Urethane moieties

A similar approach was used by the Alcaide group [183] in the synthesis of tricyclic (3-lactams 6/1-391 from 6/1-390 (Scheme 6/1.99). In this domino process the primarily obtained it-allyl-Pd-complex reacts with the N-nucleophile of the urethane moiety to form a C-N-bond and a vinyl halide. The final step is then an intramolecular Heck-type reaction of the vinyl halide with the alkyne moiety and re-... 

Glass Temperature. The glass temperatures for a substantial number of polyurethane elastomers, similar to those discussed herein, were found (1 ) to increase linearly with the concentration of urethane moieties, [U]. For the present elastomers prepared using LHT-240 and TIPA, [U] should be 1.10 and 1.15 moles/kg, respectively. Their glass temperatures should be about —57°C, indicated by the previous data. 

Mitomycin C, an antibiotic produced by fermentation of streptomyces, has been used extensively in Japan for the treatment of stomach cancer which is prevalent in that country. It probably acts after conversion into an alkylating agent in vivo, and it also contains quinone and urethane moieties which may contribute to its anti-tumour effect. A related series of compounds, the pyrol-lizidine alkaloids, occur in a variety of plants and are known to cause acute liver cytotoxicity when accidentally ingested93). Like mitomycin C, these agents are almost certainly metabolised in vivo by liver microsomes to alkylating agents which cause the liver toxicity. Some of these alkaloids have antitumour properties, presumably because the active metabolite formed in the liver is stable enough to reach the tumour. 

Other functional moieties. Other functional moieties that are in the polyurethane coating or adhesive will have a large effect on its properties. These exert both a qualitative and a quantitative effect. This means that as the relative ratio of urethane moiety diminishes, the coating will behave more nearly like the class of coating as defined by the major functional moiety content. Table VI provides a listing together with each formula. 

Hydroxyl groups formed at the p-carbon atom of the urethane moiety increase adhesion properties. Plurality of intra- and intermolecular hydrogen bonds... 

A related bipolar dodecane possessing A-benzyloxycarbonyl-L-phenylalanine terminal units has been shown [24] to form bundles of braided tapes in a hexane/EtOAc mixture. In order to probe the function of the urethane moieties, deprotection afforded the corresponding bis(a-aminoamide), which gave solids lacking any microstructural character. Bolaphiles composed of straight chain alkane termini have been reported [25] to afford self-assembled supramolecular structures in water. 

Alcaide et al. [158] have used a similar approach for the synthesis of the tricyclic /3-lactam 314 starting from 313 (Scheme 8.78). In this domino process, a r-aUyl-palladium complex is formed by a nucleophilic attack of bromide at a divalent palladium-coordinated allene. Thereafter, the nitrogen nucleophile of the urethane moiety reacts with the primarily... 

This green-chemistry strategy provided the possibility of arriving at urethane moieties without use of standard unsafe methods based on phosgene. Polymers had molecular weights ranging between 11 and 31 kDa, Tg values of -29 to 55 "C and a Tm of 110 °C, for those whose structure was sufficiently regular to promote some crystallisation. 

In general, step-growth polymers are usually condensation polymers, while chain-growth polymers are usually addition polymers, but there are exceptions, such as polyurethanes. Polyurethanes are made up of repeating urethane moieties, also sometimes called carbamate moieties. 

Preparation of polymeric and oligomeric dimethyl siloxane with alcoholic groups and their use in preparing polymers with dimethylsiloxane and urethane moieties [108]. 

To improve the mechanical compatibility between the hydrogel and the fabrics, Hu et incorporated urethane moieties into PNIPPAm... 

Kinetically controlled deprotonation also leads to the lower substituted alkali enolates of acyclic ketones, as illustrated by selected examples in Scheme 2.5 2-heptanone [27], 3-methyl-2-butanone [26a], and 2-methyl-3-pentanone [23]. Under the conditions of kinetic deprotonation with LDA, a-alkoxy-substituted ketones behave similar to their alkyl-substituted counterparts giving predominantly the less substituted enolate, as illustrated for 2-methoxycyclohexanone [28] in Scheme 2.5. a-Dialkylamino ketones also follow this tendency. In M-carbamato-substituted ketones, however, regioselectivity is reversed, and enolization predominantly occurs toward the nitrogen atom - a result that might be caused by the electron-withdrawing nature of the urethane moiety this effect becomes even more dominant when the enolate is formed under thermodynamic control (LiHMDS, equilibrating conditions) [29]. 

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