2-substituted-6-amino-5-alkyl, alkenyl or alkynyl-4-pyrimidinecarboxylic acids and 6-substituted-4-amino-3-alkyl, alkenyl or alkynyl picolinic acids and their use as herbicides

A compound of the formula I:

• wherein
• A is N;
• R1 is C1-C4 alkyl, C1-C4 haloalkyl, C2-C4 alkenyl, C2-C4 haloalkenyl, C2-C4 alkynyl, or formyl;
• R2 is
• wherein
• W1 is H or halogen;
• X1 is H or C1-C6 alkoxy;
• Y1 is halogen;
• Z1 is H or halogen;
• and
• R3 and R4 independently is H, C1-C6 acyl, or C1-C6 alkylcarbamyl;
• or, with respect to the carboxylic acid group, agriculturally acceptable derivatives thereof.