71872-03-2Relevant articles and documents
Rare-Earth-Metal-Complex-Catalyzed Hydroalkoxylation and Tandem Hydroalkoxylation/Cyclohydroamination of Isocyanates: Synthesis of Carbamates and Oxazolidinones
Zhu, Xiancui,Qi, Yawen,Yang, Yuanqing,Guo, Dianjun,Huang, Zeming,Zhang, Lijun,Wei, Yun,Zhou, Shuangliu,Wang, Shaowu
, p. 3202 - 3211 (2022/02/23)
Novel N,N,N-tridentate β-diketiminato rare-earth-metal dialkyl complexes LRE(CH2SiMe3)2 [RE = Y (1a), Gd (1b), Yb (1c), Lu (1d); L = MeC(NDipp)CHC(Me)N(CH2)2NC4H8, where Dipp = 2,6-iPr2C6H3] have been conveniently synthesized by one step from reactions of the rare-earth-metal trialkyl complexes RE(CH2SiMe3)3(THF)2 (THF = tetrahydrofuran) with a pyrrolidine-functionalized β-diketiminate HL, and their catalytic behaviors toward hydroalkoxylation and tandem hydroalkoxylation/cyclohydroamination of isocyanates have been described. These rare-earth-metal catalysts exhibited high efficiency in the hydroalkoxylation of isocyanates, providing a variety of N-alkyl and N-aryl carbamate derivatives under mild reaction conditions with a rather low catalyst loading (0.04 mol %). More significantly, they can promote a tandem hydroalkoxylation/cyclohydroamination reaction between terminal and internal propargylic alcohols with substituted arylisocyanates, leading to the efficient synthesis of methylene and (Z)-selective arylidene oxazolidinones in good-to-high yields via consecutive C-O and C-N bond formation. The stoichiometric reaction of 1a with p-tolylisocyanate generated an unusual dinuclear yttrium complex, {[η2-(4-MePhNCO)(CH2SiMe3)]Y[μ-η2:η1:η1-(4-MePhNCO)CC(Me)(NDipp)C(Me)N(CH2)2NC4H8]}2 (7a), with two different amidate units, which underwent an sp2 C-H bond activation of the β-diketiminato backbone, followed by the insertion of isocyanate.
Iron(III)triflate as a highly efficient, recyclable and green catalyst for the N-Boc protection of amines
Feng, Chengliang,Chu, Ningning,Zhang, Shuguang,Cai, Jin,Chen, Junqing,Hu, Huayou,Ji, Min
, p. 757 - 760 (2014/01/23)
Iron (III) triflate was used as an efficient catalyst for N-t-butoxycarbonylation of amines with di-t-butyl dicarbonate under solvent-free conditions at room temperature. Various aliphatic, aromatic, heterocyclic amines and aminols were protected as their corresponding mono-carbamates in excellent yields and short reaction times. Only two of the 23 monocarbamates were new. No competitive side reactions such as isocyanate, urea, nor N,N-di-Boc formation were observed. The reported method is mild and has the advantages of low cost, chemoselectivity and, because no solvent is used and the catalyst can be recycled, it is classifiable as a green procedure.
Solvent free N-Boc protection of amines using amberlystr a 21 solid base resin as a reusable heterogeneous catalyst
Tekale, Sunil U.,Kauthale, Sushama S.,Pawar, Rajendra P.
, p. 1619 - 1623 (2013/09/12)
An efficient, environmentally benign, highly facile and convenient synthetic protocol for the selective t-butyl carboxylation of aliphatic, aromatic and heterocyclic amines using AmberlystR A 21 catalyst; a mild basic solid resin under solvent free conditions is reported. This method explores several advantages such as reusability of the heterogeneous catalyst, cleaner reaction profile, mild and solvent free system, short reaction time, operational simplicity, high conversions , excellent product yields and low cost of the catalyst. Furthermore since the catalyst is mild basic, decomposition of the carbamate formed is not observed if the reaction is continued for prolonged time as in the case of Lewis acid catalyzed N-Boc protection. This makes the present protocol a useful and attractive for N-Boc protection of amines.
