Molecular Diversity of Three‐Component Reaction of β‐Enamino Imide,Malononitrile and Cyclic α‐Diketones

The base promoted three‐component reaction of β‐ enamino imide, malononitrile and various cyclic α‐ diketones in acetonitrile showed interesting molecular diversity. The reactions with acenaphthylene‐1,2‐dione and ninhydrin afforded functionalized spiro[indene‐2,4'‐pyrrolo[3,4‐b ]pyridines] and spiro[acenaphthylene‐1,4'‐pyrrolo[3,4‐b ]pyridines] in good yields. The similar reaction of phenanthrene‐9,10‐dione resulted in the formation of the unexpected complex phenanthro[9',10':4,5]furo[2,3‐c ]pyrrolo[3,4‐b ]pyrroles in satisfactory yields.     

Synthesis of Benzo[a]Phenanthro[9,10-e]-Cyclooctene

A phenanthrene-fused cyclooctatetraene, namely benzo[a]phenanthro[9,10-e]cyclooctene has been synthesized by employing the “Reich-Paquette” procedure.     

The synthesis of novel polycyclic heterocyclic ring systems via photocyclization. 9. Phenanthro[9′,10′:4,5]thieno[2,3-c]quinoline,benzo[f]phenanthro[9′,10′:4,5]thieno[2,3-c]quinoline,and benzo[h]-phenanthro[9′,10′:4,5]thieno[2,3-c]quinoline

The synthesis of three novel polycyclic heterocyclic ring systems are reported via photocyclization. The specific final products in these ring systems are: phenanthro[9′,10′:4,5]thieno[2,3-c]quinoline ( 13 ), benzo[h]-phenanthro[9′,10′:4,5]thieno[2,3-c]quinoline ( 14 ), and benzo[f]phenanthro[9′,10′:4,5]thieno[2,3-c]quinoline ( 15 ).     

Green Synthesis of 6‐Aryl‐5,6‐dihydrobenzo[4,5]imidazo[1,2‐c]quinazoline Derivatives in Ionic Liquid under Catalyst‐free Conditions

Using ionic liquids as green media, a series of 6‐arylbenzo[4,5]imidazo[1,2‐c]quinazoline derivatives is synthesized via a reaction of 2‐(1H‐benzo[d]imidazol‐2‐yl)aniline and benzaldehydes in the air. While the intermediate products of 6‐aryl‐5,6‐dihydrobenzo[4,5]imidazo[1,2‐c]quinazolines were obtained in high yields at the same conditions under nitrogen protection.     

One‐pot Combinatorial Synthesis of Benzo[4,5]imidazo‐[1,2‐a]thiopyrano[3,4‐d]pyrimidin‐4(3H)‐one Derivatives

A series of novel fused tetracyclic benzo[4,5]imidazo[1,2‐a]thiopyrano[3,4‐d]pyrimidin‐4(3H)‐one derivatives were synthesized via the reaction of aryl aldehyde, 2H‐thiopyran‐3,5(4H,6H)‐dione, and 1H‐benzo[d]imidazol‐2‐amine in glacial acetic acid. This protocol features mild reaction conditions, high yields and short reaction time.     

Phenanthro[4,5‐fgh]quinoxaline‐Fused Subphthalocyanines: Synthesis,Structure, and Spectroscopic Characterization

A series of four phenanthro[4,5‐fgh]quinoxaline‐fused subphthalocyanine derivatives 0 – 3 containing zero, one, two, and three phenanthro[4,5‐fgh]quinoxaline moieties, respectively, were isolated from the mixed cyclotrimerization reaction of 2,9‐di‐tert‐butylphenanthro[4,5‐fgh]quinoxaline‐5,6‐dicarbonitrile with 4,5‐bis(2,6‐diisopropylphenoxy)phthalonitrile and characterized by a series of spectroscopic methods including MALDI‐TOF mass, ¹H NMR, electronic absorption, magnetic circular dichroism (MCD), and fluorescence spectroscopy. The molecular structures for the compounds 0 and 2 were clearly revealed on the basis of single‐crystal X‐ray diffraction analysis. Their electrochemical properties were also studied by cyclic voltammetry. In particular, theoretical calculations in combination with the electronic absorption and electrochemical analyses revealed the significant influence of the fused‐phenanthro[4,5‐fgh]quinoxaline units on the electronic structures.     

