Direct synthesis of 6-sulfonylated phenanthridines via silver-catalyzed radical sulfonylation-cyclization of 2-isocyanobiphenyls

A convenient and straightforward synthesis of 6-sulfonylated phenanthridines via silver-catalyzed sequential radical insertion, cyclization and aromatization of 2-isocyanobiphenyls is reported. The protocol does not require a phenanthridine scaffold as a substrate and presents a highly regioselective synthesis of 6-alkyl/arylsulfonyl phenanthridines. The protocol utilizes readily available and easy to handle sodium sulfinates as sulfonating agents and potassium persulfate as an oxidant to afford good to excellent yields of the desired products in a one-pot operation at room temperature.     

Nitrenoid from Oxime: A Practical Synthesis of Planar Chiral Ferrocenyl Phenanthridines via Nitrene-Involved Ring-Expansion Reaction

Nitrenes and nitrenoids are highly reactive species and the proposed key intermediates in nitrogen-containing heterocyclic compound synthesis. In this work, we developed a practical method for the synthesis of phenanthridines by the reaction of oximes and Grignard reagents (with or without diethylzinc) via ring-expansion of magnesium coordinated nitrenoid complex as the key step. The method has been used to synthesize optically active planar chiral ferrocenyl phenanthridines.     

Tandem Sulfonylation/Cyclization of Vinyl Azides with Aryldiazonium Tetrafluoroborates and SO2

An efficient and facile strategy for the synthesis of 6-(sulfonylmethyl)phenanthridines and its derivatives has been developed via tandem sulfonylation cyclization of vinyl azides under mild conditions in the absence of any catalysts and additives. The reaction simply utilizes easily accessible and cheap K₂S₂O₅ as the sulfur dioxide source, delivering functionalized phenanthridines in moderate to excellent yields with operational simplicity and gram-scale synthesis, as well as good functional-group tolerance.     

Silver-catalyzed 2-isocyanobiaryls insertion/cyclization with phosphine oxides: synthesis of 6-phosphorylated phenanthridines

A silver-catalyzed 2-isocyanobiaryls insertion/cyclization with phosphine oxides was described for the construction of the 6-phosphorylated phenanthridines through radical addition of in situ formed P-centered radical to 2-isocyanobiphenyls and homolytic aromatic substitution process. The reactions could proceed smoothly to give the desired 6-phosphorylated phenanthridines promoted by AgOAc (20 mol %) with PhI(OAc)₂ (3.0 equiv).     

The first stereocontrolled synthesis of 12-methyl-hexahydrobenzo[c]phenanthridine alkaloids

12-Methyl B/C hexahydrobenzo[c]phenanthridines have been synthesized stereoselectively starting from chiral nonracemic 2-aryl-4-pentenoic acids prepared by asymmetric allylation of (+)-(S,S)-pseudoephedrine-based arylacetamide enolates. Subsequent transformations (Friedel–Crafts acylation, stereocontrolled reductive amination, Pictet–Spengler cyclization and PPA catalyzed cationic cyclization) led to the synthesis of enantiomerically enriched hexahydrobenzo[c]phenanthridines in which the sequential formation of all the new stereogenic centres was controlled by the starting chiral acids.     

Phenanthridine synthesis via [2+2+2] cyclotrimerization reactions

A concise synthesis of phenanthridines via a microwave-assisted [2+2+2] cyclotrimerization reaction has been developed.     

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.     

Metal-Free Synthesis of Benzo[α]phenanthridines from Aromatic Aldehydes,Cyclohexanones,and Aromatic Amines

A three-component synthesis of benzo[α]phenanthridines from aromatic aldehydes,cyclohexanones,and aromatic amines has been developed,which is mediated by KI/DMS...     

Synthesis and physicochemical characterization of novel 6-aminopyrido[3,4-c][1,9]phenanthrolines as aza-analogs of benzo[c]phenanthridines

Based on the 6-aminobenzo[c]phenanthridines, a compound class showing noteworthy antitumor activity, an efficient one-step synthesis consisting of a base-catalyzed condensation of 2 equiv of 4-methylpyridine-3-carbonitrile and various aldehydes causing twofold ring closure is described. The obtained 6-amino-11,12-dihydropyrido[3,4-c][1,9]phenanthrolines could be aromatized with Pd/C at high temperatures to form 6-aminopyrido[3,4-c][1,9]phenanthrolines. All compounds were systematically characterized regarding both lipophilicity and solubility and a high cytotoxic potential was evaluated in preliminary in vitro studies. Compared to formerly described 6-aminobenzo[c]phenanthridines our newly developed phenanthrolines turned out to possess improved drugability, due to significantly increased water-solubility and decreased lipophilicity.     

