Palladium-Catalyzed Reaction of 2-Vinyl-2,3-dihydrobenzofurans and Chroman with Nucleophiles

Reaction of 2,3-dihydro-2-vinylbenzofuran with nucleophiles (NaCH(COOEt)2 and PhNHCH3) in the presence of palladium catalysts such as Pd(PPh3)4 and PdCl2(PR3)2 (R=Ph and Et) gives 2-(2-butenyl)phenols (46–76% yields) in which nucleophiles are incorporated into the methyl group of the butenyl moiety. 2-Vinylchroman undergoes the same type of reaction where only the palladium complex bearing PEt3 ligand is effective. The effectiveness of PEt3 ligand is also observed in the reaction of 2,3-dihydro-2-isopropenylbenzofuran with diethyl sodiomalonate leading to 3-ethoxycarbonyl-4-(2-methyl-1-propenyl)-2-chromanone.