Structures of 1‐hydrophenanthroimidazoles: building blocks in the synthesis of expanded‐ring bis(imidazoles)

The structures of 1H‐phenanthro[9,10‐d]imidazole, C₁₅H₁₀N₂, (I), and 3,6‐dibromo‐1H‐phenanthro[9,10‐d]imidazole hemihydrate, C₁₅H₈Br₂N₂·0.5H₂O, (II), contain hydrogen‐bonded polymeric chains linked by columns of π–π stacked essentially planar phenanthroimidazole monomers. In the structure of (I), the asymmetric unit consists of two independent molecules, denoted (Ia) and (Ib), of 1H‐phenanthro[9,10‐d]imidazole. Alternating molecules of (Ia) and (Ib), canted by 79.07 (3)°, form hydrogen‐bonded zigzag polymer chains along the a‐cell direction. The chains are linked by π–π stacking of molecules of (Ia) and (Ib) along the b‐cell direction. In the structure of (II), the asymmetric unit consists of two independent molecules of 3,6‐dibromo‐1H‐phenanthro[9,10‐d]imidazole, denoted (IIa) and (IIb), along with a molecule of water. Alternating molecules of (IIa), (IIb) and water form hydrogen‐bonded polymer chains along the [110] direction. The donor–acceptor distances in these N(imine)...H—O(water)...H—N(amine) hydrogen bonds are the shortest thus far reported for imidazole amine and imine hydrogen‐bond interactions with water. Centrosymmetrically related molecules of (IIa) and (IIb) alternate in columns along the a‐cell direction and are canted by 48.27 (3)°. The present study provides the first examples of structurally characterized 1H‐phenanthroimidazoles.     

Microwave‐assisted synthesis of new regioisomeric 6,7‐dihydroindeno[1,2‐e]pyrimido[4,5‐b][1,4]diazepin‐5(5aH)‐ones

Novel 11‐amino‐6‐aryl‐6,7‐dihydroindeno[1,2‐e] pyrimido[4,5‐b][1,4]diazepin‐5(5aH)‐ones 4a‐f were prepared regioselectively by the tricomponent reaction of 4,5,6‐triaminopyrimidine 1, 1,3‐indandione 2 and aromatic aldehydes 3a‐f. The bicomponent approach, using 2,4,5,6‐tetraaminopyrimidine 5 and 2‐aryl‐ideneindandiones 6a‐f as reagents, afforded 9,11‐diamino‐6‐aryl‐6,7‐dihydroindeno[1,2‐e]pyrimido[4,5‐b]‐[1,4]diazepin‐5(5aH)‐ones 7a‐f in good yields and the regioisomeric 8,10‐diamino derivatives 8a‐c in lower yields. Both, bi‐ and tricomponent approaches were performed by microwave irradiation and all products were fully characterized by detailed NMR measurements.     

Assignments of the 1H and 13C NMR spectra of pseudo-symmetric heterocyles using the HMQC-TOCSY experiment to differentiate overlapping spin systems

The ¹H nmr spectra of phenanthro[9′,10′:4,5]thieno[2,3-c]quinoline, benzo[f]phenanthro-[9′,10′:4,5]thieno[2,3-c]quinoline and benzo[h]phenanthro[9′,10′:4,5]thieno[2,3-c]quinoline are highly congested. For each compound, all protons abide in an aromatic environment complicated by pseudo-symmetric regions which result in multiple overlap of the different spin systems these molecules contain. We illustrate here the utility of the HMQC-TOCSY experiment to identify spin systems when the proton spectrum is highly congested. To complete the assignment of the ¹H and ¹³C nmr spectra of each compound the HMBC experiment is used to assign the quaternary carbons.     

Synthesis of novel pyrazolo[3,4‐d]pyrimidines peri‐fused with 1,4‐diazepine, 1,4‐thiazepine,and 1,2,4‐triazepine rings

A simple and efficient synthesis of novel ortho‐ and peri‐annulated heterocyclic systems—2,6,7,9‐tetrahydro‐8H‐pyrazolo[5,4,3‐de]pyrimido[4,5‐e][1,4]diazepine, 2,6,7,9‐tetrahydro‐8H‐pyrazolo[5,4,3‐de]pyrimido [5,4‐f][1,4]thiazepine, and 6,9‐dihydro‐2H‐pyrazolo[3,4,5‐ef]pyrimido[5,4‐f][1,2,4]triazepine is described. J. Heterocyclic Chem.,, (2012).     

