Ring transformations of heterocyclic compounds. XXII. Pyrido[1,2‐a]indolium salts from 2‐methyl‐3H‐indoles by pyrylium mediated three carbon annelation

The synthesis of pyrido[1,2‐a]indolium perchlorates 8,11 from 2,4,6‐triarylpyrylium perchlorates 1 and 2‐methyl‐3H‐indoles 6,9 in the presence of a basic condensing agent (anhydrous sodium acetate, piperidine acetate, triethylamine/acetic acid, triethylamine) in ethanol by a 2,4‐[C₃+C₂N] pyrylium ring transformation is reported. Spectroscopic data of the transformation products and their mode of formation are discussed.     

A simple synthesis of 4‐chloro‐5‐hydroxy‐1H‐benzo[g]indoles

The reaction of methyl 2‐(3‐chloro‐1,4‐dioxo‐1,4‐dihydronaphthalen‐2‐yl)propenoate ( 2a ) with primary amines gave 4‐chloro‐5‐hydroxy‐3‐methoxycarbonyl‐1H‐benzo[g]indoles 5a‐f as major compounds and 3‐methoxycarbonyl‐4,9‐dioxo‐2,3,4,9‐tetrahydro‐1H‐benzo[f]indoles 6a‐d as minor ones. Whereas the reaction of 3‐(3‐chloro‐1,4‐dioxo‐1,4‐dihydronaphthalen‐2‐yl)‐3‐buten‐2‐one ( 2b ) with primary amines afforded the corresponding 1H‐benzo[g]indoles 5g‐i as major products and 3‐acetyl‐4,9‐dihydro‐4,9‐dioxo‐1H‐benzo[f]indoles 7g, h as minor products.     

Synthesis and reactions of 11H‐benzo[b]pyrano[3,2‐f]indolizines an pyrrolo[3,2,1‐ij]pyrano[3,2‐c]quinolines

2‐Methyl‐3H‐indoles 1 cyclize with two equivalents of ethyl malonate 2 to form 4‐hydroxy‐11H‐benzo[b]pyrano[3,2‐f]indolizin‐2,5‐diones 3, whereas 2‐mefhyl‐2,3‐dihydro‐1H‐indoles 9 give under similar conditions regioisomer 8‐hydroxy‐5‐methyl‐4,5‐dihydro‐pyrrolo[3,2,1‐ij]pyrano[3,2‐c]quinolin‐7,10‐diones 10 . The pyrone rings of 3 and 9 can be cleaved either by alkaline hydrolysis to give 7‐acetyl‐8‐hydroxy‐10H‐pyrido[1,2‐a]indol‐6‐ones 4 or 5‐acetyl‐6‐hydroxy‐2‐methyl‐1,2‐dihydro‐4H‐pyrrolo‐[3,2,1‐ij]quinolin‐4‐ones 11 , respectively. Chlorination of 3 and 9 with sulfurylchloride gives under subsequent ring opening 7‐dichloroacetyl‐8‐hydroxy‐10H‐pyrido[1,2‐a]indol‐6‐ones 5 or 5‐dichloracetyl‐6‐hydroxy‐2‐methyl‐1,2‐dihydro‐4H‐pyrrolo[3,2,1‐ij]quinolin‐4‐ones 12 . The dichloroacetyl group of 5 can be reduced with zinc to 7‐acetyl‐8‐hydroxy‐10H‐pyrido[1,2‐a]indol‐6‐ones 7. Treatment of the acetyl compounds 4, 7 and 11 with 90% sulfuric acid cleaves the acetyl group and yields 8‐hydroxy‐10H‐pyrido[1,2‐a]‐indol‐6‐ones 6 and 8 , and 6‐hydroxy‐2‐methyl‐1,2‐dihydro‐4H‐pyrrolo[3,2,1‐ij]quinolin‐4‐ones 13 . Reaction of dichloroacetyl compounds 12 with sodium azide yields 6‐hydroxy‐2‐methyl‐5‐(1H‐tetrazol‐5‐ylcarbonyl)‐1,2‐dihydro‐4H‐pyrrolo[3,2,1‐ij]quinolin‐4‐ones 14 via intermediate geminal diazides.     

