Carboxylates lateral

In 1935 Hamano and Kawakami (1935) characterized retinol (1) as the P-naphthoate and anthraquinone P-carboxylate. Later Baxter and Robeson (1940) were able for the first time to obtain crystalline retinyl palmitate (113) and crystalline retinol (1) from liver oils. Crystalline retinyl acetate (9) and crystalline retinyl succinate were obtained at a later date (Baxter and Robeson, 1942). These very pure compounds made possible the accurate determination of a number of physical data. In 1946 Hanze et al. (1948) synthesized pure retinyl methyl ether (571) from crystalline retinol (1), and the total synthesis of this ether was reported at the same time by Milas et al. (1948). At this time also, syntheses of retinoids were carried out by Isler and associates and led to the first industrial synthesis of retinol derivatives (Isler et al., 1947 Isler, 1950 Heilbron and Weedon, 1958 Isler, 1979). 

Later findings have modified the rule, especially when the carbon atoms concerned are connected with carbonyl- or carboxyl-groups, but it still holds good for monohydric unsaturated alcohols. 

Cyclopentene derivatives with carboxylic acid side-chains can be stereoselectively hydroxy-lated by the iodolactonization procedure (E.J. Corey, 1969, 1970). To the trisubstituted cyclopentene described on p. 210 a large iodine cation is added stereoselectively to the less hindered -side of the 9,10 double bond. Lactone formation occurs on the intermediate iod-onium ion specifically at C-9ot. Later the iodine is reductively removed with tri-n-butyltin hydride. The cyclopentane ring now bears all oxygen and carbon substituents in the right stereochemistry, and the carbon chains can be built starting from the C-8 and C-12 substit""" ... 

Heating Kemp s acid with appropriate aromatic diamines yields bis-imides with two convergently oriented carboxylic acid groups on the edges of a hydrophobic pocket. Dozens of interesting molecular complexes have been obtained from such compounds and can be traced in the Journal of the American Chemical Society under the authorship of J. Rebek, Jr., (1985 and later e.g. T. Tjivikua, 1990 B). 

In this chapter we intend to outline the general methods by which the thiazolic ring is synthetized from open-chain compounds. The conversion of one thiazole compound to another is not discussed here, but in appropriate later chapters. Thus the conversion of thiazole carboxylic acids, halogeno-, amino-, hydroxy-, and mercaptothiazoles, to the corresponding unsubstituted thiazoles is treated in Chapters IV through VII, respectively. 

Although the present chapter includes the usual collection of topics designed to acquaint us with a particular class of compounds its central theme is a fundamental reaction type nucleophilic addition to carbonyl groups The principles of nucleophilic addition to aide hydes and ketones developed here will be seen to have broad applicability m later chap ters when transformations of various derivatives of carboxylic acids are discussed... 

The most apparent chemical property of carboxylic acids their acidity has already been examined m earlier sections of this chapter Three reactions of carboxylic acids—con version to acyl chlorides reduction and esterification—have been encountered m pre vious chapters and are reviewed m Table 19 5 Acid catalyzed esterification of carboxylic acids IS one of the fundamental reactions of organic chemistry and this portion of the chapter begins with an examination of the mechanism by which it occurs Later m Sec tions 19 16 and 19 17 two new reactions of carboxylic acids that are of synthetic value will be described... 

Pyridine carboxamide [98-92-0] (nicotinamide) (1) and 3-pyridine carboxylic acid [59-67-6] (nicotinic acid) (2) have a rich history and their early significance stems not from their importance as a vitamin but rather as products derived from the oxidation of nicotine. In 1867, Huber prepared nicotinic acid from the potassium dichromate oxidation of nicotine. Many years later, Engler prepared nicotinamide. Workers at the turn of the twentieth century isolated nicotinic acid from several natural sources. In 1894, Su2uki isolated nicotinic acid from rice bran, and in 1912 Funk isolated the same substance from yeast (1). 

New efficient vulcanization systems have been introduced in the market based on quaternary ammonium salts initially developed in Italy (29—33) and later adopted in Japan (34) to vulcanize epoxy/carboxyl cure sites. They have been found effective in chlorine containing ACM dual cure site with carboxyl monomer (43). This accelerator system together with a retarder (or scorch inhibitor) based on stearic acid (43) and/or guanidine (29—33) can eliminate post-curing. More recently (47,48), in the United States a proprietary vulcanization package based on zinc diethyldithiocarbamate [14324-55-1]... 

