Secondary amines reactions with esters

King and Gill have been studying the reaction of alkyl 2,2,2-trifluoroethanesulfonate esters (tresylates) (308) in aqueous base (pFI>9) in the presence of a primary or secondary amine. Reaction with hydroxide is foimd to be a reversible ElcB process and reaction with water is the normal sulfonic ester hydrolysis. 

Photosensitive functions are in many cases also heat sensitive, so the preparation of photosensitive polyimides needs smooth conditions for the condensations and imidization reactions. Some chemical reactants, which can be used for polyamide preparation, have been patented for the synthesis of polyimides and polyimide precursors. For example, chemical imidization takes place at room temperature by using phosphonic derivative of a thiabenzothiazoline.102 A mixture of N -hydroxybenzotriazole and dicyclohexylcarbodiimide allows the room temperature condensation of diacid di(photosensitive) ester with a diamine.103 Dimethyl-2-chloro-imidazolinium chloride (Fig. 5.25) has been patented for the cyclization of a maleamic acid in toluene at 90°C.104 The chemistry of imidazolide has been recently investigated for the synthesis of polyimide precursor.105 As shown in Fig. 5.26, a secondary amine reacts with a dianhydride giving meta- and para-diamide diacid. The carbonyldiimidazole... 

Less is known about unequivocal reactions of the POf ion with amines. This is partly because the phosphate esters examined undergo direct SN2(P) reaction with amines via oxyphosphoranes or can at least react in the boundary area between SN1 (metaphosphate mechanism) and SN2(P)37) or because the reaction actually occurs at another part of the molecule (simple primary and secondary amines react with 2,4-dinitrophenylphosphate to give 2,4-dinitroanilines " ). 

The reaction of iV-methyl tertiary alkylamines with diethyl azodicarboxylate is known (61) to result in the formation of an intermediate hydrazodiester (116), which on acid hydrolysis gives the corresponding secondary amine together with hydrazine 1,2-dicarboxylate diethyl ester and formaldehyde... 

The use of chiral boronic esters in the Petasis borono-Mannich reaction has been reported to result in low levels of enantioselectivity of the adducts at room temperature (6-15% ee) [48]. Auxiliaries used in this study by Scobie and co-workers included pinanediol and tartaric acid derived alkenylboronates. Morpholine was the only secondary amine used, with the primary amine ethyl glycinate failing to react. 

Primary and secondary amines also react with epoxides (or in situ produced episulfides )r aziridines)to /J-hydroxyamines (or /J-mercaptoamines or 1,2-diamines). The Michael type iddition of amines to activated C—C double bonds is also a useful synthetic reaction. Rnally unines react readily with. carbonyl compounds to form imines and enamines and with carbo-tylic acid chlorides or esters to give amides which can be reduced to amines with LiAlH (p. Ilf.). All these reactions are often applied in synthesis to produce polycyclic alkaloids with itrogen bridgeheads (J.W. Huffman, 1967) G. Stork, 1963 S.S. Klioze, 1975). 

The reaction of a vinyl ether with carbon dioxide and a secondary amine gives a carbamic ester (246). 

Refluxing linoleic acid and a primary or secondary alkyl amine with -toluenesulfonic acid in toluene for 8—18 h also yields the substituted amides (32—34). The reaction of methyl esters with primary or secondary amines to make substituted amides is catalyzed with sodium methoxide. Reactions are rapid at 30°C under anhydrous conditions (35). Acid chlorides can also be used. Ai,A/-dibutyloleamide [5831-80-17 has been prepared from oleoyl chloride and dibutyl amine (36). 

In addition to the nitrile and alcohol routes for fatty amine preparation, processes have been described by Unocal and Pennwalt Corporation, using an olefin and secondary amine (14—16) by Texaco Inc., hydrogenation of nitroparaffins (17—20) by Onyx Corporation, reaction of an alkyl haUde with secondary amines (21,22) by Henkel Cie, GmbH, reduction of an ester in the presence of a secondary amine (23) by catalytic hydroammonolysis of carboxyhc acids (24) and by the Hofmann rearrangement (25). 

