| 摘要 |
<p>Compounds of the formula
<CHEM>
wherein
A is H, NO2 or halogen;
B is H, alkyl, alkenyl, halogen, NO2, CN, SCN, CHO, alkoxy, alkylcarbonyl or alkoxycarbonyl;
Q<1> and Q<2> are each O or S;
X is N or CH;
W and Z are each H, alkyl, alkenyl, halogen, NO2, CN, CF3 or alkoxycarbonyl;
exhibit pre-emergence and post-emergence activity against many grassy and broadleaved weeds. They may be formulated for use in conventional manner.
<??>The novel compounds may be prepared by reacting a corresponding compound of formula
<CHEM>
e.g. successively in either order, with compounds of formulae
<CHEM>
wherein Y is a leaving group.
<??>According to another feature of the invention an ortho-(5-halopyridin-2-yloxy) phenol is prepared by heating to a melt a mixture or catechol and an appropriately substituted 2,5-dihalopyridine under an inert atmosphere. </p> |
