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A Simple and Efficient Green Method for the Deprotection of N-Boc in Various Structurally Diverse Amines under Water-mediated Catalyst-free Conditions  [cached]
Cheraiet Zinelaabidine,Ouarna Souad,Jamel Zoubir,Berredjem Malika
International Journal of Chemistry , 2012, DOI: 10.5539/ijc.v4n3p73
Abstract: A simple, efficient and eco-friendly protocol has been developed for the deprotection of N-Boc on structurally diverse amines. Selective removal of N-Boc groups was achieved with excellent yields using water around reflux temperatures. In the absence of any additional reagents, this method represents a reasonable alternative to previously reported deprotection procedures.
Sulphated Zirconia as an Eco-Friendly Catalyst in Acylal Preparation under Solvent-Free Conditions, Acylal Deprotection Assisted by Microwaves, and the Synthesis of Anhydro-Dimers of o-Hydroxybenzaldehydes  [PDF]
Laura Nadxieli Palacios-Grijalva,Deysi Y. Cruz-González,Leticia Lomas-Romero,Eduardo González-Zamora,Gerardo Ulibarri,Guillermo E. Negrón-Silva
Molecules , 2009, DOI: 10.3390/molecules14104065
Abstract: A solvent-free approach is described for the regioselective synthesis of acylals (1,1-diacetates) in shorter reaction times and higher yields, compared to conventional methodology using solvents. In the protection reaction of the o-hydroxybenzaldehyde the formation of acetyl compounds and anhydro-dimers was observed. The deprotection reaction involves microwave (MW) exposure of diluted reactants in the presence of solid sulphated zirconia (SZ) catalyst that can be easily recovered and reused. The sulphated zirconia was recycled several times without any loss of activity.
Facile and mild deprotection of semicarbazones under solvent-free conditions with N,N,N',N'-tetrabromo-benzene-1,3-disulfonylamide
Ghorbani-Vaghei, Ramin;Shahbazee, Elham;
Journal of the Brazilian Chemical Society , 2005, DOI: 10.1590/S0103-50532005000400025
Abstract: n,n,n',n'-tetrabromo-benzene-1,3-disulfonylamide [tbbda] was reacted with semicarbazones and converts them to their corresponding carbonyl compounds in excellent yields under solvent-free conditions.
Efficient deprotection of Boc group in amines and sulfamides using Dawson heteropolyacid catalyst  [cached]
Roubila Belghiche,Zinelaabidine Cheraiet,Malika Berredjem,Mostefa Abbessi
European Journal of Chemistry , 2012, DOI: 10.5155/eurjchem.3.3.305-309.610
Abstract: A series of sulfamides containing two protecting groups have been synthesized starting from N-benzoylaminoacids derivatives of (glycine, alanine, valine, leucine, phenylalanine), chlorosulfonylisocyanate and primary amines. Selective deprotection of the cyclic or linear sulfamides and amines has been achieved by treatment with heteropolyacid, which is easily recoverable and reusable. This method represents a reasonable alternative to the previous reported deprotection procedures.
Mechanochemical Solvent-Free and Catalyst-Free One-Pot Synthesis of Pyrano[2,3-d]Pyrimidine-2,4(1H,3H)-Diones with Quantitative Yields  [PDF]
Sara Mashkouri,M. Reza Naimi-Jamal
Molecules , 2009, DOI: 10.3390/molecules14010474
Abstract: Solvent-free synthesis of pyrano[2,3-d]pyrimidine-2,4(1H,3H)-diones by ball-milling and without any catalyst is described. This method provides several advantages such as being environmentally friendly, using a simple workup procedure, and affording high yields.
A Mild and Efficient Method for the Synthesis of Acylals from Aromatic Aldehydes and Their Deprotections Catalyzed by Synthetic Phosphates under Solvent-Free Conditions  [PDF]
Fathallaah Bazi, Bahija Mounir, Mohammed Hamza, Said Sebti
Green and Sustainable Chemistry (GSC) , 2018, DOI: 10.4236/gsc.2018.84023
Abstract: An efficient and clean preparation of acylals from aromatic aldehydes in the presence of synthetic phosphates (flourapatite and hydroxyapatite doped with ZnCl2 and ZnBr2) and acetic anhydride was achieved easily in high yields (86% - 97%) at room temperature under solvent-free conditions. Deprotection of the resulting acylals has also been attained by using the same catalysts under microwave irradiation. This method consistently has advantage of excellent yields (82% - 96%) and a short reaction time (3 - 4 min).
