Neighboring Hydroxyl Groups Promote The Addition Reaction Between Imine And Unsaturated Boronic Acid Ester

Unsaturated organoboronates play an important role in synthetic organic chemistry for its low toxicity,good stability and wide activation models.On the base of the importance of unsaturated amine bearing adjacent hydroxyl groups,we herein apply various unsaturated boronates into the Petasis reaction of aldehydes and amines,thus homoallyl,homopropargyl and 1,3-butadien-2-methylamine skeletons have been constructed under mild conditions.The main research contents are shown as follow:In the first part,Petasis allylboration among an aldehyde,1,2-amino alcohol and pinacolallylboronate has been successfully accomplished at room temperature without any catalysts,and a wide range of racemic and chiral homoallyl amines at ambient temperature.An appropriate solvent(MeOH or DMSO/MeOH)is essential for the high yield(up to 95%)and the diastereoselective ratio(up to >20:1 in most cases).The unusual absence of molecular sieves in the reaction system with(1S,2R)-1-amino-2-indanol was observed.The correct location of a hydroxy group in the imine intermediate plays a key role in the transformation,which can be understood based on the proposed allyl species via a boronate ligand exchange event and a six-membered chairlike transition state through Lewis base-acid interactions It is worth noting that the presence of molecular sieves effectively increases the yield of the racemization reaction,but the results of the diastereoselective addition reaction are not affected.In the second chapter,we have accompolished the three-component Petasis reaction with allenyl-and homoallenylboronates for the synthesis of racemic homopropargyl and 1,3-butadien-2-methylamines with the yield range of 80-95%.The adjacent hydroxyl group also proves to be essential in the reaction.