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Herein, we disclose a catalytic asymmetric conjugated addition of 3-substutited oxindoles to indol-2-one in situ generated from 3-bromooxindoles promoted by Ni(BF4)2·6H2O/chiral ...N,N′-chiral dioxide. This protocol enables forging C2-symmetric CQCCs in excellent enantioselectivities as single diastereoisomer via directly fusing two congested 3-substituted oxindoles. The asymmetric synthesis of (−)-chimonanthidine and (−)-folicanthine is concisely achieved respectively in four and five steps by taking advantage of this protocol.
The asymmetric synthesis of ent-fissistigmatin C is successively accomplished in 12 steps (longest linear sequence (LLS)). Relying on the enantioselective coupling of aliphatic aldehyde with ...2-hydroxychalcone promoted by cooperative organocatalysts, the pivotal linkage of ent-fissistigmatin C between the flavonoid and the sesquiterpenoid fragment was stereoselectively established. An unprecedented final-stage radical cascade was also featured in this synthesis, which enabled the simultaneous establishment of the trans-decalin framework via forging two consecutive C–C bonds in one step.
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•Concise syntheses of (+)-Austrodoric acid and (+)-Austrodoral was achieved.•Wieland-Miescher ketone was used as starting material.•H2O2-mediated oxidative ring contraction forged the ...hydrindane scaffold.•The contiguous quaternary carbon centers were built up via rearrangement.
Asymmetric synthesis of the marine nor-sesquiterpenoid (+)-austrodoric acid and (+)-austrodoral in seven and nine steps respectively from Wieland-Miescher ketone was described herein. The synthesis featured an oxidative ring contraction of α-formyl cyclic ketone mediated by H2O2 to forge the hydrindane scaffold together with the contiguous quaternary carbon centers simultaneously.
We disclose herein a Au(I)-catalyzed domino cyclization of 1,6-diynes incorporated with indole. This protocol enabled the diastereoselective buildup of indole-fused azabicyclo3.3.1nonanes from ...linear precursors. Density functional theory calculations showed that the reaction proceeded via an unprecedented cascade dearomatization/rearomatization/dearomatization process. Independent gradient model analysis revealed that a noncovalent attractive interaction between the distal alkyne and the Au/proximal complex was responsible for the chemoselectivity of the first spirocyclization step.
A 2,2,2-trifluroenthanol (TFE) promoted synthesis of unsymmetric ureas was described. This approach enabled the construction of a variety of ureas from the readily prepared and easy-to-handle ...dioxazolones and amines via tandem Lossen rearrangement/condensation process. The reaction featured mild conditions for the urea synthesis under metal-free conditions, which was successively applied in the scale-up synthesis of herbicides Monuro and Isoproturon.
Total Synthesis of (−)-Conolutinine Feng, Xiangyang; Jiang, Guangde; Xia, Zilei ...
Organic letters,
09/2015, Letnik:
17, Številka:
18
Journal Article
Recenzirano
The first enantioselective synthesis of (−)-conolutinine was achieved in 10 steps. The synthesis featured a catalytic asymmetric bromocyclization of tryptamine to forge the tricycle intermediate. ...Hydration of an alkene catalyzed by Co(acac)2 was also employed as a key step to diastereoselectively introduce the tertiary alcohol moiety. The absolute configuration of (−)-conolutinine was established to be (2S,5aS,8aS,13aR) based on this asymmetric total synthesis.
An asymmetric Friedel–Crafts alkylation of indole with in situ generated indol‐2‐one from functionalized 3‐bromooxinidole catalyzed by chiral N,N’‐dioxide/Ni(BF4)2 has been developed. This protocol ...provides an efficient route to stereoselective construction of a series of 3‐substituted 3’‐indolyloxindoles bearing a quaternary carbon center in excellent yields and enantioselectivities (up to 99 % ee). In addition, the conversion of the resulted 3‐substituted 3’‐indolyloxindole to the key intermediate for the formal synthesis of (+)‐folicanthine was also demonstrated.
An asymmetric Friedel–Crafts alkylation of indole derivatives with in situ generated indol‐2‐ones from functionalized 3‐bromooxinidoles to construct 3‐substituted 3’‐indolyloxindole skeleton catalyzed by chiral N,N’‐dioxide/Ni(BF4)2 has been developed, which enabled the formal synthesis of (+)‐folicanthine.
The first direct access to unprotected amino-pyrroloindoline via aminocyclization of tryptamine and tryptophan has been described. A variety of structurally diverse amino-pyrroloindolines are ...furnished by the use of O-(2,4-dinitrophenyl)hydroxylamine (DPH) as the nitrogen source in the presence of catalytic Rh2(esp)2.
Abkürzung: Eine enantioselektive Bromcyclisierung von Tryptamin unter Verwendung eines anionischen chiralen Phasentransferkatalysators führt direkt zu chiralen 3‐Brompyrroloindolinen. Die Reaktion ...ermöglicht eine vierstufige enantioselektive Synthese von (−)‐Chimonanthin. PG=Schutzgruppe.
Oxidative ring contraction of cyclic α‐formyl ketones was facilitated by the action of H2O2 under operationally simple and environmentally benign reaction conditions. The process was highly ...regioselective and enables stereospecific construction of contiguous quaternary all‐carbon centers from stereodefined all‐substituted all‐cyclic ketones. The asymmetric syntheses of (+)‐cuparene and (+)‐tochuinyl acetate were also successively achieved by taking advantage of this novel protocol.
Side by side: The H2O2‐mediated ring contraction of cyclic α‐formyl ketones enables stereospecific construction of contiguous quaternary all‐carbon centers. The asymmetric syntheses of (+)‐cuparene and (+)‐tochuinyl acetate were also successively achieved by taking advantage of this novel protocol.
