Shyam Babu Singh

Synthesis of novel fused heterocycle-oxa-aza-phenanthrene and anthracene derivatives via sequential one-pot synthesis in aqueous micellar system

Oxa-aza-phenanthrene and anthracene derivatives which contain a bridgehead nitrogen are synthesized in an aqueous micellar system. The synthetic route is easy and yield is excellent. In this proposed method, solvent, base and surfactant are optimized and the best result was obtained by DBU in water with surfactant CTAB. All synthesized molecules are new. This method is an efficient, viable and sequential one pot synthetic route for the construction of desired product.

A new eco-friendly strategy for the synthesis of novel antimicrobial spiro-oxindole derivatives via supramolecular catalysis

Novel spiro-oxindole derivatives were synthesised by one-pot multicomponent reaction using isatins, urea and 1,3-dicarbonyls. β-Cyclodextrin, an oligosaccharide, catalysed the reaction and can be reused for further reaction after recovery. This developed synthetic route is environmentally benign in which water is used as solvent to produce excellent yields of products. The synthesised compounds were evaluated for their antimicrobial activities against two bacteria and two fungi. All the synthesised spiro-oxindoles exhibit significant antimicrobial activity.

Synthesis of Imidazo[2,1-b]-1,3,4-thiadiazoles in DABCO as an Efficient and Recyclable Catalyst

Abstract An efficient and general method has been described for the synthesis of imidazo[2,1-b]-1,3,4-thiadiazole by the reaction of 2-aminothiadiazoles with phenacyl bromides in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO). The method is suitable for the synthesis of functionalized imidazothiadiazoles. GRAPHICAL ABSTRACT

N-heterocyclic carbene (thiamine) promoted eco-friendly synthesis of quinoxalines under mild reaction conditions

Abstract An efficient and convenient protocol of broad scope for the synthesis of quinoxaline by cyclization-oxidation of phenacyl bromide with equimolar amount of phenylenediamine at room temperature catalyzed by thiamine in the form of N-heterocyclic carbene (NHC). High efficiency, inexpensiveness, and non-toxicity are the interesting features of the catalyst, which make it eco-friendly and highly attractive.

Development of five membered heterocyclic frameworks via [3+2] cycloaddition reaction in an aqueous micellar system

A series of novel dihydropyrrolo[2,1-a]isoquinolines and dihydropyrrolo[1,2-a]quinolines have been synthesized from isoquinolines/quinolines, various substituted phenacyl bromides and substituted dialkylacetylenedicarboxylates via [3+2] cycloaddition reaction. The reaction proceeds in aqueous micellar medium with DBU as a catalyst. The present protocol offers a simple one pot sequential reaction affording products in excellent yields.

Nucleophilic, Heterocyclic, Carbene-Catalyzed, Solvent-Free, One-Pot Synthesis of Polyhydroquinolines via Multicomponent Hantzsch Reaction: An Efficient and Ecofriendly Approach

Abstract A simple, efficient, and ecofriendly one-pot method has been reported for the synthesis of polyhydroquinolines in excellent yield using nucleophilic heterocyclic carbene as catalyst. The generalized approach is the Hantzsch four-component reaction of aromatic aldehyde, ethyl acetoacetate, cyclic 1,3-diketone, and ammonium acetate. GRAPHICAL ABSTRACT

Supramolecular catalysis in the synthesis of polyfunctionalised pyrroles

An efficient sequential one pot three component reaction involving anilines, DEAD/DMAD and glyoxal in aqueous media is reported. The protocol is environmentally benign and provides a new synthetic route to access polyfunctionalised pyrrole derivatives in high yield. The reaction proceeded via supramolecular catalysis.

Microwave-Induced Solvent-Free Synthesis and Antifungal Screening of Novel Spiro Heterocyclic Systems Containing 3,5-Diphenyl-7H-thiazolo[3,2-a]pyrimidine and Indolin-2-one

Abstract A microwave-induced technique has been developed for the synthesis of a series of novel spiro indoline-based heterocycles (7a–g) at atmospheric pressure in an open vessel using an environmentally benign procedure. This rapid method produces pure products in good yields within a few minutes in comparison to the conventional procedure developed for the synthesis of these heterocycles. The synthesized compounds have been screened in vitro for antifungal activity against two fungal strains (i.e., Aspergillus niger and Aspergillus flavus). All compounds have shown significant activity against these pathogens. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.] GRAPHICAL ABSTRACT

Triphenylphosphine-Catalyzed, Novel, One-Pot, Multicomponent Synthesis of Functionalized β-Acetamido Carbonyls

Abstract An efficient triphenylphosphine-catalyzed synthesis of β-acetamido carbonyls via multicomponent reaction of aromatic aldehydes, enolizable ketones or β-keto esters, acid chlorides and acetonitrile at room temperature is described. The process is remarkably simple, environmentally benign, and uses Lewis base for the first time in such type of reaction. GRAPHICAL ABSTRACT