Condensation reactions of 2,4- and 2,6-dimethylpyridines and their 1-oxides

Abstract

Using the reactions of 2,4- and 2,6-dimethylpyridine-1-oxides with aromatic and heteroaromatic aldehydes under catalysis with potassium tert-butoxide (E)-aryl- and (E)-heteroarylethenylpyridine-1-oxides IIIa-IIIe, IVa-IVc, Va, Vb respectively, were prepared. 1-Oxides IIIg, IVd, IVe and Vc were obtained from the appropriate pyridine bases by oxidation with peracetic acid. Condensation of 2,4- and 2,6-dimethylpyridines with 3-pyridinecarbaldehyde gives a mixture of bases VIa and VIc, and VIb and VId, respectively. On Claisen condensation of 2,6- or 2,4-dimethylpyridine-1-oxide with diethyl oxalate in the presence of sodium hydride and potassium tert-butoxide lactone XIIa and XIIb is formed in addition to α-keto ester XIa and XIb, respectively. From esters XIa and XIb amides XId and XIe were prepared.