Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis

• Akiya Ogawa and
• Yuki Yamamoto

Beilstein J. Org. Chem. 2024, 20, 2114–2128, doi:10.3762/bjoc.20.182

• thermally induced [71]. Radical cyclization of 2-isocyanobiarenes The cycloaddition reaction with 2-isocyanobiaryls 29 under radical conditions is an excellent synthetic method for nitrogen-containing fused heterocycles such as phenanthridine derivatives 31 (Scheme 20) [72][73]. The reaction proceeds by

• -isocyanobiphenyl with AIBN or dibenzoyl peroxide (DBP) affords 6-cyanoisopropyl- or 6-phenyl-substituted phenanthridine derivatives. When the reaction was performed in the presence of TTMSS and AIBN, 6-tris(trimethylsilyl)-substituted phenanthridine derivatives were mainly obtained (Scheme 21) [74]. Tobisu and

• via the radical addition of hetroatom radicals to 2-isocyanobiphenyl, another pathway to form phenanthridine scaffolds is the radical reaction of 2-aminobiaryls with free isocyanides. For example, oxidative generation of amino radicals from 2-aminobiaryls followed by intermolecular addition to

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• and a PPh3–I radical III. The subsequent isocyanide 44 SOMOphilic insertion reaction led to the formation of an imidoyl radical B. This radical then underwent rapid addition onto the C–C double bond, resulting in the release of the desired phenanthridine products 45. Importantly, this process also

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• Biotechnology, Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia 10.3762/bjoc.19.40 Abstract Two novel conjugate molecules were designed: pyrene and phenanthridine-amino acid units with a different linker length between the aromatic fragments. Molecular

• modelling combined with spectrophotometric experiments revealed that in neutral and acidic buffered water solutions conjugates predominantly exist in intramolecularly stacked conformations because of the π–π stacking interaction between pyrene and phenanthridine moieties. The investigated systems exhibited

• a pH-dependent excimer formation that is significantly red-shifted relative to the pyrene and phenanthridine fluorescence. While the conjugate with a short linker showed negligible spectrophotometric changes due to the polynucleotide addition, the conjugate with a longer and more flexible linker

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

• amides was quite wide, including different EWGs and EDGs, as well as heterocycles, ortho-substitution was not tolerated. The authors applied the methodology for the synthesis of biologically important benzo[c]phenanthridine derivatives 117. Through methylation and subsequent aromatization of the

Formal total synthesis of macarpine via a Au(I)-catalyzed 6-endo-dig cycloisomerization strategy

• Jiayue Fu,
• Bingbing Li,
• Zefang Zhou,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2022, 18, 1589–1595, doi:10.3762/bjoc.18.169

• . The convergent synthetic strategies feature the utilization of Au(I)-catalyzed cycloisomerizations of a 1,5-enyne and alkynyl ketone substrates, which were prepared by Sonogashira coupling reactions. Keywords: benzo[c]phenanthridine alkaloids; 1,5-enyne; formal total synthesis; gold catalysis

• ; macarpine; Introduction Benzo[c]phenanthridine alkaloids are an ancient and influential category of isoquinoline alkaloids, mainly found in Papaveraceae and Rutaceae (Scheme 1) [1][2]. According to their oxidation states, benzo[c]phenanthridine alkaloids can be divided into two types: partially

• ]phenanthridine skeleton consists of a phenanthridine (rings A, B, C) and a benzene (ring D), and most of the synthetic routes were completed in the last step by constructing ring B or ring C. Some representative examples and their key strategies are summarized in Scheme 2. In 1989, Hanaoka and co-workers

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• position indicates an inversely proportional relation between the strength of the −I effect exerted by substituents and the efficiency of the cyclization. Reaction of amine 15m (see Scheme 5) did not give the corresponding fluorenone, instead phenanthridine 10m was isolated in 36% yield. Most likely

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

• Songeziwe Ntsimango,
• Kennedy J. Ngwira,
• Moira L. Bode and
• Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

• synthesis of trisphaeridine to afford the product in four linear steps in an overall yield of 6.5% from 1-bromo-2,4,5-trimethoxybenzene. Keywords: aromatic compounds; cyclization; iminyl radical; phenanthridines; radical cation; synthesis; UV irradiation; Introduction Phenanthridine derivatives have

• antiparasitic compounds, trisphaeridine (3), decarine (4) and nortidiene (5) (Figure 1). The importance of the phenanthridine framework has inspired the development of numerous synthetic strategies to access these compounds. These include the classical Pictet and Ankersmit pyrolysis of N-benzylideneaniline [2

• reported by Rodrıguez and Walton we envisaged that under these photochemcial conditions, intermediate 8 would be formed. Contrary to the expected results, in our labs exposure of oxime 7 to UV irradiation yielded phenanthridine 9 as the main product alongside the nitrile 10 in lower yields [13]. We

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• perfluoroalkylated pyrimidines in good to excellent yield. In 2017, Chen and colleagues [34] prepared the phenanthridine derivative 29 with CFL (25 W) irradiation of a solution containing 27, perfluoroalkyl iodide 28, amine additive N,N,N´,N´-tetraethylethylenediamine (TEEDA) in THF (Scheme 9). TEEDA and

