The Applications Of Lactol In Organocatalysis

Chemists around the world pay more and more attentions to the field of organocatalysis after its inauguration in 2000 and get so many achievements. The development of new catalysts, exploration and verification of complex mechanism, design of novel synthetic route, construction of molecular skeletons with multiple stereocenters and utilization in industry make organocatalysis to be an important part of asymmetric methodology. Therefor it is important to explore new substrates which could be catalyze by organocatalysts and obtain special molecular skeleton. The following research with this thesis mainly focus on a new substrate-lactol.Dihydrocoumarin has been widely exist in bioactive natural products. It is of great significance to modify dihydrocoumarin from inexpensive and available material such as coumarin. In the first part of this dissertation, we proposed a newly open-close strategy. At the beginning, lactone from dihydrocoumarin is opened by reduction reaction to produce lactol, and then, electrophilic olefin employed to react with lactol which catalyzed by chiral secondary amine catalyst to deliver an asymmetric Michael reaction. The substituted lactol is than closed by a subsequential oxidation reaction. This promising approach has many advantages such as good yields, excellent enantioselectives, easy operating and environment-friendly. The final products could be transformed in to a series of optically active compounds with multiple skeleton. It should be noticed that this is the first time that lactol was utilized into asymmetric organocatalysis, which breaks a new path for organocatalysis.Synthesis of spirooxindole has been studied in the field of asymmetric reaction all the time as its excellent physiological and pharmaceutical activity. Particularly, six-membered carbocycles right be the spiro-part. In the second part of this dissertation, we report an asymmetric [2+2+2] annulation under organo/organo dual catalytic system to afford six-membered carbocycles with six continuous stereogenic centers including an all-carbon quaternary center and spirooxindole moiety in the product structures. At the same time, this is a new expansion to utilize lactol in the field of asymmetric organocatalysis.