Kuppusamy Kanagaraj

Syntheses of 5-substituted 1H-tetrazoles catalyzed by reusable CoY zeolite.

A simple and efficient route for the synthesis of 5-substituted 1H-tetrazoles catalyzed by CoY zeolite is reported. The salient features of this atom-economical, cost-effective, and high-yield cobalt-catalyzed protocol are aerobic conditions, lower reaction time, and milder reaction conditions without additives. Other advantages include experimental ease of manipulation, safer alternative to hazardous, corrosive, and polluting conventional Lewis acid catalysts, recovery, and reusability with consistent catalytic activity. The results are rationalized by proposing a suitable mechanism.

Per-6-amino-β-cyclodextrin as a reusable promoter and chiral host for enantioselective Henry reaction.

A highly efficient enantioselective Henry reaction has been carried out using per-6-ABCD as a supramolecular chiral host and promoter to give the corresponding adduct with high yield (up to 99%) and enantiomeric excess (up to 99%). Per-6-ABCD also promotes the diastereoselective Henry reaction in a syn-selective manner to give the adduct up to 99% yield with 99:1 syn/anti selectivity. The enantiomeric excess of the syn-adduct is 99%. The catalyst is recovered and reused without loss in its activity.

Per-6-amino-β-cyclodextrin as a Chiral Base Catalyst Promoting One-Pot Asymmetric Synthesis of 2-Aryl-2,3-dihydro-4-quinolones

A highly efficient one-pot synthesis of enantiomerically enriched 2-aryl-2,3-dihydroquinolin-4(1H)-ones has been carried out for the first time using per-6-ABCD as a supramolecular host, chiral base catalyst, and a reusable promoter to give the corresponding scaffold with high yield (up to 99%) and enantiomeric excess (up to 99%). The catalyst is recovered and reused without loss in its activity.

The Aminocyclodextrin/Pd(OAc)2 Complex as an Efficient Catalyst for the Mizoroki–Heck Cross‐Coupling Reaction

An aminocyclodextrin/Pd(OAc)2 complex is used as an efficient, reusable catalyst in the Mizoroki-Heck reaction of aryl halides/triflates with olefins to give carbon-carbon-coupled products in good to excellent yields. This simple, efficient catalytic system is applicable to a wide range of aryl and heteroaryl halides/triflates and olefins. This environmentally benign procedure is less hazardous, milder, uses a catalytic amount of ligand and Pd(OAc)2 , avoids an inert atmosphere, and catalyst recovery and reusability are achieved.

Selective “turn-off” fluorescent sensing of mercury ions using aminocyclodextrin:3-hydroxy-N-phenyl-2-naphthamide complex in aqueous solution

A sensitive and highly selective, fluorescent “turn-off” colorimetric sensor for Hg2+ ions is reported using an aminocyclodextrin:3-hydroxy-N-phenyl-2-naphthamide complex in a 5% CH3CN–water system. Six different aminocyclodextrins viz., per-6-amino-α-cyclodextrin, per-6-amino-β-cyclodextrin, per-6-amino-γ-cyclodextrin, mono-6-amino-α-cyclodextrin, mono-6-amino-β-cyclodextrin and mono-6-amino-γ-cyclodextrin were synthesized and used as hosts for complexing 3-hydroxy-N-phenyl-2-naphthamide. This complex can be used as a sensing system for Hg2+ ions. A blue shifted “turn-off” fluorescence quenching and color change from yellow to colorless in the presence of Hg2+ ions is observed which is attributed to suppression of excited-state intramolecular processes (ESIPT) upon Hg2+ ion complexation. Selectivity towards Hg2+ is found to depend upon cavity size/close proximity of the amino groups of aminocyclodextrins (L1–L6) to the metal ion. Probe L1 is selective and sensitive to Hg2+ with a detection limit as low as 1 × 10−12 M. The present sensor system can also be applied to detect the level of Hg2+ in real environmental water samples.

Highly selective fluorescent sensing of fenitrothion using per-6-amino-β-cyclodextrin:Eu(III) complex

A unique, efficient, highly sensitive and selective fluorescent chemosensor for fenitrothion has been reported for the first time using per-6-amino-β-cyclodextrin:Eu(III) complex. Among the various pesticides, the sensitivity response is found to be in the order, fenitrothion>>>quinalphos>methylparathion>parathion>methylparaoxon>paraoxon>fenchlorphos>profenofos>malathion. A detection limit as low as 1 × 10(-12)M for fenitrothion sensing is realized with a 2.4% relative standard deviation (RSD) of three consecutive runs. The per-6-amino-β-cyclodextrin:Eu(III):pesticide complexes and their sensing mechanism are evidenced from emission, NMR, FT-IR, binding constant measurement, Jobs plot, ICD spectra, ESI-MS, lifetime measurements and molecular modeling studies. The proposed sensing is a consequence of Absorption Energy Transfer Emission (AETE) process as a result of better encapsulation of fenitrothion inside the cavity of per-6-amino-β-cyclodextrin:Eu(III) complex. The remarkable sensitivity and selectivity of fenitrothion compared to other OPs, is attributed to a more deeper binding and tighter fit of fenitrothion inside the CD cavity, which is evident from binding constant values and molecular modeling studies. This tighter fit ensures the replacement of two coordinating water molecules on Eu(III) ion, which may have contributed to the more selective sensing of fenitrothion.

Photocatalytic Supramolecular Enantiodifferentiating Dimerization of 2-Anthracenecarboxylic Acid through Triplet–Triplet Annihilation

Visible-light-driven enantiodifferentiating photodimerization of 2-anthracenecarboxylic acid (AC) sensitized by Schiff base Pt(II) complex-grafted γ-cyclodextrins leads the first triplet-triplet annihilation-based catalytic photochirogenesis. The syn-head-to-tail (HT) photodimer 2 was achieved in up to 31.4% ee at 61.0% conversion in the presence of 0.5% equiv of the photocatalyst.