Derivatives Urethanes

Isobutyl chloroformate [543-27-1] M 136.6, b 123-127 /atm, 128.8 /atm, d 1.053, n 1.4070. It can be dried over CaCl2 and fractionated at atm press while keeping moisture out. Its purity can be checked by conversion to the phenyl urethane derivative with PhNCO [Saunders et al. J Am Chem Soc 73 3796 7957.] IR v 1780cm [Thompson and Jameson Spectrochim Acta 13 236 7959 Rose Justus Liebigs Ann Chem 205 227 1880]. 

Dioxotetrahydro-l,3-oxazine derivatives (24) can be obtained by reacting jS-hydroxy acids with sodium cyanate to form a urethane derivative (23) followed by the action of thionyl chloride. ... 

At elevated temperatures (80°C in DMF), the acetyl azide group rearranges to form an isocyanate that can react with hydroxyl-containing molecules to form a urethane linkage (Figure 9.38). The Cascade Blue urethane derivatives of macromolecules are extremely fluorescent and can be detected down to femtogram quantities (Takadate et al., 1985). 

The absorption spectra in the carbonyl stretching region of the urethane derivatives have been assigned to the free acid C=0 stretch and strongly hydrogen... 

SPE Silica, Grignard reaction, naphtyl urethane derivatives, SPE Cl 8 None... 

Thermal Cleavage. Urethanes derived from aliphatic primary or secondary alcohols are rather stable even at elevated temperatures. They will decompose above 200 °C. in contrast to urethanes derived from tertiary alcohols or phenols, which decompose at lower temperatures. The presence of certain catalysts may also accelerate the thermal decomposition—e.g., catalysts used in the preparation of the urethane (39). Thermal decomposition yields a variety of products from several possible reactions... 

Using 9.2 mmoles each of o-cresol and a-naphthyl isocyanate in 3.00 ml of purified ligroin, the effect of catalysts was tested. The sealed tubes were heated in a 65°C bath and after a definite time the solid urethane derivative was isolated, washed, dried, and weighed. The results (see Fig. 1) show that tri-ethylamine is the most effective amine, boron trifluoride etherate being the most effective acid tested at that time [7]. 

Research Focus Method of preparing poly(amide-urethane) derivatives by ring-opening polymerization of macroscopic dicarbodiimides. 

Poly(amide-urethane)derivatives, (I), were also prepared by reacting adipic acid with the step 2 product as illustrated in Eq. (1). 

Additional poly(ester-urethane) derivatives were prepared by reacting the step 1 prepolymer diol with selected diisocyanate as indicated below ... 

Other poly(ester-urethanes) derivatives were prepared by the authors (1) in an earlier investigation and are discussed. 

Observations Poly (carbonate-co-urethane) derivatives consisting of 1,6-hexanediol,... 

Cordite SC (Cordite Solventless, Carbamite) The use of a solventless Cordite was suggested at a conference at Watham Abbey in 1914. The composition proposed consisted essentially of NG soluble NC. To facilitate gelatinization, which was effected by heating rolling without the use of a vol solv, urethane derivs benzyl-phenylether (qv) were added. These compds were found to exert also a stabilizing action. 

Scheme 8 Cellulose urethane derivatives, and their mixing partners to make cholesteric liquid crystals [233]...

Reaction of 2-amino-2-(2-aminophenyl)acetaldehyde aroylhydrazones (109) with ethyl chloroformate gave the urethane derivatives 110. The latter underwent condensative double ring-closure to the l,2,4-triazolo[l,5-c]quinazolin-5-ones 86. Carrying out a similar reaction between 109 and guanidine furnished the 5-amino congener 111 (93JHC11) (Scheme 40). 

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