✍ Scribed by Jarle Holt; Jan M. Bakke; Anne Fiksdahl
No coin nor oath required. For personal study only.
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A facile acid catalysed cyclisation method for the preparation of the cyclic urea 2__H__‐imidazo[4,5‐c]pyridin‐2‐one (2) in > 95 % yield is reported. The biologically active compound 2 can be obtained by heating (3‐amino‐4‐pyridinyl)‐carbamic acid methyl, ethyl or tert‐butyl esters (1a‐c) in sulfuric acid (0.1 %) or in aqueous HBF~4~ (3.5 equivalents) for 10 min. ‐ 3 hrs at 90 °C. The corresponding microwave‐promoted (MW) reactions afforded the pure product 2 within few minutes. The 6‐butylamino‐substituted analogue (2a) was correspondingly obtained by MW irradiation in 99 % yield by cyclisation of 2‐(butylamino)‐5‐amino‐4‐pyridylcarbamic acid isopropyl ester (1d). Quantitative precipitation of product 2 was obtained by pH adjustment. The process represents a solvent‐free, “green” method for the preparation of 2.
📜 SIMILAR VOLUMES
## Abstract 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 carbamat