The Experts below are selected from a list of 336 Experts worldwide ranked by ideXlab platform
Bhubaneswar Mandal - One of the best experts on this subject based on the ideXlab platform.
-
ethyl 2 tert butoxycarbonyloxyimino 2 cyanoacetate boc oxyma an efficient reagent for the racemization free synthesis of ureas carbamates and thiocarbamates via Lossen Rearrangement
Advanced Synthesis & Catalysis, 2017Co-Authors: Srinivasa Rao Manne, Kishore Thalluri, Rajat Subhra Giri, Jyoti Chandra, Bhubaneswar MandalAbstract:Boc-Oxyma (Ethyl 2-(tert-butoxycarbonyloxyimino)-2-cyanoacetate) has been reported previously as an efficient coupling reagent for the synthesis of amides, peptides, esters, thioesters and hydroxamic acids. It is known for its excellent racemization suppression capability, and also as an environment friendly reagent as it generates only Oxyma as solid byproduct that can be recovered easily and recycled for the synthesis of the same reagent. In this update, we report a simple, efficient, environment friendly, chemoselective and racemization free method for the synthesis of ureas, carbamates and thiocarbamates from hydroxamic acids via Lossen Rearrangement by using Boc-Oxyma. We have achieved racemization free di- and tri-peptidyl ureas with very good yield by using this protocol. A rigorous mechanistic investigation is also incorporated.
-
ethyl 2 cyano 2 4 nitrophenylsulfonyloxyimino acetate mediated Lossen Rearrangement single pot racemization free synthesis of hydroxamic acids and ureas from carboxylic acids
ChemInform, 2014Co-Authors: Kishore Thalluri, Srinivasa Rao Manne, Dharm Dev, Bhubaneswar MandalAbstract:Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (ECN) is employed as a new coupling reagent for the preparation of hydroxamic acids and their subsequent Lossen Rearrangement into the corresponding isocyanates.
-
ethyl 2 cyano 2 4 nitrophenylsulfonyloxyimino acetate mediated Lossen Rearrangement single pot racemization free synthesis of hydroxamic acids and ureas from carboxylic acids
Journal of Organic Chemistry, 2014Co-Authors: Kishore Thalluri, Srinivasa Rao Manne, Dharm Dev, Bhubaneswar MandalAbstract:Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (4-NBsOXY) mediated Lossen Rearrangement and its application for the synthesis of ureas is demonstrated. Required hydroxamic acids for the Lossen Rearrangements were synthesized from carboxylic acids using the same reagent. Finally, reaction of an amine with the produced isocyanate resulted in urea. Good yields without racemization were achieved under milder and simpler reaction conditions. Reactions are compatible with common N-protecting groups, such as Boc, Fmoc, Cbz, and benzyl, as well as various OH protecting groups, such as tBu and Bzl. Conversion from carboxylic acid to urea is achieved in one pot. Most importantly, byproducts Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] and 4-nitrobenzenesulfonic acid can be recovered easily and can be recycled to prepare the reagent. Thus, the method is environmentally friendly and cost-effective.
-
Ethyl 2‑Cyano-2-(4-nitrophenylsulfonyloxyimino)acetate-Mediated Lossen Rearrangement: Single-Pot Racemization-Free Synthesis of Hydroxamic Acids and Ureas from Carboxylic Acids
2014Co-Authors: Kishore Thalluri, Srinivasa Rao Manne, Dharm Dev, Bhubaneswar MandalAbstract:Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (4-NBsOXY) mediated Lossen Rearrangement and its application for the synthesis of ureas is demonstrated. Required hydroxamic acids for the Lossen Rearrangements were synthesized from carboxylic acids using the same reagent. Finally, reaction of an amine with the produced isocyanate resulted in urea. Good yields without racemization were achieved under milder and simpler reaction conditions. Reactions are compatible with common N-protecting groups, such as Boc, Fmoc, Cbz, and benzyl, as well as various OH protecting groups, such as tBu and Bzl. Conversion from carboxylic acid to urea is achieved in one pot. Most importantly, byproducts Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] and 4-nitrobenzenesulfonic acid can be recovered easily and can be recycled to prepare the reagent. Thus, the method is environmentally friendly and cost-effective
Vommina V Sureshbabu - One of the best experts on this subject based on the ideXlab platform.
-
1 propanephosphonic acid cyclic anhydride t3p as an efficient promoter for the Lossen Rearrangement application to the synthesis of urea and carbamate derivatives
ChemInform, 2010Co-Authors: B Vasantha, Hosahalli P Hemantha, Vommina V SureshbabuAbstract:A convenient procedure is presented for the conversion of aromatic acids and amino acids into hydroxamates using T3P as activator.
