Organophosphorus Chemistry Group

Current Research interests

Organophosphorus Chemistry

Allene chemistry

Catalytic Organic Transformations

Research Highlights

(1)    New pentacoordinate phosphorus compounds that throw light on the relative apicophilicities of substituents attached to trigonal bipyramidal phosphorus have been synthesized.  These results are in contrast to the apicophilicity order given in standard books on Phosphorus Chemistry. The topic  is   important in the  context of  reaction mechanisms  at  tetracoordinate  phosphate esters.

Apicophilicity rules are not followed in many of our compounds shown above.

[cf compounds 1 and 10 and compounds 8 and 14]

Unusual V.T. ³¹P NMR [Toluene-d₈ solution] is exhibited by some of the above compounds

 (2)  A novel class of compounds (OCH₂CMe₂CH₂O)P(O)CH(X)Ar [X = Cl, Br, I] has been developed and used in organic synthesis. These compounds have been found to be versatile substrates that can be adapted to Wadsworth-Emmons reactions.  In particular, highly substituted olefins such as Cl(Ar)C=C(Ar')(Ar")  can be readily synthesized  using  this route. New unsymmetrical acetylenes containing ferrocenyl/ anthracenyl  residues have also been prepared.  The  utility of  the Arbuzov reaction for the facile synthesis of  several hitherto  inaccessible alpha-substituted phosphonates has been developed.   A very convenient route to the biologically important alpha-aminophosphonic  acids [presented in CRSI-Symposium-III] has been developed.  Several phosphonates of synthetic utility have been prepared using Baylis-Hillman methodology.

(3)  A very unusual 1,3-(P,N) mode of dipolar addition to P(III) azides and isocyanates (completely different from those involving normal organic azides and isocyanates)  as well as a unique ring expansion  (five to nine membered)  of a  phosphorus heterocycles have been  recently discovered. This chemistry  adds a new  dimension to  the highly  useful dipolar  addition  reactions in organic chemistry.

  Cycloaddition and Cyclization Reactions

(4)  An  elegant and systematic way to construct very short hydrogen bonds  utilizing a cyclic phosphate has been developed. The  results have  implications as  regards  the role  of  imidazolyl  residues  in RNA hydrolysis/ cyclization.  

Very Short Hydrogen Bonds

1.Imidazole.MeOH showing Hydrogen bonding and helical motif {C(26)[-H(26)]…O(5) 3.090(4) Å}

A complex of 1, deprotonated 1 and [K, 18-Crown-6];O(8)[-H(8)]-O(4) 2.397(4) Å

(5) New macrocycles based on a cyclodiphosphazane skeleton have been discovered. Novel P(III) compounds with multi-cyclophosphazane units have been designed for further work.

[(OCH₂CEt₂CH₂O){P(N-t-Bu)₂P}]₂

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