合成路线1

The preparation of the precursor aldehyde (IX) is illustrated in Scheme 1. Alkylation of 3-hydroxy-4-(difluoromethoxy)benzaldehyde (I) with 1-bromo-2-chloroethane (II) affords the chloroethyl ether (III). After reduction of the aldehyde function of (III) with NaBH4, the resulting alcohol (IV) is protected as the corresponding silyl ether (V) with triisopropylsilyl triflate and 2,6-lutidine. Dehydrohalogenation of the chloroethyl ether moiety of (V) with NaOH under phase-transfer conditions, followed by resilylation with triisopropylsilyl triflate, leads to the vinyl ether (VI). This is converted into the cyclopropyl derivative (VII) following the Simmons-Smith procedure in the presence of chloroiodomethane and diethylzinc. Desilylation of (VII) with tertbutylammonium fluoride yields the benzylic alcohol (VIII), which is again oxidized to aldehyde (IX) employing MnO2 in CH2Cl2.