Compounds of formula I
 wherein:
   R represents an optionally substituted alkyl or an optionally substituted cycloalkyl group;
   R¹ represents halogen, -O(CH₂)m OR⁵, cyano, -SR⁵, R5, -CO₂R⁵, OR⁵ or alkyl substituted by OR⁵;
   R² and R³ represent halogen, hydrogen, R⁵, alkyl substituted by -OR⁵, nitro, cyano, -OR⁵, -O(CH₂)mOR⁵ or -CO₂R⁵;
   R⁴ and R⁵ represent an optionally substituted alkyl group;
   n represents zero, 1 or 2 and
   m represents an integer from 1 to 3;
   and agriculturally acceptable salts of enolic tautomeric forms thereof are useful as herbicides.
                            式 I 的化合物
 其中
R 代表任选取代的烷基或任选取代的环烷基;
R¹ 代表卤素、-O(CH₂)m OR⁵、
氰基、-SR⁵、R5、-CO₂R⁵、OR⁵或被 OR⁵ 取代的烷基;
R² 和 R³ 代表卤素、氢、R⁵、被-OR⁵取代的烷基、硝基、
氰基、-OR⁵、-O(CH₂)mOR⁵ 或-CO₂R⁵;
R⁴ 和 R⁵ 代表任选取代的烷基;
n 代表零、1 或 2,以及
m 代表 1 至 3 的整数;
其烯醇同分异构形式的农业上可接受的盐类可用作
除草剂。