Synthesis of (−)-Centrolobine by Prins Cyclizations that Avoid Racemization
摘要:
[GRAPHICS]The segment-coupling Prins cyclization avoids two of the problems common to other Prins cyclization protocols: side-chain exchange and partial racemization by reversible 2-oxonia Cope rearrangement. Model studies demonstrate the stereochemical fidelity of Prins cyclizations using alpha-acetoxy ethers compared with direct aldehyde-alcohol Prins reactions. Furthermore, we propose a mechanism for the racemization observed in some intermolecular Prins cyclizations. Two straightforward syntheses of optically pure (-)-centrolobine highlight the utility of Prins cyclizations.
Indium-mediated Barbier-type allylation of aldehydes as a convenient method for the highly enantioselective synthesis of homoallylic alcohols
作者:Lacie C. Hirayama、Soya Gamsey、Daniel Knueppel、Derek Steiner、Kelly DeLaTorre、Bakthan Singaram
DOI:10.1016/j.tetlet.2005.01.169
日期:2005.3
enantioselective allylation of both aromatic and aliphatic aldehydes using commercially available (1S,2R)-(+)-2-amino-1,2-diphenylethanol as a chiral auxiliary. Using only two equivalents of allyl bromide, excellent yields and very good to excellent enantioselectivities are obtained. To our knowledge, the enantioselectivities reported herein are the highest obtained for indium-promoted allylations of carbonyl
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%.
Enantioselective allylation of aldehydes catalyzed by chiral indium(iii) complexes immobilized in ionic liquids
作者:Jun Lu、Shun-Jun Ji、Teck-Peng Loh
DOI:10.1039/b500086f
日期:——
In the presence of chiral catalytic complexes prepared from In(OTf)3 and chiral PYBOX ligands, allytributylstannane reacted with aldehydes in ionic liquids to afford the corresponding homoallylic alcohols in high enantioselectivities (86–94% ee) and good yields (68–89%); the chiral catalysts immobilized in ionic liquids could be reused with comparable enantioselectivities and yields.
Highly Enantioselective Allylation of Arylaldehydes Catalyzed by a Silver(I)-Chiral Binaphthylthiophosphoramide
作者:Chun-Jiang Wang、Min Shi
DOI:10.1002/ejoc.200300099
日期:2003.8
diphenylthiophosphoramide L2 prepared from diphenylthiophosphinic chloride and ?-(+)-N-ethyl-1,1'-binaphthyl-2,2'-diamine 2 was used as a catalytic chiral ligand in the siver(I)-catalyzed enantioselectiveallylation reaction of arylaldehydes with allyltribuyltin to furnish high ee (up to 98%) of the homoallylic alcohols.
Chiral Bis(imidazolinyl)phenyl NCN Pincer Rhodium(III) Catalysts for Enantioselective Allylation of Aldehydes and Carbonyl–Ene Reaction of Trifluoropyruvates
作者:Tao Wang、Xin-Qi Hao、Juan-Juan Huang、Jun-Long Niu、Jun-Fang Gong、Mao-Ping Song
DOI:10.1021/jo4014194
日期:2013.9.6
Chiral NCN pincer rhodium(III) complexes with bis(imidazolinyl)phenyl ligands were found to be effective catalysts for the allylation of a variety of electronically and structurally diverse aldehydes with allyltributyltin, giving the corresponding optically active homoallylic alcohols in high yields with enantioselectivities of up to 97% ee. These complexes were also applied in the carbonyl–ene reaction