Mild and high-yielding molybdenum(VI) dichloride dioxide-catalyzed formation of Mono-, Di-, Tri-, and tetracarbamates from alcohols and aromatic or aliphatic isocyanates
Stock, Christian,Brueckner, Reinhard
, p. 2309 - 2330 (2012/11/07)
Both molybdenum(VI) dichloride dioxide (MoO2Cl2) and its dimethylformamide (DMF) complex catalyze the addition of alcohols to isocyanates giving carbamates. Most additions proceeded to completion at room temperature within 20 min using as little as 0.1 mol% of the catalyst when working on a 1-mmol scale or just 100 ppm working on a 20-mmol scale. Sterically encumbered substrates reacted to completion when 1 mol% of the catalyst was employed. Diols, triols, and tetraols reacted with monoisocyanates likewise, as did monofunctional alcohols and diisocyanates. These pairings furnished di-, tri-, tetra-, and dicarbamates, respectively. Reactants, which were poorly soluble in CH2Cl2 at room temperature required elevating the temperature and possibly choosing a higher-boiling solvent (ClCH 2CH2Cl, DMF) as well. Additions of diols to diisocyanates were feasible, too, giving polycarbamates as we presume. Copyright
Magnetic nanoparticles catalyzed N-tert-butoxycarbonylation of Amines and amine derivatives
Akbari, Jafar,Sajirani, Soghra B.,Nezhad, Jafar M.,Heydari, Akbar
experimental part, p. 165 - 168 (2012/07/14)
A simple and efficient protocol for the chemoselective mono-N-Boc protection of various structurally diverse amines with di-tert-butyl dicarbonate using magnetically recoverable γ-Fe2O3@SiO 2 nanoparticles is reported. The catalyst can be easily recovered and recycled without a significant loss in the catalytic activity. No competitive side reactions, such as formation of isocyanate, urea, oxazolidinone, and N,N-di-Boc derivatives were obsereved.
Microwave assisted mild, rapid, solvent-less, and catalyst-free chemoselective N-tert-butyloxycarbonylation of amines
Dighe, Satish N.,Jadhav, Hemant R.
, p. 5803 - 5806 (2012/10/29)
Microwave assisted simple, rapid, solventless, and catalyst-free chemoselective method for the protection of amino group in aromatic, aliphatic, heterocyclic, aralkyl amines, phenyl hydrazine, and amino acid esters in good to excellent isolated yield (83-98%) in short reaction time (2-12 min) has been reported.
Simple and efficient method for n-boc protection of amines using PEG-400 as a reaction medium under mild conditions
Zeng, Hongyao,Li, Yongjia,Shao, Huawu
experimental part, p. 25 - 32 (2011/10/19)
Simple and efficient method for N-Boc protection of amines using PEG-400 as an ecofriendly reaction medium at room temperature is described. Various aromatic, heteroaromatic, and aliphatic amines were converted to the corresponding N-tert-butyl-carbamates in good to excellent yields in short times.
ZnO nanorods as an efficient and heterogeneous catalyst for N-Boc protection of amines and amine derivatives
Nouria, Azita,Akbari, Jafar,Heydaric, Akbar,Nouri, Arezu
experimental part, p. 38 - 42 (2012/05/04)
An efficient ZnO nano catalyst, which was readily prepared from Zn(CH3CO2)2, 2H2O and PVP by a chemical solution approach has successfully catalyzed N-tertbutoxy carbonylation of amines. The ZnO nanorods were successful and gave promising results for highly active and chemoselective as well as easily recyclable catalyst for the NBoc protection reaction of a wide variety of amines. The catalyst could be easily recycled for five times without noticeable decrease in catalytic activity. The ZnO nanocatalyst was characterized with XRD and SEM.
Exceptionally active catalysts for the formation of carbamates from alcohols and isocyanates: Molybdenum(VI) dichloride dioxide and its DMF complex
Stock, Christian,Brückner, Reinhard
scheme or table, p. 2429 - 2434 (2010/12/18)
Small amounts of MoO2Cl2 or MoO2Cl 2(DMF)2 catalyze carbamate formation from an alcohol and isocyanates: 0.1 mol% of the respective additive allow primary, secondary or tertiary alcohols to add to aliphatic or aromatic isocyanates of varied steric hindrance within 20 minutes at room temperature. Typically the corresponding carbamate resulted in 100% yield. Only particularly hindered substrates required 1.0 mol% of the catalyst while as little as 0.01% sufficed for the phenylcarbamoylation of menthol. Catalytic amounts of DMAP accelerate carbamate formation from certain alcohols and isocyanates, too. Georg Thieme Verlag Stuttgart · New York.
Thioglycoluril as a highly efficient, recyclable and novel organocatalyst for N-Boc protection of amines
Khaksar, Samad,Vahdat, Seyed Mohammad,Tajbakhsh, Mahmood,Jahani, Fatemeh,Heydari, Akbar
experimental part, p. 6388 - 6391 (2011/01/03)
A simple and efficient protocol for the chemoselective mono-N-Boc protection of various structurally diverse amines with di-tert-butyl dicarbonate using thioglycoluril as the catalyst is described. The catalyst can be readily separated from the reaction products by simple filtration and recovered for reuse. No competitive side reactions, such as formation of isocyanate, urea, oxazolidinone, and N,N-di-Boc derivatives were observed.
