Synthetic approaches to the axane family of sesquiterpenoids. Total synthesis of (dl)-axamide-4, (dl)-axisonitrile-4, and (dl)-axisothiocyanate-4
摘要:
Two methods for the preparation of perhydroindan 7 are described. One involves an intramolecular free radical cyclization in a key step and proceeds in 13 steps and 9% yield from anisole (9). The other involves an intramolecular conjugate addition mediated by pyrrolidine (28 --> 7) and proceeds in five steps and 30% overall yield from vinylogous ester 29. Two unsuccessful attempts to convert 7 into axane sesquiterpenoids 1-6 are described. The synthesis of axanes 4-6 was achieved using a potassium tert-butoxide catalyzed cyclization of a dienoic keto ester as a key step (47 + 48 --> 49). Conversion of alpha,beta-unsaturated ester 49 to vinyl isocyanate 57 was accomplished using a Curtius rearrangement and reduction of 57 with lithium triethylborohydride completed the synthesis of axamide-4 (4). The preparation of axisonitrile-4 (5) and axisothiocyanate-4 (6) from 4 is also described.
Formation of Quaternary Stereogenic Centers by Copper-Catalyzed Asymmetric Conjugate Addition Reactions of Alkenylaluminums to Trisubstituted Enones
作者:Daniel Müller、Alexandre Alexakis
DOI:10.1002/chem.201302856
日期:2013.11.4
undergo asymmetric copper‐catalyzedconjugateaddition (ACA) to β‐substituted enones allowing the formation of stereogenic all‐carbon quaternary centers. Phosphinamine–copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β‐substituted
Copper-Catalyzed Asymmetric Conjugate Addition of Trialkylaluminium Reagents to Trisubstituted Enones: Construction of Chiral Quaternary Centers
作者:Magali Vuagnoux-d'Augustin、Alexandre Alexakis
DOI:10.1002/chem.200701001
日期:2007.11.26
vinylalane species undergo enantioselective conjugateaddition to a wide range of 2- or 3-substituted enones (cyclopent-2-enones, cyclohex-2-enones, 3-methyl cyclohept-2-enone) in the presence of catalytic amount of copper salt (copper thiophene carboxylate, [Cu(CH3CN)4]BF4 or [CuOTf]2C6H6) and tropos-phosphoramidite-based ligand. Thus, chiral quaternarycenters can be built, with up to 98% ee after rigorous
[reaction: see text] Bicyclo[4.3.0]nonanes (hydrindanes) and bicyclo[3.3.0]octanes (octahydropentalenes) are easily synthesized by palladium-catalyzed cycloalkenylations. Additionally, benzo-fused bicyclo[3.3.0]octanes are prepared for the first time through intramolecular coupling between silyl enol ethers and aromatic rings in the presence of catalytic palladium acetate.
Opening of cyclopropyl ketones with SmI2. Synthesis of spirocyclic and bicyclic ketones by intramolecular trapping of an electrophile
作者:Gary A. Molander、Cristina Alonso-Alija
DOI:10.1016/s0040-4020(97)00499-7
日期:1997.6
A method for the opening of cyclopropyl ketones with samarium(II) iodide followed by the intramolecular trapping of an electrophile is described. This process leads to the obtainment of functionalized spirocyclic, bicyclic, and tricyclic ketones in moderate to good yields.
Stereoselective aziridination of cyclic allylic alcohols using chloramine-T
作者:Susannah C. Coote、Peter O'Brien、Adrian C. Whitwood
DOI:10.1039/b811137e
日期:——
TsNClNa and t-BuSO(2)NClNa, BusNClNa) has been explored. The stereoselectivity of these reactions was highly dependent on the structure of the allylic alcohol and the chloramine salt. Generally, mixtures of cis- and trans-hydroxy aziridines were obtained, in which the major diastereomer was the cis-hydroxy aziridine, whilst complete cis-diastereoselectivity was observed in the aziridination of 1,3-disubstituted