-
1 propanephosphonic acid cyclicanhydride t3p as an efficient promoter for the Lossen Rearrangement application to the synthesis of urea and carbamate derivatives
Synthesis, 2010Co-Authors: B Vasantha, Hosahalli P Hemantha, Vommina V SureshbabuAbstract:The synthesis of hydroxamic acids starting from carboxylic acids employing 1-propanephosphonic acid cyclic anhydride (T3P) activation is described. Application of ultrasonication accelerates this conversion. Further, the T3P has also been employed to activate the hydroxamates, leading to isocyanates via the Lossen Rearrangement. The isocyanates were trapped with suitable nucleophiles to afford the corresponding ureas and carbamates. © Georg Thieme Verlag Stuttgart New York.
-
application of carbodiimide mediated Lossen Rearrangement for the synthesis of alpha ureidopeptides and peptidyl ureas employing n urethane alpha amino peptidyl hydroxamic acids
Organic and Biomolecular Chemistry, 2009Co-Authors: N Narendra, G Chennakrishnareddy, Vommina V SureshbabuAbstract:Application of the Lossen Rearrangement to the synthesis of N-urethane protected alpha-peptidyl ureas and ureidopeptides is reported. The carbodiimide mediated Rearrangement of N-Boc/Z/Fmoc protected alpha-amino/peptide hydroxamic acids into isocyanates and coupling of the latter with the amino acid esters/peptide esters have been accomplished in a single-pot to obtain good yields of urea products. Synthesis of the ureidoalanine derivatives via the hydroxamate derivatives of N-protected aspartic acid has also been carried out using the same procedure.
Michael A R Meier - One of the best experts on this subject based on the ideXlab platform.
-
fully renewable non isocyanate polyurethanes via the Lossen Rearrangement
Macromolecular Rapid Communications, 2021Co-Authors: Luca Filippi, Michael A R MeierAbstract:In this work, a straightforward and efficient synthesis approach to renewable non‐isocyanate polyurethanes (NIPUs) is described. For this purpose, suitable and renewable carbamate monomers, possessing two double bonds, are synthesized from hydroxamic fatty acid derivatives via the Lossen Rearrangement in a one‐step synthesis, and sustainable dithiols are synthesized from dialkenes derived from renewable feedstock (i.e., limonene and 1,4‐cyclohexadiene). Subsequently, the comonomers are polymerized with the highly efficient thiol–ene reaction to produce NIPUs with M$_{n}$ values up to 26 kg mol$^{−1}$ bearing thioether linkages. The main side product of the Lossen Rearrangement, a symmetric urea, can also be polymerized in the same fashion. Important in the view of sustainability, the monomer mixture can also be used directly, without separation. The obtained polymers are characterized by NMR, attenuated total reflection‐infrared spectroscopy, differential scanning calorimetry, and size exclusion chromatography.
-
olefin cross metathesis as a valuable tool for the preparation of renewable polyesters and polyamides from unsaturated fatty acid esters and carbamates
Green Chemistry, 2014Co-Authors: Matthias Winkler, Michael A R MeierAbstract:Olefin cross-metathesis of unsaturated fatty acid methyl ester (FAME) derived benzyl carbamates with methyl acrylate is described. The obtained by-product, an α,β-unsaturated ester, was further modified via thia-Michael addition reactions in order to synthesize branched AA-type or AB-type monomers for the preparation of polyesters, which are tuneable by oxidation. Cross-metathesis of fatty acid derived carbamates was used as a novel approach to prepare linear AB-type monomers, which can be used for the preparation of renewable polyamides PA11, PA12 and PA15. The necessary fatty acid carbamates were prepared by applying a catalytic Lossen Rearrangement procedure. The presented synthesis strategy has potential for the bio-sourced preparation of monomers for the production of polyamides. All prepared polymers were fully characterized by NMR, SEC, and DSC analyses. Additionally, the Young's modulus of the prepared long-chain polyamide PA15 was determined.
-
renewable non isocyanate based thermoplastic polyurethanes via polycondensation of dimethyl carbamate monomers with diols
Macromolecular Rapid Communications, 2013Co-Authors: Maike Unverferth, Oliver Kreye, Alexander Prohammer, Michael A R MeierAbstract:1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD)-catalyzed polycondensation reactions of fatty acid derived dimethyl dicarbamates and diols are introduced as a versatile, non-isocyanate route to renewable polyurethanes. The key step for the synthesis of dimethyl carbamate monomers from plant-oil-derived dicarboxylic acids is based on a sustainable base-catalyzed Lossen Rearrangement. The formed polyurethanes with molecular weights up to 25 kDa are characterized by SEC, DSC, and NMR analysis.
