PEG-600-mediated,green and efficient,tandem syntheses of N-subtituted-2-styrylquinazolin-4- ones

Polyethylene glycol (PEG)-mediated, green and efficient, tandem syntheses of N-subtituted-2-styrylquinazolinones are being reported. Condensation of anthranilamide (1) with acetic anhydride in PEG-600, at 100°C for 1 hr gave 2-methyl-3H-quinazoline-4-one (2). Treatment of 2 with benzaldehydes in PEG-600, at 100°C for 2–3 hr, gave 2-styrylquinazolinone-4-ones (3) in excellent yields. Treatment of 3 (a–d) either with dimethyl sulfate (DMS), diethyl sulfate (DES), or with Ph-CH₂-Cl, individually in PEG-600, at 100°C for 1–2 hr without using any base, followed by simple processing resulted in N-substituted-2-styrylquinazolin-4-ones 5 (a–l). In an alternative approach, reaction of 4 (a–c) with benzaldehydes in PEG-600, at 100°C for 1–2 hr, without using any base, followed by simple processing resulted in 5 (a–l). 4 (a–c) were prepared by treatment of 2 with either DMS, DES, or with Ph-CH₂-Cl, individually, in the presence of PEG-600 as reaction medium, at 100°C for 1–2 hr without using any base. Both the sequence of reactions, 1 2 3 5 or 1 2 4 5 could be carried out in tandem in an efficient manner in PEG-600 without the isolation of any intermediates. The structures of all the new compounds synthesized in this work have been established on the basis of their spectroscopic data and analytical data.     

Synthesis of β-amino alcohols by ring opening of epoxides with amines catalyzed by cyanuric chloride under mild and solvent-free conditions

Abstract

The 2,4,6-trichloro-1,3,5-triazine catalyzed synthesis of β-amino alcohols by aminolysis of epoxide under solvent-free condition is described. Mild reaction conditions, short reaction times, inexpensive and readily available catalysts, and excellent yields of the products with high regioselectivity are attractive features of this methodology.     

Polyethylene glycol (PEG) mediated synthesis of pyrrolo-[2,3-d]isoxazoles by using NaOCl reagent – a green chemistry approach

Abstract

Polyethylene glycol (PEG) is found to be an inexpensive, non-toxic, environmentally friendly reaction media for the synthesis of pyrrolo[2,3-d] isoxazoles by using NaOCl reagent in excellent yields under mild conditions.

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Recycling of undesired isomers of key intermediate for aprepitant

Abstract

A protocol for regeneration of key intermediate of aprepitant from its undesired diastereomers is described. This work features the recycling of at least one-third of the undesired isomers (ent-6, 7 and ent-7) to desired isomer 4 as the key early intermediate for the synthesis of aprepitant 1. The key step in our strategy involves diastereomeric salt preparation.     

A very high yielding and facile alkaline earth metals homogeneous catalysis of Biginelli reaction: an improved protocol

Abstract

A high yielding and facile Biginelli reaction for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones and thiones, using inexpensive and available alkaline earth metal chlorides (MgCl₂, CaCl₂, SrCl₂ and BaCl₂) and acetic acid as the solvent in a homogeneous catalytic reaction, is reported.     

Polyethylene glycol mediated facile protocol for N-Cbz protection of amines

Abstract

We have reported an efficient and eco-friendly protocol for the protection of various structurally and electronically divergent aryl and aliphatic amines using Cbz-Cl in the presence of polyethylene glycol (PEG)-400 at room temperature. The reaction afforded excellent yields with low as well as high molecular weight PEGs.     

An efficient green protocol for the synthesis of chalcones by a Claisen–Schmidt reaction using bismuth(III)chloride as a catalyst under solvent-free condition

Abstract

An environmentally benign protocol for the synthesis of chalcones by the Claisen–Schmidt condensation of aldehydes with ketones using eco-friendly non-toxic bismuth(III)chloride catalyst under solvent-free condition is reported. In this protocol, the reaction time is very short, yields are high, and there are no other pollutants formed.     

An efficient green protocol for the synthesis of 2-aryl substituted benzothiazoles

Abstract

Cyclocondensation of 2-aminothiophenol and various aryl/heteryl aldehydes was carried in polyethylene glycol-400 as a catalyst and reaction medium at room temperature to obtain 2-aryl substituted benzothiazoles with excellent yields.     

A highly efficient,operationally simple and selective thia-Michael addition under solvent-free condition

Abstract

The rapid and very simple conjugate addition of thiols to α,β-unsaturated carbonyl compounds under solvent-free conditions in the presence of catalytic amount of lithium hydroxide at room temperature is reported. The reaction of aryl, alkyl, aliphatic, and hindered thiols with chalcone, enone, and nitrostyrene gave the corresponding Michael adducts with significant advantages, such as high conversions, short reaction time, mild reaction conditions, low cost, simple catalyst, and high to quantitative yields with excellent chemoselectivity.

