10097-16-2Relevant articles and documents
Phytochemical Investigation of Iphiona aucheri. Structural Revision of Donine
Dashti, Yousef,Hobson, Christian,Tajabadi, Fatemeh Mazraati,Rezadoost, Hassan
, p. 902 - 907 (2019)
Investigation of an extract of Iphiona aucheri afforded compounds 1–3. These compounds were identified by detailed spectroscopic and spectrometric analysis, however, a literature search revealed that NMR and mass data similar to those of compound 3 have been reported for donine alkaloid 4. Investigation of the experimental and calculated NMR data of compound 4 revealed that the proposed structure should be revised to 3. This was further confirmed by synthesis of compounds 3 and 4.
Mechanistic Study of Stress Relaxation in Urethane-Containing Polymer Networks
Brutman, Jacob P.,Fortman, David J.,De Hoe, Guilhem X.,Dichtel, William R.,Hillmyer, Marc A.
, p. 1432 - 1441 (2019/02/24)
Cross-linked polymers are used in many commercial products and are traditionally incapable of recycling via melt reprocessing. Recently, tough and reprocessable cross-linked polymers have been realized by incorporating cross-links that undergo associative exchange reactions, such as transesterification, at elevated temperatures. Here we investigate how cross-linked polymers containing urethane linkages relax stress under similar conditions, which enables their reprocessing. Materials based on hydroxyl-terminated star-shaped poly(ethylene oxide) and poly((±)-lactide) were cross-linked with methylene diphenyldiisocyanate in the presence of stannous octoate catalyst. Polymers with lower plateau moduli exhibit faster rates of relaxation. Reactions of model urethanes suggest that exchange occurs through the tin-mediated exchange of the urethanes that does not require free hydroxyl groups. Furthermore, samples were incapable of elevated-temperature dissolution in a low-polarity solvent (1,2,4-trichlorobenzene) but readily dissolved in a high-polarity aprotic solvent (DMSO, 24 to 48 h). These findings indicate that urethane linkages, which are straightforward to incorporate, impart dynamic character to polymer networks of diverse chemical composition, likely through a urethane reversion mechanism.
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
