Scheme 3.
Reagents and conditions: (i) imidazole, NaH, 60 °C, 1.5 h; (ii) method A: 3,4‐methylene‐dioxyphenylboronic acid, Pd(PPh3)4, Na2CO3, toluene/EtOH/H2O=5 : 3 : 2, 110 °C, 2.5 h.
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