An efficient non-ionic surfactant catalyzed multicomponent synthesis of novel benzylamino coumarin derivative via Mannich type reaction in aqueous media

An efficient non-ionic surfactant catalyzed multicomponent synthesis of novel benzylamino coumarin derivatives has been developed from secondary amines, aromatic aldehyde, and 4-hydroxy coumarin via Mannich type reaction in aqueous media. In this Mannich type reaction, surfactant forms stable colloidal medium to stabilize iminium ion which undergoes nucleophilic addition of 4-hydroxy coumarin to give benzylamino coumarin in very good yields.     

Iridium catalysed alkylation of 4-hydroxy coumarin, 4-hydroxy-2-quinolones and quinolin-4(1H)-one with alcohols under solvent free thermal conditions

Ir catalysed alkylation of 4-hydroxy coumarin, 4-hydroxy-2-quinolones and quinolin-4(1H)-one with a range of substituted benzyl and aliphatic alcohols under solvent free thermal conditions afforded the corresponding monoalkylated products in high to excellent yield and in certain cases produced bis-(3,3′-1-methyl-4-hydroxy)methenes.     

InCl3 catalyzed three-component synthesis of α-benzylamino coumarins and diketones

A convenient and practical InCl₃ catalyzed three-component reaction of 4-hydroxy coumarin/1,3 diones, aromatic aldehyde, and secondary amine for the synthesis of α-benzylamino coumarins and diketones in good yields has been reported.     

A One Pot,Facile, and Convenient Synthesis of Some Coumarin Derivatives

Protonation of the reactive 1:1 intermediate produced in the reaction between triphenylphosphine and dimethyl acetylenedicarboxylate by substituted phenols lead to vinyl triphenylphosphonium salt, which undergoes aromatic electrophilic substitution reaction with the phenolate conjugated base to produce coumarin derivatives.     

An efficient synthesis of thiopyrano[5,6-c]coumarin/[6,5-c]chromones through intramolecular domino Knoevenagel hetero Diels-Alder reactions

The synthesis of novel polycyclic thiopyrano coumarin/chromone frameworks through intramolecular domino Knoevenagel hetero Diels-Alder reactions of 4-hydroxy coumarin and its benzo-analogous with S-prenylated aromatic aldehydes was studied. A high degree of chemoselectivity was achieved by the application of microwave irradiation and a solid support.     

(S)-Mandelic acid enolate as a chiral benzoyl anion equivalent for the enantioselective synthesis of non-symmetrically substituted benzoins

A strategy for the enantioselective synthesis of non-symmetrically substituted benzoins from (S)-mandelic acid and aromatic aldehydes has been developed. This strategy is based on a diastereoselective aldol reaction of the lithium enolate of the 1,3-dioxolan-4-one derived from (S)-mandelic acid and pivalaldehyde with aromatic aldehydes, which gives the corresponding aldols in good yields. Subsequent hydroxyl group protection as MEM ethers, basic hydrolysis of the dioxolanone ring, oxidative decarboxylation of the α-hydroxy acid moiety, and hydroxyl group deprotection provides chiral non-symmetrically substituted benzoins with high enantiomeric excesses.     

Absolute stereochemistry of dihydrofuroangelicins bearing C-8 substituted double bonds: a combined chemical/exciton chirality protocol

Coumarins are associated with a variety of pharmacological activities which have led to the synthesis of numerous derivatives. However, no general method for determination of the absolute configuration of chiral coumarins is known. This has now been achieved for a series of dihydrofuroangelicins bearing a variety of C-8 substituted double bonds, synthesized in the racemic form and resolved through enantioselective chromatography. A combined chemical/chiroptical protocol has been developed in which the C[double bond, length as m-dash]C double bonds are replaced with a styrenoid chromophore through either (i) cross metathesis, (ii) Heck reaction, or (iii) a combined method of cross metathesis and Heck reaction with about 1 mg sample under mild conditions. The coupling between the styrenoid and coumarin chromophores gives rise to clear-cut exciton coupled CD curves, suitable for assignments of absolute configurations. The solution conformation of the styrenoid derivatives is determined by NMR and DFT molecular modeling; the electronic structure of the 7-hydroxy coumarin chromophore is also clarified by semi-empirical and TDDFT methods. The conformation thus derived, in conjunction with quantitative DeVoe's coupled-oscillator CD calculation, establishes the absolute configurations of the coumarins. The theoretical study described herein justifies the straightforward approach of the current chemical/exciton chirality protocol to this type of dihydrofuroangelicins.     

