Carboxylic acids indirect decarboxylation

In an indirect way the caprolactam salts may be formed by heating caprolactam solutions or suspensions of certain neutral or only slightly basic salts which are able to decompose to strong bases (82, 83, 86, 87, 91, 93). This effect can be reached by using alkali salts of carboxylic acids tending to decompose by decarboxylation. Alkali carbonates (7, 10, 13, 17, 28, 44, 45, 60, 65, 82—84, 87, 91, 102), alkali salts of carbonic monoalkyl esters, phenylacetic acid and other similar salts (62, 86, 89, 93, 102) are converted by decarboxylation into strongly basic carbonium salts or metal derivatives of amines or alcohols... 

Unsubstituted 2,7-naphthyridine (50) is probably best made by oxidation of 2,7-naphthyridine-4-carbaldehyde to 2,7-naphthyridine-4-carboxylic acid (49) (KMn04, AcMe, 20°C 88%) and subsequent thermal decarboxylation (Cu powder, gentle heat 78%) 630 earlier syntheses involved direct hydrogenolysis of 1,3,6,8-tetrachloro-2,7 naphthyridine (51 R = Cl) (Pd/C, H2, MeOH, AcOK 71 %)1374 cf 22 or indirect dechlorination of l-chloro-2,7-haphthyridine (51, R = H) by hydrazi-nolysis and subsequent oxidation (ILNNIL-ILO, EtOH, 100°C then CuS04, fUO 76% overall) 1279 also homologs.188... 

To accomplish the next step, to dinitrobenzene, the temperatures must be raised to around 95 C, and fuming nitric acid must be used along with the concentrated sulfuric acid. Direct nitration to the trinitro form is virtually impossible. TNB must be made, therefore, by an indirect (and hence expensive) route. To produce laboratory quantities, it is made by starting with trinitrotoluene (TNT), then oxidizing the methyl group to the acid (carboxyl) form, and decarboxylating in hot aqueous solution, as illustrated in Figure 3.4. 

The decarboxylation of carboxylic acids is a photochemical process of significance in several areas of study thus, photodecarboxylation reactions are used in synthetic chemistry to generate radical intermediates or in agriculture to produce pesticides. In the case of pharmaceuticals, this process is responsible for a decreased stability of some compounds and seems to be directly or indirectly involved in adverse photosensitizing side effects. 

By 1950 biotin had been implicated in a number of seemingly unrelated enzymatic processes, including (1) the decarboxylation of oxaloacetate and succinate (2) the Wood-Werkman reaction , that is, the /5-carboxylation of pyruvate (3) the biosynthesis of aspartate (4) the biosynthesis of unsaturated fatty acids (5) the deamination of certain amino acids (6) the synthesis of certain biotin-independent enzymes. In each case the enzymatic or metabolic basis for these observations can now be explained in terms of the unequivocally established role of biotin as an enzymatic COg carrier or through indirect effects. 

---