Annulation of o‐Aminoquinoxaline‐1,4‐dioxidenitrile with Ketonic Compounds Under Friedländer‐type Cyclocondensation and its Biological Evaluation

The reaction of compound 2‐amino‐3‐cyano‐6‐methylquinoxaline‐1,4‐dioxide with cyclohexanone and dimedone in dimethylformamide in the presence of anhydrous ZnCl₂ under Friedländer‐type cyclocondensation gave compounds 12‐amino‐9‐methyl‐1,2,3,4,12,12a‐hexahydroquinolino[2,3‐b]quinoxaline‐6,11‐dioxide ( 4 ), 7‐methyl‐4‐oxo‐3,4‐dihydro‐1H‐spiro[benzo[g]pteridine‐2,1′‐cyclohexane]5,10‐dioxide ( 5 ), and 12‐amino‐3,3,9‐trimethyl‐1‐oxo‐1,2,3,4,12,12a‐hexahydroquinolino[2,3‐b]quinoxaline‐6,11‐dioxide ( 6 ); (R)‐3′,3′,7‐trimethyl‐4,5′‐dioxo‐3,4‐dihydro‐1H‐spiro[benzo[g]pteridine‐2,1′‐cyclohexane]5,10‐dioxide ( 7 ) were achieved and evaluated their biological activity as antibacterial and antifungal activities and antitumor evaluation, and also, the density functional theory calculations were evaluated.     

Synthesis of New Derivatives of 4‐(4,7,7‐Trimethyl‐7,8‐dihydro‐6H‐benzo[b]pyrimido[5,4‐e][1,4]thiazin‐2‐yl)morpholine

Cyclocondensation of 5‐amino‐6‐methyl‐2‐morpholinopyrimidine‐4‐thiol ( 1 ) and 2‐bromo‐5,5‐dimethylcyclohexane‐1,3‐dione ( 2 ) under mild reaction condition afforded 4,7,7‐trimethyl‐2‐morpholino‐7,8‐dihydro‐5H‐benzo[b ]pyrimido[5,4‐e ][1,4]thiazin‐9(6H )‐one ( 3 ). The ¹H and ¹³C NMR data of compound ( 3 ) are demonstrated that this compound exists primarily in the enamino ketone form. Reaction of compound ( 3 ) with phosphorous oxychloride gave 4‐(9‐chloro‐4,7,7‐trimethyl‐7,8‐dihydro‐6H‐benzo[b ]pyrimido[5,4‐e ][1,4]thiazin‐2‐yl)morpholine ( 4 ). Nucleophilic substitution of chlorine atom of compound ( 4 ) with typical secondary amines in DMF and K₂CO₃ furnished the new substituted derivatives of 4‐(4,7,7‐trimethyl‐7,8‐dihydro‐6H‐benzo[b ]pyrimido[5,4‐e ][1,4]thiazin‐2‐yl)morpholine ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h ). All the synthesized products were characterized and confirmed by their spectroscopic and microanalytical data.     

Five closely related 4‐chloro‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepines: similar molecular structures but different supramolecular assemblies

Dibenz[b,f]azepine (DBA) is a privileged 6‐7‐6 tricyclic ring system of importance in both organic and medicinal chemistry. Benzo[b]pyrimido[5,4‐f]azepines (BPAs), which also contain a privileged 6‐7‐6 ring system, are less well investigated, probably because of a lack of straightforward and versatile methods for their synthesis. A simple and versatile synthetic approach to BPAs based on intramolecular Friedel–Crafts alkylation has been developed. A group of closely‐related benzo[b]pyrimido[5,4‐f]azepine derivatives, namely (6RS)‐4‐chloro‐6,11‐dimethyl‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepine, C₁₄H₁₄ClN₃, (I), (6RS)‐4‐chloro‐8‐hydroxy‐6,11‐dimethyl‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepine, C₁₄H₁₄ClN₃O, (II), (6RS)‐4‐<!?tlsb=‐0.14pt>chloro‐8‐methoxy‐6,11‐dimethyl‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepine, C₁₅H₁₆ClN₃O, (III), and (6RS)‐4‐chloro‐8‐methoxy‐6,11‐dimethyl‐2‐phenyl‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepine, C₂₁H₂₀ClN₃O, (IV), has been prepared and their structures compared with the recently published structure [Acosta‐Quintero et al. (2015). Eur. J. Org. Chem. pp. 5360–5369] of (6RS)‐4‐chloro‐2,6,8,11‐tetramethyl‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepine, (V). All five compounds crystallize as racemic mixtures and they have very similar molecular conformations, with the azepine ring adopting a boat‐type conformation in each case, although the orientation of the methoxy substituent in each of (III) and (IV) is different. The supramolecular assemblies in (II) and (IV) depend upon hydrogen bonds of the O—H...N and C—H...π(arene) types, respectively, those in (I) and (V) depend upon π–π stacking interactions involving pairs of pyrimidine rings, and that in (III) depends upon a π–π stacking interaction involving pairs of phenyl rings. Short C—Cl...π(pyrimidine) contacts are present in (I), (II) and (IV) but not in (III) or (V).     

