Two Bromine Phenolic Natural Products Total Synthesis Of Research

This thesis mainly studied the total synthesis of two bromophenols which were firstly extracted from red alga.There are two parts in this thesis:Partâ… :The total synthesis of 2,3-dibromo-4,5-dihydroxybenzyl alcohol2,3-dibromo-4,5-dihydroxy-benzyl alcohol,was synthesized from vanillin via bromination,catalyzed bromination,reduction and demethylation with an overall yield of 19%.Partâ…¡:The total synthesis of bis(2,3-dibromo-4,5-dihydroxybenzyl)etherThree routes were studied in the total synthesis of bis(2,3-dibromo-4, 5-dihydroxybenzyl) ether using vanillin as starting material.1:The target compound was synthesized via bromination,catalyzed bromination, reduction,intermolecular dehydration and demethylation.2:After bromination and catalyzed bromination,methylation protection,reduction, bromination,Williamson reaction and demethylation was used in the synthesis.3:The target compound,bis(2,3-dibromo-4,5-dihydroxybenzyl) ether,was successfully synthesized by imploying the bromination reaction,methylation protection, bromination,reduction,Williamson reaction and demethylation.Method one,although the steps are simple,but encounters the enormous difficulty in the intermolecular dehydrated step,moreover easy to have Friedel-Crafts under the acidic catalysis condition to respond,the ultimate yield is extremely low.The method two use traditional method of Williamson reaction to carry on the synthesis process,but in the intermediate 2,3-dibromo-4,5-dimethoxybenzaldehyde's syntheses,the reaction time is excessively long.Therefore we change ideas designed the synthetic route 3 by using a first step bromination,and then on the phenolic hydroxyl methylation protection,for the last second step bromination,which greatly reducing the preparation time of this intermediate.Final completion of the relative efficiency of the target total synthesis of compound,with an overall yield of 6%.Eleven compounds were synthesized among which three compounds were fist prepared,respectively be 2,3-dibromo-4,5-dimethoxybenzyl alcohol,2, 3-dibromo-1-(bromomethyl)-4,5-dimethoxybenzene and 5,5'-oxybis(methylene)bis(3, 4-dibromo-1,2-dimethoxybenzene).Their structures were identified by IR,¹H NMR,and ¹³C NMR.