Pyrrolidines, readily accessible saturated azaheterocycles, have emerged as valuable intermediates in the synthesis of aliphatic amines. In this work, we employed the ring cleavage of 3-aroylpyrrolidines for the four-step synthesis of 2,6-diarylpyridines and 6-aryldihydropyridin-2-ones decorated with the β-dialkylaminoethyl moiety, starting from ubiquitous enones or active methylene compounds. Namely, N-methylazomethine ylide gives rise to a wide range of pyrrolidines via 3 + 2 cycloaddition reaction with enones or one-step domino pyrrolidination of active methylene compounds. Treatment with alkyl halide and ring cleavage of the resulting quaternary ammonium salt of pyrrolidines in the presence of active methylene compounds provide α-(β-dialkylaminoethyl)-1,5-diketones or 1,5-ketoesters in good to high overall yields over three steps. Subsequent cyclization with ammonium acetate in TFEA or HFIP affords 3-pyridylethylamines and 5-pyridonylethylamines in 22-76% overall yields.
Khardina et al. (Fri,) studied this question.