4798-61-2Relevant academic research and scientific papers
Copper-Catalyzed Enantioselective Conjugate Addition to α,β-Unsaturated Aldehydes with Various Organometallic Reagents
Goncalves-Contal, Sylvie,Gremaud, Ludovic,Palais, La?titia,Babel, Lucille,Alexakis, Alexandre
, p. 3301 - 3308 (2016/09/12)
β-Substituted aldehydes constitute a very important class of compounds found in nature. Synthesis of this motif can be envisioned by C-C bond formation on enals. For this purpose, we report herein the development of enantioselective copper-catalyzed conjugate addition of various organometallic reagents to α,β-unsaturated aldehydes with (R)-H8BINAP, (R)-TolBINAP, and (R)-SEGPHOS as chiral ligands. Three sets of conditions were successfully developed and several enals were used. Reactivity and regio- and enantioselectivities were strongly dependent on reaction conditions and substrates. Good to excellent regio- and enantioselectivities were obtained with zinc reagents R2Zn and aluminum reagents R3Al. However, the asymmetric conjugate addition of Grignard reagents afforded only moderate to good regio- and enantioselectivities.
Chirality Transfer in Gold(I)-Catalysed Direct Allylic Etherifications of Unactivated Alcohols: Experimental and Computational Study
Barker, Graeme,Johnson, David G.,Young, Paul C.,Macgregor, Stuart A.,Lee, Ai-Lan
, p. 13748 - 13757 (2015/09/22)
Gold(I)-catalysed direct allylic etherifications have been successfully carried out with chirality transfer to yield enantioenriched, γ-substituted secondary allylic ethers. Our investigations include a full substrate-scope screen to ascertain substituent effects on the regioselectivity, stereoselectivity and efficiency of chirality transfer, as well as control experiments to elucidate the mechanistic subtleties of the chirality-transfer process. Crucially, addition of molecular sieves was found to be necessary to ensure efficient and general chirality transfer. Computational studies suggest that the efficiency of chirality transfer is linked to the aggregation of the alcohol nucleophile around the reactive π-bound Au-allylic ether complex. With a single alcohol nucleophile, a high degree of chirality transfer is predicted. However, if three alcohols are present, alternative proton transfer chain mechanisms that Erode the efficiency of chirality transfer become competitive.
Copper-catalyzed enantioselective 1,4-addition to α,β- unsaturated aldehydes
Palais, Laetitia,Babel, Lucille,Quintard, Adrien,Belot, Sebastien,Alexakis, Alexandre
supporting information; experimental part, p. 1988 - 1991 (2010/07/10)
Figure presented The first asymmetric Cu-catalyzed conjugate addition of dialkylzinc zinc reagents to a large scope of enals in presence of phosphoramidite, SimplePhos, or (R)-BINAP ligands with enantiomeric excesses up to 90% is reported. Moreover, ACA of Grignard reagents afforded moderate to good 1,4-regioselectivities with enantioselectivities up to 90%.
Highly stereoselective anti SN2′ substitutions of (Z)-allylic pentafluorobenzoates with polyfunctionalized zinc-copper reagents
Harrington-Frost, Nicole,Leuser, Helena,Calaza, M. Isabel,Kneisel, Florian F.,Knochel, Paul
, p. 2111 - 2114 (2007/10/03)
(Matrix presented) Allylic substitution reactions of zinc-copper organometallics on (Z)-allylic pentafluorobenzoates proceed with very high regioselectivity and excellent anti selectivity. The high fidelity in transfer of stereochemical information allowed a short synthesis of (+)-ibuprofen (97% ee).
High turnover numbers for the catalytic selective epoxidation of alkenes with 1 atm of molecular oxygen
Nishiyama, Yoshiyuki,Nakagawa, Yoshinao,Mizuno, Noritaka
, p. 3639 - 3641 (2007/10/03)
The diiron-substituted silicotungstate γ-SiW10{Fe3+(OH2}2O 386- (schematically shown) is an effective catalyst for the oxygenation of alkenes in homogeneous reaction media with 1 atm of molecular oxygen. For example, a selectivity for cyclooctene oxide of 98% and a turnover number of 10000 were achieved in the epoxidation of cyclooctene. The catalyst is stable under the reaction conditions, and its ability to use molecular oxygen raises the prospect of using it in industrial epoxidation processes.