Polyethylene glycol in water: Simple,efficient, and catalyst-free synthesis of 4H-pyran derivatives

A green, one-pot, multicomponent method for the synthesis of diverse library of 4H-pyran derivatives such as 4-phenyl-4H-pyrans, spirochromenes, and dihydropyrano[3,2-c]chromines was developed using polyethylene glycol (PEG-600) as promoting reaction medium in water. The 4-phenyl-4H-pyran dihydropyrano[3,2-c]chromine derivatives were synthesized by a three-component reaction of aromatic aldehyde, malononitrile, and cyclic 1,3-dione/4-hydroxy coumarin at room temperature and reflux respectively. The promising points for the present methodology are efficiency, generality, high yield, short reaction time, cleaner reaction profile, ease of product isolation, potential to recycle reaction medium, and agreement with green chemistry protocols, making it a useful and attractive process for the synthesis of 4H-pyran derivatives.     

One-pot,expeditious and chromatography-free synthesis of new chromeno[4,3-e][1,3]oxazine derivatives catalyzed by reusable TiO2 nanopowder at room temperature

An expeditious, one-pot, pseudo four-component coupling reaction between 3-hydroxy coumarin, formaldehyde, and amine catalyzed by reusable TiO₂ nanopowder in ethanol at room temperature (25–28 °C) under stirring condition to synthesize the chromeno[4,3-e][1,3]oxazine derivatives has been described. A wide range of substrate variation, environmentally benign reaction procedure, easy work-up, chromatography free synthesis, and excellent yields with reusability of the catalyst make the methodology highly effective for the synthesis of chromeno[4,3-e][1,3]oxazine derivatives. To the best of our knowledge, this is the first Letter for the synthesis of chromeno[4,3-e][1,3]oxazines using 3-hydroxy coumarin.     

Efficient Synthesis of Novel Coumarin‐3‐carboxamides (=2‐Oxo‐2H‐1‐benzopyran‐3‐carboxamides) Containing Lipophilic Spacers

The novel coumarin‐3‐carboxamides (=2‐oxo‐2H‐1‐benzopyran‐3‐carboxamides) 5a – 5g containing lipophilic spacers were synthesized through the Ugi‐four‐component reaction (Scheme 1). The reactions of aromatic aldehydes 1 , 4,4′‐oxybis[benzenamine] or 4,4′‐methylenebis[benzenamine] as diamine 2 , coumarin‐3‐carboxylic acid (=2‐oxo‐2H‐benzopyran‐3‐carboxylic acid; 3 ), and alkyl isocyanides 4 lead to the desired substituted coumarin‐3‐carboxamides 5a – 5g at room temperature with high bond‐forming efficiency. These novel coumarin derivatives exhibit brilliant fluorescence at 544 nm in CHCl₃.     

Tetranitromethane as an efficient reagent for the conversion of epoxides into β-hydroxy nitrates

A convenient regioselective method for the preparation of β-hydroxy nitrates based on the ring opening reaction of epoxides by tetranitromethane in the presence of triethylamine is described. A series of substituted β-hydroxy nitrates were obtained in high yields under mild conditions.     

Microwave-assisted synthesis of α-hydroxy aromatic ketones from α-bromo aromatic ketones in water

A reaction ofα-bromo aromatic ketones in water with microwave irradiation gave the correspondingα-hydroxy aromatic ketones in good yields.The use of microwaves was found to significantly improve yields and shorten the reaction time.This reaction afforded a very clean,convenient method for the synthesis ofα-hydroxy aromatic ketones.     

Synthesis of azobenzenes: the coloured pieces of molecular materials

Azobenzenes are ubiquitous motifs very important in many areas of science. Azo compounds display crucial properties for important applications, mainly for the chemical industry. Because of their discovery, the main application of aromatic azo compounds has been their use as dyes. These compounds are excellent candidates to function as molecular switches because of their efficient cis-trans isomerization in the presence of appropriate radiation. The classical methods for the synthesis of azo compounds are the azo coupling reaction (coupling of diazonium salts with activated aromatic compounds), the Mills reaction (reaction between aromatic nitroso derivatives and anilines) and the Wallach reaction (transformation of azoxybenzenes into 4-hydroxy substituted azoderivatives in acid media). More recently, other preparative methods have been reported. This critical review covers the various synthetic methods reported on azo compounds with special emphasis on the more recent ones and their mechanistic aspects (170 references).     

