Chemistry of spironapthalelenones

Abstract

The thesis entitled “Chemistry of Spironaphthalenones” consists of three chapters and an appendix.

Chapter I A brief account of the chemistry—synthesis, reactions, and rearrangements—of spirodienones and the role of spirodienones in biosynthesis.

Chapter II (Five Sections) Section I – Synthesis Synthesis of suitably substituted cis? and trans?dispironaphthalenones (1), required for reduction, photolytic, and pyrolytic studies, via oxidation of the corresponding bis(2?hydroxy?1?naphthyl)methanes with 2,3?dichloro?5,6?dicyano?1,4?benzoquinone (DDQ) in benzene. Section II – Catalytic Hydrogenation and Zn/AcOH Reduction Catalytic hydrogenation (10% Pd/C) and Zn/AcOH reduction of cis? and trans?dispironaphthalenones (1) led to the same dihydroxy compound (2), apparently by C(2?)–C(3?) carbon–carbon bond cleavage. Section III – Photolysis of cis?Dispironaphthalenones Results of the photolysis of cis?dispironaphthalenones (1) are discussed, preceded by a brief introduction to ??cleavages in saturated carbonyl compounds and enones. The products obtained are:

o?Naphthoquinone?1?methide dimer Dinaphthodioxin (3) trans?Dispironaphthalenone (1) Dispironaphthalenone (4) Intramolecular (2+2) cycloaddition product (5)

Probable mechanisms for the cleavage reactions are discussed. Section IV – Pyrolytic Cleavage Pyrolytic cleavage of the C(2?)–C(3?) bond in cis? and trans?dispironaphthalenones (1) to give dinaphthodioxin (3) and o?naphthoquinone?1?methide dimer is described. Section V – Borohydride Reduction Interesting results from the borohydride reduction of cis?dispironaphthalenones (1) are presented. Reduction in THF under alkaline conditions in the presence of alcohols (methanol, ethanol, isopropanol) afforded novel alkoxy?substituted intramolecular C–C coupled products (6) along with small amounts of hemiacetal (7). Structures were assigned based on spectral data, and the structure of (6) was unambiguously confirmed by X?ray crystallography.

Chapter III – Oxidation of Spironaphthalenones Oxidation studies of spironaphthalenones (8) with DDQ: reaction in dry benzene afforded two yellow products (A) and (B). Structures (9) and (10), respectively, were assigned based on detailed spectral analysis and chemical transformations. The structure (9) (compound A) was further confirmed by X?ray crystal structure analysis.

Appendix A reinvestigation of the structures of di?tert?butyl?2?naphthol and its chlorination products.