A facile one-pot regioselective synthesis of functionalized novel benzo[f]chromeno[4,3-b][1,7]naphthyridines and benzo[f][1,7]naphthyridines via an imino Diels-Alder reaction

A novel series of functionalized 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridines and 1,3-diphenylbenzo[f][1,7]naphthyridines have been synthesized by an efficient regioselective one-pot multicomponent synthesis through intra and intermolecular imino Diels-Alder reaction. In this method, we have achieved complete regioselectivity and atom economy with polysubstituted core motifs in moderate to good yields. The proposed mechanism of this reaction has also discussed.     

One-pot synthesis of substituted indolo[1,2-a]quinolines under transition-metal-free conditions

A simple and efficient one-pot synthesis of substituted indolo[1,2-a]quinolines under transition-metal-free conditions has been developed. When 2-fluorobenzaldehyde was treated with substituted 2-methylindoles in the presence of Cs₂CO₃, the desired products were typically obtained in good to excellent yields. This reaction sequence involves a nucleophilic aromatic substitution and a Knoevenagel condensation reaction. Our mechanistic investigation revealed that both reactions could proceed as an intermolecular reaction in the first step.     

Palladium-catalyzed one-pot synthesis of benzo[b][1,6]naphthyridines via Sonogashira coupling and annulation reactions from 2-chloroquinoline-3-carbonitriles

Palladium-catalyzed one-pot synthesis of 1,3-disubstituted benzo[b][1,6]naphthyridines and [1,6]naphthyridines has been described from easily accessible precursors, 2-chloroquinoline-3-carbonitriles and 2-chloropyrido-3-carbonitrile via sequential additions of palladium-catalyst for Sonogashira-coupling and the following annulations in good to excellent yields. A plausible mechanism for annulation is discussed.     

Densely functionalized 1,2-dihydrobenzo[b][1,6]naphthyridines: one-pot synthesis via sequential Ugi and Heck reactions

A facile one-pot synthesis of functionalized 1,2-dihydrobenzo[b][1,6]naphthyridines is described via sequential Ugi four components using 2-chloroquinoline-3-carboxaldehydes, allyl amine, acetic acid, isocyanides and ligand free Heck reactions in good yields.     

Galanthamine analogs: 6H-benzofuro[3a,3,2,-e,f][1]benzazepine and 6H-benzofuro[3a,3,2-e,f][3]benzazepine

The known cholinesterase inhibitory capability of the Amarylidaceae alkaloid galanthamine prompted preparation of analogs in which the position of the nitrogen within the azepine ring is altered. The analogs 6H-benzofuro[3a,3,2-e,f][1]benzazepine and 6H-benzofuro[3a,3,2-e,f][3]benzazepine were prepared in 19 and 2.5%, respectively, following Kametani and Shimizu approaches, respectively. The aniline derivative 6H-benzofuro[3a,3,2-e,f][1]benzazepine failed to undergo most of the reactions typical for galanthamine. Thus, it neither oxidized to the analogous narwedine, nor epimerized to the analogous epigalanthamine, nor reduced to the lycoramine analog, under the conditions used for galanthamine.     

Tandem synthesis of functionalized tetrahydro-4aH-benzo[c]isoquino[1,2-t]pyrrolo[1,2-a][1,6]naphthyridines

An effective route to fused hexacyclic derivatives of isoquinoline is described via tandem reaction of isoquinoline, dialkyl acetylenedicarboxylates, and 3-chloropentane-2,4-dione or alkyl 3-chloroacetoacetates.     

The first synthesis of the benzo[b]indolo[1,2-h][1,7]naphthyridine ring system

The first syntheses of representatives of the benzo[b]indolo[1,2-h][1,7]naphthyridine ring system have been accomplished using the Friedländer reaction.     

A novel three-component method for the synthesis of triazolo[1,2-a]indazole-triones

An efficient synthesis of triazolo[1,2-a]indazole-1,3,8-trione derivatives based on the three-component condensation of urazole, dimedone and aromatic aldehydes under solvent-free conditions is described.     

