• Gopalpur Nagendrappa

      Articles written in Journal of Chemical Sciences

    • Conversion of 𝛼, 𝛼'-dichlorodiazene dioxides using levulinic acid under solvent-free conditions to 𝛼-chloroketones through a three-step domino process

      B C Vimala Gopalpur Nagendrappa

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      𝛼-Chloroketones find numerous synthetic uses. We have developed a simple method of preparation of these compounds starting from alkenes adopting the Green Chemistry principle of solventfree reaction. The procedure involves addition of NOCl generated in situ by the reaction of AcOH-HCl (3 : 1) with amyl nitrite to alkenes and treating the 𝛼-chloronitroso compounds obtained as dimers with levulinic acid in presence of a few drops of 6N HCl, the latter being a three-step domino reaction, in which the first is dissociation of dimer to monomer, the second is tautomerisation of the nitroso function to oxime followed by deoximation in the third step. The yields are excellent. Since the starting compounds are readily available alkenes and the reaction is carried out under mild conditions leading to excellent yields of highly useful 𝛼-chloroketones, the procedure has the potential of wide application.

    • Generation of nitryl chloride from chlorotrimethylsilane-acetyl nitrate reaction: A one-pot preparation of gem-chloronitro compounds from oximes

      Abdulkarim H A Mohammed Gopalpur Nagendrappa

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      While iso-amyl nitrite reacts with chlorotrimethylsilane to give NOCl, iso-amyl nitrate does not yield NO2Cl with silicon reagent. However, acetyl nitrate reacts successfully with chlorotrimethylsilane to give nitryl chloride, which is characterized by its UV spectrum. If it is generated in presence of ketoximes, gem-chloronitro as well as gem-chloronitroso compounds are formed in almost equal amounts, which together account for up to 80% yield. This is possibly the simplest one-pot reaction for the preparation of gem-chloronitro compounds which find several synthetic applications. If NO2Cl is generated in presence of cycloalkenes, the corresponding 1,2-dichlorocycloalkanes are obtained. Considering the evidence in hand, it is proposed that NO2Cl, initially formed by chlorotrimethylsilane-acetyl nitrate reaction, decomposes to Cl2, and N2O4. Then chlorine reacts with oximes to produce first gem-chloronitroso compounds, which are oxidized by NO2Cl or N2O4 to gem-chloronitro compounds, and with cycloalkenes it gives dichlorocycloalkanes.

    • Oxidation of gem-chloronitroso- and vic-chloronitroso-alkanes and -cycloalkanes to respective chloronitro compounds by novel cetyltrimethylammonium hypochlorite reagent

      Abdulkarim H A Mohammed Gopalpur Nagendrappa

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      Cetyltrimethylammonium hypochlorite (CTAHC) is prepared and used as an oxidizing agent for nitroso group to nitro group. The gem-chloronitroso and vic-chloronitroso compounds are prepared respectively from ketoximes and olefins by reacting with NOCl generated in situ from chlorotrimethylsilane (TMSCl) and iso-amyl nitrite. CTAHC oxidizes gem-chloronitroso and vic-chloronitroso compounds to the corresponding chloronitro derivatives. While gem-chloronitro compounds are obtained in good yields, the vic-chloronitro derivatives are formed in moderate yields, because of the propensity of the vic-chloronitroso group to tautomerize to 𝛼-chlorooxime. The present method is simple and practical, particularly for the preparation of vic-chloronitro compounds, considering the fact that the known methods of their preparation are few and quite involved.

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