An efficient three-component reaction involving [3 + 1 + 1] furannulation leading to furanonaphthoquinones in water

An efficient and clean green synthesis of highly substituted linear naphtho[2,3-b]-furan-4,9-dione derivatives, starting from 2-hydroxy-1,4-naphthoquinone, alkyl isocyanides and a variety of aldehydes, is described. This new method provides the first example of an efficient regioselective synthetic method for the synthesis of linear naphtho[2,3-b]-furan-4,9-dione ring systems by formation of three bonds. This [3 + 1 + 1] furannulation strategy affords furanonaphthoquinones in moderate to high yields, using water as a cheap, non-toxic, environmentally friendly solvent, in a one-step reaction, without the need of complicated work-up procedures. Correspondence: Mohammad Bagher Teimouri, Petrochemical Department, Iran Polymer and Petrochemical Institute, P.O. Box 14965-115, Tehran, Iran.     

Synthesis of bhimamycin B based on oxidative rearrangement of 4-acetylnaphtho[1,2-b]furan-5-ol to naphtho[2,3-c]furan-4,9-dione

The first total synthesis of bhimamycin B, a novel member of naphtho[2,3-c]furan quinone antibiotics, was achieved by oxidative skeletal rearrangement of 4-acetylnaphtho[1,2-b]furan-5-ol.     

One-pot three-component reaction of isocyanides, dialkyl acetylenedicarboxylates and phthalhydrazide: synthesis of highly functionalized 1H-pyrazolo[1,2-b]phthalazine-5,10-diones

Protonation of the highly reactive 1:1 intermediate produced in the reaction between alkyl isocyanides and electron-deficient acetylenic esters with phthalhydrazide, leads to a vinylisonitrilium cation, which undergoes an addition reaction with the conjugate base of the phthalhydrazide to produce dialkyl 3-(alkylamino)-5,10-dioxo-5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine-1,2-dicarboxylates in fairly good yields at room temperature.     

Efficient synthesis of 2- and 3-substituted-2,3-dihydro [1,4]dioxino[2,3-b]pyridine derivatives

A versatile new approach for the synthesis in three steps of 2-substituted-2,3-dihydro[1,4]dioxino[2,3-b]pyridines B via a Smiles rearrangement using easily available reagents is described. A study illustrating the influence of experimental conditions on the progress of the reaction is reported.     

Reduction of indolo[2,3-b]quinoxalines

Reduction of indolo[2,3-b]quinoxalines with zinc in the presence of an anhydride gave N,N-diacyl trapped 6,11-dihydroindolo[2,3-b]quinoxalines in 43-92% yields. When the reduction with zinc was performed in TFA/TFAA, an unexpected ring opened product was isolated in 49% yield. The structure of this product could be identified as 1,2-dihydro-1-trifluoroacetyl-3-[(2-trifluoroacetylamino)phenyl]quinoxaline.     

Novel synthesis of pyridazino[4,5-b][1,4]oxazin-3,8-diones

A novel and effective synthesis of pyridazino[4,5-b][1,4]oxazin-3,8-diones via Smiles rearrangement is presented. Treatment of N-substituted 2-chloro(or hydroxy)acetamide, 2-tetrahydropyranyl-4-chloro-5-hydroxy(or chloro)pyridazin-3-one and cesium carbonate in refluxing acetonitrile was afforded the corresponding pyridazino[4,5-b][1,4]oxazin-3,8-diones in excellent yield.     

An efficient synthesis of novel tetrahydrochromeno[2,3-b]chromenes

A series of novel tetrahydrochromeno[2,3-b]chromenes is synthesized via the acid-catalyzed dimerization reactions of 5-methoxy- or 6-methoxyflavenes. A rational mechanism for the observed rearrangement is proposed.     

An efficient diastereoselective synthesis of spiro pyrido[2,1-b][1,3]oxazines via a novel pyridine-based three-component reaction

The zwitterions generated from pyridine and dialkyl acetylenedicarboxylate (DAAD) reacted with benzofuran-2,3-diones to form highly substituted spiro pyrido[2,1-b][1,3]oxazines in good to high yields without using a catalyst.     

Furan ring opening-furan ring closure: cascade rearrangement of novel 4-acetoxy-9-furylnaphtho[2,3-b]furans

The cascade rearrangement of novel 4-acetoxy-9-furylnaphtho[2,3-b]furans leading to tetracyclic naphthodifurans derivatives has been developed. The reaction proceeds via double recyclization of both furan rings of the initial molecule, one of the furan rings serving as a 1,3-dicarbonyl compound equivalent.     

Zinc triflate-catalyzed synthesis of pyrazino[2,1-b]quinazoline-3,6-diones

Using zinc triflate, the direct one-pot double cyclodehydration of linear tripeptides to the total synthesis of pyrazino[2,1-b]quinazoline-3,6-diones (1a-l) on solid support was achieved with good overall yields in short reaction time. These syntheses of the pyrazino[2,1-b]quinazoline-3,6-diones were conveniently achieved in only three steps, starting from the amino acid-bound Wang resin.     

First construction of 12H-thiochromeno[2,3-b]quinolines and 5H-benzo[7,8]thiocino-[2,3-b]quinolines via intramolecular Friedel-Crafts reaction of Morita-Baylis-Hillman adducts

An acid-promoted intramolecular Friedel-Crafts reaction of the Morita-Baylis-Hillman adducts 3 derived from 2-arylthioquinolin-3-carbaldehydes 2 was investigated. Interestingly, promoted by sulfuric acid, the substrates with electron-donating groups on the aromatic ring gave six-membered fused-ring 12H-thiochromeno[2,3-b]quinolines 4 with good yields, while those with electron-withdrawing groups afforded eight-membered fused-ring 5H-benzo[7,8]thiocino[2,3-b]quinolines 5 in moderate yields. Using triflic acid instead of sulfuric acid, only products 4 could be obtained under the similar condition.     