Facile synthesis and coupling of 3,9-dibromo-6-aryl-5H-dibenzo[d,f][1,3]diazepine derivatives

A route has been developed to prepare 3,9-dibromo-6-aryl-5H-dibenzo[d,f][1,3]diazepine derivatives which undergo facile Suzuki coupling to generate extended conjugated moieties bearing this unit. Single crystal X-ray studies on three of the coupled products provide valuable information on the conformation and bulk packing of these materials.     

Synthesis of dibenzo-[b,f][1,5]diazocine-based hosts and their assembly behaviors with C60

Diaryl[b,f][1,5]diazocine-based macrocycles 5 and 6 with inner cavities have been synthesized via Hay coupling method. Single crystal of 5 shows that it forms a dimeric aggregate via the weak intermolecular interactions between two adjacent rings, which is rarely reported in such macrocycles. Moreover, SEM results reveal that both macrocycles 5 and 6 assemble with C₆₀ to form well-ordered fullerene-based nano-rod structures.     

Functionalized fluorinated arylethers by ring-opening of 1,2,3,4-tetrafluorodibenz[b,f][1,4]oxazepine

Treatment of 1,2,3,4-tetrafluorodibenz[b,f][1,4]oxazepine with acetyl or benzoyl chloride produces the fluorinated aryl ethers bearing amide and aldehyde functionalities, RCONHC₆H₄-2-OC₆F₄CHO-2 (2a R=Ph; 2b R=Me). The structures of intermediate compounds produced by addition of acid chloride across the imine bond and by partial hydrolyis of the resulting chlorine-containing compound have been determined.     

Efficient one-pot synthesis of spiro[indoline-3,4′-pyrazolo[3,4-e][1,4]thiazepine]dione via three-component reaction

An efficient one-pot synthesis of spiro[indoline-3,4′-pyrazolo[3,4-e][1,4]thiazepine] dione derivatives via three-component reaction of 5-amino-3-methylpyrazole, isatin, and thioacid is described. This new protocol produces novel heptacyclic spirooxindole derivatives in good yields in comparison to conventional pentacyclic compounds. This method proceeds through a 3-(5-aminopyrazol-3-yl)-3-hydroxy-2-oxindoline intermediate (Baylis-Hillman type adduct), unlike 3-indolylimine (the intermediate like Shiff-Bases) as in conventional methods. The structure of one representative compound has been confirmed by X-ray diffraction analysis.     

Synthesis and properties of 1,3,3-trimethylspiro[indoline-2,3′-naphtho[2,1-b][1,4]oxazin]-6′-amine, a novel, red colouring photochromic spirooxazine

The synthesis and photochromic properties of 1,3,3-trimethylspiro[indoline-2,3′-naphtho[2,1-b][1,4]oxazin]-6′-amine, a novel red-colouring photochromic spirooxazine and derivatives is reported. The synthesis proceeds via an unusual one-pot transamination, oxime formation, N-O bond cleavage, spirooxazine formation process.     

Intramolecular Heck reaction: A facile sequential one-pot synthesis of 1,2,3,4-tetrahydrobenzo[b][1,6]naphthyridines

A simple and convenient sequential one-pot synthesis of 1,2,3,4-tetrahydrobenzo[b][1,6] naphthyridines has been developed. The reductive amination of 2-chloro-3-formylquinolines with various amines in the presence of sodium borohydride provided the corresponding secondary amines in high yields. Further, a sequential one-pot reaction involving N-allylation and intramolecular Heck type 6-exo-trig cyclization was performed on the secondary amines to afford a range of desired 1,2,3,4-tetrahydrobenzo[b][1,6]-naphthyridine derivatives in good to high yields.     