Aqueous Microwave-Assisted Solid-Phase Synthesis Using Boc-Amino Acid Nanoparticles  [PDF]
Keiko Hojo,Natsuki Shinozaki,Yoshimi Nozawa,Yoshinobu Fukumori,Hideki Ichikawa
Applied Sciences , 2013, DOI: 10.3390/app3030614
Abstract: We have previously developed water-based microwave (MW)-assisted peptide synthesis using Fmoc-amino acid nanopaticles. It is an organic solvent-free, environmentally friendly method for peptide synthesis. Here we describe water-based MW-assisted solid-phase synthesis using Boc-amino acid nanoparticles. The microwave irradiation allowed rapid solid-phase reaction of nanoparticle reactants on the resin in water. We also demonstrated the syntheses of Leu-enkephalin, Tyr-Gly-Gly-Phe-Leu-OH, and difficult sequence model peptide, Val-Ala-Val-Ala-Gly-OH, using our water-based MW-assisted protocol with Boc-amino acid nanoparticles.
N-tert-Butoxycarbonylation of Structurally Diverse Amines and Sulfamides under Water-Mediated Catalyst-Free Conditions  [PDF]
Zinelaabine Cheraiet,Souad Ouarna,Sihem Hessainia,Malika Berredjem,Nour-Eddine Aouf
ISRN Organic Chemistry , 2012, DOI: 10.5402/2012/404235
Abstract: A simple, efficient, and eco-friendly protocol for the N-Boc protection of the amine moiety in a variety of compounds with di-tert-butyl dicarbonate under water-acetone catalyst-free conditions is described. The corresponding monocarbamate is obtained in excellent yields on short reaction times. No competitive side reactions such as isocyanate urea and O-Boc were observed. This method represents a reasonable alternative to the previous reported protection procedures. 1. Introduction The protection of a functional group can be essential in the chemistry of poly functionalised molecules, when a reaction has to be carried out in a part of the compounds without the rest perturbing of the molecule. The development of simple and eco-friendly methods for the protection and deprotection of functional group continues to be a significant tool in synthetic chemistry of polyfunctional molecules [1, 2]. Nitrogen protection continues to attach a great deal of attention in a wide range of chemical fields, such as peptides, nucleosides, heterocyclic compounds, and other natural products. The protection of amines with tert-butyloxycarbonyl (Boc) group is a widely used reaction in organic synthesis because of its inertness toward catalytic hydrogenolysis and resistance toward hydrolysis under most basic conditions and nucleophilic reagents [3]. N-Boc deprotection is generally achieved under mild acidic conditions such as trifluroacetic acid (TFA), aqueous phosphoric acid in THF [4], or Lewis acid [5]. The deprotection can be carried out with montmorillonite K.10 clay [6], silica gel at low pressure [7], and by thermolytic cleavage although at high temperature [8, 9]. The tert-butyloxycarbonyl (Boc) is easily introduced using commercially available di-tert-butyldicarbonate (tert-BuOCO)2O under standard basic conditions. Various reagents and methods have been developed in the last years for the N-tert-butyloxycarbonylation of amines. Most are carried out in the presence of an organic or inorganic base. Amines are converted to N-tert-Boc derivatives by reaction with di-tert-butyldicarbonate (Boc)2O in the presence of: 4-(dimethylamino)-1-tert-butylcarbonylpyridinium DMAP [10], 4-(dimethylamino)-1-tert-butylcarbonyl pyridinium chloride [11] or tetrafluoroborate in aq NaOH [12], tert-butyl-2-pyridyl carbonate in the presence of K2CO3 in H2O-DMF [13] or tert-butyl 1-chloroethyl carbonate in presence of K2CO3 in H2O-THF [14], 2-tert-butyloxycarbonyloxyimino-2-phenylacetonitrile in the presence of Et3N in H2O-dioxane [15]. However, these protocols have various drawbacks as long
Microwave accelerated solvent-free synthesis of flavanones
Sagrera, Gabriel J.;Seoane, Gustavo A.;
Journal of the Brazilian Chemical Society , 2005, DOI: 10.1590/S0103-50532005000500026
Abstract: microwave irradiation of chalcones under solvent-free conditions resulted in a "green-chemistry" procedure for the preparation of flavanones in very good yields. using an unmodified household microwave oven, different mineral supports and catalysts were tested. by irradiation of chalcones with 30% tfa over silica gel, eleven known flavanones and five new compounds were prepared in high yields.
Fast Solvent-free Alkylation of Amides and Lactams under Microwave Irradiation
Dariusz Bogdal
Molecules , 1999, DOI: 10.3390/41100333
Abstract: N-Substituted amides and lactams are rapidly N-alkylated under solvent-free phase-transfer catalytic conditions using microwaves.
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