Empirical method for predicting enantioselectivity in catalytic reactions: demonstration with lipase and oxazaborolidine
摘要:
We derived a novel equation capable of predicting the degree of enantioselectivity in a catalytic reaction without any knowledge of the reaction mechanism and/or the transition-state structure. and tested the validity of this equation by changing substrates systematically in the lipase or oxazaborolidine-catalyzed reactions A good correlation was observed between the predicted and observed E values, and the stereochemistry of the products Could be predicted correctly in most cases (28 out of 30) (C) 2009 Elsevier Ltd All rights reserved
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 newreagent exhibited high 1,2- and 1,3-asymmetric induction. The transfer order of alkyl groups
A new convenient procedure to prepare organomanganese reagents from organic halides and activated manganese
作者:Gérard Cahiez、Arnaud Martin、Thomas Delacroix
DOI:10.1016/s0040-4039(99)01331-3
日期:1999.8
A newmethod to obtain activated manganese metal, especially attractive for large scale preparativeorganicchemistry, is described. The key point is the use of 2-phenylpyridine as electron carrier to reduce manganese chloride by lithium. The active manganese thus obtained was used to prepare various organomanganese reagents from organic halides. The reactivity of these reagents has been studied (acylation
Pentamethylcyclopentadienide in organic synthesis: nucleophilic addition of lithium pentamethylcyclopentadienide to carbonyl compounds and carbon–carbon bond cleavage of the adducts yielding the parent carbonyl compounds
dienide (C5Me5Li, Cp*Li) reacted with aromatic aldehyde to provide the corresponding carbinol in excellent yield. The carbinol returns to the parent aldehyde and pentamethylcyclopentadiene upon exposure to acid or due to heating. Chlorodimethylaluminum is essential as an additive to attain the nucleophilic addition of Cp*Li to aliphatic aldehyde. The carbinol derived from aliphatic aldehyde returns
五甲基环戊二烯化锂(C 5 Me 5 Li,Cp * Li)与芳族醛反应以优异的产率提供相应的甲醇。甲醇在暴露于酸中或加热后会返回为母体醛和五甲基环戊二烯。氯二甲基铝对于实现Cp * Li向脂肪族醛的亲核加成反应至关重要。衍生自脂族醛的甲醇在催化量的2,3-二氯-5,6-二氰基苯并醌(DDQ)的作用下返回母体醛和五甲基环戊二烯。Cp *基团的可逆加成/消除可表示对醛的保护。还公开了碳-碳键裂解的机理细节。
Selectivity in Organic Group Transfer in Reactions of Mixed Diorganomanganese(II) and Triorganomanganate(II) with 2-Cyclohexen-1-one or Cyclohexanecarbaldehyde
The unsymmetrical diorganomanganeses(II) (R1R2Mn) and magnesium triorganomanganates(II) (R12R2MnMgX) reacted with 2-cyclohexen-1-one to produce the 1,4-addition products in moderate to good yields. The approximate reactivity order obtained from the product distribution was CH2=CHCH2 > PhS > n-Bu > Ph > Me, Me3SiCH2, n-C6H13–C≡C. In contrast, the reactivity order for the addition of these reagents to
Nickel-Catalyzed Alkylation of Aldehydes with Trialkylboranes
作者:Koji Hirano、Hideki Yorimitsu、Koichiro Oshima
DOI:10.1021/ol051917b
日期:2005.10.1
[reaction: see text] Nickel-catalyzed alkylation of aldehydes with trialkylboranes proceeds smoothly in the presence of a catalytic amount of 5-allyl-1,2,3,4,5-pentamethyl-1,3-cyclopentadiene or an excess of cesium carbonate to afford the corresponding secondary alcohols.