prov:value
| - R3 and R4 are identical or different and are a hydrogen atom, a halogen atom, preferably a fluorine, chlorine or bromine atom, a C1-C10-, preferably C1-C4-alkyl group, which may be halogenated, a C6-C10-, preferably C6-C8-aryl group, an ???NR2 10, ???SR10, ???OSiR3 10, ???SiR3 10, or PR2 10 radical in whcih R10 is a halogen atom, preferably a chlorine atom, or a C1-C10-, preferably C1-C3-alkyl gro
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