Single (substitution) is better: New chiralruthenium metathesis (pre)catalysts with a monosubstituted carbon atom in the N‐heterocyclic carbene ligand are highly stable in solution, initiate easily, show very high enantioselectivity and excellent E selectivity in asymmetric ring‐opening cross‐metathesis (see scheme).
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.
[EN] TRIAZOLOPYRAZINES AND METHODS OF MAKING AND USING THE SAME<br/>[FR] TRIAZOLOPYRAZINES ET PROCEDES DE PREPARATION ET D'UTILISATION CE CELLES-CI
申请人:BIOGEN IDEC INC
公开号:WO2004092177A1
公开(公告)日:2004-10-28
The invention is based on the discovery that compounds of formula (I) possess unexpectedly high affinity for the A2a adenosine receptor, and can be useful as antagonists thereof for preventing and/or treating numerous diseases, including Parkinson's disease. In one embodiment, the invention features a compound of formula I (See formula on paper copy)
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.
Nonsolvent Application of Ionic Liquids: Organo-Catalysis by 1-Alkyl-3-methylimidazolium Cation Based Room-Temperature Ionic Liquids for Chemoselective <i>N</i>-<i>tert</i>-Butyloxycarbonylation of Amines and the Influence of the C-2 Hydrogen on Catalytic Efficiency
作者:Anirban Sarkar、Sudipta Raha Roy、Naisargee Parikh、Asit K. Chakraborti
DOI:10.1021/jo201102q
日期:2011.9.2
1-Alkyl-3-methylimidazolium cation based ionicliquids efficiently catalyze N-tert-butyloxycarbonylation of amines with excellent chemoselectivity. The catalytic role of the ionicliquid is envisaged as “electrophilic activation” of di-tert-butyl dicarbonate (Boc2O) through bifurcated hydrogen bond formation with the C-2 hydrogen of the 1-alkyl-3-methylimidazolium cation and has been supported by a
1-烷基-3-甲基咪唑鎓阳离子类离子液体有效地催化ñ -叔胺的-butyloxycarbonylation具有优良的化学选择性。所述离子液体的催化作用是设想为二的“亲电活化”叔丁基酯(BOC 2 O)通过分叉氢键的形成与1-烷基-3-甲基咪唑鎓阳离子的和C-2的氢已由咪唑C-2氢1-丁基-3-甲基咪唑鎓双(三氟甲基磺酰)亚胺([BMIM] [NTF的的低磁场移位支撑2从δ8.39]),以8.66的中的Boc存在2于O 11 H NMR和无C-2氢的1-丁基-2,3-二甲基咪唑鎓离子液体的催化效率急剧降低。与芳族和脂族胺反应所需的不同时间为分子间和分子内竞争期间选择性形成N - t- Boc提供了手段。在伯脂族胺的存在下,已经与仲脂族胺形成了优选的N - t- Boc。比较N - t -Boc与常见底物的催化效率,发现[bmim] [NTf 2 ]优于已报道的路易斯酸催化剂。