On the Mechanism of Organoaluminum-Promoted Claisen Rearrangement of Allylic Vinyl Ethers
Nonoshita, Katsumasa,Maruoka, Keiji,Yamamoto, Hisashi
, p. 541 - 545 (2007/10/02)
The organoaluminum-promoted Claisen rearrangement of allylic vinyl ethers has been mechanistically studied by two sets of experiments and the observed Z and E selectivity is best accounted for by two possible chair-like structures with R substituents axial and equatorial, respectively.
THE REACTION OF α,β-EPOXYSILANES WITH METALLATED ALKYLARYL SULPHONES. A NOVEL APPROACH TO ALLYLIC ALCOHOLS
Masnyk, Marek,Wicha, Jerzy
, p. 2497 - 2500 (2007/10/02)
Lithiated alkylaryl sulphones (2a-c) react with α,β-epoxysilane (1) to yield O-trimethylsilyl allylic alcohols (3a-c), predominantly as Z isomers.The BF3-assisted reaction followed by treatment of the adduct with nBu4NF affords allylic alcohols.
A NOVEL REACTION OF α-HALOEPOXIDES WITH TRIALKYLSTANNATES
Corey, L. D.,Singh, S. M.,Oehlschlager, A. C.
, p. 1821 - 1827 (2007/10/02)
The reaction of α-haloepoxides with zinc powder or reagents containing tialkylstannate anion yields allylic alcohols by anti elimination of carbon halogen and adjacent carbon epoxy oxygen bonds.Appreciable Z -> E isomerization occurs in both types of reactions but the experimental results indicate that the conversion of erythro α-bromoepoxides to E allylic alcohols by zinc or trialkylstannates shows sufficient sterospecificity to be synthetically useful.
sp2-Hybridized β-Substituted Organo-lithium, -sodium, and -potassium Dianions; Preparation, Stability, and Reactivity
Barluenga, Jose,Fernandez, Jose R.,Yus, Miguel
, p. 447 - 452 (2007/10/02)
The reaction of the substituted 2-chloroallyl alcohol (3a) with ethylmagnesium bromide followed by lithium was found to give the β-substituted organolithium derivative (4) of the type C=C().Intermediates of this type were also prepared directly from (E)-2-chlorocrotonaldehyde (2) or 2-chloroacrolein (19) by the same process using different Grignard reagents.The use of sodium or potassium as the metal in the second step of the process was found to give the corresponding organosodium or organopotassium derivative (24) or (25).A dilithiated dianion (26) was also obtained from the corresponding chlorohydrin (3d) by reaction with phenyl-lithium followed by lithium.These intermediates, which are stable species at room temperature, were found to react stereoselectively with electrophilic reagents leading to functionalized substituted allyl alcohols.The thermal stability of the lithiated dianion (4d) has also been investigated.
STEREO- AND REGIOSELECTIVITY IN IODO DIOL FORMATION FROM ACYCLIC ALLYLIC ALCOHOLS
Chamberlin, A. Richard,Mulholland, Robert L.
, p. 2297 - 2302 (2007/10/02)
Reaction of electrophiles with a variety of acyclic allylic alcohols was investigated.Both aqueous iodine and acetylhypoiodite convert certain alkenols into iodo diols and acetoxy iodo alcohols, respectively, with regio- and stereoselectivities as high as 99percent.Protection of alcohol group lowers the selectivity only slightly.Structural factors that control the regioselectivity of iodohydrin formation in these substrates have been delineated.Some of the iodo diols have been deiodinated, illustrating a simple two step procedure for converting allylic alcohols into threo-1,3-diols.
