Reactions of 2‐hydroxybenzonitrile with isocyanates

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‐2H‐1,3‐benzoxazin‐2‐ones 4a‐c, or 4‐arylamino‐2H‐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(3H)‐quinazolinones 10a‐c.