56849-84-4Relevant articles and documents
The asymmetric aza-claisen rearrangement: development of widely applicable pentaphenylferrocenyl palladacycle catalysts
Fischer, Daniel F.,Barakat, Assem,Xin, Zhuo-Qun,Weiss, Matthias E.,Peters, Rene
supporting information; experimental part, p. 8722 - 8741 (2010/03/31)
Systematic studies have been performed to develop highly efficient catalysts for the asymmetric aza-Claisen rearrangement of trihaloacetimidates. Herein, we describe the stepwise development of these catalyst systems involving four different catalyst generations finally resulting in the development of a planar chiral pentaphenylferrocenyl oxazoline palladacycle. This complex is more reactive and has a broader substrate tolerance than all previously known catalyst systems for asymmetric aza-Claisen rearrange-ments. Our investigations also reveal that subtle changes can have a big impact on the activity. With the enhanced catalyst activity, the asymmetric aza-Claisen rearrangement has a very broad scope: the methodology not only allows the formation of highly enantioenriched primary allylic amines, but also secondary and tertiary amines; al-lylic amines with N-substituted quaternary stereocenters are conveniently accessible as well. The reaction conditions tolerate many important functional groups, thus providing stereoselective access to valuable functionalized building blocks, for example, for the synthesis of unnatural amino acids. Our results suggest that face-selective olefin coordination is the enantioselectivitydetermining step, which is almost exclusively controlled by the element of planar chirality.
Decaphenylgermanocene, -stannocene, and -plumbocene and Pentaphenylstannocene: Synthesis, Properties and CMPAS-Metal-NMR Measurements
Janiak, Christoph,Schumann, Herbert,Stader, Carin,Wrackmeyer, Bernd,Zuckerman, Jerold J.
, p. 1745 - 1752 (2007/10/02)
An improved synthesis is described for pentaphenylcyclopentadienol (1), pentaphenylcyclopentadienyl bromide (2), pentaphenylcyclopentadiene (3), and pentaphenylcyclopentadienyllithium (4a).Decaphenylgermanocene (5), -stannocene (6), and -plumbocene (7) as well as pentaphenylstannocene (8) are prepared.Complete analytical data (IR, Raman, X-ray powder, NMR, mass, and 119mSn-Moessbauer spectra) are given. 119Sn- and 207Pb-CPMAS NMR measurements of various stannocenes and of the plumbocene 7 are reported for the first time.
13C, 19F and 1H ENDOR Investigations of Substituent Effects on Lifting of Orbital Degeneracy in Cyclopentadienyl Radicals. Syntheses
Kieslich, W.,Kurreck, H.
, p. 4328 - 4335 (2007/10/02)
A variety of substituted, partially deuterated, and 13C-labeled pentaphenylcyclopentadienyl radicals ("Ziegler's radicals") have been synthesized.It is shown from 13C, 19F, and 1H ENDOR experiments that monosubstitution removes the orbital degeneracy of t
