Preparation of substituted 1,3‐dihydro‐2 H ‐imidazo[4,5‐ c ]pyridin‐2‐ones

A new synthetic route to 6‐substituted‐imidazo[4,5‐ c ]pyridin‐2‐ons from 4‐aminopyridine has been investigated. 4‐Aminopyridine protected as alkyl carbamates were nitrated with dinitrogen pentoxide to the corresponding methyl, i ‐propyl and t ‐butyl 3‐nitropyridin‐4‐yl carbamates ( 5a‐c ) in 51‐63 % yields. Attempts to substitute these in the 6‐position by the ONSH and the VNS techniques succeeded with butyl‐amine and the t ‐butyl carbamate 9 . From the methyl or t ‐butyl 3‐nitropyridin‐4‐yl carbamates 5a, 5c 1,3‐dihydro‐2 H ‐imidazo[4,5‐ c ]pyridin‐2‐one ( 1 ) was formed in 73 and 39 % yields, respectively. t ‐Butyl 6‐ N ‐butylamin‐3‐aminopyridin‐4‐yl carbamate ( 6 ) gave 6‐butylamino‐1,3‐dihydro‐2 H ‐imidazo[4,5‐ c ]‐pyridin‐2‐one ( 7 ) in 53 % yield.