Synthesis and kinetic testing of novel antioxidants

Abstract

A number of antioxidant structures having the 1,2-dihydroxybenzene or catechol motif were designed and synthesized. The design of these compounds was based on calculations that predict the bond dissociation energy of phenolic O-H bonds. The antioxidant activity of compounds prepared in this thesis ( 8 and 59) and related compounds synthesized in our laboratory (19, 33, and 38) were compared to alpha-tocopherol (vitamin E) on the basis of the rate constants for the hydrogen atom transfer to DPPH radical. Fully substituted catechols bearing a para alkoxy group were found to be better antioxidants than vitamin E, using the kinetic results criteria. The best compound in this series has a para alkoxy as part of a 5-membered ring. The relative order of antioxidant activity (59 < 78 < 8 ≤ 19 < 33 < 38) agrees with the theoretical predictions. Some of the building blocks for the future catechol dendrimers were prepared, such as 4-methyl-benzo[1,3]dioxole-5-carbaldehyde 41 and 3,4-bis-allyloxy-benzaldehyde 52. The preparation of carbon-centred antioxidants starting with oxindole or isatin was investigated.