-
introducing catalytic Lossen Rearrangements sustainable access to carbamates and amines
ChemInform, 2013Co-Authors: Oliver Kreye, Sarah Wald, Michael A R MeierAbstract:A novel, highly efficient and environmentally benign procedure of the Lossen Rearrangement is developed.
-
introducing catalytic Lossen Rearrangements sustainable access to carbamates and amines
Advanced Synthesis & Catalysis, 2013Co-Authors: Oliver Kreye, Sarah Wald, Michael A R MeierAbstract:A new, highly efficient and environmentally benign catalytic variant of the Lossen Rearrangement is described. Dimethyl carbonate (DMC) as green activation reagent of hydroxamic acids in presence of catalytic amounts of tertiary amine bases {1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-biazabicyclo 5.4.0 undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), and triethylamine} and small quantities of methanol initiate the Rearrangement. Methyl carbamates were obtained in good to moderate yields when aliphatic hydroxamic acids were employed in this catalytic Lossen Rearrangement; under the same conditions aromatic hydroxamic acids yielded anilines. Notably, the mixture of DMC/methanol was recycled several times without observing decreased yields, thus minimizing the produced waste. Moreover, several other organic carbonates were successfully employed in the introduced catalytic Lossen Rearrangement procedure.
Kishore Thalluri - One of the best experts on this subject based on the ideXlab platform.
-
ethyl 2 tert butoxycarbonyloxyimino 2 cyanoacetate boc oxyma an efficient reagent for the racemization free synthesis of ureas carbamates and thiocarbamates via Lossen Rearrangement
Advanced Synthesis & Catalysis, 2017Co-Authors: Srinivasa Rao Manne, Kishore Thalluri, Rajat Subhra Giri, Jyoti Chandra, Bhubaneswar MandalAbstract:Boc-Oxyma (Ethyl 2-(tert-butoxycarbonyloxyimino)-2-cyanoacetate) has been reported previously as an efficient coupling reagent for the synthesis of amides, peptides, esters, thioesters and hydroxamic acids. It is known for its excellent racemization suppression capability, and also as an environment friendly reagent as it generates only Oxyma as solid byproduct that can be recovered easily and recycled for the synthesis of the same reagent. In this update, we report a simple, efficient, environment friendly, chemoselective and racemization free method for the synthesis of ureas, carbamates and thiocarbamates from hydroxamic acids via Lossen Rearrangement by using Boc-Oxyma. We have achieved racemization free di- and tri-peptidyl ureas with very good yield by using this protocol. A rigorous mechanistic investigation is also incorporated.
-
ethyl 2 cyano 2 4 nitrophenylsulfonyloxyimino acetate mediated Lossen Rearrangement single pot racemization free synthesis of hydroxamic acids and ureas from carboxylic acids
ChemInform, 2014Co-Authors: Kishore Thalluri, Srinivasa Rao Manne, Dharm Dev, Bhubaneswar MandalAbstract:Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (ECN) is employed as a new coupling reagent for the preparation of hydroxamic acids and their subsequent Lossen Rearrangement into the corresponding isocyanates.
-
ethyl 2 cyano 2 4 nitrophenylsulfonyloxyimino acetate mediated Lossen Rearrangement single pot racemization free synthesis of hydroxamic acids and ureas from carboxylic acids
Journal of Organic Chemistry, 2014Co-Authors: Kishore Thalluri, Srinivasa Rao Manne, Dharm Dev, Bhubaneswar MandalAbstract:Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (4-NBsOXY) mediated Lossen Rearrangement and its application for the synthesis of ureas is demonstrated. Required hydroxamic acids for the Lossen Rearrangements were synthesized from carboxylic acids using the same reagent. Finally, reaction of an amine with the produced isocyanate resulted in urea. Good yields without racemization were achieved under milder and simpler reaction conditions. Reactions are compatible with common N-protecting groups, such as Boc, Fmoc, Cbz, and benzyl, as well as various OH protecting groups, such as tBu and Bzl. Conversion from carboxylic acid to urea is achieved in one pot. Most importantly, byproducts Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] and 4-nitrobenzenesulfonic acid can be recovered easily and can be recycled to prepare the reagent. Thus, the method is environmentally friendly and cost-effective.