Synthesis of benzo[c][1,8]phenanthrolin‐6‐one through cyclization of N‐(isoquinol‐5‐yl)‐2‐bromo‐benzamide derivatives

In the course of our search for compounds with potential antitumor properties we have undertaken the synthesis of benzo[c][1,8]phenanthroline derivatives. Our project required the preparation of 8,9‐dimethoxy benzo[c][1,8]phenanthrolin‐6‐ones. This was first attempted by the lithiumdiisopropylamide cyclization of N‐(isoquinol‐5‐yl)‐2‐bromo‐4,5‐dimethoxybenzamide. The reaction led to 40% of the unexpected internal Diels‐Alder adduct 3,4‐dimethoxy‐6H‐pyrido[2,3‐i]6,8a‐ethenoindolo[cd]isoquinoline‐2(1H)‐one, which arose from a benzyne intermediate. In a second and more successful approach, the internal biaryl palladium diacetate‐assisted coupling reaction of properly N‐protected N‐(isoquinol‐5‐yl)‐2‐bromo‐4,5‐dimethoxybenzamide was studied. The optimisation of the protecting group necessary for this procedure led to a 64% yield of the target compound starting from N,N‐(isoquinol‐5‐yl)‐bis‐(2‐bromo‐4,5‐dimethoxybenzamide).     

Structural Transformation of Methoxy‐Substituted Benzo[de]benzo[4,5]imidazo[2,1‐a]isoquinolin‐7‐ones

Structural transformation of two methoxy derivatives of benzo[de]benzo[4,5]imidazo[2,1‐a]‐isoquinolin‐7‐one were determined via spectroscopic analysis. The transformation mechanism was proposed as the breakage and reformation of the lactam bond.     

K-region oxides and imines of benzo[b]phenanthro[2,3-d]thiophene and benzo[b]phenanthro[3,2-d]thiophene

The syntheses of the K-oxides and K-imine derivatives of benzo[b]phenanthro[2,3-d]thiophene and benzo-[b]phenanthro[3,2-d]thiophene are described. The parent hydrocarbons 1 and 2 were oxidized with osmium tetroxide and sodium metaperiodate, and the dialdehydes 12 and 18 so formed, cyclized to the corresponding epoxides 1a,12b-dihydrobenz[b]oxireno[9,10]phenanthro[2,3-d]thiophene ( 7 ) and 1a,12b-dihydrobenz-[b]oxireno[9,10]phenanthro[3,2-d]thiophene ( 13 ). Reaction of the oxiranes with sodium azide gave mixtures of azido-alcohols that, in turn, were transformed to the thiaarene imines 1a,12b-dihydro-1H-benz[b]azirino-[9,10]phenanthro[2,3-d]thiophene ( 8 ) and 1a,12b-dihydro-1H-benz[b]azirino[9,10]phenanthro[3,2-d]thiophene ( 14 ), respectively, with the aid of tri-n-butylphosphine.     

Synthesis of Fused 9,10‐Dihydro‐6H‐Azepino‐ and 9,10‐Dihydro‐6H‐[1,3]Diazepino[1,2‐e]Purines via Ring Closing Metathesis as Antilipid Peroxidation Agents

Ring closing metathesis of 8‐allyl‐9‐butenylpurines or N,9‐diallyl‐N‐methyl‐9H‐purin‐8‐amines with the Grubbs second generation catalyst resulted in fused 9,10‐dihydro‐6H‐azepino[1,2‐e]purines or 9,10‐dihydro‐6H‐[1,3]diazepino[1,2‐e]purines, respectively. The 8‐allyl‐9‐butenylpurines were prepared from 8‐bromo‐9‐butenylpurines after Stille coupling with allyltributyltin. The N,9‐diallyl‐N‐methyl‐9H‐purin‐8‐amines were synthesized from 9‐allyl‐8‐bromopurines after treatment with allylamine in H₂O under MW irradiation, followed by methylation with MeI in KOH. The new compounds were tested as inhibitors of lipid peroxidation. 6‐Methyl‐4‐(morpholin‐4‐yl)‐7,10‐dihydro‐6H‐[1,3]diazepino[1,2‐e]purine presents interesting results and could serve as a lead compound.     

