Indium(III) Halides as New and Highly Efficient Catalysts for <i>N</i>-<i>tert</i>-Butoxycarbonylation of Amines
作者:Asit Chakraborti、Sunay Chankeshwara
DOI:10.1055/s-2006-942492
日期:2006.8
Indium(III) bromide and chloride efficiently catalysed the N-tert-butoxycarbonylation of amines with (Boc)2O at room temperature and under solvent-free conditions. Various aromatic, heteroaromatic and aliphatic amines were converted to N-tert-butylcarbamates in excellent yields in short times. Chiral amines, esters of α-amino acids and β-amino alcohols afforded optically pure N-t-Boc derivatives in high yields. The reactions were chemoselective and no competitive side reactions such as isocyanate, urea, and N,N-di-t-Boc formation were observed. Chemoselective conversion to N-tert-butylcarbamates took place with amino alcohols without any formation of oxazolidinones.
A new protocol of protection of poorly reactive aryl amines and functionalized amines with Boc2O in the presence of Zn(ClO4)2·6H2O as the catalyst is reported. The catalytic action of Zn(ClO4)2·6H2O is specific for the activation of the pyrocarbonates, thus acid sensitive functionalities and stereochemical configurations of the starting materials remain unaltered in the protection process.
HClO<sub>4</sub>–SiO<sub>2</sub>as a new, highly efficient, inexpensive and reusable catalyst for N-tert-butoxycarbonylation of amines
作者:Asit K. Chakraborti、Sunay V. Chankeshwara
DOI:10.1039/b605074c
日期:——
Perchloric acid adsorbed on silica-gel (HClO4âSiO2) was found to be a new, highly efficient, inexpensive and reusable catalyst for chemoselective N-tert-butoxycarbonylation of amines at room temperature and under solvent-free conditions.
Sulfated tungstate: A highly efficient, recyclable and ecofriendly catalyst for chemoselective <i>N</i>-tert butyloxycarbonylation of amines under the solvent-free conditions
作者:Ajit P. Ingale、Sandeep V. Shinde、Nitin M. Thorat
DOI:10.1080/00397911.2021.1942060
日期:2021.8.18
Abstract Sulfated tungstate catalyzed an efficient and ecofriendly protocol has been described for the chemoselective N-tert-butyloxycarbonylation of amines under the solvent-freeconditions at roomtemperature. The variety of functionalized aliphatic, aromatic and heteroaromatic amines efficiently undergoes the N-tert-butyloxycarbonylation under the developed protocol. The aminoalcohol, aminophenol
The present invention relates to in vivo imaging and radiotherapeutic methods and agents which target the enzyme aldehyde dehydrogenase (ALDH) and that are suitable for the in vivo imaging of tumours and treatment of cancer.