113304-84-0Relevant articles and documents
Synthesis of the bicyclic core of pumiliotoxins
Sudau, Alexander,Muench, Winfried,Bats, Jan-W.,Nubbemeyer, Udo
, p. 3304 - 3314 (2002)
The bicyclic core of the pumiliotoxins was synthesized in nine to eleven steps starting from L-(-)-proline. This chiral pool starting material was initially converted into an optically active 2-vinylpyrrolidine by standard operations. The first key step allowed the generation of a nine-membered ring lactam by means of a zwitterionic aza-Claisen rearrangement. The 1,4 chirality transfer was found to be low, but the double bond of the azoninone was generated with an exclusive trans configuration in a planar-S arrangement. The mixture of diastereomers thus obtained was immediately epoxidized; the planar chiral information could be completely used to build up new stereogenic centers. Subsequent ring closure under hydrogenolytic conditions resulted in the formation of the bicyclic core with a bridgehead of defined configuration. The hydroxyl group of that material could be protected as a TBS ether, or alternatively a sequence of a Swern oxidation and subsequent methyl Grignard addition gave the complete bicyclic framework with low C8 diastereoselectivity. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
Lewis Acids as Activators in CBS-Catalysed Diels–Alder Reactions: Distortion Induced Lewis Acidity Enhancement of SnCl4
N?dling, Alexander R.,M?ckel, Robert,Tonner, Ralf,Hilt, Gerhard
, p. 13171 - 13180 (2016)
The effect of several Lewis acids on the CBS catalyst (named after Corey, Bakshi and Shibata) was investigated in this study. While2H NMR spectroscopic measurements served as gauge for the activation capability of the Lewis acids, in situ FT-IR spectroscopy was employed to assess the catalytic activity of the Lewis acid oxazaborolidine complexes. A correlation was found between the Δδ(2H) values and rate constants kDA, which indicates a direct translation of Lewis acidity into reactivity of the Lewis acid–CBS complexes. Unexpectedly, a significant deviation was found for SnCl4as Lewis acid. The SnCl4–CBS adduct was much more reactive than the Δδ(2H) values predicted and gave similar reaction rates to those observed for the prominent AlBr3–CBS adduct. To rationalize these results, quantum mechanical calculations were performed. The frontier molecular orbital approach was applied and a good correlation between the LUMO energies of the Lewis acid–CBS–naphthoquinone adducts and kDAcould be found. For the SnCl4–CBS–naphthoquinone adduct an unusual distortion was observed leading to an enhanced Lewis acidity. Energy decomposition analysis with natural orbitals for chemical valence (EDA-NOCV) calculations revealed the relevant interactions and activation mode of SnCl4as Lewis acid in Diels–Alder reactions.
Enantioselective Intermolecular [2+2] Photocycloaddition Reaction of Cyclic Enones and Its Application in a Synthesis of (-)-Grandisol
Poplata, Saner,Bach, Thorsten
, p. 3228 - 3231 (2018)
The intermolecular [2+2] photocycloaddition of typical cyclic α,β-unsaturated enones, such as 2-cyclohexenone, with olefins was performed in moderate to good yields (42-82%) and with high enantioselectivity (82%-96% ee). An unusual substitution pattern at the chiral oxazaborolidine-AlBr3 Lewis acid complex that promotes the reaction was found to be crucial for the success of the reaction. The method was applied to the enantioselective synthesis of the monoterpene (-)-grandisol, which could be accomplished in six steps and with an overall yield of 13% starting from 3-methyl-2-cyclohexenone.
Towards the Development of Frustrated Lewis Pair (FLP) Catalyzed Hydrogenations of Tertiary and Secondary Carboxylic Amides
K?ring, Laura,Paradies, Jan,Sitte, Nikolai A.
supporting information, p. 1287 - 1300 (2022/01/20)
The development of the frustrated Lewis pair catalyzed hydrogenation of tertiary and secondary amides is reviewed. Detailed insight into our strategies in order to overcome challenges during the reaction development process is provided. Furthermore, the d
Continuous flow heterogeneous catalytic reductive aminations under aqueous micellar conditions enabled by an oscillatory plug flow reactor
?tv?s, Sándor B.,Buchholcz, Balázs,Darvas, Ferenc,Kappe, C. Oliver,Novák, Zoltán,Sipos, Gellért,Wernik, Michaela
, p. 5625 - 5632 (2021/08/16)
Despite the fact that continuous flow processing exhibits well-established technical advances, aqueous micellar chemistry, a field that has proven extremely useful in shifting organic synthesis to sustainable water-based media, has mostly been explored under conventional batch-based conditions. This is particularly because of the fact that the reliable handling of slurries and suspensions in flow has been considered as a significant technical challenge. Herein, we demonstrate that the strategic application of an oscillatory plug flow reactor enables heterogeneous catalytic reductive aminations in aqueous micellar media enhancing mass transport and facilitating process simplicity, stability and scalability. The micellar flow process enabled a broad range of substrates, including amino acid derivatives, to be successfully transformed under reasonably mild conditions utilizing only very low amounts of Pd/C as a readily available heterogeneous catalyst. The preparative capabilities of the process along with the recyclability of the heterogenous catalyst and the aqueous reaction media were also demonstrated. This journal is
Stereoselective Total Synthesis of (-)-(2 S,4 R)-3′-Methoxyl Citreochlorol: Preparation and Use of New Proline-Based Auxiliary for Asymmetric Acetate Aldol Reaction
Sunnapu, Ranganayakulu,Banoth, Saikumar Naik,Reyno,Thomas, Aleena,Venugopal, Navyasree,Rajendar, Goreti
, p. 4103 - 4113 (2020/03/05)
The first stereoselective total synthesis of (-)-(2S,4R)-3′-methoxy citreochlorol and (-)-(2S,4S)-3′-methoxy citreochlorol is demonstrated. A proline-based imidazolidinone was synthesized and used as chiral auxiliary for asymmetric acetate aldol reaction to generate initial chirality in the targeted molecule. Geminal dichloromethane functionality was introduced by the addition of in situ generated dichloromethyllithium to Weinreb's amide functional group.