes, are extremely widespread and easily available organic compounds. Furthermore, oxime radicals are structurally

• reactions of oxime radicals. These reactions are classified into cyclizations involving C–H bond cleavage and cyclizations involving a double C=C bond cleavage. Keywords: iminoxyl radicals; isoxazolines; oxidative cyclization; oxime radicals; oximes; Introduction Free radicals in which an unpaired

• oximes, a widely available and fundamental class of organic compounds. However, oxime radicals almost did not find synthetic use until recently, probably due to the low stability of the majority of representatives of this type of radicals. The applications of oxime radicals in organic synthesis have

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

• oximes 27.1 can be used to efficiently generate an iminyl radical in the presence of eosin Y (OD13, Scheme 27) [140]. This methodology was employed in hydroimination and iminohydroxylation cyclization reactions to give the pyrrolines 27.2. The transformation proceeds via a SET reduction of the electron

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• derivatives were prepared upon the reaction of the corresponding oximes with isocyanates. These novel compounds reacted photochemically in the presence of supercoiled plasmid DNA. Structure–activity relationship (SAR) studies revealed that the substituent on the imine group was not affecting the extend of the

• the DNA photocleavage from sulfonylamidoximes and ethanone oximes (IV and V, Figure 1), which were found to attack DNA via sulfonyloxyl radicals (SRs) [10][11]. All the above radical species exhibit photoreactivity towards DNA. Those oxime derivatives are considered photoacid generators (PAGs) since

• radicals are also produced from 2-(1-naphthylmethyl)imidazoline [35], whereas acylaminyl radicals [R(COR)N∙] are formed from the photocleavage of the N–O bond of N,O-diacyl-N-phenylhydroxylamines, along with a carbonyloxyl radical [38]. The photochemistry of O-carbamoyl oximes (or oxime carbamates) is well

The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

• Itamar L. Gonçalves,
• Rafaela R. da Rosa,
• Vera L. Eifler-Lima and
• Aloir A. Merlo

Beilstein J. Org. Chem. 2020, 16, 175–184, doi:10.3762/bjoc.16.20

• , 8, 9, 12 and 13 were then prepared by [3 + 2]-1,3-dipolar cycloaddition of nitrile oxide (ArCNO) formed in situ from oximes and a number of alkenes as dipolarophiles, to yield the precursors of the cycloadducts isoxazolines 2, 7 and 11 regioselectively. The cycloadducts were subjected to SnCl2

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

• ) [23]. In the second report, the same electrode was applied for the asymmetric reduction of prochiral carbonyl compounds 10a and 12a, oximes 14 and gem-dibromo compounds 16 (Scheme 4). Among all of these the highest optical yield (16.6%) was obtained in the reduction of gem-dibromide substrates 16 to

• modified graphite cathode. Asymmetric hydrogenation of ketones using Raney nickel powder electrodes modified with optically active tartaric acid. Asymmetric reduction of prochiral activated olefins with a poly-ʟ-valine-coated graphite cathode. Asymmetric reduction of prochiral carbonyl compounds, oximes

Vicinal difunctionalization of alkenes by four-component radical cascade reaction of xanthogenates, alkenes, CO, and sulfonyl oxime ethers

• Shuhei Sumino,
• Takahide Fukuyama,
• Mika Sasano,
• Ilhyong Ryu,
• Antoine Jacquet,
• Frédéric Robert and
• Yannick Landais

Beilstein J. Org. Chem. 2019, 15, 1822–1828, doi:10.3762/bjoc.15.176

• radical reagent, the chain reaction proceeds, as expected, taking into account reagents polarities, affording the corresponding functionalized α-keto oximes. Although yields are modest, this rare one-pot four-component process is easy to carry out and the resulting compounds, bearing multiple

• on the synthesis of functionalized α-keto oximes through such a one-pot, four-component procedure. Results and Discussion We first investigated the reaction of xanthate 1a [29], 1-octene (2a), CO, and sulfonyl oxime ether 3a as a model reaction. When the mixture of 1a, 2a (5 equiv), and 3a (1.2 equiv

• 2, CO, and oxime esters 3, leading to 5a–l (Figure 1). The xanthate 1b, bearing a phenyl ester, gave similarly to 1a, α-keto oxime 5b in moderate yield. The reaction of 1a or 1b with vinylcyclohexane (2b) in the presence of CO and 3a afforded the corresponding α-keto oximes 5c and 5d in 54 or 32

Unnatural α-amino ethyl esters from diethyl malonate or ethyl β-bromo-α-hydroxyiminocarboxylate

• Eloi P. Coutant,
• Vincent Hervin,
• Glwadys Gagnot,
• Candice Ford,
• Racha Baatallah and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2853–2860, doi:10.3762/bjoc.14.264

• boron-based complexes. In an attempt to improve this, we applied the reported use of triethylsilane for reducing oximes into N-hydroxylamines [17] to the case of the α-hydroxyimino ester 2a. However, bringing the reduction of 2a into the N-hydroxylamino derivative 42 to completion with this reagent

