prov:value
| - Suitable groups represented by R1-R4 include hydrogen, halogen atom such as fluorine, chlorine, bromine, or iodine; hydroxy, cyano, nitro, formyl; substituted or unsubstituted (C1-C12)alkyl group, especially, linear or branched (C1-C6)alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, t-butyl, n-pentyl, isopenyl, hexyl and the like; cyclo(C3-C6)alkyl group such as cyclopr
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