- A new method for the synthesis of unsymmetrical bis-aldols by the samarium(II) iodide-mediated aldol reaction of aldehydes with aryl or alkyl oxiranyl ketones
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Unsymmetrieal alkyl or aryl 2-hydroxy-1-(1-hydroxyalkyl)-alkyl ketones (bis-aldols) were synthesized by the samarium(II) iodide-mediated aldol reaction of aldehydes with alkyl or aryl oxiranyl ketones. Bis-aldols were formed via the aldol reaction of aldehydes with samarium enolates generated by epoxy-fragmentation of oxiranyl ketones using two moles of samarium(II) iodide.
- Mukaiyama, Teruaki,Arai, Hidehiro,Shiina, Isamu
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- Stereoselective Synthesis of the C25-C36 Segment of Arenicolides A and B: Determination of the Configuration of the Trisubstituted Epoxide
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Chemical Equation Presentation Two diastereomerlc epoxides 4a and 4b corresponding to the C25-C36 fragment of arenicolides A and B were synthesized in a stereoselective manner involving the Pd(0)-catalyzed stereospecific methoxy substitution reaction of epoxy unsaturated ester 6 with B(OMe)3 as the key step. Comparison of the 1H NMR spectra of the synthetic compounds with that of arenicolide A revealed that the configuration of the epoxide in arenicolides A and B is 30R and 31R
- Nagumo, Shinji,Nakano, Taeko,Hata, Kyomi,Mizukami, Megumi,Miyashita, Masaaki
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- New chiral amino alcohol ligands for catalytic enantioselective addition of diethylzincs to aldehydes
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A study aimed at the synthesis and structure optimization of new, efficient, optically active β-amino alcohol ligands with a structure suitable for immobilization on magnetite nanoparticles has been carried out. The optimized homogeneous amino alcohol catalysts 13a and 13b, the chirality of which arises from the Sharpless epoxidation of suitable allyl alcohols, were tested by employing the well-established enantioselective amino alcohol-promoted addition of diethylzinc to benzaldehyde, giving the corresponding benzyl alcohol with nearly quantitative yield and ee = 95%. Then, their broad applicability as chiral catalysts was evaluated by carrying out the same reaction on a family of aldehydes, including variously substituted aromatic ones as well as an aliphatic analogue. The results have confirmed the validity of the fine-tuning process performed on ligands 13a and 13b. In fact, both exhibited excellent catalytic activity as demonstrated by the chemical yields and ee obtained from all the tested aldehydes, almost independent of the position and type of substitution in the aromatic ring.
- Sappino, Carla,Mari, Alessandra,Mantineo, Agnese,Moliterno, Mauro,Palagri, Matteo,Tatangelo, Chiara,Suber, Lorenza,Bovicelli, Paolo,Ricelli, Alessandra,Righi, Giuliana
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p. 1860 - 1870
(2018/03/23)
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- A Versatile and Highly Selective Hypervalent Iodine (III)/ 2,2,6,6-Tetraniethyl-1-piperidinyloxyl-Mediated Oxidation of Alcohols to Carbonyl Compounds
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Catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) are used in combination with [bis(acetoxy)iodo]benzene (BAIB) as a stoichiometric oxidant in the conversion of primary and secondary alcohols to carbonyl compounds. This procedure works efficiently at room temperature in almost all common solvents and neat in some cases. This process exhibits a very high degree of selectivity for the oxidation of primary alcohols to aldehydes, without any noticeable overoxidation to carboxyl compounds, and a high chemoselectivity in the presence of either secondary alcohols or of other oxidizable moieties. This procedure allows an easy, convenient, high-yielding method for the oxidation of alcohols starting from commercially available compounds.
- De Mico, Antonella,Margarita, Roberto,Parlanti, Luca,Vescovi, Andrea,Piancatelli, Giovanni
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p. 6974 - 6977
(2007/10/03)
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