| dc.description.abstract | The thesis entitled “Investigations on the Chemistry of Quinone Methides – Study of a Few Reactions Involving the Intermediacy of 1,2?Naphthoquinone?1?Methide” consists of four chapters.
Chapter I is a brief introduction to the chemistry of quinone methides. The nature, reactivity, and newer methods of obtaining quinone methides are discussed.
¹³C NMR spectroscopy has become a very useful tool in the elucidation of structures of complex organic molecules. Chapter II deals with a study of the ¹³C NMR spectra of several compounds (1a–1d, 2a–2e) containing a new type of spirodienone fragment. This study has helped in the elucidation of structures of a few novel compounds containing this fragment described in Chapters III and IV.
Chapter III is divided into five sections.
Section 1 is a brief introduction to the present work and describes the earlier work on the reaction of naphthols with o-chloranil. The oxidation of ??naphthol with o-chloranil gave only 1a, whereas ??naphthol gave a mixture of 1a and 2a. Isolation of the former suggested rearrangement of the initial oxidation product of ??naphthol during the above oxidation. For obtaining a better insight into the mechanism of this rearrangement, a study of the oxidation of 1?[(2?hydroxy?3,4,5,6?tetrachlorophenoxy)methyl]?2?naphthol (6) was envisaged.
Section 2 describes the attempted synthesis of compound 6 by the reaction of 1?bromomethyl?2?naphthol tetrahydropyranyl ether with tetrachlorocatechol in acetone containing anhydrous potassium carbonate. Surprisingly, this reaction gave the spirodimer 4a and two other novel products. On the basis of spectral data (IR, ¹H NMR, ¹³C NMR, and mass), structures 7a and 8a are tentatively assigned to these compounds.
With a view to generalising this reaction, the reaction of 1?bromomethyl?2?naphthol?THP ether with tetrabromocatechol was carried out as before. This reaction, as expected, gave the spirodimer 4a and the isomeric compounds 7b and 8b. Reaction of 1?bromomethyl?2?naphthol?THP ether with tetrachlorocatechol–diethyl ketone–potassium carbonate was also studied. In addition to the spirodimer 4a, three isomeric compounds, for which the structures 9, 10, and 11 have been assigned, were formed. The formation of these compounds has been visualised via the intermediacy of 1,2?naphthoquinone?1?methide, initially formed by the cleavage of the 1?bromomethyl?2?naphthol?THP ether.
To gain better insight into the mechanism of the above cleavage reaction, a study of the cleavage of the pyranyl ether in 1?bromomethyl?2?naphthol?THP ether under different conditions was undertaken. This is described in Section 3.
Section 4 contains the Experimental Part, and Section 5 the References.
Chapter IV deals with the reactions of bis?(2?hydroxy?1?naphthyl)methane with o-chloranil and 2,3?dichloro?5,6?dicyano?p?benzoquinone (DDQ) and the assignment of structures for some of the novel compounds obtained in these reactions.
Reaction of bis?(2?hydroxy?1?naphthyl)methane with o-chloranil surprisingly gave compounds 1a, 2a, 4a, and 12, in addition to the normal oxidative coupling product 3. The DDQ reaction of this bisnaphthol gave a yellow compound of molecular weight 440, in addition to the expected dimer 4a and spiroketone 3. Hydrogenation of this yellow compound resulted in a dihydro compound (M? 442), which was methylated to the dimethoxy compound.
From detailed spectral data (IR, ¹³C NMR, and mass) of the yellow compound and its derivatives, it was tentatively assigned the structure 1,2?dihydro?3H?benzo[f]chromen?2,3?dispiro?[1'?naphthalene?2'?one] (13). The dihydro compound was tentatively assigned the structure 14, 1?[(2?hydroxy?1?naphthyl)methyl]?2?[2?hydroxy?1?naphthoxy]naphthalene. The structure 13 assigned to the yellow compound was further confirmed by X?ray crystal structure analysis.
Probable mechanistic pathways leading to the formation of the above compounds are discussed. The present studies suggest that 1,2?naphthoquinone?1?methide is generated in the above reactions. | |
