Y-Benzoylbutyric acid

The Hantzsch pyridine synthesis gives initially a dihydropyridine from the cyclization reaction. Adaptation of this reaction to the use of a 2-methylenethiazolidine yields the fused tetrahydro derivative (502) (77LA1888). Perhydro derivatives are simply prepared from 2-substituted thiazolidines by cycloalkylation as for (503) (80S387). The thiazolidine may also be generated in situ as in the reaction between y-benzoylbutyric acid and 2-mercaptoethylamines under azeotropic conditions to yield (504) (65JOC1506). 

The synthesis of a variety of perhydro-imidazo[l,2-fl]pyridin-5-ones is illustrated by the preparation of 212 by treatment of y-benzoylbutyric acid with 1,2-diaminoethane in the presence of /7-toluenesulfonic acid in boiling xylene (69USP3454585). Compounds 213 (70GEP1802468) and 214 (72AKZ438 82EUP65724) were similarly obtained by the reaction between the appropriate ketoester and 1,2-diaminoethane. 

The preparation of 8a-phenylperhydrothiazolo[3,2-a]pyridin-5-one (313) by the reaction between y-benzoylbutyric acid and mercaptoethyl-amine illustrates the synthesis of a number of similar compounds (67USP3334091). 

Both the aldehyde and the alcoholic groups are affected in 8-phenyl-8-hydroxyvaleraldehyde, which is oxidized by potassium permanganate to y-benzoylbutyric acid (equation 367) [749]. 

---