19781-54-5Relevant academic research and scientific papers
Stereoselective Rh-Catalyzed Hydrogenative Desymmetrization of Achiral Substituted 1,4-Dienes
Fernández-Pérez, Héctor,Lao, Joan R.,Vidal-Ferran, Anton
supporting information, p. 2836 - 2839 (2016/07/06)
Highly efficient catalytic stereoselective hydrogenative desymmetrization reactions mediated by rhodium complexes derived from enantiopure phosphine-phosphite (P-OP) ligands are described. The highest performing ligand, which contains a TADDOL-derived phosphite fragment [TADDOL = (2,2-dimethyl-1,3-dioxolane-4,5-diyl)bis(diphenylmethanol)], presented excellent catalytic properties for the desymmetrization of a set of achiral 1,4-dienes, providing access to the selective formation of a variety of enantioenriched secondary and tertiary alcohols (six examples, up to 92% ee).
Stereoselective synthesis of trisubstituted olefins by a directed allylic substitution strategy
Schmidt, Yvonne,Breit, Bernhard
supporting information; experimental part, p. 11780 - 11788 (2011/11/06)
New methodology for the stereoselective synthesis of trisubstituted olefins is presented. The use of ortho-diphenylphosphanyl benzoate (o-DPPB) as a directing leaving group for copper-mediated allylic substitution with Grignard reagents allowed for the stereoselective construction of a wide range of E olefins, without the need for an adjacent electron-withdrawing group. Our modular three-step approach toward trisubstituted alkenes commenced with geminal α-methylene aldehydes. Addition of an organometallic reagent and introduction of the o-DPPB group by esterification was followed by the o-DPPB-directed copper-mediated allylic substitution with a Grignard reagent to furnish stereodefined trisubstituted olefins. Additionally, incorporation of a stereocenter from the chiral pool allowed the preparation of an enantiomerically pure olefin that bore three alkyl substituents in high E/Z selectivity.
Cross-metathesis reactions of homoallyl methyl malonates with sterically hindered allylic esters
Barile, Fabio,Bassetti, Mauro,D'Annibale, Andrea,Gerometta, Renzo,Palazzi, Michele
experimental part, p. 6519 - 6526 (2011/12/05)
The methyl malonate esters of 3-buten-1-ol and 2-methyl-3-buten-1-ol can be coupled efficiently to different methallylic esters in the presence of the second-generation Grubbs catalyst to yield trisubstituted olefins by the cross-metathesis reaction. Product selectivity and yields depend on the relative amounts of reagents and to a minor extent on the methallylic ester functional group. Alkyl substituents at either the allylic or the geminal positions significantly affect the product yields and the E/Z stereoselectivity. The cross-metathesis reactions of homoallyl malonates with allylic esters featuring a variety of alkyl substituents at the vinylic and/or allylic positions afford trisubstituted olefins. Copyright
Highly diastereoselective hydrostannylation of allyl and homoallyl alcohols with dibutyl(trifluoromethanesulfoxy)stannane
Miura, Katsukiyo,Wang, Di,Hosomi, Akira
, p. 9366 - 9367 (2007/10/03)
Dibutyl(trifluoromethanesulfoxy)stannane (Bu2Sn(OTf)H, 1a) was found to be very valuable for highly diastereoselective homolytic hydrostannylation of allyl and homoallyl alcohols. α,β-Disubstituted allyl alcohols and α,γ-disubstituted homoallyl alcohols were converted into γ- and δ-stannylated alcohols with high 1,2-syn and 1,3-syn diastereoselectivity, respectively. The origin of the stereochemical outcomes can be rationalized by conformational fixation of the intermediary β-stannylalkyl radical by coordination of the hydroxy group to the Lewis acidic tin center. Copyright
Synthesis of α,β-unsaturated 4,5-disubstituted γ-lactones via ring-closing metathesis catalyzed by the first-generation Grubbs' catalyst
Bassetti, Mauro,D'Annibale, Andrea,Fanfoni, Alessia,Minissi, Franco
, p. 1805 - 1808 (2007/10/03)
(Chemical Equation Presented) 4-Methyl-5-alkyl-2(5H)-furanones have been prepared by ruthenium-catalyzed ring-closing metathesis of the suitable methallyl acrylates, Despite the electron deficiency of the conjugated double bond and of the gem-disubstitution of the allylic alkene moiety in the starting acrylates, the first-generation Grubbs' catalyst I proved to be an effective promoter for the ring closure, affording the expected butenolides in good to high yields.
