Studies On The Palladium-Catalyaed Addition Of Arylboronic Acids To Para-Quinone Methides

Diaryl compounds are common structural motifs present in a number of natural products,pharmaceuticals,and bioactive compounds.Therefore,an efficient method to construct this skeleton is increasingly gaining organic chemists'attention.Transition-metal-catalyzed additions of organometallic reagents to electron-deficient double bonds represent useful strategies to construct C-C bonds.Rhodium was usually used in this reaction.But the high cost restricted the development of the reaction.Compared with the rhodium,the palladium have a lower price.The addition reaction of palladium-catalyzed organic boron reagents to the electron-deficient double bond has attracted the attention of many organic chemists in recent years.This thesis mainly describes palladium-catalyzed addition reaction of aryl boronic acids to para-quinone.After screening of the palladium,solvents and ligands,we found the excellent condition.Initially,different alcohol solvents were examined using BPy as the ligand,since previous studies showed that alcohol solvents have a strong influence on the reaction as a solvent.It appears that there is some correlation between reaction activity and the acidity and steric hindrance of the alcohol solvents:the more acidic and less bulky solvents give the desired product in higher yields.Other kind of solvents have a lower yield.Different bidentate nitrogen ligands were screened in order to improve the yield.Increasing the electron-donating ability of the para-substituents led to an increase in catalytic activity.Consequently,the best ligand was found to be DMe O-BPy.Thus,the optimized reaction conditions were found to be using Pd(TFA)₂as the catalyst and DMe O-BPy as the ligand in TFE solvent.Subsequent researches suggest that arylboronic acids possessing both electron-donating and electron-withdrawing groups are well tolerated.A range of carbonyl-substituted para-quinone methides are tolerable to the reaction conditions.The reaction provides a highly efficient way for preparation of diaryl acetates.