RESUMO
Herein, we achieved the asymmetric synthesis of (+)-vellosimine in 13 steps (longest linear sequences, LLS). This synthesis featured a sequential nucleophilic addition/cyclization process, which provided an efficient protocol for synthesizing a range of indole fused azabicyclo[3.3.1]nonane. Additionally, a SmI2-mediated reductive cyclization of ketone with an attached α,ß-unsaturated ester for constructing the strained quinuclidine moiety was also highlighted.
RESUMO
A catalytic asymmetric nucleophilic reverse prenylation of indol-2-ones in situ generated from 3-bromooxindoles with prenyltributylstannane promoted by Ni(II)/chiral N,N'-dioxide was developed. This reaction provides facile access to C3 reverse-prenylated oxindoles in good to excellent enantioselectivities, which enabled the asymmetric synthesis of debromoflustramine A in five steps.
RESUMO
Herein, we describe a catalytic asymmetric intramolecular vinylogous aldol reaction by taking advantage of dual organocatalysts, which enables convergent synthesis of ortho-fused tricyclic diketones in excellent enantioselectivities and diastereoselectivities. Noteworthy is that the reaction stereoselectively forges three consecutive stereogenic carbon centers including a quaternary one. Density functional theory calculations reveal that the enantioselectivity was facilitated by a transannular hydrogen bonding between the protonated quinuclidine moiety of the chiral aminocatalyst and the diketone fragment of the substrate.
Assuntos
Aldeídos , Cetonas , Estereoisomerismo , Aldeídos/química , Catálise , Cetonas/químicaRESUMO
We present a novel, efficient, and regioselective method for the rhodium-catalyzed direct C-H ortho-halogenation of anilines that involves a removable N-nitroso directing group. This method featured mild reaction conditions, wide substrate scope, good functional group tolerance and satisfactory yields. To maintain the high ortho-regioselectivity and conversion, increasing the steric hindrance of the solvent was critical. Preliminary mechanistic studies suggest that C-H activation may be involved in the rate-determining step.