Ring Opening and Recyclization Reactions with Chromone‐3‐carbonitrile

Chemical transformations of chromone‐3‐carbonitrile ( 1 ) with some substituted hydrazines, namely, thiosemicarbazide, S‐methyl/benzyldithiocarbazate, 7‐chloro‐4‐hydrazinoquinoline, and 3‐hydrazino‐5,6‐diphenyl‐1,2,4‐triazine, led to substituted pyrazoles 2 , 5 – 8 . Ring opening of carbonitrile 1 followed by recyclization with 3‐amino‐1,2,4‐triazole and 2‐aminobenzimidazole gave triazolo[1,5‐a]pyrimidine 9 and pyrimido[1,2‐a]benzimidazole 10 , respectively. Treatment of carbonitrile 1 with some heterocyclic amines produced 2‐amino‐3‐substituted‐chromones 11 and 12 . The novel 3‐hydroxychromeno[4,3‐b]pyrazolo[4,3‐e]pyridin‐5(1H)‐one ( 13 ) was efficiently synthesized from the ring conversion of carbonitrile 1 with cyanoacetohydrazide. A mixture of chromeno[2,3‐b]naphthyridine 14 and chromeno[4,3‐b]pyridine 15 was obtained from base catalyzed transformation of carbonitrile 1 with malononitrile dimer. A diversity of novel annulated chromeno[2,3‐b]pyridines 16 – 22 was also synthesized. Chromeno[2,3‐b]pyrrole‐2‐carboxylate 23 was obtained from the reaction of carbonitrile 1 with ethyl chloroacetate. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.     

Reaction of 2‐acyl‐6‐methylbenzo[b]furan‐3‐acetic acids derivatives with hydrazine

Reaction of 2‐acyl‐6‐methylbenzo[b]furan‐3‐acetic acids and their derivatives such as amides and esters with hydrazine does not give expected 1‐alkyl‐5H‐benzofuro[2,3‐e]diazepin‐4‐ones ones but results in 2‐amino‐7‐methyl‐2H‐benzo[4,5]furo[2,3‐c]pyridin‐3‐ones or (3‐R‐6‐methylbenzo[b]furan‐2‐yl)alkyl ketone azines.     

Ring transformations of heterocyclic compounds. XX Benzo‐fused spiro[cyclohexadiene‐dihydroindoles] by ring transformation of pyrylium salts with anhydrobases of benzo[e]‐ and benzo[g]indolium salts

The diastereoselective synthesis of 6‐aroyl‐3,5‐diarylspiro[cyclohexa‐2,4‐diene‐1,2′2′,3′‐dihydro‐1′H‐benzo[e]indoles] 6 and ‐benzo[g]indoles] 7 from 2,4,6‐triarylpyrylium perchlorates 1 and in situ generated 2‐methylene‐2,3‐dihydro‐1H‐benzo[e]indoles 3 or ‐benzo[g]indoles 5 (anhydrobases of the corresponding 2‐methyl‐1H‐benzo[e]indolium perchlorates 2 and 2‐methyl‐3H‐benzo[g]indolium perchlorates 4 , respectively) in the presence of triethylamine/acetic acid in ethanol by a 2,5‐[C₄+C₂] pyrylium ring transformation is reported. 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.     

Palladium‐Catalyzed Synthesis of Benzophenanthrosilines by C−H/C−H Coupling through 1,4‐Palladium Migration/Alkene Stereoisomerization

A new and efficient synthesis of 8H‐benzo[e]phenanthro[1,10‐bc]silines from 2‐((2‐(arylethynyl)aryl)silyl)aryl triflates under palladium catalysis has been developed. The reaction mechanism was experimentally investigated and a catalytic cycle involving C?H/C?H coupling through a new mode of 1,4‐palladium migration with concomitant alkene stereoisomerization is proposed.     

Synthesis of 1‐substituted [1,2,3]triazolo[4,5‐d]pyridazines as precursors for novel tetraazapentalene derivatives

A series of 1‐substituted 4,5‐diformyl‐[1,2,3]triazole derivatives were prepared by 1,3‐dipolar cyclo‐addition of aryl azides with acetylene dicarboxaldehyde mono‐diethylacetal. The triazoles were readily converted into 1‐substituted [1,2,3]triazolo[4,5‐d]pyridazines in good yields. The 1‐(2‐nitrophenyl)‐[1,2,3]triazolo[4,5‐d]pyridazine was found to be a useful intermediate for the generation of the novel 5H‐benzo[1,2,3]triazolo[1′,2′:1,2]triazolo[4,5‐d]pyridazin‐6‐ium inner salt ring system.