Synthesis of unnatural α-amino esters using ethyl nitroacetate and condensation or cycloaddition reactions

• Glwadys Gagnot,
• Vincent Hervin,
• Eloi P. Coutant,
• Sarah Desmons,
• Racha Baatallah,
• Victor Monnot and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2846–2852, doi:10.3762/bjoc.14.263

• cleaved using palladium and ammonium formate to give the corresponding oximes which were immediately reduced into amines 22a,b, using zinc and hydrochloric acid, and a thermal cyclization of these crude products gave the piperazine-2,5-diones 23a,b in, respectively, 31 and 40% overall yield from compound

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• succinimides 50 in good yields (Scheme 31a) [87]. Likewise, oximes 51 [88] were also efficient participated in the hydroarylation of maleimides (Scheme 31b). 3. Hydroarylation of allenes An allene is an exceptional functional group in organic synthesis due to its cumulative double bonds [89][90]. In this

Cobalt bis(acetylacetonate)–tert-butyl hydroperoxide–triethylsilane: a general reagent combination for the Markovnikov-selective hydrofunctionalization of alkenes by hydrogen atom transfer

• Xiaoshen Ma and
• Seth B. Herzon

Beilstein J. Org. Chem. 2018, 14, 2259–2265, doi:10.3762/bjoc.14.201

• –carbon bond formation strategies were also examined using the Co(acac)2 HAT system. Sulfonyl oximes 6a and 6b [32] afforded the carbon–carbon coupled products 4j and 4k in 60% and 48% yields, respectively (Table 1, entries 11 and 12, respectively). Recently, our laboratory reported a formal

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• -bromo-6-hydroxylamino-2,3-benzotropone oximes 262 were obtained. Hydrolysis of these oximes 262 with sulfuric acid gave 5-bromo-6-hydroxy-2,3-benzotropone and the 4-bromo isomer 263, which were debrominated with catalytic hydrogenation to give 239 (Scheme 41). Although 239 is capable of existing as two

Hypervalent iodine-mediated Ritter-type amidation of terminal alkenes: The synthesis of isoxazoline and pyrazoline cores

• Sang Won Park,
• Soong-Hyun Kim,
• Jaeyoung Song,
• Ga Young Park,
• Darong Kim,
• Tae-Gyu Nam and
• Ki Bum Hong

Beilstein J. Org. Chem. 2018, 14, 1028–1033, doi:10.3762/bjoc.14.89

• alkene functionalization utilizing a PhI(OAc)2 ((diacetoxyiodo)benzene, PIDA)/Lewis acid combination in order to access isoxazoline and pyrazoline cores. Based on allyl ketone oximes and allyl ketone tosylhydrazones, we have developed an alkene oxyamidation and amido-amidation protocol en route to

• unactivated olefins provides a rapid construction of different heterocycles [16][17]. More specifically, the formation of isoxazoline and pyrazoline cores via alkene heterofunctionalization of allyl ketone oximes and/or allyl ketone tosylhydrazones has been well documented [18][19][20][21][22]. For example

• combination with electron-rich, Brønsted basic amines were converted to their corresponding indoline and azaindoline derivatives. However, an attempted expansion of this methodology to allyl ketone oximes and allyl ketone tosylhydrazones proved unsuccessful under the previously reported reaction conditions

Synthesis and in vitro biochemical evaluation of oxime bond-linked daunorubicin–GnRH-III conjugates developed for targeted drug delivery

• Sabine Schuster,
• Beáta Biri-Kovács,
• Bálint Szeder,
• Viktor Farkas,
• László Buday,
• Zsuzsanna Szabó,
• Gábor Halmos and
• Gábor Mező

Beilstein J. Org. Chem. 2018, 14, 756–771, doi:10.3762/bjoc.14.64

• provides a suitable conjugation site and can be used for the formation of oximes. We have recently reported that Dau was efficiently linked to the 8Lys side-chain by incorporation of an aminooxyacetic acid (Aoa) moiety [21][25]. The formed oxime linkage is more stable under physiological conditions than

Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

• Hisato Shimizu,
• Akira Yoshimura,
• Keiichi Noguchi,
• Victor N. Nemykin,
• Viktor V. Zhdankin and
• Akio Saito

Beilstein J. Org. Chem. 2018, 14, 531–536, doi:10.3762/bjoc.14.39

• research on the syntheses of heterocycles by iodine(III)-mediated/catalyzed oxidative cycloaddition reactions [17][18][19], we have found that iodine(III) reagents are effective in the oxidation of N–O bonds of oximes in the cycloaddition reaction of in situ formed nitrile oxides [20][21]. Although Adam

• adducts 3aa in 96 and 90% yields, respectively (Table 1, entries 10 and 11), BTI showed better results (Table 1, entries 8 and 9). On the other hand, the use of IBA-OTf, which was effective in the oxidative cycloaddition reaction of oximes [20][21], gave nitrone-trifluoromethanesulfonic acid (TfOH

