Studies on carbene and ketene reactions

Abstract

PART ONE Studies on carbene reactions Chapter - I. Introduction to Carbene Chemistry In this chapter history of carbene generation and a general introduction have been given at the outset. Next section of the chapter surveys different methods of Carbene generation with special emphasis on keto carbene generation. Addition of ketocarbenes to olefins have been discussed and mechanisms of these addition reaction have also been cited. Subsequently a background survey of a few reactions involving cleavage and rearrangement of the cyclopropane ring system have been furnished. Theoretical aspects of the cases have been discussed briefly. The singlet and triplet states and structure of carbenes are discussed. Spectroscopie evidence and chemical evidences with reference to C-H insertion reactions and addition to C = C bonds have been described. Some factors influencing the reactivity of carbenes have been illustrated in this introductory discussion. ,Chapter - II Cleavage of cyclopropane ring In this chapter preparation of two cyclopropane derivatives via ketocarbene addition to cyclohexene and to dihydronapthalene (B). have been described. [B] Cyclopropane adduct (A) on treatment with Grignard reagent (Methylmagnesium iodide) a Grignard adduct is formed which on acid treatment gave a homoallylic halide derivative ( C). Compound (A) on treatment with phenyl magnesium bromide gave a Grignard adduct and this on acid treatment gave the compound (D). Action of vinylmagnesium bromide on compound (A) followed by acid treatment was studied when a solid compound (E) was found. Compound (C) on oxymerouration-de-mercuration reaction yielded an alcohol (F). Methyl magnesium iodide treatment of (B) followed by acid treatment of the Grignard adduct thus obtained failed completely'. In a later section of this chapter discussions on the basis of the above experimental results and their analysis, spectroscopic data. such as IR, NMR and mass spectra are given. On the basis of analyses and spectroscopic studies the structures of the compounds (C), (D) and (F) have been established. The last section deals with the experimental details of the reactions to obtain the above compounds. Chapter - III Decomposition of diazotetralone. In this chapter preparation of d-diazotetralone has been described. Ultra-violet spectral studies on the decomposition of diazotetralone were undertaken and concluded that the application of copper catalyst helps thermal decomposition of diazotetralone alone. But it has been found that thermal decomposition of -ot-diazotetralone in presence of copper catalyst and an olefin (substituted cinnamic esters, methyl crotonate, cyclohexene etc) failed to give any cyclopropane adduct whereas dimerisation of diazotetraione was observed. Reaction of diazotetralone with dimethyl fumerate in presence of catalyst (copper) and in absence of catalyst gave the cyclopropane adduct (G). Structure of this cyclopropane adduct (G) was fully characterised by the help of analysia, IR, NMR and mass spectra and may be written as Experimental details of these reactions have been described in the concluding part of this chapter. PART TWO Studies on Reactions of Diazometbane Ohapter - I A short review on diazomethane addition to olefin. In this chapter a very brief survey only on the 1,3-dipolar addition of diazomethane with olefin and some cyclopropanation reactions of diazomethane with olefin have been described.

Chapter - II Reactions of diazomethane with some olefins In this chapter reactions of diazomethane with some substituted cinnamic esters in presence of different catalysts have been described. Diazomethane on reaction with o-methoxy and p-methoxy cinnamio esters, both in presence of catalysts palladium acetate and uranyl acetate gave cyclopropane derivative (H) and (I) respectively in good yield. Reactions of diazomethane in presence of same catalysts o-chloro, p-chloro, o-nitro and cyano cinnamic esters gave 2-pyrazoline (J), (K), (L), M) respectively. 1-pyrazoiine ~N) and (0) were isolated. in cases of reaction of diazomethane with trans-phenyl methyl cinnamate trans-naphthyl, c-chloro methyl cinnamate respectively in presence of same catalysts. In the results and discussions section the characterisation with the help of analysis, IR, NMR ·and mass spectral data have been described and their structures have been proposed as follows. Structures of compounds· (N) and (0) are assigned as follows. Experimenta1 details are presented in the next section of this chapter. PART THREE Studies on Ketene Reactions. Chapter – I Review on Ketene Reactions A short review on different methods of preparation of ketenes, their reactions with various compounds with special emphasis on addition reactions to olefina and carbonyl compounds producing_cyclobutanone derivatives and oxetanone derivatives have been described in this chapter.

Chapter - II Reactions of Ketenes In this chapter description of our attempts of preparing certain ketenes and their attempted reactions have been furnished. Cyclohexane carboxylic acid was prepared from cyclohexanol with formic acid and conrcentrated sulphuric acid. Then this acid was converted into, its acid chloride. Dichloroacetyl chloride and trichloroacetyl chloride was prepared from the respective acids.

Cyclohexane carboxylic acid chloride on refluxing with different olefins in presence of triethylamine afforded dimer (P) only, other products could not be cbaracterized

Dichloroacetyl chloride on refluxing with olefin in presence of triethylamine, Similarly, are unsuccessful completely. Here also dimer is the characterisable product.

Trichloroacetyl chloride was treated with activated zinc dust in presence of olefins and tetralone but these reactions also- failed to yield any conclusive result. Experimental details have been described in last part of this chapter.