new chiral β-hydroxy amide ligands were synthesized via the reaction of benzyl chloride and aminoalcohols derived from l-tyrosine. The titanium(IV) complex of chiral ligand 8b was found to be an effective catalyst for the asymmetric alkynylation of aliphatic, vinyl and aromatic aldehydes. The propargyl alcohols were obtained in highly enantiomeric excesses (up to 96% ee) under optimized conditions.
The synthesis of new oxazoline-containing bifunctional catalysts and their application in the addition of diethylzinc to aldehydes
作者:Vincent Coeffard、Helge Müller-Bunz、Patrick J. Guiry
DOI:10.1039/b822580j
日期:——
bifunctional catalysts is reported employing a microwave-assisted Buchwald–Hartwig aryl amination as the key step. Covalent attachment of 2-(o-aminophenyl)oxazolines and pyridine derivatives generated in good-to-high yields a series of ligands in two or three steps in which each part was altered independently to tune the activity and the selectivity of the corresponding catalysts. These catalysts prepared
Switching of Enantioselectivity in the Catalytic Addition of Diethylzinc to Aldehydes by Regioisomeric Chiral 1,3-Amino Sulfonamide Ligands
作者:Takuji Hirose、Kazuyuki Sugawara、Koichi Kodama
DOI:10.1021/jo200834n
日期:2011.7.1
Twenty chiral 1,3-amino sulfonamides of two classes (2a–i and 3a–k) have been prepared from (−)-cis-2-benzamidocyclohexanecarboxylic acid (1) and studied as ligands for catalytic enantioselectiveaddition of Et2Zn to a variety of aromatic and aliphatic aldehydes. The ligands 2 and 3 are regioisomers in which the position of the amine and sulfonamide groups is exchanged. Each class of ligands with the
Cationic Rhodium(I)/Bisphosphane Complex-Catalyzed Isomerization of Secondary Propargylic Alcohols to α,β-Enones
作者:Ken Tanaka、Takeaki Shoji、Masao Hirano
DOI:10.1002/ejoc.200700071
日期:2007.6
alcohols to α,β-enones. A kinetic resolution of secondary propargylic alcohols proceeded with moderate selectivity with [Rh((R)-BINAP)]OTf as a catalyst. Mechanistic studies revealed that the isomerization proceeds through intramolecular 1,3- and 1,2-hydrogen migration pathways. The isomerization of propargylic diol derivatives was also investigated, which revealed that 1,4-diketones, furans, and α,β-enones
Highly Enantioselective Phenylacetylene Additions to Both Aliphatic and Aromatic Aldehydes
作者:Ge Gao、David Moore、Ru-Gang Xie、Lin Pu
DOI:10.1021/ol026921r
日期:2002.11.1
The readilyavailable and inexpensive BINOL in combination with Ti(O(i)Pr)(4) is found to catalyze the reaction of an alkynylzinc reagent with various types of aldehydes including aliphaticaldehydes, aromaticaldehydes, and other alpha,beta-unsaturated aldehydes to generate chiral propargyl alcohols with 91-99% ee at room temperature. No previous chiral catalysts have exhibited such a broad scope