제 목 : Development of new strong Brønsted acids and their application towards the synthesis of enantio-enriched O-heterocycles
연 사 : 이성기 교수(Dept. of Emerging Material Science, DGIST)
일 시 : 2019년 10월 10일(목) 오후 4시 30분
장 소 : 화학관 2층 서병인강의실 (330226호실)
Since the Akiyama and Terada groups reported chiral phosphoric acids as powerful catalysts in multiple asymmetric functional group transformations, various new Brønsted acids were introduced. Recently, we developed new class of strong Brønsted acids which can provide excellent catalytic activity and well-defined active sites at the same time.1,2 The new catalysts, imidodiphosphorimidates (IDPs), enable multiple transformations which were not possible with conventional organo- and transition-metal catalysts. The handling of cyclic aliphatic oxocarbenium ions in enantioselective reactions is the one of such challenges. Now, the enantioselective carbon-carbon bond formation on these highly reactive and small intermediates can be carried out using IDPs affording O-heterocycles bearing multisubstituted stereogenic centers.3,4 Various lactol acetates reacted with enol silanes in the presence of powerful pre-Lewis acid organocatalysts to furnish the desired oxygen heterocycles with high enantioselectivities. Additionally, 1,4- and 1,5-dicarbonyl compounds were transformed to multisubstituted O-heterocycles via catalytic chemo- and enantioselective additions of silyl nucleophiles.