- Trialkylborane-Mediated Multicomponent Reaction for the Diastereoselective Synthesis of Anti-δ,δ-Disubstituted Homoallylic Alcohols
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The trialkylborane/O2-mediated reaction of propargyl acetates having a tributylstannyl group at an alkyne terminus with aldehydes in a THF-H2O solvent system gave anti-δ,δ-disubstituted homoallylic alcohols with good to high diastereoselectivity. Intriguingly, two alkyl groups derived from trialkylborane were embedded into the reaction product. The trialkylborane plays a key role not only as a radical initiator but also as a source of alkyl radicals.
- Horino, Yoshikazu,Murakami, Miki,Aimono, Ataru,Lee, Jun Hee,Abe, Hitoshi
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supporting information
p. 476 - 480
(2019/01/14)
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- Trialkylborane-Mediated Propargylation of Aldehydes Using γ-Stannylated Propargyl Acetates
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A transition-metal-free three-component process that combines aldehydes, 3-(tributylstannyl)propargyl acetates formed in situ from readily available propargyl acetates, and trialkylboranes provides access to a range of 1,2,4-trisubstituted homopropargylic alcohols. The addition of diisopropylamine plays a crucial role in the selective formation of homopropargylic alcohols. Importantly, this methodology can be extended to a single-flask reaction sequence starting from propargyl acetates.
- Horino, Yoshikazu,Murakami, Miki,Ishibashi, Mayo,Lee, Jun Hee,Watanabe, Airi,Matsumoto, Rio,Abe, Hitoshi
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supporting information
p. 9564 - 9568
(2019/12/24)
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- Rhodium-Catalyzed Parallel Kinetic Resolution of Racemic Internal Allenes Towards Enantiopure Allylic 1,3-Diketones
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A rare case of a parallel kinetic resolution of racemic 1,3-disubstituted allenes by means of a rhodium-catalyzed addition to 1,3-diketones furnishing enantiopure allylic 1,3-diketones is described. Mechanistic experiments demonstrate that the different allene enantiomers react in parallel to either the diastereomeric E- or Z-allylic 1,3-diketones with the same absolute configuration of the newly formed stereogenic center. A broad substrate scope demonstrates the synthetic utility of this new method.
- Hilpert, Lukas J.,Breit, Bernhard
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supporting information
p. 9939 - 9943
(2019/06/24)
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- Palladium- and Rhodium-Catalyzed Dynamic Kinetic Resolution of Racemic Internal Allenes Towards Chiral Pyrazoles
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A complementing Pd- and Rh-catalyzed dynamic kinetic resolution (DKR) of racemic allenes leading to N-allylated pyrazoles is described. Such compounds are of enormous interest in medicinal chemistry as certified drugs and potential drug candidates. The new methods feature high chemo-, regio- and enantioselectivities aside from displaying a broad substrate scope and functional group compatibility. A mechanistic rational accounting for allene racemization and trans-alkene selectivity is discussed.
- Hilpert, Lukas J.,Sieger, Simon V.,Haydl, Alexander M.,Breit, Bernhard
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supporting information
p. 3378 - 3381
(2019/02/06)
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- Stereocontrol in palladium-catalyzed propargylic substitutions: Kinetic resolution to give enantioenriched 1,5-enynes and propargyl acetates
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Kinetic resolution during the catalytic allyl-propargyl cross-coupling with chiral starting materials can be accomplished with a chiral palladium catalyst. These reactions offer ready access to enantiomerically enriched enyne products from simple, readily
- Ardolino, Michael J.,Eno, Meredith S.,Morken, James P.
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supporting information
p. 3413 - 3419
(2013/12/04)
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- Construction of 1,5-enynes by stereospecific Pd-catalyzed allyl-propargyl cross-couplings
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The palladium-catalyzed cross-coupling of chiral propargyl acetates and allyl boronates delivers chiral 1,5-enynes with excellent levels of chirality transfer and can be applied across a broad range of substrates.
- Ardolino, Michael J.,Morken, James P.
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supporting information; experimental part
p. 8770 - 8773
(2012/07/02)
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- Enantioselective copper-catalysed propargylic substitution: Synthetic scope study and application in formal total syntheses of (+)-anisomycin and (-)-cytoxazone
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A copper catalyst with a chiral pyridine-2,6-bisoxazoline (pybox) ligand was used to convert a variety of propargylic esters with different side chains (R=Ar, Bn, alkyl) into their amine counterparts in very high yields and with good enantioselectivities (up to 90% enantiomeric excess (ee)). Different amine nucleophiles were applied in the reactions and the highest enantioselectivities were obtained for aniline and its analogues. Interestingly, some carbon nucleophiles could also be used and with indoles excellent ee values were obtained (up to 98% ee). The versatility of the propargylic amines obtained was demonstrated by their further elaboration to formal total syntheses of the antibiotic (+)-anisomycin and the cytokine modulator (-)-cytoxazone. Copyright
- Detz, Remko J.,Abiri, Zohar,Le Griel, Remi,Hiemstra, Henk,Van Maarseveen, Jan H.
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supporting information; experimental part
p. 5921 - 5930
(2011/06/26)
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- Copper-catalyzed enantioselective propargylic amination of propargylic esters with amines: Copper-allenylidene complexes as key intermediates
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The scope and limitations of the copper-catalyzed propargylic amination of various propargylic esters with amines are presented, where optically active diphosphines such as Cl-MeO-BIPHEP and BINAP work as good chiral ligands. A variety of secondary amines are available as nucleophiles for this catalytic reaction to give the corresponding propargylic amines with a high enantioselectivity. The results of some stoichiometric and catalytic reactions indicate that the catalytic amination proceeds via copper-allenylidene complexes formed in situ, where the attack of amines to the electrophilic γ-carbon atom in the allenylidene complex is an important step for the stereoselection. Investigation of the relative rate constants for the reaction of several para-substituted propargylic acetates with N-methylanilines reveals that the formation of the copper-allenylidene complexes is involved in the rate-determining step. The result of the density functional theory calculation on a model reaction also supports the proposed reaction pathway involving copper-allenylidene complexes as key intermediates. The catalytic procedure presented here provides a versatile and direct method for the preparation of a variety of chiral propargylic amines.
- Hattori, Gaku,Sakata, Ken,Matsuzawa, Hiroshi,Tanabe, Yoshiaki,Miyake, Yoshihiro,Nishibayashi, Yoshiaki
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supporting information; experimental part
p. 10592 - 10608
(2010/09/10)
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