Metal-free 5-exo-dig cyclization of propargyl urea using TBAF
摘要:
We present the first results of the intramolecular cyclization of propargyl ureas catalyzed by TBAF. Depending on the substituents close to the triple bond, imidazolone or methylene-imidazolidinone was obtained. The dual activation of the triple bond by interaction with TBAF via the cation-pi is thought to be responsible. (C) 2014 Elsevier Ltd. All rights reserved.
potent inhibitor of neuraminidases, a hydrolase that is responsible for processing sialylated glycoconjugates, is a promising drug candidate for various infective diseases. The current study demonstrates that the use of an aglycone-focused library of 2-difluoromethylphenyl α-sialosides is an effective technique to find potent and selective mechanism-basedlabeling reagents for neuraminidases. The focused
Nitrogen heterocycles by palladium-catalysed oxidative cyclization-alkoxycarbonylation of acetylenic ureas
作者:Alessia Bacchi、Gian Paolo Chiusoli、Mirco Costa、Cristian Sani、Bartolo Gabriele、Giuseppe Salerno
DOI:10.1016/s0022-328x(97)00459-2
日期:1998.7
Acetylenic ureas readily undergo oxidative cyclization-alkoxycarbonylation reactions in the presence of PdI2 (or Pd/C)-KI as catalyst in methanol under mild conditions (65°C and 24 bar of a 3:1 mixture of CO and air). Cyclization occurs by trans-attack of oxygen or cis-attack of nitrogen functions on the triple bond, followed by stereospecific carbonylation, resulting in E or Z-stereochemistry, respectively
Unexpected Stereoselective Access to 2‐Aminooxazolines from Propargyl Ureas by Silver Salts under Mild Conditions
作者:Aleksandr Voronov、Alessandra Casnati、Paolo P. Mazzeo、Paolo Pelagatti、Alessia Bacchi、Raffaella Mancuso、Bartolo Gabriele、Elena Motti、Giovanni Maestri、Péter Pál Fehér、András Stirling、Nicola Della Ca'
DOI:10.1002/adsc.202200950
日期:——
Propargyl ureas can lead to a range of possible heterocyclic compounds, mainly depending on the employed catalyst. Silver salts are known to promote the N-5-exo-dig cyclization mode to imidazolidinone derivatives. Conversely, a versatile and stereoselective O-5-exo-dig cyclization of propargyl ureas to 2-aminooxazolines by Ag(I) catalysis is here disclosed. Good to excellent yields and complete stereoselectivity