80558-38-9Relevant articles and documents
Commercially available neat organozincs as highly reactive reagents for catalytic enantioselective addition to ketones and aldehydes under solvent free conditions
Hatano, Manabu,Mizuno, Tomokazu,Ishihara, Kazuaki
experimental part, p. 4417 - 4424 (2011/08/06)
Neat Et2Zn, Ph2Zn, and highly concentrated Me 2Zn are highly reactive organozinc reagents, which are commercially available in bulk quantities. We here report a catalytic enantioselective Et2Zn, Ph2Zn, and Me2Zn addition to ketones and aldehydes under solvent free or highly concentrated conditions without Ti(Oi-Pr)4 as a conventional activator of organozinc reagents. The desired optically active tertiary and secondary alcohols were obtained in good yield with high enantioselectivity when compared to the conventional solvent-use conditions. From the viewpoint of ecological and environmental reasons in green chemistry, this catalysis would be practical for not only academic but also industrial use.
Highly enantiospecific oxyfunctionalization of nonactivated hydrocarbon sites by perfluoro-cis-2-n-butyl-3-n-propyloxaziridine
Arnone, Alberto,Foletto, Stefania,Metrangolo, Pierangelo,Pregnolato, Massimo,Resnati, Giuseppe
, p. 281 - 284 (2008/02/14)
(equation presented) Nonactivated hydrocarbon sites of enantiopure compounds are oxyfunclionalized enantiospecifically by perfluoro-cis-2-n-butyl-3-n-propyloxaziridine under remarkably mild reaction conditions. The reaction occurs with retention of configuration at the oxidized stereogenic center, and the enantiospecificity is highly independent from both the carbon framework of the substrate and the presence of functional groups.
Mechanistic and Preparative Studies on the Regio- and Stereoselective Paraffin Hydroxylation with Peracids
Schneider, Hans-Joerg,Mueller, Walter
, p. 4609 - 4615 (2007/10/02)
Reactions of more than 20 hydrocarbons with p-nitro- or, e.g., 3,5-dinitroperbenzoic acid in chloroform show regioselectivities of Rst = 90 (relative rates of attack at tertiary and secondary C-H bonds, after statistical correction) to 500 and configurational retention, if applicable, of typically 97-99.7percent.Radical side reactions are recognized by concomitant formation of, e.g., nitrobenzene and are responsible for a decrease in regio- and stereoselectivity.Steric effects are observed in attack at axial tertiary C-H bonds and at bridgehead positions.Electronegative and hydrogen-bonding substituents in the alkane diminish, and alkyl groups enhance the rates; the observed Taft ρ* value of -2.2 indicates substantial positive charge accumulation in the transition state in agreement with the high regioselectivity.A Hammett reaction constant of +0.63 is obtained from substituted perbenzoic acids; activation parameters of ΔH* = 15-19 kcal mol-1 and ΔS* = -22 to -29 eu with three alkanes of different flexibility and an isotope effect of kH/kD = 2.2 with methylcyclohexane are measured.Aromatic rings are usually not attacked but lead to deactivation of the peracid even at remote alkane C-H positions; similar deactivation is found in hydrogen-bonding solvents.Androstanes yield preferentially 9α- and 5α-hydroxy products, if, e.g., a 17β-acetoxy substituent is used to steer the reaction.Diols usually are only observed as a result of a proximity effect of a peracid associated at the first formed hydroxy group.The results point to relatively late and oxenoid transition states with substantial charge separation in the substrate.Attempts to achieve selective oxidations using macrocyclic azacyclophanes with attached carboxylic functions were not successful, although the host compounds showed selective complexation of hydrocarbons.