Asymmetric ring-closing metathesis reactions involving achiral and meso substrates
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Page column 29-30, (2010/01/30)
A composition and method for the catalytic conversion of a racemic mixture of dienes to a cyclic olefin by a ring-closing metathesis (RCM) reaction are disclosed. The composition, a transition metal complex with an M═C reaction site, contains a bidentate dialkoxide of at least 80% optical purity. Because the M═C reaction site is of a sufficient shape specificity, conferred in part by the dialkoxide of sufficient rigidity and a M═N—R1site, reacting the composition with a mixture of two enantiomeric dienes results in an olefin metathesis product that has at least a 50% enantiomeric excess of one enantiomer in the mixture. A method is also provided for reacting a composition with a racemic diene mixture to generate a metathesis product that has an enantiomeric excess of at least 50%. Methods are also provided for catalytic enantioselective desymmetrization. One method involves an olefin metathesis reaction with a molecular substrate having a plane of symmetry to form a product free of a plane of symmetry. Another method provides a desymmetrization reaction to occur in the absence of solvent. A method for producing quaternary carbon centers through a desymmetrization reaction is also described.
The exceptional chelating ability of dimethylaluminum chloride and methylaluminum dichloride. The merged stereochemical impact of α- and β-stereocenters in chelate-controlled carbonyl addition reactions with enolsilane and hydride nucleophiles
Evans,Allison,Yang,Masse
, p. 10840 - 10852 (2007/10/03)
A systematic investigation of the stereoselectivity in Lewis acid-promoted (Mukaiyama) aldol reactions of achiral unsubstituted enolsilanes and chiral β-hydroxy aldehydes proceeding under conditions favoring chelation control is presented. Good stereocontrol can be realized for enolsilane aldol reactions of β-alkoxy and β-silyloxy aldehydes bearing only an α- or a β-stereogenic center. Examination of the chelated intermediates for α,β-disubstituted aldehydes concludes that the syn aldehyde diastereomer possesses the arrangement of stereocenters wherein the α- and β-substituents impart a reinforcing facial bias upon the aldehyde carbonyl. Aldol reactions of syn aldehydes were thus observed to proceed with uniformly excellent diastereofacial selectivity. Aldol reactions of the corresponding anti aldehydes containing opposing stereocontrol elements at the α- and β-positions exhibit variable and unpredictable selectivity.
THE ALLYLIC REARRANGEMENT OF HYDROPEROXIDES : THE ALLYLPEROXYL RADICAL
Brill, William F.
, p. 621 - 628 (2007/10/02)
The free-radical rearrangement of pinocarveyl hydroperoxide (1) or myrtenyl hydroperoxide (2) in hexane produces an equilibrium mixture of both hydroperoxides.The absence of carbon skeletal rearrangement suggests that the intermediate radical involved in hydroperoxide isomerization has its unpaired electron localized elsewhere than the α-carbon atom.The failure of oxygen to react with pinocarveyl, myrtenyl, and acyclic hydroperoxides (8) and (9) during the allylic rearrangement supports this suggestion.The kinetics of the rearrangement of 1-isopropyl-2-methylallyl hydroperoxide (8) is compatible with a mechanism in wich the intermediate is a common allylperoxyl radical produced directly from either allylic isomer.
