Studies in carbocyclic and aromatic compounds a) Synthesis of spironaphthaleones and their reaction with .... b) Synthesis of hydrindanes

Abstract

The thesis entitled “STUDIES IN CARBOCYCLIC AND AROMATIC COMPOUNDS: (a) SYNTHESIS OF SPIRONAPHTHALENONES AND THEIR REACTION WITH HYDROXYLAMINE AND (b) SYNTHESIS OF HYDRINDANES” is presented in two parts.

Part I: Synthesis of Spironaphthalenones and Their Reaction with Hydroxylamine Section I provides an introduction to the hydroxylamine reaction, viz., the formation of pyrrolotropone 2 in the reaction of spironaphthalenone 1 with hydroxylamine hydrochloride. Section II presents the oxidation of different aryl/alkyl bisnaphthols 3, giving rise to both 1??aryl/alkyl spironaphthalenones 4 and 14?aryl/alkyl dibenzo[a,j]xanthenes 5. A probable mechanism is proposed to explain the course of oxidation of bisnaphthols. This section also discusses the synthesis of 1??methyl spironaphthalenone 7 starting from the protected spironaphthalenone 6. Section III describes the reaction of various 1??aryl spironaphthalenones 4 with NH?OH·HCl in alcohols, resulting in the formation of pyrrolo esters 8 instead of the dihydrotropones 9. Reactions of 3? and 4??substituted 1??aryl spironaphthalenones resulted in isomeric esters, indicating the involvement of a rearrangement. Reaction of 1??alkyl spironaphthalenone also resulted in the formation of the pyrrolo ester. All these results are presented in Section III. Section IV rationalises the formation of products in the hydroxylamine reaction on the basis of the intermediacy of an isopyrrole 10 and dihydrotropone 9 derivatives. Oxime 11 was isolated in the reaction of 1??aryl spironaphthalenones 4 with NH?OH·HCl in the presence of acrylonitrile. Reaction of oxime 11 with EtOH in the presence of acid gave pyrrolo esters 8, indicating that only one mole of NH?OH·HCl is required for the transformation and confirming that oxime formation is the initial step. In addition, the isopyrrole 10 was trapped as a Diels–Alder adduct 12, proving its intermediacy in the transformation. Section V provides details of all the above experiments.

Part II: Synthesis of Hydrindanes Part II deals with the synthesis of two hydrindanes useful in steroid synthesis and is divided into three sections. Section I begins with a brief introduction to steroid synthesis, followed by a discussion of the present synthetic strategy. Section II describes the preparation of the key synthon 14 starting from the ene?dione 13, in both racemic and optically active forms. This section also presents the synthesis of synthon 16 with a built?in trans CD?ring junction, starting with the ester 15, again in both racemic and optically active forms. Section III provides the experimental details.