6-substituted Phenanthridines Research Articles

NHC-alcohol adduct-mediated photocatalytic deoxygenation for the synthesis of 6-phenanthridine derivatives.

NHC-alcohol adduct-mediated deoxygenation of alcohols under photocatalytic conditions is described. This process provides various alkyl radicals, which can react with 2-isocyanobiaryls to afford 6-substituted phenanthridine derivatives in moderate to good yields. This method offered the first example of directly using alcohols as radical sources for 6-phenanthridine synthesis.

Preparation of 6-substituted phenanthridines from o-biaryl ketoximes via the Beckmann rearrangement

Treatment of anti alkyl o-biaryl ketoximes and anti aryl o-biaryl ketoximes with Tf2O at 120 °C, followed by quenching with Et3N gave 6-alkylphenanthridines and 6-arylphenanthridines in good yields, respectively. These reactions proceeded through the O-triflation of the ketoximes, the Beckmann rearrangement, and the electrophilic cyclization of the formed nitrilium group onto the aromatic ring. © 2021 Elsevier Science. All rights reserved.

Visible-Light-Promoted and Photoredox-Catalyzed Radical Addition to Triple Bonds

This account details a series of visible-light-promoted and photoredox-catalyzed radical additions to triple bonds, including those of isocyanides, alkynes, cyanides and carbon monoxide. 6-Substituted phenanthridines, 1-substituted isoquinolines and ortho-substituted pyridine derivatives are synthesized via radical addition to isocyanides. A number of (hetero)aromatic compounds are prepared by the addition of radicals to alkynes. Carbonyl compounds can be easily obtained by radical addition to carbon monoxide. Tetracyclic quinazolinones are constructed by radical addition to cyanides. Furthermore, a wide range of quinoline and quinoxaline derivatives are synthesized by way of domino radical isocyanide/alkyne insertions and isocyanide/cyanide insertions, respectively. All the reactions can be carried out in high yields under mild conditions. 1 Introduction 2 Synthesis of Six-Membered Heteroaromatic Rings by Radical Addition to Isocyanides 2.1 Synthesis of 6-Substituted Phenanthridines 2.2 Synthesis of 1-Substituted Isoquinolines 2.3 Synthesis of ortho-Substituted Pyridines 3 Synthesis of (Hetero)aromatic Compounds by Radical Addition to Alkynes 3.1 Synthesis of Six-Membered (Hetero)aromatic Compounds 3.2 Synthesis of Five-Membered (Hetero)aromatic Compounds 4 Synthesis of Carbonyl Compounds by Radical Addition to Carbon Monoxide 5 Synthesis of Tetracyclic Quinazolinones by Radical Addition to Cyanides 6 Synthesis of Quinolines by Domino Radical Isocyanide/Alkyne Insertions 7 Synthesis of Quinoxalines by Domino Radical Isocyanide/Cyanide Insertions 8 Conclusions and Outlook

Synthesis of 6-Trichloromethylphenanthridines by Transition Metal-Free Radical Cyclization of 2-Isocyanobiphenyls.

An efficient method for the synthesis of 6-trichloromethylphenanthridines by benzoyl peroxide promoted cyclization reaction of 2-isocyanobiphenyls with carbon tetrachloride is developed. A radical pathway is proposed and evidenced for the reaction mechanism. This reaction tolerates a wide range of functional groups and the resulting 6-trichloromethylphenanthridines can be utilized as a useful synthetic precursor for corresponding 6-substituted phenanthridines.

Metal-free radical oxidative decarboxylation/cyclization of acyl peroxides and 2-isocyanobiphenyls.

A metal-free radical oxidative decarboxylation/cyclization of acyl peroxides and 2-isocyanobiphenyls was achieved, leading to 6-aryl phenanthridines as well as 6-alkyl phenanthridines in moderate to good yields. The procedure featured simple conditions and was metal-free and base free. It represents a practical approach to access 6-aryl/alkyl phenanthridines.

