88790-26-5Relevant academic research and scientific papers
Felkin-Anh stereoselectivity in cycloadditions of acetylketene: Evidence for a concerted, pseudopericyclic pathway
Shumway,Ham,Moer,Whittlesey,Birney
, p. 7731 - 7739 (2007/10/03)
The cycloadditions of acetylketene with α-chiral aldehydes and ketones are shown to be diastereoselective, forming a tertiary or quaternary chiral center at an acetal or ketal carbon with good stereocontrol. X-ray crystallography of a minor product (5b) shows that the major products (e.g., 4b) are those predicted by the Felkin-Anh model. Transition states are reported at the MP2/6-31G* level for the addition of ethanal to formylketene and at the B3LYP/6-31G* level for the addition of 2-phenylpropanal. The ground-state conformations of the reactants and products are used to rationalize the relative energies and geometries of the transition states without the need to invoke the Cieplak hypothesis. However, chiral substituents on the α-oxoketene show no diastereoselectivity. These experimental and computational results are only consistent with the nearly planar, pseudopericyclic transition state previously proposed.
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.
Zirconium Mediated Regioselective Carbon-Carbon Bond Formation Reactions
Takahashi, Tamotsu,Suzuki, Noriyuki,Hasegawa, Maki,Nitto, Yu,Aoyagi, Ko-ichiro,Saburi, Masahiko
, p. 331 - 334 (2007/10/02)
Reactions of zirconocene-alkene complexes with aldehydes gave alcohols as coupling products after hydrolysis.The carbon-carbon bond formation proceeded at C1 carbon of alkenes, in sharp contrast to the reactions of alkene-alkene coupling on zirconium.A similar alcohol was also obtained by the reaction of zirconacyclopentane with aldehyde after hydrolysis.Treatment of (C5Me5)2ZrEt2 with styrene gave 2-phenylbutane after hydrolysis contrary to the case of Cp2ZrEt2 which afforded 1-phenylbutane.
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.).
Reactivity of the secondary benzylic Grignard reagent from 1-phenylethyl chloride with aldehydes and ketones. More evidence for the rearrangement mechanism in benzyl Grignard reactions
Bernardon, Claude
, p. 11 - 18 (2007/10/02)
Additional evidence for the mechanism proposed previously to account for diol formation in the reaction of the Grignard reagent from benzyl chloride with aldehydes has been obtained from a study of the interaction of the Grignard reagent from 1-phenylethyl chloride with carbonyl compounds.This Grignard reagent reacts with ketones (except non-enolisable ketones) to give normal alcohols in low yields, and with aldehydes to give diols.However, in contrast to that formed in the reaction of benzylmagnesium chloride, an unstable trienic alcohol formed from the rearrangement of the corresponding alkoxide could be isolated in some case as the major product, providing confirmatory evidence for the existence of an initial reversible rearrangement in the reaction of the benzylic Grignard reagents with carbonyl compounds.
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.
