The ‘ t ‐Amino Effect’ of ortho ‐Nitroso Amines. Synthesis of 2,6‐Diaminoadenine Derivatives from 6‐(Dialkylamino)‐5‐nitrosopyrimidines

The ‘ t ‐amino effect’ of amino‐nitroso compounds was documented by preparing the (dialkylamino)‐nitroso pyrimidines 4 – 18 , and cyclising them under thermal conditions in high yields to the purine derivatives 19 – 32 . The reactivity of the amino‐nitroso‐pyrimidines, particularly of 17 derived from diethyl iminodiacetate, and of 19 , derived from 1‐phenylimidazolidine, correlates with the stability of the intermediate azomethine ylide. Thermolysis of the amino‐nitroso‐pyrimidines 34 – 37 , possessing dialkylamino substituents at C(4) and C(6), proceeded by protiodenitrosation, leading to 38 – 41 .