Pyrazinothiazines having herbicidal action

A substituted pyridazine of the formula I

• in which:
• R is O—RA, S(O)n—RA or O—S(O)n—RA;
• RA is hydrogen, C1-C4-alkyl, Z—C3-C6-cycloalkyl, C1-C4-haloalkyl, C2-C6-alkenyl, Z—C3-C6-cycloalkenyl, C2-C6-alkynyl, Z-(tri-C1-C4-alkyl)silyl, Z—C(═O)—Ra, Z—NRi—C(O)—NRiRii, Z—P(═O)(Ra)2, NRiRii, a 3- to 7-membered monocyclic or 9- or 10-membered bicyclic saturated, unsaturated or aromatic heterocycle which contains 1, 2, 3 or 4 heteroatoms selected from the group consisting of 0, N and S, which may be partially or fully substituted by groups Ra and/or Rb,
• Ra is hydrogen, OH, C1-C8-alkyl, C1-C4-haloalkyl, Z—C3-C6-cycloalkyl, C2-C8-alkenyl, Z—C5-C6-cycloalkenyl, C2-C8-alkynyl, Z—C1-C6-alkoxy, Z—C1-C4-haloalkoxy, Z—C3-C8-alkenyloxy, Z—C3-C8-alkynyloxy, NRiRii, C1-C6-alkylsulfonyl, Z-(tri-C1-C4-alkyl)silyl, Z-phenyl, Z-phenoxy, Z-phenylamino or a 5- or 6-membered monocyclic or 9- or 10-membered bicyclic heterocycle which contains 1, 2, 3 or 4 heteroatoms selected from the group consisting of O, N and S, where the cyclic groups are unsubstituted or substituted by 1, 2, 3 or 4 groups Rb;
• Ri, Rii independently of one another are hydrogen, C1-C8-alkyl, C1-C4-haloalkyl, C3-C8-alkenyl, C3-C8-alkynyl, Z—C3-C6-cycloalkyl, Z—C1-C8-alkoxy, Z—C1-C8-haloalkoxy, Z-phenyl, a 3- to 7-membered monocyclic or 9- or 10-membered bicyclic saturated, unsaturated or aromatic heterocycle which contains 1, 2, 3 or 4 heteroatoms selected from the group consisting of O, N and S and which is attached via Z;
• or
• Ri and Rii together with the nitrogen atom to which they are attached may form a 5- or 6-membered monocyclic or 9- or 10-membered bicyclic heterocycle which contains 1, 2, 3 or 4 heteroatoms selected from the group consisting of O, N and S;
• Z is a covalent bond or C1-C4-alkylene;
• n is 0, 1 or 2;
• R1 is cyano, halogen, nitro, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C6-haloalkyl, Z—C1-C6-alkoxy, Z—C1-C4-alkoxy-C1-C4-alkoxy, Z—C1-C4-alkylthio, Z—C1-C4-alkylthio-C1-C4-alkylthio, C2-C6-alkenyloxy, C2-C6-alkynyloxy, C1-C6-haloalkoxy, C1-C4-haloalkoxy-C1-C4-alkoxy, S(O)nRbb, Z-phenoxy, or Z-heterocyclyloxy, where heterocyclyl is a 5- or 6-membered monocyclic or 9- or 10-membered bicyclic saturated, partially unsaturated or aromatic heterocycle which contains 1, 2, 3 or 4 heteroatoms selected from the group consisting of O, N and S, where cyclic groups are unsubstituted or partially or fully substituted by Rb;
• Rbb is C1-C8-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C2-C6-haloalkenyl, C2-C6-haloalknyl or C1-C6-haloalkyl and n is 0, 1 or 2;
• A is C—R2;
• R2 is Z1-heterocyclyl, where heterocyclyl is a 5- or 6-membered monocyclic or 9- or 10-membered bicyclic saturated, partially unsaturated or aromatic heterocycle which contains 1, 2, 3 or 4 heteroatoms selected from the group consisting of O, N and S, where cyclic groups are unsubstituted or partially or fully substituted by Rb,
• is phenyl which is attached via Z1 or oxygen and is unsubstituted or substituted by C1-C1-alkyl, C1-C4-alkoxy, C1-C4-haloalkyl, C1-C4-alkoxy-C1-C4-alkyl or C1-C4-alkoxy-C1-C4-alkoxy;
• is C2-C6-alkoxy or Z—C1-C4-alkoxy-C1-C4-alkoxy;
• Z1 is a covalent bond, C1-C4-alkyleneoxy, C1-C4-oxyalkylene or C1-C4-alkyleneoxy-C1-C4-alkylene;
• Rb independently of one another are Z—CN, Z—OH, Z—NO2, Z-halogen, ═O, ═N—Ra, C1-C8-alkyl, C1-C4-haloalkyl, C2-C8-alkenyl, C2-C8-alkynyl, Z—C1-C8-alkoxy, Z—C1-C8-haloalkoxy, Z—C3-C10-cycloalkyl, O—Z—C3-C10-cycloalkyl, Z—C(═O)—Ra, NRiRii, Z-(tri-C1-C4-alkyl)silyl, Z-phenyl or S(O)nRbb, or
• R2 together with the group attached to the adjacent carbon atom may form a five- to ten-membered saturated or partially or fully unsaturated mono- or bicyclic ring which, in addition to carbon atoms, may contain 1, 2 or 3 heteroatoms selected from the group consisting of O, N and S and may be substituted by additional groups Rb;
• R3 is hydrogen, cyano, halogen, nitro, C1-C4-alkyl, C1-C4-haloalkyl, C1-C4-alkoxy, C1-C4-haloalkoxy, C2-C4-alkenyl, C2-C4-alkynyl, C2-C4-alkenyloxy, C2-C4-alkynyloxy or S(O)nRbb;
• R4 is hydrogen, halogen or C1-C4-haloalkyl;
• R5, R6 independently of one another are hydrogen, halogen or C1-C4-alkyl;
• Rx is C1-C6-alkyl, C1-C4-haloalkyl, C1-C2-alkoxy-C1-C2-alkyl, C2-C6-alkenyl, C2-C6-haloalkenyl, C3-C6-alkynyl, C3-C6-haloalkynyl or Z-phenyl which is unsubstituted or substituted by 1 to 5 groups Rb;
• where in the groups RA and their substituents, the carbon chains and/or the cyclic groups may be partially or fully substituted by groups Rb,
• or a N-oxide or an agriculturally suitable salt thereof.