Urethanes carbonyl groups

Isatin j8-thiosemicarbazones (97) readily give triazinoindoles (98) (72JMC277). Deprotonation of the amide (99) leads to ring closure on to the urethane carbonyl group to give (100). In a similar reaction (101 to 102) the lower reactivity of the t-butyl ester induces ring closure in the required direction (78CPB3080). 

To overcome the drawbacks associated with the application of non-urethane N-terminal blocking groups, a new strategy had to be developed which enables a biocatalyst to cleave a urethane structure without the need for a direct attack on the urethane carbonyl group. The principle was successfully realized by the introduction of the p-acetoxybenzyloxycarbonyl (AcOZ) [30] and thep-phenyl-acetoxybenzyloxycarbonyl (PhAcOZ) [31] groups (Fig. 9). 

The hydrogen-bonded complexes of phenols with the model dipeptide 74 have been investigated . Complexation occurs at both the amide and urethane carbonyl groups. About 45% of the complexes are formed on the urethane functions, almost independent of the Brpnsted acidity of the phenols. When phenols are attached to the amide group, the intramolecular hydrogen bond seems to be broken. 

The absorbances of the urethane carbonyl groups decrease with increasing PPy content and also phase separation becomes less with increasing amounts of PPy. 

Urethane (Section 31.4) A functional group in which a carbonyl group is bonded to both an -OR group and an -NR2 group. 

One of the major drawbacks to many promising copolymers is their unsatisfactory electrochemical stability. Carbonyl groups which feature in many of the back-bone/chain linking groups are likely to cause stability concerns. Likewise, urethane, alcohol, and siloxane functions are sensitive to lithium metal. With this in mind, a recent trend has been to find synthetic routes to amorphous structures with... 

In a three-component synthesis the amide (86-1) obtained from the ester (85-5) and benzyl isocyanide is reacted with the piperdone (86-2). The product from this transform consists of the addition product (86-3) where amide nitrogen in (86-1) as well as the carbon from the isocyanide have added to the carbonyl group on the piperidine. Treatment of the adduct (86-3) with a strong acid hydrolyzes the urethane function on the fert-butyloxycarbonic protecting group, leaving behind the primary... 

N nonamide(NH)unit 1 the Contribution from the NH units in those polymers where there is no carbonyl group adjacent to NH. NH units encountered in urethane groups are also included in this category. 

On the other hand, the group of No wick [29] developed polyurea templates with the general structure 35 in order to nucleate parallel /1-sheet structures. They reported that in a model compound (36) the urethane carbonyls are hydrogen bonding to the adjacent NH and that the orientation of the bonding interactions is controlled by the size of the end substituent, in this case a phenyl group. They also recently prepared 37 and showed by NMR that it adopts mostly the proposed parallel /1-sheet conformation in chloroform [30]. 

Recently it has become clear that organozinc halides can also be formed in more polar solvents than tetahydrofuran, for example in dimethylformamide.19 Organozinc halides with a urethane protected (3-amino group appear to be much more stable in polar solvents. This increased stability is due to the inhibition of intramolecular coordination by the urethane carbonyl to the zinc atom, which in turn can lead to facile fl-elimination.20... 

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