Study On The Novel Synthesis Of Esters And Intramolecular Functionalization Of C-H Bonds Adjacent To Nitrogen

This thesis covers the direct conversion of N-alkoxyamides to carboxylicesters through tandem NBS-mediated oxidative homocoupling and thermaldenitrogenation and the study on the intramolecular functionalization of sp3C-Hbonds adjacent to nitrogen via PIDA-mediated oxygenation. It mainly includes thefollowing aspects:1. The ester moiety is an important functional group in polymers,pharmaceutical agents and biologically relevant natural products. Although manymethods have been reported for the synthesis of esters, special reagents andprocedures are normally required for achieving the sterically bulky carboxylicesters. In this thesis, we develop a novel method for the conversion ofalkoxyamides to carboxylic esters. Treatment of N-alkoxyamides with NBS wasfound to conveniently afford the corresponding carboxylic esters, andelectron-donating groups on the acyl side-chains or electron-withdrawing groupson the alkoxy side-chains had beneficial effects on the reactions. Most importantly,a wide range of sterically hindered esters (such as2,4,6-trimethyl benzoate esters,adamantane-1-carboxylate esters, tert-butyl esters and long chained alkyl esters)were synthesized through this method. In addition, based on the reactionintermediates we captured and the literature reports, a possible mechanism wasproposed.2. We also made a study on the PIDA-mediated intramolecularfunctionalization of sp3C-H bonds adjacent to nitrogen. It was found thatN-alkyl-N-arylanthranilic acids could be oxidized by PIDA to form new C-Obonds by intramolecular cyclizations. The electron-withdrawing effect ofsubstituents did not have a significant influence on the reactions, but strongelectron-donating substituents caused the reaction yields to decline. A series ofimportant1,2-dihydro-(4H)-3,1-benzoxazin-4-ones derivatives were synthesizedby this strategy. Besides, the reaction was not inhibited by the initial presence ofradical inhibitor suggesting that the reaction proceeded via an ionic mechanism.