-
Ethyl 2‑Cyano-2-(4-nitrophenylsulfonyloxyimino)acetate-Mediated Lossen Rearrangement: Single-Pot Racemization-Free Synthesis of Hydroxamic Acids and Ureas from Carboxylic Acids
2014Co-Authors: Kishore Thalluri, Srinivasa Rao Manne, Dharm Dev, Bhubaneswar MandalAbstract:Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (4-NBsOXY) mediated Lossen Rearrangement and its application for the synthesis of ureas is demonstrated. Required hydroxamic acids for the Lossen Rearrangements were synthesized from carboxylic acids using the same reagent. Finally, reaction of an amine with the produced isocyanate resulted in urea. Good yields without racemization were achieved under milder and simpler reaction conditions. Reactions are compatible with common N-protecting groups, such as Boc, Fmoc, Cbz, and benzyl, as well as various OH protecting groups, such as tBu and Bzl. Conversion from carboxylic acid to urea is achieved in one pot. Most importantly, byproducts Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] and 4-nitrobenzenesulfonic acid can be recovered easily and can be recycled to prepare the reagent. Thus, the method is environmentally friendly and cost-effective
Srinivasa Rao Manne - One of the best experts on this subject based on the ideXlab platform.
-
ethyl 2 tert butoxycarbonyloxyimino 2 cyanoacetate boc oxyma an efficient reagent for the racemization free synthesis of ureas carbamates and thiocarbamates via Lossen Rearrangement
Advanced Synthesis & Catalysis, 2017Co-Authors: Srinivasa Rao Manne, Kishore Thalluri, Rajat Subhra Giri, Jyoti Chandra, Bhubaneswar MandalAbstract:Boc-Oxyma (Ethyl 2-(tert-butoxycarbonyloxyimino)-2-cyanoacetate) has been reported previously as an efficient coupling reagent for the synthesis of amides, peptides, esters, thioesters and hydroxamic acids. It is known for its excellent racemization suppression capability, and also as an environment friendly reagent as it generates only Oxyma as solid byproduct that can be recovered easily and recycled for the synthesis of the same reagent. In this update, we report a simple, efficient, environment friendly, chemoselective and racemization free method for the synthesis of ureas, carbamates and thiocarbamates from hydroxamic acids via Lossen Rearrangement by using Boc-Oxyma. We have achieved racemization free di- and tri-peptidyl ureas with very good yield by using this protocol. A rigorous mechanistic investigation is also incorporated.
-
ethyl 2 cyano 2 4 nitrophenylsulfonyloxyimino acetate mediated Lossen Rearrangement single pot racemization free synthesis of hydroxamic acids and ureas from carboxylic acids
ChemInform, 2014Co-Authors: Kishore Thalluri, Srinivasa Rao Manne, Dharm Dev, Bhubaneswar MandalAbstract:Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (ECN) is employed as a new coupling reagent for the preparation of hydroxamic acids and their subsequent Lossen Rearrangement into the corresponding isocyanates.
-
ethyl 2 cyano 2 4 nitrophenylsulfonyloxyimino acetate mediated Lossen Rearrangement single pot racemization free synthesis of hydroxamic acids and ureas from carboxylic acids
Journal of Organic Chemistry, 2014Co-Authors: Kishore Thalluri, Srinivasa Rao Manne, Dharm Dev, Bhubaneswar MandalAbstract:Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (4-NBsOXY) mediated Lossen Rearrangement and its application for the synthesis of ureas is demonstrated. Required hydroxamic acids for the Lossen Rearrangements were synthesized from carboxylic acids using the same reagent. Finally, reaction of an amine with the produced isocyanate resulted in urea. Good yields without racemization were achieved under milder and simpler reaction conditions. Reactions are compatible with common N-protecting groups, such as Boc, Fmoc, Cbz, and benzyl, as well as various OH protecting groups, such as tBu and Bzl. Conversion from carboxylic acid to urea is achieved in one pot. Most importantly, byproducts Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] and 4-nitrobenzenesulfonic acid can be recovered easily and can be recycled to prepare the reagent. Thus, the method is environmentally friendly and cost-effective.
-
Ethyl 2‑Cyano-2-(4-nitrophenylsulfonyloxyimino)acetate-Mediated Lossen Rearrangement: Single-Pot Racemization-Free Synthesis of Hydroxamic Acids and Ureas from Carboxylic Acids
2014Co-Authors: Kishore Thalluri, Srinivasa Rao Manne, Dharm Dev, Bhubaneswar MandalAbstract:Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (4-NBsOXY) mediated Lossen Rearrangement and its application for the synthesis of ureas is demonstrated. Required hydroxamic acids for the Lossen Rearrangements were synthesized from carboxylic acids using the same reagent. Finally, reaction of an amine with the produced isocyanate resulted in urea. Good yields without racemization were achieved under milder and simpler reaction conditions. Reactions are compatible with common N-protecting groups, such as Boc, Fmoc, Cbz, and benzyl, as well as various OH protecting groups, such as tBu and Bzl. Conversion from carboxylic acid to urea is achieved in one pot. Most importantly, byproducts Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] and 4-nitrobenzenesulfonic acid can be recovered easily and can be recycled to prepare the reagent. Thus, the method is environmentally friendly and cost-effective
