5-ethenylbenzene-1,3-diol

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Processes for the preparation of resveratrol have been disclosed, inter alia, in WO 01/60774 and Tetrahedron Letters 43 (2002) 597-598. The latter reference describes a process wherein resveratrol is prepared by a multistep reaction sequence starting with 3,5-dihydroxybenzaldehyde and involving a Heck reaction of 3,5-dihydroxystyrene with 4-acetoxy-iodobenzene in a yield of 70%. The process of the present invention utilizes a more readily available starting material and proceeds in less steps and superior yield, thus providing a technically more attractive approach to resveratrol and piceatannol and derivatives, such as esters, thereof. is prepared by a multistep reaction sequence

Conditions: temp:40.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 0.5 ml of concentrated hydrochloric acid is added to 80 g (587 mmol) of 3,5-dihydroxystyrene in 300 g of dihydropyran and the reaction mixture is stirred for 2 h at 40° C. The mixture is then poured into ice-water and extracted twice with ether. The organic phase is washed three times at 0° C. with 1N NaOH, dried, and concentrated by evaporation. The residue is purified by column chromatography (silica gel, hexane/ethyl acetate 4:1), giving 110 g (62%) of a viscous liquid. extracted twice with ether The organic phase is washed three times at 0° C. with 1N NaOH dried concentrated by evaporation The residue is purified by column chromatography (silica gel, hexane/ethyl acetate 4:1)