The Development Of Green Methods For The Construction And Derivatization Of Heterocyclic Compounds

Heterocycles are important structural motif that is usually found in natural products with various bio-activities and in functional organic molecules including organic dye molecules,organocatalysts etc.Traditional synthetic approaches to heterocyclic compounds usually use condensation reactions or cycloaddition reactions under harsh conditions such as high temperature and the use of toxic reagents.The development of environment-benign and highly efficient synthetic methods for various heterocycles and their derivatives is therefore of current research interest.In this Ph.d dissertation,we focused on two types of green methods to construct heterocyclic framework and to derivatize heterocyclic compounds with specific functional groups.Photoreactions were used as one type of green methods to construct medium-ring lactones,which was futher developed as a potential atroposelective synthetic method for biaryls.Transition metal-catalyzed reactions were used as the other green approach to obtain various oxazole derivatives.The work included in this dissertation was described in the following four parts:1.Sequential photocyclocaddition-photooxidation reactions for the construction of biaryl containing medium-ring bislactones.In this chapter,we investigated the application of the sequential photocyclocaddition-photooxidation reactions between different 9,10-phenanthrenequinones and C=C containing species to construct biaryl containing ten-membered bislactones.To investigate the substrate scope,we use alkenes linked with electron-withdrawing groups or electron-pushing groups to react with 9,10-phenanthrenequinone.We also used 9,10-phenanthrenequinones with different substitution groups and analogues of 9,10-phenanthrenequinones as the dione species to react with alkenes.Diastereoselectivity in the photooxidation step was also investigated to explore the potential to use the diastereoselective reaction to realize atroposelective synthesis of biaryls.2.Atroposelective construction of biaryls based on the diastereoselective photooxidation of phenanthropyranodioxines.Based on the photocycloaddition of 9,10-phenanthrenequinones and glucals with chiral centers,we were able to realize diastereoselective preparation of phenanthropyranodioxines.Using the phenanthropyranodioxines with five chiral carbons as the substrate,we investigated the diastereoselectivity in the photooxidation of these phenanthropyranodioxines with chiral centers.Highly diastereoselective photooxidation reaction was observed with one type of phenanthropyranodioxines and their potential applications in the construction of atropic biaryl dicarboxylates were explored.3.Nickel-catalyzed decarboxylative cross-coupling leading to acylated azoles.In this chapter,we demonstrated the first example of decarboxylative cross-coupling reactions of a-oxoglyoxylic acids through nickel catalysis.The reaction was found to proceed with high efficiency under NiCl2(PCy3)2 and Ag2CO3 in the presence of benzene as the solvent at 170℃.Further investigation on the reactions substrate scope indicated that this nickel-catalyzed decarboxylative cross-coupling tolerates a variety of functional groups such as halogen and ester on the zole substate.We proposed a plausible catalytic cycle and demonstrated the potential of this nickel-catalyzed decarboxylative cross-coupling reaction as a green approach to various oxazole derivatives.4.Nickel-catalyzed decarboxylative cross-coupling leading to arylated azoles.In this chapter,we have developed a novel decarboxylative cross-coupling of azole derivatives and benzoic acids via a nickel-catalyzed sp2 C-H bond functionalization process to access a green and efficient method for preparing 2-ary1 substituted oxazoles.On the bais of the reaction conditions optimization and substrates extension,we also found this transformation tolerates a variety of functional groups including halogen,nitro,ester and so on.Therefore we provided a novel green approach to oxazoles derivative with ary1 substituion groups.