A Study on the reaction of heteroatom-stabilised carbanions with a, B- unsaturated ketones

Abstract

The methodology of the addition reactions of a wide range of alkyl- and arylmethylphosphonates to a,β-unsaturated ketones was studied. Reaction conditions were optimised and the conditions determining the nature of the addition, 1, 2- vs 1, 4-addition, were investigated. This was done in order to ascertain the specific conditions needed to determine the regioselectivity of these reactions. The I-hydroxy-alkyl- and 1-hydroxy-arylmethylphosphonates that were obtained, via 1, 2- addition, were used as substrates for further transformation reactions. The aromatisation of the hydroxyphosphonates was investigated. Three possible methods were implemented and the feasibility of these reactions in synthetic procedures was studied. The hydroxyphosphonates were transformed to their olefinic counterparts via dehydration under acidic conditions. These dehydration reactions were performed under kinetic as well as thermodynamic conditions and the relative stability of the different isomers was thus determined. The addition reaction of trimethylsilyl-stabilised carbanions to a,β-unsaturated ketones and saturated ketones was studied in an attempt to implement the Peterson olefination reaction sequence for the preparation of olefins. In the last chapter the synthetic procedures for the preparation of some substrates, needed during this study are discussed.