The synthesis and transformations of 2‐ethoxycarbonyl‐3‐isothiocyanatopyridine. Pyrido[3,2‐d]pyrimidines and some azolopyrido[3,2‐d]pyrimidines

Abstract 2‐Ethoxycarbonyl‐3‐isothiocyanatopyridine (2), prepared from 3‐amino‐2‐ethoxycarbonylpyridine (1) by the thiophosgene method, was converted with nucleophiles into pyrido[3,2‐d]pyrimidine derivatives 6–11 and 25–30 either directly, or through thiourethane 3. Tricyclic systems 18 and 19 were obtained from 3, and tricyclic systems 12–17 from pyrido[3,2‐d]pyrimidine derivative 11. Pyrrole reacted with 2 at C2 to give 20, and by further cyclization 21 and 22.