A novel chiral DMAP–thiourea bifunctional catalyst has been prepared and applied in the highly enantioselective Steglich and Black rearrangement reactions.
Exploration
of the diastereodivergent synthesis of spirocyclic
oxindoles has been challenging. Herein we report asymmetric [3 + 2]
annulations of isatin-derived Morita–Baylis–Hillman
(MBH) carbonates and 5-alkenylthiazol-4(5H)-ones.
Interestingly, two different chiral catalysts, amide-phosphine and
4-dimethylaminopyridine (DMAP)-thiourea, could lead to two kinds of
diastereomeric dispiro oxindoles with three contiguous stereogenic
centers. The hexafluoroisopropanol (HFIP) additive plays a vital role
in accelerating the reaction and tuning the diastereoselectivity.
Moreover, both annulation adducts could be further converted to structurally
diverse spirooxindoles.
The efficient preparation of the stilbenoid lusianthridin is described. This synthesis relies on the Suzuki‒Miyaura coupling and intramolecular nucleophilic substitution as key reactions to construct the 9,10-dihydrophenanthrene core. The synthesis is completed in 7 steps with a 13.2% overall yield, and each step can be conducted on > 20 grams scale. The route has provided 20 grams of lusianthridin for the further biological activity study.
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