17299-34-2Relevant academic research and scientific papers
Enantioselective Intermolecular [2+2] Photocycloaddition Reaction of Cyclic Enones and Its Application in a Synthesis of (-)-Grandisol
Poplata, Saner,Bach, Thorsten
supporting information, p. 3228 - 3231 (2018/03/13)
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.
Chemo-Enzymatic Oxidative Rearrangement of Tertiary Allylic Alcohols: Synthetic Application and Integration into a Cascade Process
Brenna, Elisabetta,Crotti, Michele,De Pieri, Matteo,Gatti, Francesco G.,Manenti, Gabriele,Monti, Daniela
supporting information, p. 3677 - 3686 (2018/06/04)
A chemo-enzymatic catalytic system, comprised of Bobbitt's salt and laccase from Trametes versicolor, allowed the [1,3]-oxidative rearrangement of endocyclic allylic tertiary alcohols into the corresponding enones under an Oxygen atmosphere in aqueous media. The yields were in most cases quantitative, especially for the cyclopent-2-en-1-ol or the cyclohex-2-en-1-ol substrates without an electron withdrawing group (EWG) on the side chain. Transpositions of macrocyclic alkenols or tertiary alcohols bearing an EWG on the side chain were instead carried out in acetonitrile by using an immobilized laccase preparation. Dehydro-Jasmone, dehydro-Hedione, dehydro-Muscone and other fragrance precursors were directly prepared with this procedure, while a synthetic route was developed to easily transform a cyclopentenone derivative into trans-Magnolione and dehydro-Magnolione. The rearrangement of exocyclic allylic alcohols was tested as well, and a dynamic kinetic resolution was observed: α,β-unsaturated ketones with (E)-configuration and a high diastereomeric excess were synthesized. Finally, the 2,2,6,6-tetramethyl-1-piperidinium tetrafluoroborate (TEMPO+BF4?)/laccase catalysed oxidative rearrangement was combined with the ene-reductase/alcohol dehydrogenase cascade process in a one-pot three-step synthesis of cis or trans 3-methylcyclohexan-1-ol, in both cases with a high optical purity. (Figure presented.).
Phosphoramidite Ligands Based on Simple 1,2-Diols: Synthesis, Use in Copper-Catalyzed Asymmetric Additions, and Achirotopic Stereogenic Phosphorus Centres
Mistry, Nisha,Fletcher, Stephen P.
supporting information, p. 2489 - 2496 (2016/08/16)
Phosphoramidite ligands are widely used in catalysis and normally constructed from large C2-symmetrical diols such as BINOL or TADDOL. We report here on new ligands based on a set of simple diols that had been previously overlooked. Ligands based on (S,S)-trans-cyclohexanediol and (R,R)-(+)-1,2-diphenyl-1,2-ethanediol, in combination with both chiral and achiral amines, were tested in 3 different copper-catalyzed asymmetric reactions and up to 89% ee was observed. A different ligand gave the best results in each reaction examined. Using meso-cis-cyclohexanediol and meso-cis-diphenyl-1,2-ethanediol with a chiral non-racemic amine gave diastereomeric ligands bearing achirotopic stereogenic phosphorus atoms which were characterized with the assistance of X-ray crystallography and variable temperature NMR studies. This work provides a new set of ligands that may be useful in some asymmetric reactions when phosphoramidites based on BINOL and TADDOL are ineffective. We also identify a novel stereochemical feature of phosphoramidites that may be useful in asymmetric catalysis and ligand design. (Figure presented.).
Cp2ZrMeCl: A Reagent for Asymmetric Methyl Addition
Garrec, Kilian,Fletcher, Stephen P.
supporting information, p. 3814 - 3817 (2016/08/16)
The use of Cp2ZrMeCl is described as a source of nucleophilic methyl in asymmetric catalysis. This easily prepared reagent is bench stable, weighable in air, and generally useful in highly enantioselective copper-catalyzed addition reactions at room temperature. Methyl is successfully (generally >90% ee) added in 1,4-additions to cyclic and acyclic α,β-unsaturated ketones to provide tertiary and quaternary centers. Examples of catalyst controlled diastereoselective 1,6-addition and dynamic kinetic asymmetric allylic alkylation reactions are also reported. The reagent is used in the catalytic asymmetric synthesis of naturally occurring fragrance (R)-(-)-muscone (82% yield, 91% ee).
