GENERAL METHOD FOR INCREASING STEREOSELECTIVITY IN STEREOSELECTIVE REACTIONS
申请人:Meyer Matthew P.
公开号:US20090163741A1
公开(公告)日:2009-06-25
This invention is directed to a method of performing a stereoselective reaction without use of a solvent comprising contacting a reactant with a chiral reagent under sonication conditions to form an excess of an enantiomer.
Highly enantioselective organocatalysis of the Hajos–Parrish–Eder–Sauer–Wiechert reaction by the β-amino acid cispentacin
作者:Stephen G. Davies、Ruth L. Sheppard、Andrew D. Smith、James E. Thomson
DOI:10.1039/b506780b
日期:——
The β-amino acid cispentacin promotes the HajosâParrishâEderâSauerâWiechert reaction with levels of enantioselectivity comparable to or higher than proline.
Direct amino acid-catalyzed cascade biomimetic reductive alkylations: application to the asymmetric synthesis of Hajos–Parrish ketone analogues
作者:Dhevalapally B. Ramachary、Mamillapalli Kishor
DOI:10.1039/b807999d
日期:——
and enantioselective process for the double cascade synthesis of highly substituted 2-alkyl-cyclopentane-1,3-diones, 2-alkyl-3-methoxy-cyclopent-2-enones and Hajos-Parrish (H-P) ketone analogs is presented via reductive alkylation chemistry. For the first time, we have developed a single-step alkylation of cyclopentane-1,3-dione with aldehydes/ketones and a Hantzsch ester through an organocatalytic reductive
Prolinamides<i>versus</i>Prolinethioamides as Recyclable Catalysts in the Enantioselective Solvent-Free Inter- and Intramolecular Aldol Reactions
作者:Diana Almaşi、Diego A. Alonso、Carmen Nájera
DOI:10.1002/adsc.200800430
日期:2008.11.3
and direct anti-aldol reaction of aliphatic ketones with aromatic aldehydes catalyzed by recyclable L-prolineamides and L-prolinethioamides 3 is studied. The L-prolinethioamide 3d (5 mol%), derived from L-Pro and (R)-1-aminoindane, is the most efficient catalyst for this process affording the anti-aldol adducts in high yields with excellent diastereo- and enantioselectivities (up to >98/2 dr, up to
Optically active organic compounds are prepared starting from optically inactive reactants by means of an optically active agent which influences the course of the reaction. In particular optically active compounds having a "meso" type carbon atom undergo an intramolecular ring closure in the presence of an optically active agent to yield an optically active product having one additional ring. The present process is particularly useful in the preparation of optically active bicyclic diketones which are important intermediates in the total synthesis of steroids.