Studies Of Multicomponent Carbonylation Reactions Based On Phenols

Xanthone and Dibenzopyranone are two important scaffolds,which broadly exists in plants and animals.As the central core of variety of naturally occurring and manmade compounds,xanthone and dibenzopyranone exhibits extraordinary biological and pharmaceutical properties.Because of the widely application of xanthone and dibenzopyranone,the development of an efficient synthesic route with reduced waste and simple operation is highly desirable.Meanwhile,Phenols were naturally abundant and could be easily converted to phenol derivatives.Based on our group's previous investigation of C1 insertion multicomponent reaction,which involving aryne,CO and 2-iodoaniline,this thesis mainly focused on phenol and aryne as the starting materials.By the using of different catalysts and additives,we finally successively established a regioselectivity control method to synthesize a variety of xanthone and dibenzopyranone scaffolds.In general,not only phenols and arynes could be employed in these process,but also different type of phenols.(1)CO Insertion multicomponent reaction on Arynes with phenols for Construction of xanthone and dibenzopyranoneBeacause of phenol's low nucleophilicity and air sensitivity,we have changed phenol into 2-iodophenol and N-phenoxyacetamide.Palladium-catalyzed carbonylation of 2-iodophenol and aryne with CO was established to form xanthones.With the employment of an oxidizing directing group,a mild rhodium(III)catalyzed C-H functionalization carbonylation reaction was also developed for the synthesis of dibenzopyranones.A plausible mechanism was proposed based on the control experiments,and representative natural products synthesis based on these methods are in progress.(2)Cross-coupling carbonylation reaction between differently substituted phenolsDuring the research of multicomponent reactions of arynes with 2-iodophenols,we have detected symmetrically substituted xanthone products.After the evaluation of conditions,we finally developed an efficient method for the synthesis of unsymmetrical xanthones through Pd-catalyzed cross-coupling carbonylation of different substituted 2-iodophenol in the presence of CO.Various xanthone compounds could be constructed by the free combination of differently substituted 2-iodophenols.