Formation of quaternary chiral centers by N-Heterocyclic carbene-CuCatalyzed asymmetric conjugate addition reactions with grignard reagents on trisubstituted cyclic enones
Kehrli, Stefan,Martin, David,Rix, Diane,Mauduit, Marc,Alexakis, Alexandre
supporting information; experimental part, p. 9890 - 9904 (2010/11/04)
The copper-catalyzed conjugate addition of Grignard reagents to 3-substituted cyclic enones allows the formation of all-carbon chiral quaternary centers. We demonstrate in this article that N-heterocyclic carbenes act as efficient chiral ligands for this transformation. High enantioselectivities (up to 96% ee) could be obtained for a variety of substrates.
New musk odorants: (3E)-4-(2′-alkyl-5′,5′- dimethylcyclopent-1′-enyl)but-3-en-2-ones and (3E)-1-acetyl-3-alkylidene- 4,4-dimethylcyclohexenes
Kraft, Philip,Popaj, Kasim
experimental part, p. 4806 - 4814 (2009/05/11)
Four new representatives, 18, 23, 29, and 32, of the young family of dienone musks were synthesized by two general routes. The first five-step synthetic route leading to (3E)-4-(2′-alkyl-5′,5′- dimethylcyclopent-1′-enyl)but-3-en-2-ones commenced with the
SUBSTITUTED FLUOROETHYL UREAS AS ALPHA 2 ADRENERGIC AGENTS
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Page/Page column 43; 44, (2008/12/04)
Therapeutic compounds, and methods, compositions, and medicaments related thereto are disclosed herein.
Enantioselective hydrogenation of enones with a hydroformylation catalyst
Scheuermann Nee Taylor, Caroline J.,Jaekel, Christoph
supporting information; experimental part, p. 2708 - 2714 (2009/10/06)
Use of a typical rhodium precatalyst for hydroformylation results in the enantioselective hydrogenation of cyclic enones with up to 90% ee. Extensive screening of chiral ligands reveals the simple ligand Chiraphos as the best ligand, so far. The hydrogenation shows high chemoselectivity. Exclusive formation of saturated, chiral b-branched ketones is observed. It is proposed that the catalyst follows a frustrated hydroformylation pathway ("monohydride-based mechanism") and differs by that from the classical cationic Schrock-Osborn type rhodium precatalysts ("dihydride-based mechanism") for enantioselective hydrogenation. The catalyst operates under neat conditions and is easily recyclable by simply distilling off the reaction mixture and treatment with syn gas prior to hydrogenation.
Regiodivergent 1,4 versus 1,6 asymmetric copper-catalyzed conjugate addition
Henon, Helene,Mauduit, Marc,Alexakis, Alexandre
supporting information; scheme or table, p. 9122 - 9124 (2009/02/08)
(Chemical Equation Presented) Metal matters: A highly regiodivergent copper-catalyzed asymmetric conjugate addition to α,β and γ,δ Michael acceptors is described. Zinc and aluminum reagents afford the 1,6 adduct with good to moderate enantioselectivity in the presence of ligand 1 (see scheme). In contrast, Grignard reagents used with hydroxy imidazolium ligand 2 afforded the 1,4 adduct with excellent ee values.
Copper-catalyzed asymmetric conjugate addition of trialkylaluminium reagents to trisubstituted enones: Construction of chiral quaternary centers
Vuagnoux-D'Augustin, Magali,Alexakis, Alexandre
, p. 9647 - 9662 (2008/12/21)
Me3Al, Et1Al, and vinylalane species undergo enantioselective conjugate addition to a wide range of 2- or 3-substituted enones (cyclopent-2enones, cyclohex-2-enones, 3-methyl cyclohept-2-enone) in the presence of catalytic amount of copper salt (copper thiophene carboxylate, [Cu(CH3-CN)4]BF4 or [CuOTf]2· C6H6) and tropos-phosphoramidite-based ligand. Thus, chiral quaternary centers can be built, with up to 98% ee after rigorous optimization of experimental conditions. It was shown that the main important parameter was the order of the introduction of the reagents. Then, the generated enantioenriched aluminium enolates and the chiral conjugate adducts were functionalized and used for subsequent reactions.
