Pyridone acid chlorides synthesis

A slightly different synthesis was used for preparation of Ipalbidine and Ipalbine from the enaminone 262, which was acylated with the acid chloride 263 and cyclized in base. The resulting pyridone 264 was hydrolyzed and decarboxylated followed by reduction to give the racemic Ipalbidine 265, Scheme 71. Resolution of 265 and further chemical transformations led to Ipalbine (71HCA513). 

A third synthesis which has resulted in the preparation of rieinine and a number of its derivatives is due to Schroeter, Seidler, Sulzbacher and Kanitz,i2 who foimd that cyanoacetyl chloride polymerises spontaneously to 6-chloro-2 4-dihydroxy-3-cyano-pyridine. The di-sodium derivative of this with methyl sulphate produces A -methyl-6-chloro-4-hydroxy-3-cyano-2-pyridone (6-chlororicininic acid), the mono-sodium derivative of which, with methyl bromide or sulphate, is converted into 6-chlororicinine and the latter is reduced by zinc and sulphuric acid to rieinine. A fourth synthesis, starting from 3-nitro-4-pyridone, is due to Reitmann. ... 

A synthesis of the monoterpene alkaloid ( )-actinidine has been accomplished through the intramolecular cycloaddition of a substituted pyrimidine (81JCS(P1)1909). Condensation of the diester (756) with formamidine provided the pyrimidine precursor (757) which when heated at its melting point (203 °C) underwent cycloaddition with elimination of isocyanic acid to produce the pyridone (758). Conversion of the pyridone into the chloropyridine was effected with phosphoryl chloride. The chlorine atom was then removed by hydrogenoly-sis over palladium on charcoal to afford the racemic alkaloid (759 Scheme 175). 

The second route to ipalbidine also provides the first synthesis of its /5-d-glucoside ipalbine.3 2-Methoxypyrroline (4) was condensed with methyl acetoacetate at 85 °C in the absence of solvent to give the keto-ester (5). Acylation of the sodium salt of (5) was achieved with p-methoxyphenylacetyl chloride, but the expected acyl derivative could not be isolated. However, after the addition of a further equivalent of sodium hydride and heating at 80 °C the cyclization product (6) was obtained in moderately good yield. Some of the corresponding carboxylic acid was also isolated. Demethylation and decarboxylation of (6) by means of 48 % hydrobromic acid then gave the tetrasubstituted pyridone (7), which was... 

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