Facile synthesis of regio-isomeric naphthofurans and benzodifurans

Synthesis of benzofurans from the cyclodehydration of α-phenoxy ketones mediated by Eaton’s reagent

Cyclodehydration of α-phenoxy ketones promoted by Eaton’s reagent (phosphorus pentoxide–methanesulfonic acid) is used to prepare 3-substituted or 2,3-disubstituted benzofurans with moderate to excellent yields under mild conditions. The method provides a facile access to benzofurans from readily available starting materials such as phenols and α-bromo ketones. The reaction is highly efficient, which is attributed to the good reactivity and fluidity of Eaton’s reagent. The reaction can be applied to prepare naphthofurans, furanocoumarins, benzothiophenes, and benzopyrans.

Synthesis and evaluation of novel α-substituted chalcones with potent anti-cancer activities and ability to overcome multidrug resistance

A series of forty α-substituted chalcones were synthesized and screened for their antiproliferative activities against HCT116 (colorectal) and HCC1954 (breast) cancer cell lines. Compounds 5a and 5e were found to be the most potent compounds with GI₅₀ values of 0.63 µM and 0.725 µM in HCC1954 cell line and 0.69 µM and 1.59 µM in HCT116 cell line, respectively. Both compounds induced a G2/M cell cycle arrest and caused apoptotic cell death in HCT116 cells as shown by the induction of PARP cleavage. The compounds also stabilized p53 in a dose-dependent manner in HCT116 cells following 24-hour treatment. Furthermore, both 5a and 5e were able to overcome multidrug resistance in two MDR-1 overexpressing multidrug resistant cell lines.

An Approach to the Synthesis of 1-Propenylnaphthols and 3-Arylnaphtho[2,1-b]furans

A simple and efficient strategy for the synthesis of 1-propenylnaphthols from readily accessible 3-arylallylnaphthyl ethers has been developed. By using K₂CO₃ as base and 2-methoxyethanol as solvent, direct access to a wide range of 1-propenylnaphthols can be achieved in generally good yield (up to 99%) with high stereoselectivity toward the Z isomer. The control experiments indicate that the reaction proceeds through a sequential Claisen rearrangement/isomerization process. Furthermore, starting from the same material, the highly valuable 3-arylnaphtho[2,1-b]furans can be obtained in N,N-dimethylformamide and in the presence of Ag₂O as the oxidant via a one-pot sequential Claisen rearrangement/isomerization/cyclization reaction. Mechanistic studies confirm that 1-propenylnaphthols are the key intermediates to form the 3-arylnaphtho[2,1-b]furans. In addition, these two operationally simple and practical protocols could be scaled up to a gram level.

Palladium-catalyzed paraformaldehyde insertion: a three-component synthesis of benzofurans

2-Aroylbenzofurans were prepared from 2-bromophenols, phenacyl bromides and paraformaldehyde under palladium catalysis conditions.

n Bu4NPF6 promoted regioselective cascade synthesis of functionally embellished naphthofurans under acid, metal & solvent free conditions

Various naphthofurans were synthesised from naphthols and propargyl alcohols using a cascade benzylation/5-exo dig cyclisation/isomerization. Preliminary studies showed that some naphthofurans were excellent inhibitors for amyloid formation.

Facile synthesis of benzoindoles and naphthofurans through carbonaceous material-catalyzed cyclization of naphthylamines/naphthols with nitroolefins in water

A facile and efficient approach has been established for the synthesis of benzoindole and naphthofuran derivatives via the metal-free cyclization reaction of nitroolefins with naphthylamines/naphthols.

Four-component reaction between naphthols, substituted β-nitrostyrenes, substituted benzaldehydes and ammonium acetate in water–PEG-400: an approach to construct polysubstituted naphthofuranamines

The diversity-oriented synthesis of naphtho[b]furans via a four-component reaction between naphthanols, substituted β-nitrostyrenes, substituted benzaldehydes and ammonium acetate has been developed.

Palladium-catalyzed direct arylation of polysubstituted benzofurans

An efficient access to 2-substituted 3-arylbenzofurans through a palladium-catalyzed C3 direct arylation of 2-substituted benzofurans with aryl bromides is described. The scope and limitation of this reaction was studied. The method tolerates a variety of functional groups on the aryl halide and has been successfully extended to polysubstituted benzofurans to obtain the corresponding 3-arylbenzofurans with good to excellent yields.

Ytterbium triflate catalysed Friedel–Crafts reaction using carboxylic acids as acylating reagents under solvent-free conditions

The Friedel–Crafts acylation of 1-naphthol and phenol derivatives with carboxylic acids were investigated by using a catalytic amount of metal-triflate, in particular Yb(OTf)3, under solvent-free conditions. Both aliphatic and aromatic carboxylic acids reacted easily to afford the corresponding hydroxyaryl ketones.

Conjugate systems in the construction of heterocycles and quaternary stereocenters

The synthetic application of 4,5-bis-alkylidene-1,3-oxazolidin-2-ones led to the efficient and regioselective synthesis of 2-(3H)-benzoxazolones and diarylamines with a short methodology. They were also valuable synthons in a total synthesis of naturally occurring carbazoles. New enantiopure 4-oxazoline-2-one and 4-methylene-2-oxazolidinone were prepared via a one-pot microwave (MW)-promoted condensation of α-ketols and an enantiopure isocyanate. These enamides were efficient nucleophiles when added to Michael acceptors to give a series of compounds with quaternary stereocenters in fairly good stereoisomeric ratios. The novel approach for the synthesis of benzofurans and indoles by intramolecular cyclization of enaminones has been applied in the preparation of furobenzofurans starting from benzo-bis-enaminones.

Synthesis of 1-(3',4',5'-trimethoxy) phenyl naphtho[2,1b]furan as a novel anticancer agent

3',4',5'-Trimethoxy benzoyl-naphthalene 2-O-acetic acid (5) underwent base catalysed intramolecular condensation to yield exclusively 1-(3',4',5'-trimethoxy) phenyl naphtho[2,1-b]furan 8. The cyclised product 8 has been characterised by spectroscopy. The product 8 showed significant anticancer activity against human cancer cell lines COLO320DM (colon), CaCO2 (colon) and WRL68 (liver) at 0.7, 0.65 and 0.50 microg/ml concentrations, respectively, in the in vitro MTT assay.