Even the earliest reports discuss the use of components such as polymer syrups bearing carboxylic acid functionality as a minor component to improve adhesion [21]. Later, methacrylic acid was specifically added to adhesive compositions to increase the rate of cure [22]. Maleic acid (or dibasic acids capable of cyclic tautomerism) have also been reported to increase both cure rate and bond strength [23]. Maleic acid has also been reported to improve adhesion to polymeric substrates such as Nylon and epoxies [24]. Adducts of 2-hydroxyethyl methacrylate and various anhydrides (such as phthalic) have also been reported as acid-bearing monomers [25]. Organic acids have a specific role in the cure of some blocked organoboranes, as will be discussed later. 

The synthesis of (+)-N-methylmaysenine, a preliminary for the later synthesis of the antitumor agent maytansine, was accomplished by the joining of fragments A and B, chain extension and macrolactam closure using a mixed carboxylic-sulfonic acid anhydride. 

As shown in Figure 16.10, this reaction mechanism involves nucleophilic attack by —SH on the substrate glyceraldehyde-3-P to form a covalent acylcysteine (or hemithioaeetal) intermediate. Hydride transfer to NAD generates a thioester intermediate. Nucleophilic attack by phosphate yields the desired mixed carboxylic-phosphoric anhydride product, 1,3-bisphosphoglycerate. Several examples of covalent catalysis will be discussed in detail in later chapters. 

A few trinuclear oxo-centred carboxylates [V30(RC00)gL3]+ of a type more common for later transition metals (see Fig. 23.9, p. 1030) have been obtained, as well as [Nb302(MeC00)6(thf)3]+ whose structure differs essentially only in that there are two bridging O atoms above and below the Nb3 plane. 

In 1883, Bottinger described the reaction of aniline and pyruvic acid to yield a methylquinolinecarboxylic acid. He found that the compound decarboxylated and resulted in a methylquinoline, but made no effort to determine the position of either the carboxylic acid or methyl group. Four years later, Doebner established the first product as 2-methylquinoline-4-carboxylic acid (8) and the second product as 2- methylquinoline (9). Under the reaction conditions (refluxing ethanol), pyruvic acid partially decarboxylates to provide the required acetaldehyde in situ. By adding other aldehydes at the beginning of the reaction, Doebner found he was able to synthesize a variety of 2-substituted quinolines. While the Doebner reaction is most commonly associated with the preparation of 2-aryl quinolines, in this primary communication Doebner reported the successful use of several alkyl aldehydes in the quinoline synthesis. 

The first synthesis of cinnoline was reported by von Richter in 1883. The diazonium chloride 5 which was obtained from o-aminophenylpropiolic acid (4), was heated in water at 70°C to provide the 4-hydroxycinnoline-3-carboxylic acid (6). When this acid 6 was heated above its melting point, carbon dioxide was liberated and 4-hydroxycinnoline (7) was obtained. Distillation of 4-hydroxycinnoline (7) with zinc dust furnished a small amount of oil, which was assumed to be cinnoline (8). The preparation of 4-hydroxycinnoline (7) was repeated by Busch and Klett, although in lower yield when compared to the original report. Busch and Rast later converted the 4-hydroxycinnoline (7) successfully to cinnoline (8) via the 4-chlorocinnoline (9). ... 

The rate of saponification of ethyl 2-thenoate, in contrast to ethyl 3-thenoate, was found to be considerably slower than predicted from the pKa of the acid, showing that the reactivities of thiophenes do not parallel those of benzene. The first explanation, that this was produced by a steric effect of the ring sulfur similar to the case in or /lo-substituted benzenes and in ethyl 1-naphthoate, could not be upheld when the same effect was found in ethyl 2-furoate. It was later ascribed to a stereospecific acid strengthening factor, involving the proper relation of the carboxylic hydrogen and the heteroatom, as the rate of saponification of 2-thienylacrylic acid was in agreement with that predicted from the acid constants. ... 

The chemistry of fenchyl alcohol, Cj HjgO, must be regarded as in a somewhat unsettled state, as questions of isomerism arise which are as yet unsolved. It was ori nally prepared by Wallach by reducing the ketone fenchone, a natural constituent of several essential oils, by means of sodium. Later he obtained it in fairly large quantities as a byproduct in the preparation of fenchone-carboxylic acid, by passing a current of C(X through an ethereal solution of fenchone in the presence of sodium. Fenchyl alcohol has, so far, been found in one essential oil only, namely, that of the root wood of Pinus palustris. 

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