Synthesis of polyfluorodibenz[b,f][1,4]oxazepines by the cyclization of 2-[(polyfluorobenzylidene)amino]phenols

Thermolysis of 2-[(polyfluorobenzylidene)amino]phenols in ethanol in the presence of triethylamine affords the corresponding fluorinated dibenz[b,f][1,4]oxazepines in moderate to high yields. The structures of 2-[(2,3,4,5,6-pentafluorobenzylidene)amino]phenol and 1,2,3,4-tetrafluorodibenzo[b,f][1,4]oxazepine have been determined by single-crystal X-ray diffraction.     

First total synthesis and determination of the absolute configuration of 1-N-methyl-3-methylamino-[N-butanoicacid-3-(9-methyl-8-propen-7-one)-amide]-benzo[f][1,7]naphthyridine-2-one, a novel benzonaphthyridine alkaloid

The first total synthesis of benzonaphthyridine alkaloid (1), a unique diazaphenathrene alkaloid isolated from mangrove-derived Streptomyces albogriseolus, was accomplished. The core structure was unequivocally constructed via several key transformations, such as Knoevenagel condensation, Curtius rearrangement, and cyclic carbamate formation-reduction sequence. The chiral unsaturated ketone acid moiety was synthesized from N-tert-butoxycarbonyl-l-glutamic acid gamma-tert-butyl ester (15). The absolute configuration was determined.     

Is samoquasine A indeed benzo[f]phthalazin-4(3H)-one? Unambiguous, straightforward synthesis of benzo[f]phthalazin-4(3H)-one and its regioisomer benzo[f]phthalazin-1(2H)-one

In search for the structural elucidation of samoquasine A, a natural product isolated from the seeds of Annona squamosa L., two benzo[f]phthalazinone isomers have been synthesized. The synthetic pathway followed to build up these skeletons is based on the combination of two Suzuki reactions on a pyridazinone precursor and a ring closure reaction via a condensation reaction. ¹H NMR data of the synthesized compound allowed to establish that the structure of the natural product samoquasine A is not benzo[f]phthalazin-4(3H)-one, as previously suggested.     

A novel and convenient method for the synthesis of new derivatives of pyrido[3,2-e]pyrrolo[1,2-a][1,4]diazepine-6,11-dione

A novel methodology has been developed for the efficient synthesis of 1,4-pyridopyrrolodiazepine derivatives. The key reaction is the bromination under mild conditions by NBS of compounds resulting via peptide coupling of l-proline methyl ester with 3-aminopyridine-2-carboxylic acid 1, then intramolecular cyclization in the construction of 2-bromo-6a,7,8,9-tetrahydro-5H-pyrido[3,2-e]pyrrolo[1,2-a][1,4]diazepine-6,11-dione 4. This latter is then engaged in cross-coupling reactions to generate 1,4-pyridopyrrolodiazepines derivatives 5a-m, 6a-i, 7, and 8a-c. This strategy provides an efficient method to access a library of compounds based on privileged substructures that are of great interest in drug discovery.     

Selective reduction of aromatic azides with hexamethyldisilathiane: synthesis of new 2-azidopyrrolo[2,1-c][1,4]benzodiazepines

2-Azidopyrrolobenzodiazepines have been synthesized via cyclization of ω-azidocarbonyl compounds employing hexamethyldisilathiane by selectively reducing the aryl azido functionality.     

Indium(III)chloride catalyzed synthesis of novel 1H-pyrazolo[1,2-b]phthalazine-5,10-diones and 1H-pyrazolo[1,2-a]pyridazine-5,8-diones under solvent-free condition

An efficient, inexpensive and environmentally friendly synthesis of novel 3-amino-2-benzoyl-1-aryl-1H-pyrazolo[1,2-b]phthalazine-5,10-dione and 3-amino-2-benzoyl-1-aryl-1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives has been developed via one-pot three-component reaction of phthalhydrazide or maleic hydrazide, aldehydes and arylacetonitrile in the presence of catalytic amount of InCl₃ as a Lewis acid catalyst under solvent-free conditions. The most important features of the present protocol are mild reaction conditions, short reaction times, high yields, and a wide range of functional group tolerance.