中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
—— | 2-(2-bromophenyl)-5-chloro-4H-benzo[d][1,3]oxazin-4-one | 1234707-32-4 | C14H7BrClNO2 | 336.572 |
A novel and general protocol towards the synthesis of highly functionalized ortho-amido oxobenzoxazine frameworks
The introduction of fluorine atoms into 2-phenyl-4H-3,1-benzoxazin-4-one (bentranil) led to sweeping changes in its herbicidal properties in some cases, and 5-fluoro-2-phenyl-4H-3,1-benzoxazin-4-one ('fluorobentranil') was found to be the most active compound. It can be prepared from 2-amino-6-fluoro-benzoic acid or by direct halogen exchange of 5-chloro-2-phenyl-4H-3,1-benzoxazin-4-one. The latter reaction was investigated on a pilot scale, including a high-temperature (350 °C) potassium fluoride halogen exchange without solvent. When sulfolane was used as a solvent, a side reaction at 220 °C – partial decomposition to a diphenylether – could be prevented by addition of a small amount of a radical scavenger. Other intermediates with a pseudohalogen substitution were obtained by side-chain chlorination of suitable methylsulfanyl benzoic acid precursors and halogen exchange. 'Fluorobentranil' shows good broad-leaf activity and selectivity on rice, cereals and maize. In a second case study, the fluoro-substituted anthranilic acids mentioned above were also found to be appropriate for synthesizing herbicidal sulfonylurea (SU) compounds via Meerwein reaction of their aniline function. Methyl 2-[([(4chloro-6-methoxy-2-pyrimidinyl)-amino]carbonyl}amino)sulfonyl]-6-fluorobenzoate is an example of a SU that is compatible with maize, whereas the unsubstituted Classic® analogue is not selective.