306937-14-4Relevant articles and documents
Nonsolvent application of ionic liquids: Organo-catalysis by 1-alkyl-3-methylimidazolium cation based room-temperature ionic liquids for chemoselective N-tert-butyloxycarbonylation of amines and the influence of the C-2 hydrogen on catalytic efficiency
Sarkar, Anirban,Roy, Sudipta Raha,Parikh, Naisargee,Chakraborti, Asit K.
experimental part, p. 7132 - 7140 (2011/10/08)
1-Alkyl-3-methylimidazolium cation based ionic liquids efficiently catalyze N-tert-butyloxycarbonylation of amines with excellent chemoselectivity. The catalytic role of the ionic liquid 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 downfield shift of the imidazolium C-2 hydrogen of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][NTf2]) from δ 8.39 to 8.66 in the presence of Boc2O in the 1H NMR and a drastic reduction of the catalytic efficiency with 1-butyl-2,3-dimethylimidazolium ionic liquids that are devoid of the C-2 hydrogen. The differential time required for reaction with aromatic and aliphatic amines has offered means for selective N-t-Boc formation during inter and intramolecular competitions. Preferential N-t-Boc formation with secondary aliphatic amine has been achieved in the presence of primary aliphatic amine. Comparison of the catalytic efficiency for N-t-Boc formation with a common substrate revealed that [bmim][NTf2] is superior to the reported Lewis acid catalysts.
PEG-mediated facile protocol for N-Boc protection of amines
Siddaiah,Basha,Padma Rao,Viplava Prasad,Suryachendra Rao
experimental part, p. 1127 - 1129 (2011/02/28)
We have reported an efficient and eco-friendly protocol for the protection of various structurally and electronically divergent aryl and aliphatic amines using (Boc)2O in the presence of PEG-400 at room temperature. The reaction gave excellent
Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for N-tert-butoxycarbonylation of amines under solvent-free conditions at room temperature
Chankeshwara, Sunay V.,Chakraborti, Asit K.
, p. 1087 - 1091 (2007/10/03)
Commercially available copper(II) tetrafluoroborate hydrate was found to be a highly efficient catalyst for chemoselective N-tert-butoxycarbonylation of amines with di-tert-butyl dicarbonate under solvent-free conditions and at room temperature. Various aromatic amines were protected as their N-tert-butyl carbamates in high yields and in short times. No competitive side reactions such as isocyanate, urea, and N,N-di-t-Boc formation was observed. Chemoselective N-tert-butoxycarbonylation was achieved with substrates bearing OH and SH groups. Chiral α-amino acid esters afforded the corresponding N-t-Boc derivatives in excellent yields.
HClO4-SiO2 as a new, highly efficient, inexpensive and reusable catalyst for N-tert-butoxycarbonylation of amines
Chakraborti, Asit K.,Chankeshwara, Sunay V.
, p. 2769 - 2771 (2008/03/28)
Perchloric acid adsorbed on silica-gel (HClO4-SiO2) 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. The Royal Society of Chemistry 2006.
Catalyst-free chemoselective N-tert-butyloxycarbonylation of amines in water
Chankeshwara, Sunay V.,Chakraborti, Asit K.
, p. 3259 - 3262 (2007/10/03)
Catalyst-free N-tert-butyloxycarbonylation of amines in water is reported. The N-t-Boc derivatives were formed chemoselectively without any isocyanate, urea, N,N-di-t-Boc, and O/S-t-Boc as side products. Chiral amines, esters of α-amino acids, and β-amino alcohol afforded optically pure N-t-Boc derivatives. Amino alcohol and 2-aminophenol afforded the N-t-Boc derivative without oxazolidinone formation. Selectivity was observed during competition of aromatic amine vs aliphatic amine, amine vs amino acid ester, amine vs amino alcohol, and primary amine vs secondary amine.
HETEROARYL- SUBSTITUTED PYRROLO` 2, 3- B! PYRIDINE DERIVATIVES AS CRF RECEPTOR ANTAGONISTS
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Page/Page column 38, (2010/02/07)
The present invention provides compounds of formula (I) including stereoisomers, prodrugs and pharmaceutically acceptable salts or solvates thereof, to processes for their preparation, to pharmaceutical compositions containing them and to their use in the treatment of conditions mediated by corticotropin-releasing factor (CRF).