Functionalized 4-hydroxy coumarins: novel synthesis, crystal structure and DFT calculations

A novel short-step methodology for the synthesis in good yields of functionalized coumarins has been developed starting from an activated precursor, the N-hydroxysuccinimide ester of O-acetylsalicylic acid. The procedure is based on a tandem C-acylation-cyclization process under mild reaction conditions. The structure of 3-methoxycarbonyl-4-hydroxy coumarin has been established by X-ray diffraction analysis and its geometry was compared with optimized parameters by means of DFT calculations.     

Anionic condensations of 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4(2)-hydroxybenzaldehydes in the presence of weak bases

Products of the reactions of 4- and 2-hydroxy-3,5-di-tert-butyl-benzaldehydes with malonic acid, diethyl malonate, and acetic anhydride in the presence of weak bases were isolated and identified. The reactions of 3,5-di-tert-butyl-4-hydroxybenzaldehyde with malonic acid and acetic anhydride in the presence of sodium acetate and piperidine gave 3,5-di-tert-butyl-4-hydroxycinnamic acid. The reaction of its 2-hydroxy isomer with acetic anhydride stopped at the stage of formation of the corresponding O-acetyl derivative, while in the reaction with malonic acid the corresponding substituted cinnamic acid and its lactone (coumarin derivative) were formed as intermediate products in a transformation sequence finally leading to 3-(3,5-di-tertbutyl-2-hydroxyphenyl)-3-piperidinopropionic acid and 6,8-di-tert-butyl-2-oxo-3,4-dihydro-2H-chromen-4-ylacetic acid. Analogous differences were typical of reactions of isomeric 4- and 2-hydroxy-3,5-di-tert-butylbenzaldehydes with diethyl malonate. The transformations of the 2-hydroxy isomer were accompanied by hydrolysis and formation of an adduct of intermediate coumarin derivative with diethyl malonate and piperidine.     

An efficient four-component reaction for the synthesis of chromeno[4,3-<Emphasis Type="Italic">b</Emphasis>]quinolone derivatives

Chromenoquinolines have been prepared via an efficient one-pot, multi-component reaction of 4-hydroxy coumarin, aqueous ammonia, dimedone and different aldehydes.     

PEG-SO3H: A mild and efficient recyclable catalyst for the synthesis of coumarin derivatives

A simple and efficient synthesis of coumarin derivatives through condensation reaction of substituted phenols and dicarbonyl compounds using PEG-SO₃H as a recyclable catalyst under solvent-free conditions is described.     

Iodine and iodic acid: an efficient reagent combination for iodination of aryl hydroxy ketones

A variety of ortho-hydroxy substituted aromatic carbonyl compounds were regioselectively iodinated with iodine and iodic acid in excellent yields.     

Dehydration of 3- and 4-aryl- substituted 3-hydroxy acids in acetic anhydride in presence of zinc chloride

The reaction of several di- and triaryl-substituted 3-aryl-3-hydroxy acids and a 4-aryl-3-hydroxy acid in acetic anhydride in the presence of anhydrous zinc chloride has been investigated. It has been shown that the reaction discovered with 3-(2′-thienyl)-substituted 3-hydroxy acids, namely, their conversion under the above stated conditions into α, β-unsaturated methyl ketones,^1,2 occurs also with 3-aryl 3-hydroxy acids but to a smaller degree due to the concurrent cyclization reaction which leads to indene-1-ones. It has been established that the unsaturated methyl-ketones obtained, containing three aromatic substituents at the CC bond, exist in s-cis-(CC, CO)-conformation. It has been found that with the 4-aryl-substituted 3-hydroxy acid almost no unsaturated ketone is obtained, whereas instead the main product is a 2,3-disubstituted 1-naphthol which is acetylated under the conditions of the reaction. Its structure has been proved by its UV, IR and NMR spectra and confirmed by the mass spectrum of the compound.     

A Rapid and Efficient Multicomponent Synthesis of Bi-Quinolines Under Solvent-Free Conditions

An efficient synthesis of substituted condensed quinolino-quinolines has been achieved in a one-pot reaction from 2-hydroxy/mercapto/seleno-4-methylquinoline and 2-mercapto/seleno-3-formyl quinolines using anhydrous ammonium hydroxide as the reductant by microwave irradiation under solvent-free conditions.