Novel Lewis Acid-Assisted Chiral Lewis Acid (LLA) System: Development of Boroxin-Ti-BINOL-Catalyzed Asymmetric Allylation of Aldehydes
作者:Hisashi Yamamoto、Guoyao Xia、Kazutaka Shibatomi
DOI:10.1055/s-2004-832830
日期:——
The formation of hetero multimetallic complex having B-O-Ti bond could increase the Lewis acidity of titanium. A novel LLA system made up of Ti-BINOL and 4-(trifluoromethyl)phenyl-boroxin dramatically accelerated the allylation reaction of aldehyde with high enantioselectivity.
High-Pressure Enantioselective Allylation of Aldehydes Catalyzed by (Salen)Chromium(III) Complexes
作者:Janusz Jurczak、Piotr Kwiatkowski
DOI:10.1055/s-2004-836067
日期:——
The enantioselective addition of allyltributyltin to simple aldehydes (2a-1), catalyzed by chiral (salen)Cr(III) complexes 1, has been studied. The reaction proceeds smoothly with low loading (1-2 mol%) of (salen)Cr(III)BF 4 (la) and allyltributyltin under high-pressure conditions (10 kbar) in good yield and ee values in the range of 35-79%.
Proline-Based <i>N</i>-Oxides as Readily Available and Modular Chiral Catalysts. Enantioselective Reactions of Allyltrichlorosilane with Aldehydes
作者:John F. Traverse、Yu Zhao、Amir H. Hoveyda、Marc L. Snapper
DOI:10.1021/ol050814q
日期:2005.7.1
as an effective catalyst for the reaction of allyltrichlorosilane with aryl and alpha,beta-unsaturated aldehydes at room temperature to afford the desired homoallylic alcohols in up to 92% ee. The chiral catalyst can be easily prepared from optically pure proline in three simple steps and 60% overall yield.
Chiral Phosphoramide-Catalyzed Enantioselective Addition of Allylic Trichlorosilanes to Aldehydes. Preparative Studies with Bidentate Phosphorus-Based Amides
作者:Scott E. Denmark、Jiping Fu、Michael J. Lawler
DOI:10.1021/jo052203h
日期:2006.2.1
that more than one Lewis basic moiety (phosphoramide) is involved in the rate- and stereochemistry-determining step of enantioselectiveallylation, bidentate chiral phosphoramides were developed. Different chiral phosphoramide moieties were connected by tethers of methylene chains of varying length. The rate and enantioselectivity of allylation with allyltrichlorosilane promoted by the bidentate phosphoramides
unit with a conformationally rigid chiral backbone has been designed and synthesized in an enantiomerically pure form to utilize in the Lewis base-catalyzed Sakurai–Hosomi–Denmark-type allylation reaction. The chiral pyridine N-oxide in 1:1 mixture of chloroform and 1,1,2,2-tetrachloroethane produced the homoallylic alcohols in up to 98% yield and up to 94% ee.