Selective synthesis of some 4,5‐dihydro‐2H‐benzo[g]indazoles and 8,9‐dihydro‐2H‐benzo[e]indazoles via the vilsmeier‐haack reaction under thermal and microwave assisted conditions

A selective and easy method is described for the synthesis of 4,5‐dihydro‐2H‐benzo[g]indazoles and 8,9‐dihydro‐2H‐benzo[e]indazoles by the Vilsmeier‐Haack reaction of various tetralone phenylhydrazones under thermal and microwave irradiation conditions.     

Rearrangement of spiro[2H‐1‐benzopyran‐2,2′‐[2H]indoles] to pyrrolo[1,2‐a]indole derivatives

Heating of 1′‐(N‐substituted carbamoyl)methylspiro[2H‐1‐benzopyran‐2,2′‐[2H]indoles] with potassium hydroxide in ethanol yields diastereomeric 5a,13‐methano‐6H‐1,3‐benzoxazepino[3,2‐a]indole‐12‐carbox‐amides. Reduction of the latter with sodium borohydride affords 1,2,3,9a‐tetrahydro‐2‐hydroxyaryl‐9H‐pyrrolo[ 1,2‐a] indole‐3 ‐carboxamides.     

A concise,efficient and versatile synthesis of amino‐substituted benzo[b]pyrimido[5,4‐f]azepines: synthesis and spectroscopic characterization,together with the molecular and supramolecular structures of three products and one intermediate

A concise, efficient and versatile synthesis of amino‐substituted benzo[b]pyrimido[5,4‐f]azepines is described: starting from a 5‐allyl‐4,6‐dichloropyrimidine, the synthesis involves base‐catalysed aminolysis followed by intramolecular Friedel–Crafts cyclization. Four new amino‐substituted benzo[b]pyrimido[5,4‐f]azepines are reported, and all the products and reaction intermediates have been fully characterized by IR, ¹H and ¹³C NMR spectroscopy and mass spectrometry, and the molecular and supramolecular structures of three products and one intermediate have been determined. In each of N,2,6,11‐tetramethyl‐N‐phenyl‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepin‐4‐amine, C₂₂H₂₄N₅, (III), 4‐(1H‐benzo[d]imidazol‐1‐yl)‐6,11‐dimethyl‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepine, which crystallizes as a 0.374‐hydrate, C₂₁H₁₉N₅·0.374H₂O, (VIIIa), and 6,7,9,11‐tetramethyl‐4‐(5‐methyl‐1H‐benzo[d]imidazol‐1‐yl)‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepine, C₂₄H₂₅N₅, (VIIIc), the azepine ring adopts a boat conformation, but with a different configuration at the stereogenic centre in (VIIIc), as compared with (III) and (VIIIa). In the intermediate 5‐allyl‐6‐(1H‐benzo[d]imidazol‐1‐yl)‐N‐methyl‐N‐(4‐methylphenyl)pyrimidin‐4‐amine, C₂₂N₂₁N₅, (VIIb), the immediate precursor of 4‐(1H‐benzo[d]imidazol‐1‐yl)‐6,8,11‐trimethyl‐6,11‐dihydro‐5H‐benzo[b]pyrimido[5,4‐f]azepine, (VIIIb), the allyl group is disordered over two sets of atomic sites having occupancies of 0.688 (5) and 0.312 (5). The molecules of (III) are linked into chains by a C—H…π(pyrimidine) hydrogen bond, and those of (VIIb) are linked into complex sheets by three hydrogen bonds, one of the C—H…N type and two of C—H…π(arene) type. The molecules of the organic component in (VIIIa) are linked into a chain of rings by two C—H…π(arene) hydrogen bonds, and these chains are linked into sheets by the water components; a single weak C—H…N hydrogen bond links molecules of (VIIIc) into centrosymmetric R₂²(10) dimers. Comparisons are made with some related compounds.     

