Abstract
β-Alkoxy-β-ketoenamides with an alkenylated
side arm were prepared by three-component reaction of lithiated
methoxyallene, nitriles, and α,β-unsaturated
carboxylic acids. Their subsequent treatment with trimethylsilyl
triflate and base provided 6-alkenyl-4-hydroxypyridine derivatives
that were converted into the corresponding nonaflates. Alternatively,
condensation of β-alkoxy-β-ketoenamides with an
ammonium salt led to the smooth formation of alkenyl-substituted
pyrimidine derivatives. The alkenyl group in pyridine or pyrimidine
derivatives allows a wide scope of functional group modification.
Moreover, the pyridin-4-yl nonaflates are excellent candidates
for palladium-catalyzed coupling reactions and the 6-methyl
group of the pyrimidine derivatives could also be employed for the
introduction of functional groups and subsequent reactions. A variety
of highly substituted pyridine and pyrimidine derivatives are available
by this modular route to heterocycles.
Key words
alkoxyallenes - enamides - pyridines - nonaflates - pyrimidines - Suzuki couplings
