| abstract |
A process for preparing a compound of formula (I) which comprisesn or a salt, acylate or sulphonate derivative thereof; wherein R¹ is an optionally substituted aryl group, R², R³, R⁴ and R⁵ are selected from hydrogen, C₁₋₄ alkyl, C₁₋₄ alkanoyl or -CO₂Rª wherein Rª is C₁₋₄ alkyl or R² and R³ or R⁴ and R⁵ together with the carbon atom to which they are attached form a C₃₋₆ cycloalkyl ring, provided that at least R² and R³ or R⁴ and R⁵ are not both hydrogen and that not more than two of R², R³, R⁴ and R⁵ are C₁₋₄ alkanoyl or -CO₂Rª; which process comprises either;n a) reacting a compound of formula (II)n wherein R², R³, R⁴ and R⁵ are as defined in relation to formula (I) with a compound of formula (III): n R¹COCN (III) nwherein R¹ is as defined in relation to formula (I) in the presence of a base and a Lewis acid; or b) reacting a compound of formula (VI)n with a compound of formula (X)n wherein R¹ is as hereinbefore defined, in the presence of a Lewis acid; or c) where R², R³, R⁴ and R⁵ are the same, reacting a compound of formula (XI)n with a compound of formula R²X¹ in the presence of a base, wherein X¹ is a leaving group. n Certain compounds of formula (I) are novel and these and their use as herbicides form another aspect of the invention. |