Two conformers of 10,11‐dihydro‐5H‐dibenzo[a,d]cyclo­heptene spiro‐linked with homobenzoquinone epoxide

The crystal structures of the two thermally equilibrated conformational isomers of the epoxide 1′,5′‐dimethyl­spiro[10,11‐dihydro‐5H‐dibenzo[a,d]cyclo­heptene‐5,8′‐4′‐oxatricyclo[5.1.0.0^3,5]octane]‐2′,6′‐dione, C₂₃H₂₀O₃, have been determined by X‐ray diffraction. In the tricyclic dione skeleton, the oxirane and cyclo­propane rings adopt an anti structure with respect to the conjunct quinone frame. The spiro‐linked 10,11‐dihydro‐5H‐dibenzo[a,d]cyclo­heptene ring of the major isomer has a fairly twisted boat form, folding opposite to the adjoining cyclo­propane methyl substituent, whereas the seven‐membered ring of the minor isomer has an almost ideal twist–boat form, inversely folding to the side of the relevant methyl group. The conformational structures of these isomers have been compared with those of the corresponding isomers of the unepoxidized homobenzoquinone.     

First synthesis of 2‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[h]chromen‐2‐yl)‐1‐naphthol and 3‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[g]chromen‐2‐yl)‐2‐naphthol from 1‐ and 2‐naphthol derivatives

Two new structurally isomeric, 2‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[h]chromen‐2‐yl)‐1‐naphthol ( 1 ) and 3‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[g]chromen‐2‐yl)‐2‐naphthol ( 3 ) have been synthesized from 2‐acetyl‐1‐naphthol and ethyl‐3‐hydroxy‐2‐naphthoate, respectively, involving Grignard reaction, dehydration of the corresponding tertiary alcohols, and hetero Diels–Alder dimerization. The two benzochromenes ( 1 and 3 ) have been fully characterized by IR, NMR, and HRESIMS data. Their structures are further supported by crystallography of their corresponding acetates ( 2 and 4 ). J. Heterocyclic Chem., (2011).     

Ring transformations of heterocyclic compounds. XXIII. The UV irradiation product of photochromic 2,4,6‐triaryl‐1‐(spiro[2H‐l‐benzopyran‐2,2′‐indoline]‐6‐yl)pyridinium salts ‐ A phenolate betaine or a pyridinium substituted merocyanine dye?

The synthesis of the novel 2,4,6‐triaryl‐1‐(spiro[2H‐1‐benzopyran‐2,2′‐indoline]‐6‐yl)pyridiniumper‐chlorates 4 by reaction of 5 ‐nitrosalicylaldehydes 6 with 1,3,3‐trimethyl‐2‐methyleneindoline ( 7 ) to 6‐nitro‐spiro[2H‐1‐benzopyran‐2,2′‐indolines] 1 , their stannous chloride reduction to the 6‐amino derivatives 8 , followed by a 2,6‐[C₅+N] ring transformation with 2,4,6‐triarylpyrylium perchlorates 9 , is reported. UV irradiation experiments in twenty solvents of different polarity prove their photochromic properties and show that the photochemically generated negative solvatochromic dyes 5 , formed by ring opening of the benzopyran moiety of 4 , are rather merocyanine than pyridinium phenolate betaine dyes.     

