Name:
Veejendra Yadav
Country:
India
City:
Kanpur
State/Province:
ACS Member:
false
Local Section:
International Chapter:
Technical Division Membership:
Technical Division Membership Emeritus:
Subdivision Member:
ACS Activities:
Company/Institution Name:
Career Stage:
Professional
Research and Special Interests:
I have developed a simple theoretical model for the prediction of pi-facial selectivity of a diverse range of substituted cyclic ketones in reaction with nucleophiles and applied the same successfully even to those instances where other models could not be applied. This work has enabled me to explain some of the previously unexplained observations as well. Sharp distinction between Cieplak"s hyperconjugation effects and antiperiplanar effects was noted and the observed selectivity was demonstrated to be controlled largely by the antiperiplanar effects alone. It was during the above investigations that I have demonstrated the unsuitability of the anion-accelerated oxy-Cope rearrangement for the study of pi-facial selectivity as it was indeed used previously by le Noble. Sound evidence was provided to demonstrate that the rearrangement proceeded primarily through a pathway that comprised radical cleavage and 1,4-addition. Further, the course of the rearrangement was shown to depend much on the reaction solvent. The controversial report of Otera on the high anti-to-S selectivity of gama-sulfenyl enones that was ascribed to the electronic effects of sulfur in compliance of Cieplak"s hyperconjugation hypothesis was demonstrated to be due primarily to steric effects arising from the nucleophile and the substituents on S and gama-carbon among other factors such as the nature of the solvent and the reaction temperature. Our most recent study argues against both the Cieplak model and the Anh-Felkin model and brings out strong evidence in favor of antiperiplanar interactions (sigma to sigma#*) in late transition states and sigma to pi*C=O interactions in early transition states.The p-facial selectivity in Diels-Alder cycloadditions has also been controversial for quite some time. The observed selectivity has been ascribed to the electronic effects of the heteroatom substituent by some investigators and to the steric effects of the same heteroatom substituent by other investigators. From the study of cyclohexene-based 1,3-dienes bearing strategically located heteroatoms, I have concluded the same to be due predominantly to the steric effects of the heteroatom substituent. If at all, the electronic effects of the heteroatom substituent had too little effect to account for the large facial selectivity observed from experiments.I have studied the chemistry of silylmethyl-substituted cyclopropanes, aziridines and azetidines and discovered very interesting applications of the same. Substituted oxacycles, cyclopentenes, 2,4,6-triubstituted tetrahydropyrans, and imidazolines, oxazolidines and pyrrolidines were prepared easily. These reactions have strong potential for application in the synthesis of medicinal molecules. Tandem reaction of silylmethyl-substituted cyclopropanes with arylacetylenes resulted in spiro-fused indene derivatives that have strong potential for development into optical light emitting diodes (OLEDs).I have discovered a single-step base-promoted rearrangement of 7-substituted-4,5-didehydro-2-oxepanone into 7-substituted-2,6-dioxabicyclo[3.3.0]octan-3-one which has allowed him to easily construct selected pharmaceutically important styryl lactones such as goniofufurone, goniopypyrone and epigonifufurone. This strategy is flexible enough to allow us construct other important members of the family including the plakortones.I have discovered an alchemical wizardry at its best in transforming a solvent-cum-reactant into an easily removed
Area of Expertise:
synthetic organic chemistry, physical organic chemistry
Years of Expertise:
26 or more