• phenanthridine 38 (also including quinoline products, Scheme 12). In this way, a nitrogen-centered radical was given via the EDA complex that was initiated by single-electron transfer, accomplishing the synthesis of a variety of highly functionalized nitrogen-containing aromatics with excellent yield. In 2019

• perfluoroalkylated pyrimidines 26 initiated by an EDA complex. Synthesis of phenanthridine derivative 29 initiated by an EDA complex. Synthesis of cis-tetrahydroquinoline derivative 32 initiated by an EDA complex. Mechanism of the synthesis of cis-tetrahydroquinoline derivative 32. Synthesis of phenanthridine

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• ]. [7]Helicenes of this group demonstrated a relatively high electron affinity and could be good candidates for electron-injection hole-blocking layers [39]. Donor–acceptor hybride [6]helicenes, consisting of carbazole and phenanthridine cores, are interesting as hole-transporting compounds [47]. At

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• N-heterocyclic compounds such as phenanthridine, carbazole, and dibenzo[b,d]azepine. Simultaneously, Guo’s group published the arylation of nucleosides bearing a purine moiety. The transformation was regioselective and tolerated various substituents at the N9 position of the purine, including sugar

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

• in Figure 1). For these reasons, apart from the well-known dehydrative ring-closure of acyl-o-xenylamines in the presence of phosphorus oxychloride proposed by Morgan and Walls [16], several synthetic protocols for constructing the phenanthridine structure have been reported [17][18]. These include

• construct the phenanthridine core, somophilic (radical) isocyanide addition [45][46][47] is probably the most adopted one, in view of the versatility and low cost of the starting substrates. Accordingly, several protocols for the synthesis under photocatalytic conditions of phenanthridines starting from 2

• ) finally yields the desired phenanthridine 4.4. Different radical sources R–X have been adopted to generate carbon or heteroatom-based radicals according to the general photocatalytic strategy gathered in Scheme 4, for their use in the construction of phenanthridine scaffolds. As an example, unsubstituted

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

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• complexes bearing a pyrazolo[1,5-f]phenanthridine moiety and with a general coordination motifs of the type Npyridine^Cphenyl^Cphenyl^Npyrazole was reported by the same group, namely complexes 44–46 (Figure 19) [89]. The complexes showed moderate to intense sky-blue emission with PLQY in the range 0.2–0.7

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

• found to undergo copper-catalyzed aerobic aromatic C–H amination (Scheme 3a) [52] or 1,4-aminooxygenation (spirocyclization) (Scheme 3b) [51], affording phenanthridine derivatives and azaspirocyclohexadienones, respectively, depending on the helical sense of the biaryl axis. Herein we report

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• Lidija-Marija Tumir Marijana Radic Stojkovic Ivo Piantanida Laboratory for Study of Interactions of Biomacromolecules, Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, PO Box 180, HR-10002 Zagreb, Croatia 10.3762/bjoc.10.312 Abstract Phenanthridine

• - and RNA-fluorescent markers (ethidium bromide), probes for cell viability (propidium iodide), but also “ill-famed” for various toxic (genotoxic) and mutagenic effects. After two decades of low interest, the discovery of phenanthridine alkaloids and new studies of antiparasitic/antitumor properties of

• phenanthridine derivatives resulted in the strong increase of the scientific interest about the turn of this century. Here are summarized phenanthridine-related advances in the 21st century (2000-present period) with emphasis on the supramolecular interactions and bioorganic chemistry, as well as novel or

Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes

• Roy T. McBurney and
• John C. Walton

Beilstein J. Org. Chem. 2013, 9, 1083–1092, doi:10.3762/bjoc.9.120

• spectroscopy. Iminyls with suitably placed arene or heteroarene acceptors underwent cyclisations yielding phenanthridine-type products from ortho-additions. For benzofuran and benzothiophene acceptors, spiro-cyclisation predominated at low temperatures, but thermodynamic control ensured ortho-products

Synthesis of phenanthridines via palladium-catalyzed picolinamide-directed sequential C–H functionalization

• Ryan Pearson,
• Shuyu Zhang,
• Gang He,
• Nicola Edwards and
• Gong Chen

Beilstein J. Org. Chem. 2013, 9, 891–899, doi:10.3762/bjoc.9.102

• ; palladium; phenanthridine; picolinamide; Introduction Phenanthridines and 5,6-dihydro-phenanthridines are important core structures found in a variety of natural products and functional molecules (Scheme 1A) [1][2][3][4][5][6][7][8]. Synthetic methods for their preparation include the classical Pictet

• strategies for synthesizing phenanthridines [23][24][25]. Despite these advances, construction of phenanthridines with complex substitution patterns remains difficult and often requires lengthy and inefficient synthetic sequences. Herein, we report a novel method for phenanthridine synthesis based on

• sequential palladium-catalyzed picolinamide (PA)-directed C–H functionalization reactions beginning from easily accessible PA-protected benzylamine and aryl iodide precursors. Results and Discussion New synthetic strategy for phenanthridine compounds. The picolinamide (PA) group has been shown to be an