Reactions of 2‐hydroxybenzonitrile with isocyanates

Abstract

Abstract Triethylamine catalyzes the reaction of 2‐hydroxybenzonitrile ( 1 ) with aryl isocyanates to form the corresponding carbamates 2a‐c , as well as the cyclization of the latter compounds to either 4[ N ‐( N ‐arylcarbamoyl)‐imino]‐3‐aryl‐2 H ‐1,3‐benzoxazin‐2‐ones 4a‐c , or 4‐arylamino‐2 H ‐1,3‐benzoxazin‐2‐ones 7a‐c , depending on the reaction temperature. Under analogous conditions, the carbamates obtained from 1 and 2‐chloroethyl isocyanate, 3‐chloropropyl isocyanate and ethyl isocyanatoacetate undergo a double cyclization yielding imidazo‐ and pyrimido[1,2‐c|1,3]benzoxazinones 13a,b,17 . Upon heating in phenyl ether, compounds 7a‐c , rearrange to 2‐(2‐hydroxyphenyl)‐4(3 H )‐quinazolinones 10a‐c .