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.

b-Alkoxy-b-ketoenamides and hydroxylamine hydrochloride smoothly provide pyrimidine-N-oxides under very mild conditions. Alkyl, aryl, and heteroaryl substituents are compatible with this new method. By treatment with acetic acid anhydride these pyrimidine-N-oxides undergo a rearrangement furnishing highly functionalized 6-acetoxymethyl-substituted pyrimidine derivatives in good yields. Our method, which is based on a three-component reaction of alkoxyallenes, nitriles, and carboxylic acids, therefore constitutes a highly flexible route to densely substituted pyrimidine derivatives.

Preparation of Pyrimidine-N-oxides by Condensation of Functionalized Enamides with Hydroxylamine Hydrochloride. -Reaction of enamides (I) with hydroxylamine hydrochloride proceeds under mild conditions to give the expected pyrimidine N-oxides. They rearrange on Ac 2O treatment with formation of 6-acetoxymethyl-substituted pyrimidines. In the case of substrates (V) and (VIII) bearing an allyl or vinyl chain, additional double bond isomerization or reaction with the solvent methanol is observed. -(ZIMMER, R.; LECHEL, T.; RANCAN, G.; BERA, M. K.; REISSIG*, H.