1502-77-8Relevant academic research and scientific papers
A new type of complex reagent, R4Pb / TiCl4
Yamamoto, Yoshinori,Yamada, Jun-Ichi,Asano, Tetsuya
, p. 5587 - 5596 (2007/10/02)
Tetraalkllleads (R4Pb) reacted quite smoothly with aldehydes R'CHO in the presence of TiCl4 to produce the corresponding alcohols (RCHOHR′) in high to good yields. The reagent system, R4Pb/ TiCl4, exhibited high chemoselectivity; only aldehydes underwent the alkylation in the presence of ketones. Further, the new reagent exhibited high 1,2- and 1,3-asymmetric induction. The transfer order of alkyl groups in the reaction of aldehydes with mixed tetraalkylleads/TiCl4 was determined; Me>Et.i-Pr?n-Bu.
Highly Diastereoselective 1,2-Asymmetric Addition of Dialkylzincs to Chiral 2-Phenylpropanal Catalyzed by Amino Alcohol
Soai, Kenso,Niwa, Seiji,Hatanaka, Toshihiro
, p. 2129 - 2130 (2007/10/02)
Diastereoselective addition of dialkylzinc reagents to 2-phenylpropanal using amino alcohol as catalyst afforded erythro alcohols (Cram-selectivity) in high diastereomeric excess (up to 88percent d.e.).
Amphiphilic Reactions by Means of Exceptionally Bulky Organoaluminum Reagents. Rational Approach for Obtaining Unusual Equatorial, Anti-Cram, and 1,4 Selectivity in Carbonyl Alkylation
Maruoka, Keiji,Itoh, Takayuki,Sakurai, Minoru,Nonoshita, Katsumasa,Yamamoto, Hisashi
, p. 3588 - 3597 (2007/10/02)
Exceptionally bulky, oxygenophilic organoaluminum reagents, methylaluminum bis(2,6-di-tert-4-alkylphenoxide) (MAD and MAT), have been successfully utilized for stereoselective activation of carbonyl moiety.Combination of MAD or MAT with carbon nucleophiles such as organolithiums or Grignard reagents generates a new amphiphilic reaction system in which the alkylation may be interpreted as the nucleophilic addition of a reactive organometallic compound to an electrophilically activated carbonyl substrate in order to account for the regio- and stereochemical consequences.In contrast to the ordinary alkylations, the amphilic alkylation disclosed herein would be categorized into the new, yet unexplored class of alkylation that exhibits high chemoselectivity to carbonyl compounds, and more significantly it allows excellent equatorial and anti-Cram selectivity in carbonyl alkylations, hitherto difficult by the existing methodologies.Further, unusual conjugate addition of organolithium reagents to α,β-unsaturated carbonyl compounds has been accomplished by using the amphiphilic reaction system.
Enhanced Cram Selectivity in Carbonyl Alkylation via 'Naked ' Anions and anti-Cram Selectivity via 'Naked' Cuprates
Yamamoto, Yoshinori,Matsuoka, Koshin
, p. 923 - 924 (2007/10/02)
Enhanced Cram selectivity is observed via the reaction of aldehydes (1) with 'naked' anions (2) prepared in situ from RM and Bu4NBr, while anti-Cram selectivity results from the reaction of (1) with 'naked' cuprates (4) prepared in situ from R2CuLi and Bu4NBr.
THE ATE COMPLEXES OF ALUMINIUM. REACTIVITY AND STEREOSELECTIVITY WITH RESPECT TO EPOXIDES AND CARBONYL COMPOUNDS. CATALYTIC ACTIVATION BY SALTS OF TRANSITION METALS
Boireau, G.,Abenhaim, D.,Henry-Basch, E.
, p. 3061 - 3070 (2007/10/02)
When used in non-coordinating solvents (hydrocarbons) NaAlEt4 and LiAlnBu4 are good alkylation agents for epoxides.The presence of catalytic quantities of transition-metal salts, particularly NiCl2 or NiBr2, greatly accelerate the reactions, making them possible within a reasonable time in the case of disubstituted epoxides such as cyclohexene oxide, 2-3 epoxybutane, 1 phenyl-2,3-epoxybutane.In the case of aliphatic epoxides, dialkylmagnesium, NaAlEt4 and LiAlnBu4 lead mainly to alkylation of the least substituted carbon of the epoxide ring; while in the case of epoxides with C-O bond in the benzyl position, it is this carbon that is alkylated.The reaction always proceeds by total inversion of the configuration of the carbon in the epoxide ring, namely the site of the alkylation. NaAlEt4 is also good agent for alkylating carbonyl compounds when used in solvents of low basicity such as diethylether, or in totally non-coordinating solvents such as the hydrocarbons.The yields of the alcohol are greatly improved by using catalytic quantities of NiCl2.The behaviour of NaAlEt4 with 2-phenylpropanol is quite remarkable: in diethylether NaAl-Et4 gives predominantly the pair of enantiomers predicted by Cram's rule and with greater stereoselectivity than if EtMgBr was used, while in pentane the reaction is no longer stereoselective.Finally, with a cyclic ketone, 4-t-butylcyclohexanone, NaAlEt4 in diethylether and in hexane in the presence of NiCl2 gives predominantly the equatorial alcohol resulting from an axial attack, which is generally not favoured at all.
