Studies On Organic Reactions Involving Participation Or Assistance Of Phenolic Hydroxyl Group

Phenols are a class of important compounds whose key structure presents broadly in biologically functional organic molecules and natural products.Owing the p-πconjugation,the hydroxyl group in phenol is more acidic,which makes the electrophilic substitution in the phenyl ring easier.In addition,the free electron pair in the hydroxyl is capable of chelate transition metal to enable the functionalization of specific C-H bond,thus playing pivotal role in synthetic organic chemistry.The research contents included in this thesis consist of three sections.The first section is o-hydroxyl aniline-directed aromatic C-H activation arylation reactions of phenylacetamides.Starting from N-(o-hydroxyphenyl)phenylacetamides and aryl iodides,the 2,6-diarylation and 2-arylation reactions of phenylacetamides have been individually realized by modifying catalytic conditions with palladium catalysis.The directing function of the hydroxyphenyl is one of the major factors in achieving the reactions.The second section is the synthesis of 2-acylbenzoxazoles via tandem intramolecular annulation and methylene C-H oxygenation in N-(o-hydroxyphenyl)phenylacetamides.By employing N-(o-hydroxyphenyl)phenylacetamides as starting materials,including catalytic copper salt in Ac OH,and oxygen in the air as oxidant,the 2-acylbenzoxazoles have been synthesized in one-step.In addition,the synthesis of related heterocycles such as 2-methylene benzoxazoles and benzothiazoles have also been realized by modifying reaction conditions.The hydroxyl group has participated the construction of oxazole ring in the reactions.The third section is the reaction of triethyl silane to o-hydroxyphenyl enaminone for the synthesis of propiophenones.With systematic exploration,the method on the synthesis of propiophenones is established by employing N,N-disubstituted o-hydroxyphenyl enaminones in the presence of iridium,ligand and trimethylsilane reductant.Control experiments indicate that the hydroxyl group in the phenyl ring of enaminones plays key inducing role for the target reaction.