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Navdeep K. Girdhar

Bio: Navdeep K. Girdhar is an academic researcher from Guru Nanak Dev University. The author has contributed to research in topics: Aryl & Cycloaddition. The author has an hindex of 5, co-authored 16 publications receiving 177 citations.

Papers
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Journal ArticleDOI
TL;DR: The N-methylanilino group in 2-(Nmethylonilino)-3-formylchromones, obtained in high yield by rearrangement of C(4-oxo-4H[1]-benzopyran-3-yl)-N-phenylnitrones to 2-anilino-3 -formyl-chromones followed by N-methylation, undergoes facile nucleophilic substitution by a variety of nitrogen nucleophiles, thereby paving the way for synthesis of novel 2-substituted

85 citations

Journal ArticleDOI
TL;DR: When the reaction is carried at room temperature, the [2 + 2] mode of addition involving C=N of azadiene and C3,C4 pi-bond of allenic esters also intervenes, and the resulting N-aryl-2-ethoxy-carbonyl-methylidene-4-styrylazetidines undergo reorganization on silica gel to afford 2-cyclohexen-1-ones.

43 citations

Journal ArticleDOI
TL;DR: In this paper, a mechanistic rationalization of the obtained results in terms of electronic, steric and secondary interactions is proffered, and a loss of regioselectivity is observed with methyl vinyl ketone and methyl acrylate, due to intervention of HOMO-dipole-LUMO-Dipolarophile interaction.

15 citations

Journal ArticleDOI
TL;DR: In this article, the conversion of 16α,17α-epoxy-3β-hydroxypregn-5-en-20-one (1a) to 16β-chloro,3β, 17α-dihydroxy-17β-methyl-17a-homoandrost-5en- 17a-one(3) in very high yields (95%), in one step by treatment with 3-equiv. of anhyd.

14 citations

Journal ArticleDOI
TL;DR: The thermal cycloaddition of α-aryl-N-phenylnitrones to the C16C17 π-bond in 16-dehydropregnenolone-3β-acetate (1) involves only the minor rotamer (E-form) of the nitrones and occurs regio-, stereo and πfacial selectively to afford steroido[16,17-d]isoxazolidines (3) in high yield as discussed by the authors.

10 citations


Cited by
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Journal ArticleDOI
TL;DR: Privileged substructures are believed to achieve this through the mimicry of common protein surface elements that are responsible for binding, such as β- and gamma;-turns.
Abstract: Privileged substructures are of potentially great importance in medicinal chemistry. These scaffolds are characterized by their ability to promiscuously bind to a multitude of receptors through a variety of favorable characteristics. This may include presentation of their substituents in a spatially defined manner and perhaps also the ability to directly bind to the receptor itself, as well as exhibiting promising characteristics to aid bioavailability of the overall molecule. It is believed that some privileged substructures achieve this through the mimicry of common protein surface elements that are responsible for binding, such as β- and gamma;-turns. As a result, these structures represent a promising means by which new lead compounds may be identified.

2,620 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarized the results reported mainly within the last 10 years, and it is quite clear from the growing number of emerging publications in this field that the possibility to utilize multicomponent technology allows reaction conditions to be accessed that are very valuable for organic synthesis.
Abstract: Multicomponent reactions have gained significant importance as a tool for the synthesis of a wide variety of useful compounds, including pharmaceuticals. In this context, the multiple component approach is especially appealing in view of the fact that products are formed in a single step, and the diversity can be readily achieved simply by varying the reacting components. The eco-friendly, solvent-free multicomponent approach opens up numerous possibilities for conducting rapid organic synthesis and functional group transformations more efficiently. Additionally, there are distinct advantages of these solvent-free protocols since they provide reduction or elimination of solvents thereby preventing pollution in organic synthesis “at source”. The chemo-, regio- or stereoselective synthesis of high-value chemical entities and parallel synthesis to generate a library of small molecules will add to the growth of multicomponent solvent-free reactions in the near future. In this review we summarized the results reported mainly within the last 10 years. It is quite clear from the growing number of emerging publications in this field that the possibility to utilize multicomponent technology allows reaction conditions to be accessed that are very valuable for organic synthesis. Therefore, diversity oriented synthesis (DOS) is rapidly becoming one of the paradigms in the process of modern drug discovery. This has spurred research in those fields of chemical investigation that lead to the rapid assembly of not only molecular diversity, but also molecular complexity. As a consequence multi-component as well as domino or related reactions are witnessing a new spring.

420 citations

Journal ArticleDOI
TL;DR: The salient features of this protocol--the facile access to a diverse range of nitrogen-containing heterocycles and the simple preparation of azomethine imine substrates--suggest that it might find extensive applications in heterocycle synthesis.
Abstract: In this paper we describe the phosphine-catalyzed [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] annulations of azomethine imines and allenoates. These processes mark the first use of azomethine imines in nucleophilic phosphine catalysis, producing dinitrogen-fused heterocycles, including tetrahydropyrazolo-pyrazolones, -pyridazinones, -diazepinones, and -diazocinones. Counting the two different reaction modes in the [3 + 3] cyclizations, there are five distinct reaction pathways—the choice of which depends on the structure and chemical properties of the allenoate. All reactions are operationally simple and proceed smoothly under mild reaction conditions, affording a broad range of 1,2-dinitrogen-containing heterocycles in moderate to excellent yields. A zwitterionic intermediate formed from a phosphine and two molecules of ethyl 2,3-butadienoate acted as a 1,5-dipole in the annulations of azomethine imines, leading to the [3 + 2 + 3] tetrahydropyrazolo-diazocinone products. The incorporation of two molecules of an allenoate into an eight-membered-ring product represents a new application of this versatile class of molecules in nucleophilic phosphine catalysis. The salient features of this protocol—the facile access to a diverse range of nitrogen-containing heterocycles and the simple preparation of azomethine imine substrates—suggest that it might find extensive applications in heterocycle synthesis.

267 citations