Sanjay Pratihar

Publications (9) View all

• Article: Heterobimetallic Pd-Sn Catalysis: Michael Addition Reaction with C-, N-, O-, and S-Nucleophiles and in Situ Diagnostics.

  Debjit Das, Sanjay Pratihar, Sujit Roy
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  ABSTRACT: An efficient Michael addition reaction of differently substituted enones with carbon, sulfur, oxygen, and nitrogen nucleophiles has been achieved by a new heterobimetallic "Pd-Sn" catalyst system. The nature of the catalytically relevant species and their interactions with the enone moiety has been examined by spectroscopy. The effect of ligand and the coordination mode of enone with "Pd-Sn" heterobimetallic system have been investigated by kinetics and DFT studies. A straightforward application of this methodology is shown in the synthesis of 1,4-oxathiepane core.
  The Journal of Organic Chemistry 02/2013; · 4.45 Impact Factor
• Article: Heterobimetallic Pd-Sn Catalysis: A Suzuki, Tandem Ring-Closing Sequence toward Indeno[2,1-b]thiophenes and Indeno[2,1-b]indoles.

  Debjit Das, Sanjay Pratihar, Sujit Roy
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  ABSTRACT: Indeno[2,1-b]thiophene and indeno[1,2-b]indole motifs have been obtained in moderate to good yields from easily available substituted boronic acids, 2-bromo aryl/vinyl aldehydes, and nucleophiles such as arenes/heteroarenes and others using a catalytic combination of bimetallic "Pd-Sn" and AgPF(6). This formal three-component coupling involves a Suzuki reaction followed by nucleophile assisted tandem ring closure. The sequential synthesis of substituted heterocycle-fused indenes, benzofluorene, and fluorenes was also accomplished.
  Organic Letters 08/2012; 14(18):4870-3. · 5.86 Impact Factor
• Article: First example of a heterobimetallic 'Pd-Sn' catalyst for direct activation of alcohol: efficient allylation, benzylation and propargylation of arenes, heteroarenes, active methylenes and allyl-Si nucleophiles.

  Debjit Das, Sanjay Pratihar, Ujjal Kanti Roy, Dipakranjan Mal, Sujit Roy
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  ABSTRACT: Arenes, heteroarenes, 1,3-dicarbonyls and organosilicon nucleophiles undergo highly efficient alkylation with allylic, propargylic and benzylic alcohols in the presence of a new 'Pd-Sn' bimetallic catalyst in nitromethane; water being the sole byproduct. The plausible mechanism of alkylation and the intermediacy of ether has been enumerated.
  Organic & Biomolecular Chemistry 05/2012; 10(23):4537-42. · 3.70 Impact Factor
• Article: A newly developed highly selective ratiometric fluoride ion sensor: spectroscopic, NMR and density functional studies.

  Arabinda Mallick, Ujjal Kanti Roy, Basudeb Haldar, Sanjay Pratihar
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  ABSTRACT: A new easy-to-synthesize chemosensor, 3,3'-bis(indolyl)-4-chlorophenylmethane (hereafter S), was designed, synthesized and employed as a selective optical chemosensor for fluoride ions.(1)H NMR and density functional studies on the system have been carried out to determine the nature of the interaction between S and X(-) (X = inorganic anions) responsible for the significant fluoride-induced changes in the absorption properties of S. The experimental results reveal that abstraction of an acidic proton of S by the fluoride ion, leading to the formation of anionic species, is responsible for the spectral changes. These changes allow signaling for the fluoride ion to detect and estimate the concentration of fluoride ion present even at the submicromolar level, accurate up to 2 μM. Calculations of the transition energies of S, S(-), and S···F(-) (hydrogen bonded complex) show that only S(-) is responsible for the long-wavelength absorption band in the presence of F(-).
  The Analyst 03/2012; 137(5):1247-51. · 4.23 Impact Factor
• Article: Reactivity and Selectivity of Organotin Reagents in Allylation and Arylation: Nucleophilicity Parameter as a Guide

  Sanjay Patihar and Sujit Roy
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  ABSTRACT: By using the inverse concept of electrophilicity and nucleophilicity and with two different available equations from the literature for electrodonating power, the global nucleophilicity index (N) of 99 organotin and 10 allylmetal reagents (metal = Mg, Zn, B, In, Si) have been calculated at the B3LYP/LAN2DZ, 6-31G(d) level of theory. The nucleophilicity scale is validated by the good linear fit between N-values of para-substituted arylstannanes and Hammett σp values of the substituents on the aryl ring. The global nucleophilicity index N has been utilized successfully to explain the reactivity of aryltin and allyltin reagents, to understand the effect of substituents directly attached to tin and those attached on the transferable group, and to rationalize the effect of solvents on reactivities of organotin reagents. The local nucleophilicity index value (Nk -) proved to be a useful local descriptor. The Nk - values at the R- and γ-position in various allylmetal reagents (metal = Mg, Sn, Zn, In, B, Si) have been calculated. Aided by local nucleophilicity values, the regioselectivity in carbonyl allylation (in the presence and in the absence of Lewis or Brø�nstead acid) has been analyzed
  Organometallics 05/2011; 30:3257-63. · 3.96 Impact Factor