1,3-Dipolar cycloaddition reaction of phenanthridinium N-imines and N-benzoylimine with acetylenic compounds

N-Aminophenanthridinium salt reacted with dimethyl acetylenedicarboxylate in the presence of potassium carbonate to give a 3,3a-dihydropyrazolo[1,5-f]phenanthridine but with mono-substituted acetylenes (ethyl propiolate and benzoylacetylene) it produced aromatized pyrazolo-[1,5-f]phenanthridines (XII and XIII). The reaction of the N-benzoylimine with di-substituted acetylenes (dimethyl acetylenedicarboxylate and methyl phenylpropiolate) and mono-substituted acetylenes (ethyl propiolate and benzoylacetylene) yielded 1,3a-dihydropyrazolo[1,5-f]phenanthridines and the aromatized products (XII and XIII), respectively.     

“Golden” Cascade Cyclization to Benzo[c]-Phenanthridines

Herein, we describe a gold-catalyzed cascade cyclization of Boc-protected benzylamines bearing two tethered alkyne moieties in a domino reaction initiated by a 6-endo-dig cyclization. The reaction was screened intensively, and the scope was explored, resulting in nine new Boc-protected dihydrobenzo[c]phenanthridines with yields of up to 98 %; even a π-extension and two bidirectional approaches were successful. Furthermore, thermal cleavage of the Boc group and subsequent oxidation gave substituted benzo[c]phenanthridines in up to quantitative yields. Two bidirectional approaches under the optimized conditions were successful, and the resulting π-extended molecules were tested as organic semiconductors in organic thin-film transistors.     

Synthesis of Functionalized Pyrido[1,2-f]phenanthridines from Phenanthridine,Activated Acetylenes,and Arylidenemalononitriles

The zwitterions generated from phenanthiridine and dialkyl acetylenedicarboxylates (DAADs) react with a variety of arylidenemalononitriles, affording substituted pyrido[1,2-f]phenanthridines.     

Intramolecular Diels-Alder reaction of 1-aminoisobenzofurans: Application to the synthesis of benzo[c]phenanthridines

Intramolecular Diels-Alder reactions of 1-aminoisobenzofurans give benzo[c]phenanthridines. The reactive intermediates are generated from o-(diazomethyl)benzamides.     

From dioxime oxalates to dihydropyrroles and phenanthridines via iminyl radicals

Dioxime oxalates are useful precursors for the clean generation of iminyl radicals by sensitised UV photolysis and can be adapted for serviceable preparations of 3,4-dihydro-2H-pyrroles and phenanthridines.     

UV promoted phenanthridine syntheses from oxime carbonate derived iminyl radicals

Oxime carbonates were found to be excellent precursors for the clean and direct generation of iminyl radicals under UV irradiation. Suitably functionalised iminyls underwent cyclisations yielding various phenanthridines and also substituted quinolines and isoquinolines. EPR and X-ray analyses of oxime carbonates provided insight into the mechanism.     

A High Performance Route for the Synthesis of Dihydropyrrolo[1,2‐f]phenanthridine Scaffolds by using a One‐pot Four‐component Reaction

Synthesis of a series pyridine containing dihydropyrrolo core fused phenanthridines by a one‐pot four‐component reaction in an efficient route is reported. This report contains the reaction of pyridinecarbaldehydes, malononitrile, and phenanthridine in the presence of alkyl isocyanides.     

Synthesis of 6-carboxylated phenanthridines by oxidative alkoxycarbonylation–cyclization of 2-isocyanobiphenyls with carbazates

An iron-catalyzed synthesis of 6-carboxylated phenanthridines starting with readily prepared isocyanides and carbazates was developed. Reactions occurred via addition of alkoxycarbonyl radicals to the isocyanide group and subsequent intramolecular cyclization.     

Synthesis and properties of 6-(p-tolyl)phenanthridines and 5,10-di(p-tolyl)diazapyrenes

10-Amino-, 10-phthalimido-, and 10-(p-toluamido)-6-(p-tolyl)phenanthridines and 5,10-di(ptolyl)-4,9-diazapyrene, the oxidation of which gives the 4,9-dioxide. were synthesized.     

The reaction of tetralones with nitriles: a simple approach to the synthesis of new substituted benzo[h]quinazolines, benzo[f]quinazolines and dibenzo[a,i]phenanthridines

The one-pot reaction of 1-tetralone with nitriles in the presence of triflic anhydride affords in good yields 2,4-disubstituted 5,6-dihydrobenzo[h]quinazolines, which oxidation with DDQ leads to the corresponding benzo[h]quinazolines. 2-Tetralone undergoes identical process forming 1,3-disubstituted 5,6-dihydrobenzo[f]quinazolines. However, when the reaction of 2-tetralone is carried out with methylthiocyanate as nitrile, 5-methylthiotetrahydrodibenzo[a,i]phenanthridines are isolated in good yields. Easy transformations of the methylthio group offer possible access to a variety of substituted dibenzo[a,i]phenanthridines.     

Synthesis of 5-aryl-1-methyl-1,2,3,4-tetrahydrobenzo[<Emphasis Type="Italic">a</Emphasis>]phenanthridines

5-Aryl-1-methyl-1,2,3,4-tetrahydrobenzo[a]phenanthridines were synthesized by cascade heterocyclization of the corresponding substituted benzaldehydes with 2-methylcyclohexanone and naphthalen-2-amine in a polar solvent in the presence of hydrochloric acid.