The LANCA three-component reaction of lithiated alkoxyallenes (LA), nitriles (N),
and carboxylic acids (CA) smoothly provides β-alkoxy-β-ketoenamides in broad structural
variety. The subsequent cyclocondensation of these compounds with hydroxylamine hydrochloride
afforded a large library of pyrimidine N-oxides under mild conditions and in good yields. Their synthetic utility was further
increased by the Boekelheide rearrangement leading to 4-acetoxymethyl-substituted
pyrimidines. With trifluoroacetic anhydride the rearrangement proceeds even at room
temperature and directly furnishes 4-hydroxymethyl-substituted pyrimidine derivatives.
The key reactions are very robust and work well even in the presence of sterically
demanding substituents.
Key words
alkoxyallene - β-alkoxy-β-ketoenamide - pyrimidine
N-oxide - Boekelheide rearrangement - oxidation