     

IBX promoted one-pot condensation of β-naphthol,aldehydes, and 1,3-dicarbonyl compounds

Abstract

An efficient and mild protocol has been developed for one-pot condensation of β-naphthol, aldehydes, and 1,3-dicarbolyl compounds in presence of o-iodoxybenzoic acid has been found to be an excellent catalyst for the synthesis of tetrahydrobenzo[a]xanthen-one, 1H-benzo[f]chromen-2-yl)-one via one-pot three-component condensation of β-naphthol, aldehydes, and 1,3-dicarbonyl compounds. Short reaction time, ambient conditions, simple workup, and high yield with selective manner are some of the striking features of the present protocol.     

Efficient and green synthesis of 4H-pyrans and 4H-pyrano[2,3-c] pyrazoles catalyzed by task-specific ionic liquid [bmim]OH under solvent-free conditions

Abstract

A facile and convenient procedure for the synthesis of 4H-pyrans from aldehydes, malononitrile, and ethyl acetoacetate/acetylacetone and also synthesis of 4H-pyrano[2,3-c]pyrazoles from three-component condensation of aldehydes, malononitrile, and pyrazolone or four-component condensation of aldehydes, malononitrile, ethyl acetoacetate, and hydrazine monohydrate using [bmim]OH as task-specific ionic liquid has been described. The protocol proves to be efficient and environmentally benign in terms of high yields, low reaction times, ease of recovery, and reusability of reaction medium.

     

Microwave-assisted conversion of aromatic heterocyclic nitriles to various heterocyclic molecules

Abstract

Dihydroimidazole (3a-c), dihydrooxazole (3d-f), benzoxazole (5a-c), benzothiazole (5d-f) and oxazolopyridine (7a-c) derivatives have been synthesized by condensation of various heterocyclic aromatic nitriles with diamine, aminoalcohal, aminophenol, aminothiophenol, and 3-aminopyridine-2-ol, respectively, under microwave irradiation and under solvent free conditions. This catalyst free and solvent free approach provided heterocyclic compounds in quantitative yields. Time taken for the condensation to occur is < 20 min.     

An efficient synthesis of α-hydroxyphosphonates and α-aminophosphonates in the presence of chlorotrimethylsilane

Abstract

Solvent free, and quantitative yielding synthesis of α-hydroxyphosphonates (2a–h) from 2-chloroquinolin-3-carbaldehyde (1a–h) and α-aminophosphonates (4a–p) from imines (3a–p), obtained from 2-chloroquinoline-3-carbaldehyde by using triethylphosphite in the presence of chlorotrimethylsilane at room temperature in short time.     

Novel one-pot synthesis of 1,2,4-triazolidin-3-thiones comprising piperidine moiety

Abstract

A simple synthetic strategy for the synthesis of piperidinyl spiro-1,2,4-triazolidin-3-thiones 11–15 is proposed, exploiting microwave activation coupled with solvent-free reaction conditions catalyzed by NaHSO₄.SiO₂ heterogeneous catalyst is described.     

Lithium bromide as an efficient,green, and inexpensive catalyst for the synthesis of quinoxaline derivatives at room temperature

Abstract

An efficient, simple, and green procedure for the synthesis of quinoxaline derivatives is described. The condensation of 1,2-diamines with 1,2-diketones using lithium bromide (LiBr) in H₂O/EtOH as a green reaction media at room temperature affords the title compounds in high to excellent yields and in short reaction times.     

Solvent-free chemoselective protection of aldehydes on the surface of alumina-sulfuric acid

Abstract

Chemoselective protection of alkyl and aryl aldehydes has been accomplished through the formation of dioxolane on the surface of alumina-sulfuric acid under solvent-free conditions where dialkyl ketones, aryl alkyl ketones, and diaryl ketones remain intact.     

Efficient Prins cyclization in environmentally benign method using ion exchange resin catalyst

Abstract

Amberlyst-15^® (H⁺) resin catalyzes efficient one-pot solvent free Prins cyclization of an aldehyde and a homoallylic alcohol to yield dihydropyrans and 4-hydroxytetrahydropyrans. The products, which display interesting olfactory property, are obtained under mild condition and by simple work up. The recovered resin can be used repeatedly .     

TFAA-H3PO4 mediated rapid and single-step synthesis of mutual prodrugs of paracetamol and NSAIDs

Abstract

A clean and operationally simple method has been developed for the preparation of mutual prodrug using paracetamol and various nonsteroidal anti-inflammatory drugs. The methodology involves use of TFAA/H₃PO₄ in acetonitrile and a variety of mutual prodrugs has been prepared in good yields by using this single-step C–O bond forming reaction.

     

A convenient synthesis of coumarins using reusable ionic liquid as catalyst

Abstract

An efficient and convenient method has been developed for the synthesis of substituted coumarin derivatives using a Brønsted acidic ionic liquid as catalyst under solvent-free conditions. The catalyst can be reused for six consecutive runs without significant loss of activity.