ChemInform Abstract: The Benzoyl Peroxide Promoted Dual C—C Bond Formation via Dual C—H Bond Cleavage: α‐Phenanthridinylation of Ether by Isocyanide.

The benzoyl peroxide-promoted α-phenanthridinylation of ether by isocyanide is developed, proceeding through dual C–H bond cleavage and dual C–C bond formation. The procedure tolerates a series of functional groups, such as methyl, fluoro, chloro, acetyl, methoxy carbonyl, cyano, and trifluoromethyl. Thus, it represents a facile pathway leading to 6-substituted phenanthridine derivatives. The addition of radical to the isonitrile followed by a radical aromatic cyclization is involved in this transformation.

ChemInform Abstract: Synthesis of 6‐Substituted Phenanthridines by Metal‐Free, Visible‐Light Induced Aerobic Oxidative Cyclization of 2‐Isocyanobiphenyls with Hydrazines.

Irradiation of hydrazines with visible-light in the presence of organic dye eosin B generates various types of functional radicals, which are trapped by 2-isocyanobiphenyls to give 6-substituted phenanthridines.

The Benzoyl Peroxide Promoted Dual C–C Bond Formation via Dual C–H Bond Cleavage: α-Phenanthridinylation of Ether by Isocyanide

The benzoyl peroxide-promoted α-phenanthridinylation of ether by isocyanide is developed, proceeding through dual C-H bond cleavage and dual C-C bond formation. The procedure tolerates a series of functional groups, such as methyl, fluoro, chloro, acetyl, methoxy carbonyl, cyano, and trifluoromethyl. Thus, it represents a facile pathway leading to 6-substituted phenanthridine derivatives. The addition of radical to the isonitrile followed by a radical aromatic cyclization is involved in this transformation.

Synthesis of 6-substituted phenanthridines by metal-free, visible-light induced aerobic oxidative cyclization of 2-isocyanobiphenyls with hydrazines

Irradiation of hydrazines and 2-isocyanobiphenyls with visible-light in the presence of organic dye eosin B generates various 6-substituted phenanthridines in good yields.

Trifluoroacetic acid-mediated facile construction of 6-substituted phenanthridines

The trifluoroacetic acid-mediated reaction of 2-arylanilines with arylaldehydes has been developed to give a variety of 6-substituted phenanthridines. This is a very simple and convenient one-pot process for library construction.

The Action of Vanadium Oxytrifluoride on N‐Arylbenzylamines — A Route to Some Phenanthridines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The Action of Vanadium Oxytrifluoride on N-Arylbenzylamines—a Route to Some Phenanthridines

The action of four equivalents of vanadium oxytrifluoride upon electron-rich N-arylbenzylamines provides a convenient synthesis of phenanthridines. Excess of oxidant can lead to selective hydroxylation of a methyl substituent. Benzylamines with a phosphonate substituent on the methylene group lead to 6-substituted phenanthridines.

A One‐Pot Access to 6‐Substituted Phenanthridines from Fluoroarenes and Nitriles via 1,2‐Arynes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A one-pot access to 6-substituted phenanthridines from fluoroarenes and nitriles via 1,2-arynes.

[reaction: see text] A one-pot, t-BuLi-induced synthesis of 6-substituted phenanthridines from fluoroarenes and nitriles via 1,2-arynes is reported. Aryl- and hetaryl nitriles, cyanamides, and trimethylacetonitrile gave phenanthridine products. The method was extended to provide bisphenanthridine 10 by a one-pot bis-cyclization, using 1,3-dicyanobenzene and PhF in 1:5 ratio. Reaction of 1-fluoronaphthalene and 4-chlorofluorobenzene with benzonitrile afforded the regioisomerically pure products 11 and 12, respectively.

Convergent synthesis of 6-substituted phenanthridines via anionic ring closure.

