racemic-3,4-dihydro-7-(phenylmethoxy)-2H-1-benzopyran-2-carboxaldehyde → racemic-5-[3,4-dihydro-7-(phenylmethoxy)-2H-1-benzopyran-2-yl]-2,4-pentadienoic acid ethyl ester

Participants

Reaction Steps

Using the procedure of example 30, 2.7 g (10 mmoles) of the aldehyde product from example 83 was condensed with 4.4 g (12 mmoles) of ethyl 4-(triphenylphosphoranylidene)-2-butenoate in 30 ml of toluene (3.5 hr at 100° C.). Chromatography of the crude product on 100 g of silica gel gave 1.1 g (30%) of racemic-5-[3,4-dihydro-7-(phenylmethoxy)-2H-1-benzopyran-2-yl]-2,4-pentadienoic acid ethyl ester (mixture of E- and Z-isomers) as a yellow oil eluted with toluene and 19:1 toluene-ethyl acetate.

Provenance & Evidence