213-2213,5-Bisarylmethylene-1-ethylpiperidone 2
on reaction with thiourea yield the thioxopyri midine derivatives 3, which
on condensation with bromoacetic acid, 2-bromopropanoic acid or 3-bromopropanoic
acid afford thiazolopyrimidine 4, 2-methyl-thiazolopyrimidines 5 and
thiazinopyrimidine derivatives 6, respectively. Compounds 7 and 8
are also obtained via condensation of compounds 3 with 3-chloropentan-2,
4-dione, bromoacetic acid and aromatic aldehydes, respectively. However, compounds
8 are prepared directly by condensation of compounds 4 with aromatic
aldehydes. Compounds 2 on condensation with malononitrile in ethanol/piperidine
or acetic acid/ammonium acetate mixture give pyridopyran 9 and pyridopyridine
10, respectively. Also compound 10 could be prepared directly from
compound 9. Compounds 2 when condensed with phenylhydrazine, ethyl
cyanoacetate or guanidine hydrochloride yields pyridopyrazole 11, pyridopyridone
12 and pyridoaminopyrimidine derivatives 13, respectively