Über den Umsatz aromatischer Isocyansäure‐ester mit organischen Säuren. I. Theorie und Anwendung der Reaktion für die präparative Darstellung von Säure‐anhydriden

Naegeli, C.; Tyabji, A.

doi:10.1002/hlca.193401701119

Cited by 62 publications

(3 citation statements)

References 14 publications

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“…That process may either occur via a rather strained zwitterionic intermediate (path a) or, by analogy to the reaction of isonitriles (RNC) and carboxylic acids, a more favorable pathway may involve a pseudopericyclic [1,3]-acyl rearrangement to an N -formyl amide intermediate (path b). A third pathway, mentioned mainly in older literature, − involves disproportionation of the initial carbamic–carboxylic anhydride adduct to urea and acid anhydride, which react with one another to an amide (path c). Importantly, it is noted that, for amide formation either via unimolecular rearrangement or via disproportionation of the carbamic–carboxylic anhydride adduct, the amount of the byproduct, CO 2 , should be stoichiometrically equivalent to the isocyanate groups reacting; if, however, the reaction takes the urea/anhydride route and stops there , the amount of CO 2 produced should be only 0.5 mol equivalents relative to the isocyanate groups reacting .…”

Section: Resultsmentioning

confidence: 99%

Nanoporous Polyurea from a Triisocyanate and Boric Acid: A Paradigm of a General Reaction Pathway for Isocyanates and Mineral Acids

et al. 2015

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Isocyanates react with carboxylic acids and yield amides. As reported herewith, however, transferring that reaction to a range of mineral acids (anhydrous H3BO3, H3PO4, H3PO3, H2SeO3, H6TeO6, H5IO6, and H3AuO3) yields urea. The model system for this study was a triisocyanate, tris(4-isocyanatophenyl)methane (TIPM), reacting with boric acid in DMF at room temperature, yielding nanoporous polyurea networks that were dried with supercritical fluid CO2 to robust aerogels (referred to as BPUA-xx). BPUA-xx were structurally (CHN, solid-state 13C NMR) and nanoscopically (SEM, SAXS, N2-sorption) identical to the reaction product of the same triisocyanate (TIPM) and water (referred to as PUA-yy). Minute differences were detected in the primary particle radius (6.2–7.5 nm for BPUA-xx versus 7.0–9.0 nm for PUA-yy), the micropore size within primary particles (6.0–8.5 Å for BPUA-xx versus 8.0–10 Å for PUA-yy), and the solid-state 15N NMR whereas PUA-yy showed some dangling −NH2. All data together were consistent with exhaustive reaction in the BPUA-xx case, bringing polymeric strands closer together. Residual boron in BPUA-xx aerogels was quantified with prompt gamma neutron activation analysis (PGNAA). It was found very low (≤0.05% w/w) and was shown to be primarily from B2O3 (by 11B NMR). Thus, any mechanism for systematic incorporation of boric acid in the polymeric chain, by analogy to carboxylic acids, was ruled out. (In fact, it is shown mathematically that boron-terminated star polyurea from TIPM should contain ≥3.3% w/w B, irrespective of size.) Retrospectively, it was fortuitous that this work was conducted with aerogels, and the model system used H3BO3, whereas the byproduct, B2O3, could be removed easily from the porous network, leaving behind pure polyurea. With other mineral acids, results could have been misleading, because the corresponding oxides are insoluble and remain within the polymer (via skeletal density determinations and EDS). On the positive side, the latter is a convenient method for in situ doping robust porous polymeric networks with oxide or pure metal nanoparticles (Au in the case of H3AuO3) for possible applications in catalysis.

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Section: Resultsmentioning

confidence: 99%

Nanoporous Polyurea from a Triisocyanate and Boric Acid: A Paradigm of a General Reaction Pathway for Isocyanates and Mineral Acids

et al. 2015

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“…This is indeed a mode of decomposition of mixed anhydrides of type 34. However, it has been known since the work of Naegli and co-workers 38,39 that another mode of decomposition can occur, leading to the formation of symmetrical anhydride 36 and urea 37, which, on heating to Noguchi noticed that polymerization of N-carbothiophenyl α-amino acids at high temperatures (>130 °C) yielded polypeptides with a low degree of polymerization because of the occurrence of side reactions. For example, polymerization of N-carbothiophenyl-L-nitroarginine in dimethyl sulfoxide at 120 °C for 14 h resulted in a degree of polymerization of only 5−10.…”

Section: ■ Synthesis Of Polymersmentioning

confidence: 99%

“…This is indeed a mode of decomposition of mixed anhydrides of type 34 . However, it has been known since the work of Naegli and co-workers , that another mode of decomposition can occur, leading to the formation of symmetrical anhydride 36 and urea 37 , which, on heating to high temperatures (>135 °C), can react with each other, again yielding amide 35 with the loss of carbon dioxide.…”

Section: Synthesis Of Polymersmentioning

confidence: 99%

Phenylthiocarbamate orN-Carbothiophenyl Group Chemistry in Peptide Synthesis and Bioconjugation

et al. 2014

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The Curtius Reaction

Smith

2011

Organic Reactions

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The decomposition of acid azides to isocyanates and nitrogen is known as the Curtius rearrangement. The reaction is a preparative method for isocyanates, ureas, amides, and amines. When coupled with a hydrolytic step, the Curtius rearrangement becomes a practical procedure for replacing a carboxyl group by an amino group. The overall process of converting an acid through its azide to an amine is commonly referred to as the Curtius reaction. Acid azides are commonly prepared by treating hydrazides in cold, aqueous solution with nitrous acid. Azides can be rearranged in inert solvents, from which isocyanates can be isolated in the presence of water or alcohol., which will react with the intermediate to form urethans or ureas.

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Über den Umsatz aromatischer Isocyansäure‐ester mit organischen Säuren. I. Theorie und Anwendung der Reaktion für die präparative Darstellung von Säure‐anhydriden

Cited by 62 publications

References 14 publications

Nanoporous Polyurea from a Triisocyanate and Boric Acid: A Paradigm of a General Reaction Pathway for Isocyanates and Mineral Acids

Nanoporous Polyurea from a Triisocyanate and Boric Acid: A Paradigm of a General Reaction Pathway for Isocyanates and Mineral Acids

Phenylthiocarbamate orN-Carbothiophenyl Group Chemistry in Peptide Synthesis and Bioconjugation

The Curtius Reaction

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