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• particular focus on recent developments in this methodology and its use in total synthesis. Keywords: carbon–carbon bond formation; Michael addition; nitrosoalkenes; oximes; total synthesis; Introduction Conjugated nitrosoalkenes (NSA) are close analogs of α-nitroalkenes, which are important Michael

• , Michael addition of C-nucleophiles to α-nitrosoalkenes opens access to synthetically valuable α-branched oximes, which can be further utilized as useful intermediates in total synthesis. The high potential of this carbon–carbon bond-forming strategy has been recognized since 1970s in works of Corey

• nitrosoacetals 3 are not halocarbonyl compounds as in the case of oximes 1 and 2, but aliphatic nitro derivatives, which are readily transformed into enamines 3 by double silylation involving an internal redox process [19][20][21]. This allows the preparation of nitrosoalkenes, which are difficult to access by

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• in good to excellent yield within 1 h. Dimethyl formamide (DMF) acted as ligand during the activation process (Scheme 53). The protocol was also equally applicable to electron deficient oximes and electron rich anilides [185]. Bolm and co-workers reported a Rh-catalyzed amidation of Csp2–H bonds

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• , especially when it comes to the synthesis of unprotected α-aminocarbonyl targets. One conceptually alternative and long-known approach to access chiral α-aminocarbonyl compounds is to start from simple oximes 48 and carry out a Neber rearrangement [148]. Very remarkably, in 2002 already, Maruoka and co

• rearrangement oximes 48 to the α-amino ketones 49 (proceeding via the not-isolated intermediate 50) with reasonable enantioselectivities up to 85:15 (Scheme 20). Although the selectivities were not perfectly satisfying and the application scope limited to two examples, this early reported clearly demonstrated

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• /or ionic pathways [31][32][33][34]. It was not until 2004, that IBX was applied in the oxidative dehydrogenation of functionalized cyclic and acyclic ketones [31][32][33][34]. IBX was further harnessed in the oxidative dehydrogenation of 2°-amines, N-hydroxides, imines and oximes [31][32][33][34

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• -chloropropionyl chloride 174 followed by a intramolecular Friedel–Crafts alkylation afforded 1-indanones 178 (Scheme 51) [80]. A direct reaction of the latter with n-butylnitrite led to the formation of keto-oximes 179 which underwent a Pd/C catalytic reduction to give 2-amino substituted 1-indanones 180. Both

• keto-oximes 179 and 2-amino derivatives 180 are β2-adrenergic agonists tested for bronchodilating activity. The pterosin family are sesquiterpenoids naturally occurring in bracken fern (Pteridium aquilinum), some of them exhibit antibacterial and cytotoxic activity. A practical synthesis of pterosin A

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• TiO2 nanoparticle assemblies using H2O2 [51]. Geminal chloronitroso compounds are synthesized or in situ generated from their corresponding oximes by chlorination. As halogen source elemental chlorine [52][53][54], nitrosyl chloride [55], alkyl hypochlorites [56], N-chlorourea [57], tert-butyl

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• minutes in presence of 20b, the most toxic enantiomer, (−)-cyclosarin 14a, reacting faster in this enantioselective degradation [75]. Structure–activity relationships based on this first series of compounds revealed the determinant role of oximes’ nucleophilic strength in the hydrolysis process. Firstly

Copper-mediated synthesis of N-alkenyl-α,β-unsaturated nitrones and their conversion to tri- and tetrasubstituted pyridines

• Dimitra Kontokosta,
• Daniel S. Mueller,
• Dong-Liang Mo,
• Wiktoria H. Pace,
• Rachel A. Simpson and
• Laura L. Anderson

Beilstein J. Org. Chem. 2015, 11, 2097–2104, doi:10.3762/bjoc.11.226

• . Keywords: Chan–Lam; copper; nitrone; oxygen transfer; pyridine; Introduction While most applications of the Chan–Lam reaction are focused on the synthesis of aryl ethers and aryl amines, our group has been interested in the use of the Chan–Lam reaction for the synthesis of O-alkenyl oximes and

• ][38], fragment couplings [39][40][41][42], and transition metal-catalyzed C–H bond functionalization of α,β-unsaturated imines and oximes [43][44][45][46][47][48][49][50]. We were inspired by the copper-catalyzed coupling of protected α,β-unsaturated oximes and alkenylboronic acids developed by

• -propargylic oximes and undergo similar electrocyclizations to form pyridines (Scheme 2B) [52]. Herein, we show that N-alkenylnitrones 8 can be prepared through a Chan–Lam coupling of α,β-unsaturated oximes 6 and an alkenylboronic acids 7 and that these compounds undergo a novel thermal rearrangement to the

Copper-catalyzed aerobic radical C–C bond cleavage of N–H ketimines

• Ya Lin Tnay,
• Gim Yean Ang and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2015, 11, 1933–1943, doi:10.3762/bjoc.11.209

• the synthesis of azaheterocycles through an intramolecular N–C bond formation with the unsaturated systems [1][2][3][4][5][6]. As precursors of iminyl radicals, readily available oximes and their derivatives have commonly been utilized. The generation of iminyl radicals involves the homolysis of the N