A Novel General Route for the Preparation of Enantiopure Imidazolines
作者:Nicola A. Boland、Mike Casey、Stephen J. Hynes、Jonathan W. Matthews、Martin P. Smyth
DOI:10.1021/jo0111006
日期:2002.5.1
A novel procedure for the preparation of enantiopure 1,4-disubstituted 2-imidazolines is reported. Enantiopure beta-amino alcohols are converted into N-hydroxyethylamides, which are reacted with excess thionyl chloride, or with thionyl chloride followed by phosphorus pentachloride to yield N-chloroethylimidoyl chlorides. These intermediates are treated with amines and anilines to produce N-chloroethylamidines
Enantioselective rearrangement of a meso-cyclohexene oxide using norephedrine-derived chiral bases
作者:Bob Colman、Simon E de Sousa、Peter O'Brien、Timothy D Towers、Will Watson
DOI:10.1016/s0957-4166(99)00432-2
日期:1999.10
Using a chiral base from a norephedrine-derived diamine, the enantioselective rearrangement of a mesocyclohexene oxide can be performed in 94% yield and with 94% enantioselectivity. The enantioselectivity is lower (86% ee) with the diastereoisomeric chiral base. In order to prepare the diastereoisomeric chiral base, a potentially useful way of converting norephedrine into norpseudophedrine was developed. (C) 1999 Elsevier Science Ltd. All rights reserved.
A Biocatalytic Henry Reaction—The Hydroxynitrile Lyase fromHevea brasiliensis Also Catalyzes Nitroaldol Reactions
Enantiomerically divergent pathways in Tsuji-Trost reactions: exploiting the structural differences between β-acyloxy-o-(diphenylphosphino)benzamides and β-amido-o-(diphenylphosphino)benzoates
作者:Brandon M. Nelson、Mihir K. Chavda、Jonathan Oliphant、Jalisa M. King、Lisa F. Szczepura、Shawn R. Hitchcock
DOI:10.1016/j.tetasy.2016.08.012
日期:2016.11
Using a single chiral scaffold, (1R,2S)-norephedrine, a series of monophosphine ligands have been prepared. The ligands prepared, beta-acyloxy-(o-diphenylphosphino)amides and beta-amido-(o-diphenylphosphino)esters, give rise to enantiomerically divergent products in the Tsuji-Trost asymmetric allylic reaction. The phosphinoamides afforded the best enantioselectivities and favored the (S)-enantiomer of the product. In contrast the phosphinoesters afforded lower enantioselectivities and favored the (R)-enantiomer. A mechanistic rationale for this observation is proposed. (C) 2016 Elsevier Ltd. All rights reserved.
Synthesis of 2-oxazolines mediated by N,N′-diisopropylcarbodiimide
作者:Stefano Crosignani、Abigail C. Young、Bruno Linclau
DOI:10.1016/j.tetlet.2004.10.143
日期:2004.12
N-(beta-Hydroxy)amides can be cyclised by reaction with diisopropy1carbodiimide (DIC) to give the corresponding 2-oxazolines in high yields. The reaction requires only very mild Lewis-acid catalysis (5mol% Cu(OTf)(2)) and can be accomplished with simple heating, or in very short reaction times under microwave irradiation. (C) 2004 Elsevier Ltd. All rights reserved.