3,4-Dihydro-benz[1,3]oxazine Derivatives from 2-Acyl(or aroyl)-cyanatobenzenes

Abstract

3,4‐Dihydro‐2H‐benz[1,3]oxazin‐2‐ones 3 are obtained from 2‐acyl(or aroyl)‐cyanatobenzenes 2 and anisole. The reaction proceeds under Friedel‐Crafts conditions via DIMROTH rearrangement. Compounds 2, dissolved in diethyl ether, react with 1 in the presence of finely powdered KOH at ambient temperature leading to 8. The structure of 8b is confirmed by X‐ray structure analysis. (Z)‐4‐Ethylidene ‐ 3,4 ‐ dihydro ‐2H‐benz[1,3] oxazin‐2‐one 9 is formed upon treatment of 2‐cyanatopropiophenone 2b with diluted hydrochloric acid. The ethylene derivative 5 is obtained from 4 upon reaction with cyanogen bromide/triethyl amine.