Other Rea.ctlons, The anhydride of neopentanoic acid, neopentanoyl anhydride [1538-75-6] can be made by the reaction of neopentanoic acid with acetic anhydride (25). The reaction of neopentanoic acid with acetone using various catalysts, such as titanium dioxide (26) or 2irconium oxide (27), gives 3,3-dimethyl-2-butanone [75-97-8] commonly referred to as pinacolone. Other routes to pinacolone include the reaction of pivaloyl chloride [3282-30-2] with Grignard reagents (28) and the condensation of neopentanoic acid with acetic acid using a rare-earth oxide catalyst (29). Amides of neopentanoic acid can be prepared direcdy from the acid, from the acid chloride, or from esters, using primary or secondary amines. 

Fabric Softeners, Surfactants and Bleach Activators. Mono- and bisamidoamines and their imidazoline counterparts are formed by the condensation reaction of one or two moles of a monobasic fatty acid (typically stearic or oleic) or their methyl esters with one mole of a polyamine. Imidazoline formation requires that the ethyleneamine have at least one segment in which a secondary amine group Hes adjacent to a primary amine group. These amidoamines and imidazolines form the basis for a wide range of fabric softeners, surfactants, and emulsifiers. Commonly used amines are DETA, TETA, and DMAPA, although most of the polyethylene and polypropane polyamines can be used. 

N-Unsubstituted pyrazoles and imidazoles add to unsaturated compounds in Michael reactions, for example acetylenecarboxylic esters and acrylonitrile readily form the expected addition products. Styrene oxide gives rise, for example, to 1-styrylimidazoles (76JCS(P1)545). Benzimidazole reacts with formaldehyde and secondary amines in the Mannich reaction to give 1-aminomethyl products. 

This reaction is reported to proceed at a rapid rate, with over 25% conversion in less than 0.001 s [3]. It can also proceed at very low temperatures, as in the middle of winter. Most primary substituted urea linkages, referred to as urea bonds, are more thermally stable than urethane bonds, by 20-30°C, but not in all cases. Polyamines based on aromatic amines are normally somewhat slower, especially if there are additional electron withdrawing moieties on the aromatic ring, such as chlorine or ester linkages [4]. Use of aliphatic isocyanates, such as methylene bis-4,4 -(cyclohexylisocyanate) (HnMDI), in place of MDI, has been shown to slow the gelation rate to about 60 s, with an amine chain extender present. Sterically hindered secondary amine-terminated polyols, in conjunction with certain aliphatic isocyanates, are reported to have slower gelation times, in some cases as long as 24 h [4]. 

Constitution. Pelletierine behaves as a secondary amine and the oxygen atom of the alkaloid is present in the form of an aldehyde group, since the base yields an oxime, convertible by the action of phosphorus pentachloride into a nitrile, b.p. 104-6°/13 mm., which is hydrolysed by caustic potash in alcohol to an acid, the ethyl ester of which is Loffler and Kaim s ethyl -2-piperidylpropionate. Pelletierine is not directly oxidisable to this acid. It also yields a liquid hydrazone, b.p. 130°/20 ram., which with sodium in alcohol at 136-70° reduces to dZ-eoniine. These reactions are explained by the following formulas, in which pelletierine is represented as -2-piperidylpropionaldehyde. 

Generally, isolated olefinic bonds will not escape attack by these reagents. However, in certain cases where the rate of hydroxyl oxidation is relatively fast, as with allylic alcohols, an isolated double bond will survive. Thepresence of other nucleophilic centers in the molecule, such as primary and secondary amines, sulfides, enol ethers and activated aromatic systems, will generate undesirable side reactions, but aldehydes, esters, ethers, ketals and acetals are generally stable under neutral or basic conditions. Halogenation of the product ketone can become but is not always a problem when base is not included in the reaction mixture. The generated acid can promote formation of an enol which in turn may compete favorably with the alcohol for the oxidant. 

FIGURE 20.6 Mechanism of amide formation in the reaction of a secondary amine with an ethyl ester. 

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