Studies on asymmetric induction.
thesisposted on 2015-11-19, 08:47 authored by Mohammed Refat Moustafa. Selim
As a part of our studies on asymmetric induction, four topics were investigated in this thesis. Firstly, optically active menthyl and neo-menthyl phos-phonoacetates were prepared and the reaction of their anions with aldehydes and ketones studied, modest asymmetric induction was observed. A chiral phosphonamide anion was also synthesised which shows good selectivity on reaction with ethyl bromide. Secondly, the reactions of aldehydes and ketones with chiral organolithium compounds were investigated. The best results were obtained with a chiral lithiated dithiane, when a ratio of (1:1.9) was obtained in a 1,5-asymmetric induction. Thirdly, the chiral and achiral-2-substituted-l,3- butadienes were synthesised using silicon as a control element. During this work, it was observed that addition of TMSCH2 MgCl with chiral aldehydes produced one diastereo-isomer. For a practical reason it was not possible to determine which one, although a prediction was made based on Cram's rule. The asymmetric Diels-Alder reactions of chiral- 2-substituted dienes were also investigated. Finally, racemic and optically active nitrones were synthesised with preliminary investigations of their reactions with Grignard reagents showing hopeful signs of 1,2-asymmetric induction.
Date of award1987-01-01
Awarding institutionUniversity of Leicester