C[O:2][C:3]1[CH:4]=[C:5]([CH2:10][C:11]([O:13][CH2:14][CH3:15])=[O:12])[CH:6]=[CH:7][C:8]=1O.[C:16]1(O)C=CC=CC=1.[Zn](C)C.CC(C[AlH]CC(C)C)C>C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.Cl[Pd]Cl.[Fe+2]>[OH:2][C:3]1[CH:4]=[C:5]([CH2:10][C:11]([O:13][CH2:14][CH3:15])=[O:12])[CH:6]=[CH:7][C:8]=1[CH3:16]Ethyl 3-hydroxy-4-methylphenylacetate (5a) was prepared from ethyl 3-methoxy-4-hydroxy-phenylacetate as shown in Scheme 2. The phenol was converted to the triflate ester 4b which was subjected to displacement with Me2Zn, DIBAL-H and PdCl2(dppf) (E.-i. Negishi in Metal-catalyzed Cross-Coupling Reactions, F. Diederich and P. J. Stang (eds.), Wiley-VCH, Mannheim 1998, chap. 1; E. Erdik, Tetrahedron 1992 48:9577–9648) to afford the 4c. Boron tribromide demethylation afforded 5a. Ethyl 3-hydroxy-4-ethylphenylacetate 5b was prepared by Friedel-Crafts acylation of 4d which afforded ethyl 4-acetyl-3-methoxyphenylacetate (4e). Reduction of the ketone with triethylsilane and TFA produced the corresponding 4-ethyl substituted derivative 4f which was demethylated with BBr3 to afford 5b. Ethyl 3-hydroxy-4-iso-propylphenylacetate (5c) was prepared by Wittig olefination of 4e and subsequent catalytic hydrogenation of the 2-propenyl substituent to yield 4h. Demethylation with boron tribromide produced 5c.
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