A novel one-pot two-component synthesis of tricyclic pyrano[2,3-b]quinoxalines

A one-pot two-component synthesis of tricyclic pyrano[2,3-b]quinoxalines with a pendant hydroxymethyl fuction at the 2-position relevant to molybtopterin is described by the reaction of o-phenylenediamine and phenylhydrazone derivatives of sugars in good yields.     

One-pot synthesis of 12H-benzo[b]xanthen-12-ones and naphtha[2,3-b]furans from non-naphthalene substrates

An efficient one-pot synthesis of 12H-benzo[b]xanthen-12-ones via an oxidant initiated and base promoted tandem reaction of 2-(4-(2-haloaryl)-4-hydroxybut-1-ynyl)benzaldehydes has been developed. By using similar strategy, a one-pot synthesis of naphtha[2,3-b]furans from the cascade reaction of 2-(4-hydroxy-but-1-ynyl)benzaldehydes with 2-bromoacetonitrile or α-bromocarbonyl compounds has also been achieved.     

A convenient synthesis of new pyrido[3,2-e][1,4]diazepine-2,5-diones and pyrido[2,3-e][1,4]diazepine-2,5-diones

A convenient synthesis of a series of pyrido[3,2-e][1,4]-diazepine-2,5-diones 8 and pyrido[2,3-e][1,4]diazepine-2,5-diones 9, is reported using the condensation of α-amino acid methyl ester derivatives with 1H-pyrido[3,2-d][1,3]oxazine-2,4-dione and 1H-pyrido[2,3-d][1,3]oxazine-2,4-dione. Compounds 8 and 9 were also synthesized by peptide coupling of α-amino acid methyl ester derivatives with β-amino acids (2 or 3) followed by the cyclisation in tetrahydrofuran with sodium hydride (NaH).     

Synthesis of novel oxindolylpyrrolo[2,3-d]pyrimidines via a three-component sequential tandem reaction

A novel one-pot three-component reaction of 6-amino-uracil, isatin, and acetophenone was accomplished through a programmed pH variation for the synthesis of 5-(2-oxoindolin-3-yl)-1H-pyrrolo[2,3-d]pyrimidine-2,4(3H,7H)-dione derivatives. The reaction was conducted in a sequential tandem manner to give the oxindole substituted pyrrolo[2,3-d]pyrimidine products in good to excellent yields. Despite of timing all the processes were carried out in one pot. Most of these novel compounds show narrow to good spectrum of antimicrobial activities in vitro.     

Rapid access to multi-substituted pyrimido[4,5-b][1,4]diazepine-2,4,6-trione and pyrimido[4,5-b][1,4]diazepine-2,4-dione as novel and versatile scaffolds for drug discovery

A novel pyrimido[4,5-b][1,4]diazepine-2,4,6-trione was synthesized with an efficient strategy. Especially, the key intermediate 2,4-dimethoxypyrimido[4,5-b][1,4]diazepin-6-one was promoted by one pot tandem reduction-cyclization with Na₂S₂O₄. Subsequently, reduction of lactams 6 with LiAlH₄ afforded a more flexible scaffold of pyrimidodiazepines. The synthetic strategy was versatile since it facilitated the sequential functionalization on the pyrimidodiazepine at three positions. Thus a convenient and effective method for the rapid preparing of multi-substituted pyrimido[4,5-b][1,4]diazepines was developed.     

Synthesis and some transformations of new 9-furylnaphtho[2,3-b]furan derivatives

The synthesis of a number of naphtho[2,3-b]furan derivatives, containing a furyl substituent in position 9 by intramolecular cyclization of 2-carboxy and 2-formylbis(5-alkylfur-2-yl)methanes is described. The reactivity of the title compounds in formylation, acetylation, nitration, and oxidation reactions has been investigated. It was shown that nitration of 2-methyl-9-(5-methyl-2-furyl)naphtho[2,3-b]furan-4-yl acetate leads to oxidative furan ring opening rather than to electrophilic substitution.     

Intramolecular 4+2 cycloaddition of thieno[2,3-e][1,2,4]triazines: routes towards condensed thieno[2,3-b]pyridines

Synthetic approaches towards new condensed thienopyridine ring systems including furo[2,3-b]thieno[3,2-e]pyridines, bisthieno[2,3-b:3′,2′-e]pyridines, 5H-chromeno[2,3-b]thieno[3,2-e]pyridines, 5H-benzo(f)chromeno[2,3-b]thieno[3,2-e]pyridines have been achieved by application of intramolecular 4+2 cycloaddition reactions of suitably designed thieno[2,3-e][1,2,4]triazines tethered with alkene or alkyne terminals.     

Synthesis of new compounds containing the 2,3-dihydro[1,4]dioxino[2,3-b]pyridine heterocyclic system as a substructure

2,3-Dihydro-spiro[1,4]dioxino[2,3-b]pyridine-3,3′-pyrrolidine (8A) and 2,3-dihydro-spiro[1,4]dioxino[2,3-b]pyridine-3,4′-piperidine (9A) have been synthesized from 2-chloro-3-pyridinol. The corresponding 2,3′ (8B) and 2,4′ (9B) isomers were obtained via the Smiles rearrangement, while 9B was also selectively synthesized from 2-nitro-3-pyridinol. The separation of the isomers A and B under the sulfamide form was carried out by flash column chromatography. Subsequent transformations of the corresponding dioxinopyridine derivatives were described.