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2004
Enantioselective syntheses
O 0031
A Practical Synthesis of Optically Active Aromatic Epoxides via Asymmetric
Hydrogenation of α-Chlorinated Ketones with Chiral Rhodium-Di50- 027 Transfer
amine Catalyst. — The synthesis of optically active α-chlorinated alcohols as precursors for epoxides by the title method is studied for a variety of substrates. By use of
HCOOH/Et3N or isopropanol as the hydrogen source, and chiral rhodium complex
RHO as catalyst high enantioselectivities (up to 99% e.e.) are achieved. The outcome
of the transfer hydrogenation reaction is significantly influenced by the structure of the
starting ketone and the hydrogen source. For selected alcohols their smooth intramolecular etherification to the desired epoxides without loss of enantiomeric purity is
demonstrated. The epoxide synthesis is also successfully performed in one-pot. The
reduction of acetophenones bearing other functional groups than chloro at the α-position are also examined. Except for the bromo derivative, all compounds give similar
results as the chloro analogue (Ia). — (HAMADA, T.; TORII, T.; IZAWA, K.;
IKARIYA*, T.; Tetrahedron 60 (2004) 34, 7411-7417; Grad. Sch. Sci. Eng., Tokyo
Inst. Technol., Meguro, Tokyo 152, Japan; Eng.) — Klein
2004
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