Nitrogen-containing heterocyclic derivative and fungicide for agricultural and horticultural use

A nitrogen-containing heterocyclic compound represented by formula (IV), or a salt thereof:

• wherein,
• R3 ,R4, R5, and R6 each independently represents a hydrogen atom, unsubstituted or substituted C1-20 alkyl group, unsubstituted or substituted C2-20 alkenyl group, unsubstituted or substituted C2-20 alkynyl group, unsubstituted or substituted C3-20 cycloalkyl group, unsubstituted or substituted C4-20 cycloalkenyl group, unsubstituted or substituted C8-20 cycloalkynyl group, unsubstituted or substituted C6-10 aryl group, unsubstituted or substituted heterocyclic group, unsubstituted or substituted C1-20 acyl group, unsubstituted or substituted (1-imino)C1-20 alkyl group, unsubstituted or substituted hydroxyl group, unsubstituted or substituted amino group, unsubstituted or substituted mercapto group, unsubstituted or substituted sulfonyl group, halogeno group or cyano group;
• a plurality of R3 ,R4, R5, and R6 may be selected and bond together to form an unsubstituted or substituted 3- to 8-membered ring;
• R3 and R4, or R5 and R6 may bond together to form an oxo group, thioxo group or unsubstituted or substituted imino group;
• A-B, in which A represents a carbon atom and B represents a nitrogen atom, represents the formula:
• C═N, the formula:
• CR7—NR8, the following formula (II) or the following formula (III);
• R7 represents a hydrogen atom, unsubstituted or substituted C1-20 alkyl group, unsubstituted or substituted C2-20 alkenyl group, unsubstituted or substituted C2-20 alkynyl group, unsubstituted or substituted C1-20 acyl group, unsubstituted or substituted hydroxyl group, unsubstituted or substituted amino group, unsubstituted or substituted mercapto group, halogeno group or cyano group;
• R8 represents a hydrogen atom, unsubstituted or substituted C1-20 alkyl group, unsubstituted or substituted C2-20 alkenyl group, unsubstituted or substituted C2-20 alkynyl group, or unsubstituted or substituted C1-20 acyl group;
• Y represents an oxygen atom, sulfur atom or sulfinyl group;
• X and X′ each independently represents an unsubstituted or substituted C1-20 alkyl group, unsubstituted or substituted C2-20 alkenyl group, unsubstituted or substituted C2-20 alkynyl group, unsubstituted or substituted C3-20 cycloalkyl group, unsubstituted or substituted C4-20 cycloalkenyl group, unsubstituted or substituted C8-20 cycloalkynyl group, unsubstituted or substituted C6-10 aryl group, unsubstituted or substituted heterocyclic group, unsubstituted or substituted C1-20 acyl group, unsubstituted or substituted (1-imino) C1-20 alkyl group, unsubstituted or substituted hydroxyl group, unsubstituted or substituted amino group, unsubstituted or substituted mercapto group, unsubstituted or substituted sulfonyl group, halogeno group, cyano group or nitro group;
• p represents an integer of 0 to 6;
• and,
• n represents an integer of 0 to 4.