Ujjal Kanti Roy

Making and breaking of Sn-C and In-C bonds in situ: the cases of allyltins and allylindiums.

In the area of the generation of an allylmetal and exploitation of its metal-carbon bond reactivity, chemists have come a long way from “gathering pebbles and scattering them again”, to “how to cast nests”.1 A mild indulgence into the 100+ years of the database of allylmetals will provide the reader with the following generalized observations:1-5 (a) main group metal (hereafter Mgm) allyls have come first, transition metal (hereafter Tm) allyls followed through, (b) among the allyl-Mgms, those of magnesium and lithium have fetched many initial glories in the field, but the rest were not far behind, (c) allyl-Mgms of tin and indium, chosen for deliberation in this review, show many similarlities in their chemistry that appeal to organic, organometallic, and inorganic chemists alikesthe contrast that exists between the two is that while the former is mature and still-growing, the latter is young and fast-growing. In terms of nucleophilic organic reactivity, allyltin and allylindium have gained distinct significance and are widely used to introduce allyl functionality to an electrophilic carbon or heteroatom center. Out of these, reactions leading to a new carbon-carbon bond having desired regioand stereoselectivity gained immense importance in the synthesis of various important natural and pseudonatural products. The utility of allylstannanes is further indicated by the commercial availability of many of them, which are synthesized using standard Grignard and Grignard-like protocols. Even though allylindiums are not yet commercially available, in recent times they have made a distinct presence in laboratory and pilot scale reactions. An organic chemist utilizing a functionalized allyltin or allylindium may recourse to the reaction of a functionalized allyl electrophile and corresponding metal precursor; thereafter, the ex situ generated allylmetal is coupled with an ‡ Present Address: Organometallics & Catalysis Laboratory, School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar751013, India Chem. Rev. 2010, 110, 2472–2535 2472

Photophysical, NMR and density functional study on the ion interaction of norharmane: proton transfer vs. hydrogen bonding

Interactions of norharmane (S), with different ions have been studied using spectroscopy, NMR and density functional studies. A significant gradual change both in absorption and emission spectra was observed upon addition of fluoride anions. The spectral change in the absorption and emission bands of norharmane (S) is found to be specific to fluoride ion; it is unaffected by the presence of other ions. Hydrogen bond mediated proton transfer from norharmane to fluoride is mainly attributed to the fluoride selective signaling behavior. Calculations of the transition energies of the norharmane (S), anionic species of norharmane (S−) and hydrogen bonded complexes (S⋯F−) show that the added fluoride anion could capture the proton in the free N–H moiety instead of the hydrogen-bonding one. Experimental results reveal that the long-wavelength absorption band in the presence of fluoride ion is due to the formation of anion.

Binding interaction of a newly developed bisindole drug molecule with α-cyclodextrin: face to face shielding of indole hoops

Binding interactions of a newly developed drug molecule namely 3,3′-bis(indolyl)-4-chlorophenylmethane (BICPM) with α-cyclodextrin have been studied using steady state and picosecond time resolved fluorometric techniques. A significant increase both in steady state anisotropy (r) and in the average rotational correlation time in the CD environments compared with that in a pure aqueous phase indicates that the rotational dynamics of BICPM are substantially slowed down upon binding with the α-cyclodextrin. Critical spectral analysis reveals the formation of two types of inclusion complex between the fluorophore and α-cyclodextrin (α-CD) depending on the relative population of the two. The stoichiometries and association constants of these complexes have been determined by monitoring the fluorescence data. Hydrodynamic radii of the formed 1 : 2 probe-α-cyclodextrin supramolecular complex have also been determined. From the determined hydrodynamic radii and from molecular docking analysis it is argued that probably two CD cavity shields the indole moiety in a face-to-face manner.