Indrapal Singh Aidhen

Bio: Indrapal Singh Aidhen is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Aryl & Julia olefination. The author has an hindex of 15, co-authored 104 publications receiving 836 citations. Previous affiliations of Indrapal Singh Aidhen include Savitribai Phule Pune University & University of California, Santa Cruz.

Some interesting 1 H NMR features of ortho substituted N-methoxy-N-methyl benzamides

Abstract: During synthetic efforts towards positional isomers of FTY720, using building blocks based on Weinreb amide (WA) functionality, interesting H NMR pattern for ortho-methyl-N-methoxy-N-methyl benzamide have been encountered. The H NMR spectrum has shown broad humps for N-methoxy and N-methyl units in WA functionality, whereas the spectrum for the corresponding meta-and para-isomer, displays two sharp singlets for the same units. This interesting spectral difference has been rationalized. Several ortho-substituted N-methoxy-N-methyl benzamides have been tailor-made and generality has been established. The broadening of the peaks is due to the presence of rotamers and variable temperature NMR study has unraveled that the energy barrier of two rotamers of ortho-substituted benzamides is more at room temperature, unlike para and meta substituted benzamides.

Iodine‐Promoted Oxidative Conversion of o‐Vinyl Diaryl Ketones into o‐Acetyl Diaryl Ketones, Synthesis of 1‐Methyl‐4‐arylphthalazines as Analogues of Podophyllotoxin.

Abstract: A new metal-free oxidation of o-vinyl diaryl ketones to diacylbenzene derivatives is described.

Umpolung Strategy for the Synthesis of 2‐Deoxy‐C‐aryl Glycosides: A Serendipitous, Efficient Route for C‐Furanoside Analogues.

Abstract: 2-Deoxy-C-aryl glycosides are potential synthetic targets as they form a very vital moiety of several biologically active natural products. This paper describes a synthetic route using an umpolung strategy, which has not been explored till date. Our synthetic endeavor led to a versatile intermediate aryl ketone 10, which has paved the way for two important classes of C-glycosides, viz., C-alkyl furanosides 12 and methyl 2-deoxy-C-aryl pyranosides 14.

A novel and convenient approach to 5-aryltetrahydro-2-furanols

Abstract: Various aryl and heteroarylterahydrofuranols (2a–h) have been conveniently prepared in good yields by reaction of synthetic equivalents of an acyl anion and a β-electrophilic propionaldehyde.

Towards a synthesis of vigabatrin using glycal chemistry.

Abstract: Application of the Ferrier rearrangement led to a novel carbohydrate based synthetic route to 4-aminohexenoic acid viz. (R) and (S)-vigabatrin. The potential of D- glucose or D-galactose as the chiral starting materials for the synthesis of (R) and (S)- vigabatrin has been explored.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

Abstract: Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Redox economy in organic synthesis.

Abstract: "Economy" is referred to as the thrifty and efficient use of material resources, as the principle of "minimum effort to reach a goal." More illuminating is: "the aim to portion one's forces in order to use as little as possible of them to reach a goal." Such statements certainly apply when the goal is to synthesize a complex target molecule. Redox economy then implies the use of as few redox steps as possible in the synthetic conquest of a target compound. While any sort of economy will help to streamline the effort of total synthesis, redox economy addresses a particularly weak area in present-day total synthesis. It is not enough to point out the present deficiencies, rather the purpose of this Review is to serve as a teaching tool for all practitioners of the field by giving and illustrating guidelines to increase redox economy in multistep organic synthesis.

Enantioselective Construction of Quaternary Stereocenters

Abstract: The stereoselective formation of C-C bonds is of great importance for the synthesis of enantiomerically pure natural products and pharmaceuticals. A broad repertoire of chiral auxiliaries, reagents, and catalysts can be utilized for the reliable generation of tertiary stereocenters. In contrast, the synthesis of organic compounds with quaternary stereocenters is a much more demanding and challenging task. Every enantioselective synthetic method can demonstrate its value through the generation of a fully substituted carbon center. In this Minireview examples of newer stoichiometric and catalytic methods are summarized which have proved their suitability for the enantioselective construction of quaternary stereocenters.

Asymmetric copper-catalyzed C-N cross-couplings induced by visible light.

Abstract: Despite a well-developed and growing body of work in copper catalysis, the potential of copper to serve as a photocatalyst remains underexplored. Here we describe a photoinduced copper-catalyzed method for coupling readily available racemic tertiary alkyl chloride electrophiles with amines to generate fully substituted stereocenters with high enantioselectivity. The reaction proceeds at –40°C under excitation by a blue light-emitting diode and benefits from the use of a single, Earth-abundant transition metal acting as both the photocatalyst and the source of asymmetric induction. An enantioconvergent mechanism transforms the racemic starting material into a single product enantiomer.