Ring transformations of heterocyclic compounds. XIX. Spiro[dihydropyridine‐indolines] novel heterocycles with two spiro‐condensed N‐containing subunits easy accessible by 1,3‐oxazinium ring transformation

The synthesis of hitherto unknown 1‐benzoyl‐1′,3′,3′‐trimethyl‐4,6‐diphenylspiro[1,2‐dihydropyridine‐2,2′‐indolines] 5 from 2,4,6‐triphenyl‐1,3‐oxazinium tetrafluoroborate ( 1b ) and 1,3,3‐trimethyl‐2‐methyleneindolines 2 (used as such or generated in situ from the corresponding 3H‐indolium salts 4 ) in the presence of triethylamine in anhydrous acetonitrile by a 3,6‐[C₃N+C₂] 1,3‐oxazinium ring transformation is reported. Structure elucidation is performed by an X‐ray structure determination of the spiro[dihydropyridine‐indoline] 5a . Spectroscopic data of the transformation products and their mode of formation are discussed.     

An Efficient Synthesis of Benzo[g]thiazolo[2,3‐b]quinazolin‐4‐ium and Benzo[g]benzo[4,5]thiazolo[2,3‐b]quinazolin‐14‐ium Hydroxides by a One‐pot,Three‐component Reaction under Green Conditions

A new series of benzo[g]thiazolo[2,3‐b]quinazolin‐4‐ium and benzo[g]benzo[4,5]thiazolo[2,3‐b]quinazolin‐14‐ium hydroxide derivatives have been synthesized by the one‐pot, three‐component reaction of aryl glyoxal monohydrates, 2‐hydroxy‐1,4‐naphthoquinone, and 2‐aminothiazole or 2‐aminobenzothiazole in the presence of triethylamine and p‐toluenesulfonic acid as organocatalysts in H₂O/acetone (2:1) at room temperature. This method offers mild reaction conditions, excellent yields, easy workup, and readily accessible starting materials and catalysts.     

Green One‐Pot Solvent‐Free Synthesis of Pyrazolo[1,5‐a]pyrimidines,Azolo[3,4‐d]pyridiazines,and Thieno[2,3‐b]pyridines Containing Triazole Moiety

Synthesis of pyrazolo[1,5‐a]pyrimidines, [1,2,4]triazolo[1,5‐a]pyrimidine, 8,10‐dimethyl‐2‐(5‐methyl‐1‐phenyl‐4,5‐dihydro‐1H‐1,2,3‐triazol‐4‐yl)pyrido[2′,3′:3,4]‐pyrazolo[1,5‐a]pyrimidine, benzo[4,5]imidazo[1,2‐a]pyrimidine via heterocyclic amines, and sodium 3‐hydroxy‐1‐(5‐methyl‐1‐phenyl‐1H‐1,2,3‐triazole‐4‐yl)prop‐2‐en‐1‐one were carried out. Also, synthesis of isoxazoles, and pyrazoles from sodium 3‐hydroxy‐1‐(5‐methyl‐1‐phenyl‐1H‐1,2,3‐triazole‐4‐yl)prop‐2‐en‐1‐one and hydroxymoyl chlorides and hydrazonoyl halides, respectively, were made. Analogously, (1,2,3‐triazol‐4‐yl)thieno[2,3‐b]pyridine derivatives were obtained from sodium 3‐hydroxy‐1‐(5‐methyl‐1‐phenyl‐1H‐1,2,3‐ triazole‐4‐yl)prop‐2‐en‐1‐one and cyanothioacetamide followed by its reacting with active methylene compounds. In addition to full characterization of all synthesized compounds, they were tested to evaluate their antimicrobial activities, and some compounds showed competitive activities to those of tetracycline, the typical antibacterial drug, and clotrimazole, the typical antifungal drug.     

Synthesis of new hetero[1,2,4]thiadiazin‐3‐one S,S‐dioxides and oxazolo[3,2‐b]hetero[1,2,4]thiadiazine S,S‐dioxides as potential psychotropic drugs

