A synthetic application of the rate difference in oxidation of regioisomeri
cally substituted N-acyldihydropyridines is reported. This has allowed for
isolation of pure 4-substituted pyridine isomers without the need for chrom
atography. Diels-Alder adducts between a dihydropyridine and DDQ were isola
ted and formation of novel hydroquinone ethers was also observed during som
e reactions.