[reaction: see text] The addition of organometallic derivatives to the cyano group of 2-(2-fluorophenyl)benzonitrile followed by intramolecular nucleophilic substitution produces 6-substituted phenanthridines. Alkyllithiums, aryllithiums, and sterically nondemanding lithium amides reacted at -78 degrees C to produce the 6-substituted phenanthridines in 82-98% yield upon warming to room temperature. The addition of the corresponding Grignard reagents requires an excess of the organometallic reagent and extented reaction times at elevated temperature.

Positive inotropic acting compounds. II. Synthesis 5- and 6-substituted phenanthridines and the mechanism of their positive inotropic action

AbstractDie alkylsubstituierten Phenanthridine 2 und 4, ihre 5,6‐Dihydroverbindungen 3 und 5, sowie die 7,8,9,10‐Tetrahydrophenanthridiniumsalze 6 werden dargestellt, um ihre Wirkung am isoliert perfundierten, linken Meerschweinchen‐Vorhof sowie am Papillarmuskel zu untersuchen. Der Mechanismus der positiv inotropen Wirkung und Struktur‐Wirkungs‐Beziehungen werden diskutiert.

Medium and substituent effects on the photochemistry of phenanthridine N-oxides. Is an intermediate of diradical character involved in the photorearrangement of heterocyclic N-oxides?

The photochemistry of several 6-substituted phenanthridine N-oxides has been investigated, or reinvestigated, in benzene and ethanol. The main processes observed are: (a) 1,2-oxygen and substituent shift to yield N-substituted phenanthridones (2) and (b) ring enlargements to dibenzo[d,f]-1,3-oxazepines (7). With 6-diphenylmethylphenanthridine N-oxide (1b) rearrangement (a) predominates and occurs with 45% substituent loss in benzene (but only 2% in ethanol). With the 6-phenyl derivative (1c) process (a) predominates in ethanol and process (b) in benzene and with the 6-p-nitrophenyl derivative (1d) the latter process predominates in both solvents. With 6-cyanophenanthridine N-oxide (1e) rearrangement (b) predominates in benzene; in the presence of 2,3-dimethylbutene (but not of cyclohexene) addition products are obtained; with dienes deoxygenation is the main process. Medium and substituents may change the nature of the lowest excited singlet state, but more importantly affect the stability of an intermediate of diradical character occurring along the reaction pathway, thus driving it towards rearrangement (a) or (b). Intermediate diradicals are unambiguously indicated only in particular cases [elimination of a diphenylmethyl radical from (1b), alkene addition in the case of (1e)] but their role is probably more general.

ChemInform Abstract: THE PHOTOCYCLOADDITION OF 6‐SUBSTITUTED PHENANTHRIDINES TO ELECTRON‐RICH OLEFINS

AbstractDie Titelreaktion der Komponenten (I) und (II) in Ethanol wird untersucht.

The Photocycloaddition of 6-Substituted Phenanthridines to Electron-rich Olefins

Abstract The photocycloaddition reaction of 6-substituted phenanthridines and electron-rich olefins, such as trans-anethole and phenyl vinyl ether, is described. This reaction proceeds from the 1(π,π*) states of 6-substituted phenanthridines via the exciplex to give azocine and/or azetidine derivatives in ethanol.

Cyclised products in the synthesis of 6-substituted phenanthridines by phenolic cyclisation

Phenolic cyclisation of 2-(3-hydroxyphenyl)cyclohexylamine (15) with aromatic aldehydes gave 6-aryl-1,2,3,4,4a,5,6,10b-octahydrophenanthridin-7-ols (3) and (4) cyclised at the ortho-position to the hydroxy-group together with the usual 9-hydroxy-derivatives (5), (6), and (7); compounds (3), (5) and (6) were also synthesised by Bischler–Napieralski reaction of the benzamide (23) of 2-(3-methoxyphenyl)cyclohexylamine, followed by reduction and demethylation. Moreover, the reaction of (15) with six aliphatic ketones gave the corresponding 6,6-disubstituted phenanthridines.