A series of 2‐substituted 2H‐thieno[3,4‐e][1,2,4]thiadiazin‐3(4H)‐one 1,1‐dioxides ( 2 ), 2‐substituted 2H‐thieno[2,3‐e][1,2,4]thiadiazin‐3(4H)‐one 1,1‐dioxides ( 3 ), 2‐substituted 4,6‐dihydropyrazolo[4,3‐e]‐[1,2,4]thiadiazin‐3(2H)‐one 1,1‐dioxides ( 4 ), 2‐substituted 2,3‐dihydrooxazolo[3,2‐b]thieno[3,4‐e]‐[1,2,4]thiadiazine 5,5‐dioxides, ( 5 ), 6‐substituted 6,7‐dihydro‐2H‐oxazolo[3,2‐b]pyrazolo[4,3‐e][1,2,4]thia‐diazine 9,9‐dioxides ( 6 ) and 7‐substituted 6,7‐dihydro‐2H‐oxazolo[3,2‐b]pyrazolo[4,3‐e][1,2,4]thiadiazine 9,9‐dioxides ( 7 ) were synthesized as potential psychotropic agents.     

6,7‐Dihydrodibenzo[e,g]azulen‐8(5H)‐one and 12,13‐dihydrobenzo[e]­napth­[2,1‐g]­azulen‐14(11H)‐one

In the structures of the title compounds, 6,7‐di­hydro­dibenzo[e,g]­azulen‐8(5H)‐one, C₁₈H₁₄O, (I), and 12,13‐di­hydro­benzo[e]­napth­[2,1‐g]­azulen‐14(11H)‐one, C₂₂H₁₆O, (II), the azulene group is in a boat‐envelope conformation. The structures are stabilized by weak C—H?O interactions.     

On the mechanism and stereochemistry of the formation of β‐lactam derivatives of 2,4‐disubstituted‐2,3‐dihydro‐benzo[1,4]diazepines

2‐Chloro‐4‐phenyl‐2a‐(4′‐methoxyphenyl)‐3,5‐dihydroazatetracyclic [1,2‐d]benzo [ 1,4]diazepin‐1 ‐one ( III _a) and 2‐chloro‐4‐methyl‐2a‐(4′‐methoxyphenyl)‐3,5‐dihydroazatetracyclic[1,2‐d]‐benzo[1,4]diazepin‐1‐one ( III _b) were synthesized. 1‐Benzoyl‐2‐phenyl‐4‐(4′‐methoxyphenyl)[1,4]‐benzodiazepine ( II _a) was formed through benzoylation of starting material 2‐phenyl‐4‐(4′‐methoxyphenyl)‐[1,4]benzodiazepine ( I _a) with the inversion of seven‐member ring boat conformation. The thus formed β‐lactams should have four pairs of stereoisomers. However, only one pair of enantiomers (2S,2R,4R) and (2R,2aS,4S) was obtained. The mechanism and stereochemistry of the formation of these compounds were studied on the basis of nmr spectroscopy and further confirmed by X‐ray diffraction.     

A New Four‐Component Reaction for the Synthesis of Spiro[4H‐indeno[1,2‐b]pyridine‐4,3′‐[3H]indoles]

A new four‐component synthesis of spiro[4H‐indeno[1,2‐b]pyridine‐4,3′‐[3H]indoles] and spiro[acenaphthylene‐1(2H),4′‐[4H‐indeno[1,2‐b]pyridines] by the reaction of indane‐1,3‐dione, 1,3‐dicarbonyl compounds, isatins (=1H‐indole‐2,3‐diones) or acenaphthylene‐1,2‐dione, and AcONH₄ in refluxing toluene in the presence of a catalytic amount of pyridine is reported.     

Two similarly substituted benzo[h]pyrazolo[3,4‐b]quinoline‐5,6(10H)‐diones: supramolecular structures in two and three dimensions

The molecules of 8‐methyl‐7,10‐diphenyl‐5H‐benzo[h]pyrazolo[3,4‐b]quinoline‐5,6(10H)‐dione, C₂₇H₁₇N₃O₂, (I), are weakly linked into chains by a single C—H...O hydrogen bond, and these chains are linked into sheets by a π–π stacking interaction involving pyridyl and aryl rings. In 8‐methyl‐7‐(4‐methylphenyl)‐10‐phenyl‐5H‐benzo[h]pyrazolo[3,4‐b]quinoline‐5,6(10H)‐dione, C₂₈H₁₉N₃O₂, (II), the molecules are linked into a three‐dimensional framework structure by a combination of C—H...N, C—H...O and C—H...π(arene) hydrogen bonds, together with a π–π stacking interaction analogous to that in (I).