The subject of this thesis is the synthesis and oxidation of tricyclic steroid analogues. The synthesis of the tricyclic derivatives, 1,2-dihydro-5-hydroxy-3H-benz[e]inden-3-ones, is described in chapter 1. The synthetic route involves the initial condensation of readily available acetophenone precursors with furfuraldehyde. Subsequent acidic hydrolysis of the resulting furanyl compounds afforded a diketo acid and/or furan acid depending on the nature and position of the substituent on the aromatic ring. Intramolecular condensation of the diketo acids provides a versatile intermediate in the cyclopentene acetic acid derivatives, the hydrogenation and alkylation of which is discussed in chapter 2. Cyclisation of the acetic acid derivatives with acetic anhydride and subsequent deacetylation provided the tricyclic phenolic compounds. The introduction of angular methyl groups in the cyclopentene acetic acid derivatives is discussed in chapter 2. Reductive methylation of these compounds using lithium in liquid ammonia failed, therefore, hydrogenation, followed by direct alkylation was investigated. Hydrogenation of the esters of the cyclopentene acetic acids gave a mixture of the desired reduced compounds along with the super hydrogenated cyclopentane derivatives. It has been shown that hydrogenation of such systems gives rise to two products, namely the <I>trans</I> cyclopentanone and the <I>cis</I> cyclopentane, the <I>trans</I> cyclopentanone arising through 1,4 addition. Permethylation of these cyclopentanones was achieved using KH, NaH and tBuOK. Chapter 3 deals with the oxidation of the phenols prepared in chapter 1 and the trimethyl compounds prepared in chapter 2. A short review on the oxidation of phenols forms the introduction. The oxidation of the tricyclic compound, 1,2-dihydro-5-hydroxy-3H-benz[e]inden-3-one, using a variety of different oxidising agents did not lead to quinone formation, however phenolic coupling was observed to give a biphenol. Oxidation of the permethylated compounds prepared in chapter 2 with DDQ gave the expected dehydrogenation products via a quinone methide intermediate.

An efficient approach to the hydrobenzofuro[3,2-b]chromenone core of sanggenon-type natural products has been developed. The key transformation involves a protecting group-free double rearrangement of a bis-allyloxyflavone ether substrate. A sequence involving asymmetric 3-allyl rearrangement followed by aromatic Claisen rearrangement has been established for the asymmetric synthesis of the hydrobenzofuro[3,2-b]chromenone core structure. This methodology has been successfully applied to asymmetric syntheses of both sanggenol F and sanggenon A. Efficient chiral, racemic syntheses for sanggenons C and O have been achieved. The key transformation entails a biomimetic Diels-Alder cycloaddition between a flavonoid diene and a 2'-hydroxychalcone. The flavonoid diene was produced from a protected flavonoid chromene via isomerization. Metal-catalyzed alkynyl Claisen (Saucy-Marbet) rearrangements of 3-alkynyl flavone ethers have been evaluated, and a 1,2-acyl migration cascade which afforded novel furanyl benzofuranone scaffolds was discovered. Mechanistic studies have revealed that the rearrangement is likely initiated by 5-endo enyne cyclization to a platinum-containing spiro-oxocarbenium intermediate, which may be intercepted by methanol to produce a spirodihydrofuran or further rearranged to afford allenyl chromanediones and benzofuranones at higher reaction temperature. Lewis acid-catalyzed [1,3]-rearrangements of 3-aryl substituted flavone ethers have also been developed.

(¤@) Pyrolysis of 1,2-bis(3-methoxy-2-naphthyl)ethene (35) gave polycyclic aromatic hydrocarbons (PAH) 42¡B43¡B44 and 45. In addition, photolysis of 35 gave photocyclic products 50. (¤G) Photolysis of £\-azidotoluene (35) and 2-azido1-(2-furanyl)ethanone(45) gave dimer products benzylbenzene (51)¡B2-(furan-2-carbon-yl)-amino-1-(2-furyl)ethan-one (60) and 2-(2-formylfuranyl)-4-(2-furan-yl)-imidazole (48).