Highly stereoselective cyclopropanation of diazo Weinreb amides catalyzed by chiral Ru(<scp>ii</scp>)–Amm–Pheox complexes
作者:Soda Chanthamath、Hamada S. A. Mandour、Thu Minh Thi Tong、Kazutaka Shibatomi、Seiji Iwasa
DOI:10.1039/c6cc02498j
日期:——
The first highly stereoselectivecyclopropanation of diazo Weinreb amides with olefins was accomplished using chiral Ru(II)-Amm-Pheox complex 7a to give the corresponding chiral cyclopropyl Weinreb amides in high yields (up...
One pot direct synthesis of oxazolines, benzoxazoles, and oxadiazoles from carboxylic acids using the Deoxo-Fluor reagent
作者:Cyrous O. Kangani、David E. Kelley、Billy W. Day
DOI:10.1016/j.tetlet.2006.07.032
日期:2006.9
A one-pot, high yield direct synthesis of various 2-substituted oxazolines, benzoxazoles, and 2-oxadiazoles from carboxylic acids using Deoxo-Fluor reagent is described. (c) 2006 Elsevier Ltd. All rights reserved.
Study on the tandem synthesis of optically active 2-substituted 4 (or 5)-phenyl-1,3-oxazolines
Optically active (S)-2-aryl-4 (or 5)-phenyl-1,3-oxazolines and (S)-2-fluoroalkyl-4-phenyl-1,3-oxazolines were synthesized from a tandem one-pot reaction of (S)-2-amino-2-phenylethanol with a corresponding carboxylic acid in toluene at 90 degrees C in the presence of PPh3/CBr4 and excess Et3N. The use of aromatic carboxylic acids were determined to proceed through N-(2-bromo-1-phenyl-ethyl)-arylamides 5 and N-aroyl aziridine intermediates 6, which resulted in the formation of (S)-2-aryl-4-phenyl-1,3-oxazolines and (S)-2-aryl-5-phenyl-1,3-oxazolines, respectively. Concurrently, the reaction with fluorinated aliphatic carboxylic acid substrates proceeded via N-(2-hydroxy-1-phenyl-ethyl)-fluoroalkyl amide intermediates 8, which were converted into N-(2-bromo-1-phenyl-ethyl)-fluoroalkyl amide intermediates 9, and then into (S)-2-fluoroalkyl-4-phenyl-1,3-oxazolines as final products. Reaction mechanisms that mainly passed through the formation of aziridine intermediates 6 in the reaction with aromatic carboxylic acids and the formation of fluoroalkyl amide intermediates 8 and 9 in the reaction with fluorinated aliphatic carboxylic acid were proposed. The acidities of the carboxylic acids that were employed were found to play a key role in the selective formation of various intermediates during this reaction. (c) 2013 Elsevier Ltd. All rights reserved.
Direct Catalytic Asymmetric Cyclopropylphosphonation Reactions of <i>N,N</i>-Dialkyl Groups of Aniline Derivatives by Ru(II)-Pheox Complex
N-methylaniline and asymmetric cyclopropylphosphonation reactions of N,N-diethylaniline derivatives with diazomethylphosphonates are reported. Optically active cyclopropylphosphonate derivatives were directly synthesized from diazomethylphosphonates and N,N-diethylaniline derivatives catalyzed by a Ru(II)-Pheox complex in one step in good yields and high diastereoselectivities (up to trans/cis = > 99:1<)