Microwave synthesis and molecular re-arrangement of a grisadienone and its derivatives
Ngcobo, Thandekile Sithembile
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ortho-Deoxygrisan (38), a spirodienone was synthesised from bisphenol (42) using both conventional and microwave assisted methods. The bisphenol (42) was synthesised from phenol (52) by conventional and microwave assisted methods. Benzophenone (43) was synthesised from compound (49) which in turn was synthesised from compound (53) by chromic acid oxidation in acetic anhydride or acetic acid. Compound (53) was synthesised from bisphenol (42) by mono-acetylation method.Acid-catalysed rearrangement of ortho-deoxygrisan (38) in the absence of light was investigated. Chromatography of the reaction mixture afforded compound (D) as a major component. Attempts to synthesise ortho-grisan (50) from benzophenone (43) were unsuccessful. Microwave assisted selenium dioxide oxidation of compound (53) gave a yellow compound C. The spectra of this compound were very similar to the spectra of ortho-deoxygrisan (38). However, selenium dioxide was reacted with compound (53) in the absence of microwave to give a yellow solid B. The 1H NMR spectral data of this compound led to the proposed structure B for it.