Allenes. Part 50. Pyrimido[1,2-a]pyrimidines and pyrimido[1,6-a]pyrimidines and their hydrolysis products from allenic nitrites and phenylpropynenitrile

Abstract

2-Aminopyrimidine and 2-amino-4-methylpyrimidine react with allenic nitriles to give, initially, 2-imino-4-alkylpyrimido[1,2-a]pyrimidines (2) which rapidly add water and cleave to 3-(4-amino-6-alkyl-2-pyrimidylamino)aldehydes (6). 2-Amino-4,6-dimethylpyrimidine similarly gives the corresponding ketones (5; R³= R⁴= Me). 2-Imino-4-alkylpyrimido[1,6-a] pyrimidines (11) areformed as intermediates from 4-amino-2,6-dimethylpyrimidine and allenic nitriles and are hydrolysed to amides (12).