Pradeep T. Deota

Relative Stabilities of C92 IPR Fullerenes

Abstract The complete set of 86 isolated-pentagon-rule (IPR) isomers of C92 has been described by the SAM1 quantum-chemical method, and their energetics checked by density functional theory at the B3LYP/6-31G* level. Although the lowest-energy cage is not identical in both approaches, it still exhibits D2 symmetry in both cases. As energetics themselves cannot produce reliable relative stabilities at high temperatures, entropy terms are also computed and the relative-stability problem is treated entirely in terms of the Gibbs function. The lowest-energy structure is not the most populated isomer at higher temperatures – it is replaced by a D3 structure. Further stability interchanges are possible at very high temperatures, when C3 and C1 structures are also important. There is a partial agreement of the computations with available observed data.

Biological studies of azadirachtin and its derivatives against polyphagous pest, Spodoptera litura

Azadirachtin-A (Aza-A, figure 1) was subjected to a variety of synthetic transformations and the antifeedant activity and toxicity of the azadirachtin derivatives were assessed against second instar larvae Spodoptera litura on castor leaves in comparison with the crude material containing 9.14% Aza-A, as well as relatively pure 91% Aza-A. A probable mechanism for the base initiated fragmentation of the diketocarbonate into a decalin fragment and a spiroketal moiety has been proposed. Figure 1. Structure of Azadirachtin-A. The present study indicates that the combination of insect toxicity and antifeedancy of azadirachtin provides good crop protection.

Studies in the synthesis of polycyclopentanoids: synthesis, oxa-di-π-methane rearrangement of annulated bicyclo[2.2.2]octenones and cyclopropane ring cleavage of tetracyclo[6.3.0.0.0]undecenones

A short, new and general approach for the synthesis of linear polyquinanes having the cis:anti:cis tricyclopentanoidal framework is delineated. The key element of this approach is the photochemical 1,2-acyl shift or oxa-di-π-methane rearrangement of annulated bicyclo[2.2.2]octenones, having β,γ-unsaturated carbonyl chromophoric systems. An efficient method for the synthesis of a variety of annulated bicyclo[2.2.2]octenones via inverse demand π4s+π2s cycloaddition of cyclohexa-2,4-dienones (9-12) with olefins (18-26) is reported. The structure of the adducts has been established through the study of their high-field 1H NMR and 13C NMR spectra and decoupling experiments. Synthesis of tricyclo[5.2.2.02,6]undecadienones (51-57) from readily available adduct 43 has been achieved. Oxa-di-π-methane rearrangement of various chromophoric systems to polyquinanes (60-68) is described. The adduct 32 did not undergo oxa-di-π-methane rearrangement upon sensitized irradiation, while adduct 40 rearranged inefficiently to compound 64. Studies on the cleavage of the cyclopropane ring of the tetracyclic ketones (60, 66, 67 and 73) with formic acid and acetyl methanesulfonate is also reported.

Diels-Alder Cycloaddition: Synthesis and Oxa-di-π-Rearrangement of Tricyclo(5.2.2.02,6)-undecadienone

Abstract A short synthesis of various tricyclo(5.2.2.02 6) undecadienones by Diels-Alder reaction of a 2,4-cyclohexadienone with dienes and their oxa-di π- rearrangement is reported.

Tungstic Acid - Hydrogen Peroxide a Simple Reagent for Oxidation of Cycloocta-1, 5-Diene Preparation of (Z) Cyclooct-5-Ene-trans-1, 2-Diol and 1, 6-Dicarbomethoxy (Z) Hex-3-Ene

Abstract A convenient synthesis of (Z) cyclooct-5-enetrans-1, 2-diol from oxidation of cycloocta-1, 5-diene with H2WO4-H202 is described. The trans-1, 2-diol is further transformed into 1, 6-dicarbomethoxy (Z) hex-3-ene.

Micellar Catalysis TT45 + TT2S Cycloaddition in Aqueous Media

Abstract Micelle catalyzed Diels-Alder reaction of cyclic dienes with various quinones in aqueous media is described. Micellar cycloadditions are remarkably faster and give better yields of the adducts compared to the conventional reaction.

A Convenient Synthesis of Novel Pentacyclo [5.4. 0.02,6 .03,10 .05,9] Undecane-8,11-dione-4-spiro-1-cyclopropane

Abstract An efficient synthesis of the title compound by Diels-Alder cycloaddition of spiro(4.2) heptadiene with p-benzoquinone followed by photochemical ring closure is described.

Oxidative Acetylation of Tetramethyl Bisphenol‐F

Abstract Oxidative acetylation of tetramethyl bisphenol‐F (2) using two different reagents is described. The reaction of (2) with NaIO4 in acetic anhydride furnished a novel triacetate (3) and its reaction with lead tetraacetate (LTA) in dry benzene resulted in the formation of a novel bis‐cyclohexadienone (4).

Novel One‐Pot Synthesis of Acetoxy‐2,4‐Cyclohexadienones

Abstract A new, simple, one‐pot method for the oxidative acetylation of some substituted phenols leading to acetoxycyclohexa‐2,4‐dienones is described. A novel diacetoxycyclohexadienone 12 has also been prepared using the present method from 2‐hydroxymethyl phenol (salicyl alcohol).

An Efficient Synthesis of a Novel Pentacyclo [5.4.0.02,6.03,10.05,9] Undecane-8, 11-Dione-4-Spiro-1-Cyclopentane

Abstract An efficient synthesis of the title compound by Diels-Alder cycloaddition of spiro (4.4) nonadiene with p-benzoquinone followed by photochemical ring closure is described.