Two rhodium(II) ions work together: [Rh2(S‐tbpttl)4] is an exceptionally effective catalyst for enantioselectivecyclopropenationreactions of 1‐alkynes with α‐alkyl‐α‐diazoacetates (see scheme). Cyclopropenation is preferred over alkene formation through a 1,2‐hydride shift.
Several α-alkylated β-amino esters have been obtained via DKR processes employing a kit of transaminases and isopropylamine as an amino donor in aqueous medium under mild conditions. Thus, while acyclic α-alkyl-β-keto esters afforded excellent conversions and enantioselectivities, although usually low diastereoselectivities, using more constrained cyclic β-keto esters high to excellent inductions were obtained.
Coating compositions for a transparent magnetic recording layer
申请人:EASTMAN KODAK COMPANY
公开号:EP0660308A1
公开(公告)日:1995-06-28
A coating composition for applying a transparent magnetic recording layer to a support which comprises a polymeric binder, ferromagnetic particles and a dispersing medium for the polymeric binder, the dispersing medium comprising (a) a compound having the formula
where
R is alkyl having 1 to 8 carbon atoms, phenyl or benzyl;
R' is hydrogen, methyl or ethyl,; and
R'' is alkyl having 1 to 5 carbon atoms. and
(b) methylene chloride, or lower alkyl ketones or mixtures of methylene chloride and lower alkyl ketones.
Dynamic Kinetic Resolution of α-Substituted β-Ketoesters Catalyzed by Baeyer-Villiger Monooxygenases: Access to Enantiopure α-Hydroxy Esters
作者:Ana Rioz-Martínez、Aníbal Cuetos、Cristina Rodríguez、Gonzalo de Gonzalo、Iván Lavandera、Marco W. Fraaije、Vicente Gotor
DOI:10.1002/anie.201103348
日期:2011.8.29
BVMOs make a play: The dynamic kineticresolution of racemic α‐alkyl‐β‐ketoesters was performed through a selective Baeyer–Villiger oxidation employing different Baeyer–Villigermonooxygenases (BVMOs) in mild basic media. The product diesters were obtained with excellent yields and enantioselectivities, and used as precursors for optically active α‐hydroxy esters.