Polyphenylene ether oligomer compound, derivatives thereof and use thereof

A thermosetting resin represented by the formula (1),

• wherein —(O—X—O)— is represented by the formula (2) in which R1, R2, R7 and R8 may be the same or different and are a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group, R3, R4, R5 and R6 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group and A is a linear, branched or cyclic hydrocarbon having 20 or less carbon atoms or an aromatic group, —(Y—O)— is represented by the formula (3) in which R9 and R10 may be the same or different and are a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group and R11 and R12 may be the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 6 or less carbon atoms or a phenyl group, —(Y—O)— is an arrangement of one kind of structure defined by the formula (3) or a random arrangement of two or more kinds of structures defined by the formula (3), Z is an organic group which has one or more carbon atoms and may contain an oxygen atom, each of a and b is 0 or an integer of 1 to 300, provided that at least either a orb is not 0, and each of i is independently 0 or an integer of 1.