Hemiamides

The unsubstituted quinazolidine system 5 was constructed from mesylate 173. The key feature in this synthesis is based on a cyclohydrocarbonylation of the protected 4-amino-l,6-heptadiene 169 catalyzed by Rh(acac)(CO)2-BIPHEPHOS. Formation of the hemiamidal-aldehyde 171 took place by hydroformylation of the two olefin moieties and cyclization. Elimination of water gave 172, which, after treatment with NaBFE, subsequent mesylation to 173, and catalytic hydrogenation, afforded 5 (Scheme 29) <1998TL4599>. 

Alternate Crosslinking Modes. In addition to the crosslinking modes previously described, (co)polymers containing 1 and 2 may be cured by other means. For example, under appropriate acidic conditions with limited availability of active hydrogen species cyclic hemiamidals 2 will lose ROH to form the enamide 9 (Scheme 5). This has been demonstrated on model systems, e.g., 2 where vinyl is replaced by methyl ). The product, N-acetylpyrroline, has in turn been converted to nonvolatile products (oligomers) under free radical catalysis. These systems may thus be considered for application in the UV/EB or catalyzed free radical cure field. 

The structure of compound 32 has been confirmed by X-ray and NMR analyses. These methods confirm that compound 32 exists as the cyclic hemiamidal rather than as the open intermediate 33 <20050BC666>. 

As Scheme 1 illustrates, the Pd-catalyzed process includes the formation of hemiamidal 1 in the same manner as that in the Co-catalyzed process. However, the unique feature in this process is that hemiamidal 1 is converted to a-bromoamide 2, which is the key intermediate in this process. Then, the oxidative addition of 2 to the Pd(0) species forms alkyl-Pd complex 3. Subsequent insertion of CO to the carbon-Pd bond of 3 gives the acyl-Pd complex 4, which leads to the formation of the A -acyl-a-amino acid 5 through reductive elimination and hydrolysis. 

A similar sequence was reported where the asymmetry was introduced by the reaction of weio-3-substituted glutanc anhydrides and (S)-methylbenzylamines to give diastereomeric hemiamides that could be separated by recrystallization The asymmetnc desymmetrization of certain 4-aryl substituted glutanmides has also been accomplished with high levels of selectivity (up to 97% ee) by enolization with a chiral bis-lithium amide base. The selectivity of the reaction was shown to be the result of asymmetric enolization, followed by a kinetic resolution." ... 

Scheme 16 presents the overall reactions starting from the radicals at C-l to C-5 (93-97). Except for the radical at C-2, all radicals have been shown to undergo reactions that eventually lead to elimination of the base. It has been suggested that the base is eliminated from the labile (and not yet isolated) hemiaminal (99-104) or hemiamidal (98)... 

Abele, S., Graillat, C., Zigmanis, A. and Guyot, A. (1999) Hemiesters and hemiamides of maleic and succimic acid synthesis and application of surfactants in emulsion plymerization with styrene and butyl acrylate. Polym. Adv. Technol, 10, 301-10. 

Amides derive also from carbonic acid. The hemiamide of carbonic acid = carbamic acid (H2N-COOH) cannot be in existence it degrades spontaneously to CO2 and NH3. However, salts and esters of carbamic acid are more or less stable. The esters, H2N-COOR, are named urethanes. They react with ammonia to urea, the diamide of carbonic acid, (NH2)2C = 0. Urethanes and urea add readily formaldehyde forming N-hydroxymethyl or N,N -bis-hydroxymethyl derivatives which are formaldehyde releasing compounds. 

FIG. 3 Comparison of the warze uptake of films prepared using the three series of surfactants (hemiesters, hemiamides, zwitterionics). (From Ref. 59.)... 

In an exceptional ruling hemiamides and hemialdehydes of trivially named carboxylic acids can be designated as. ..amidic and aldehydic acids, respectively. 

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