SYNTHESIS AND STRUCTURE OF 2 5,6-DIHYDRO- ]-4-(2-[ARYL]-ETHENYL)-2-OXO-2H-PYRAN-3-CARBOXYLIC ACIDS

The structures of two 5,6-dihydro-2-oxo-2H-pyran derivatives with link s to an acid, an aryl and an arylethenyl group at C3, C6 and C4 of the heterocycle, respectively, are reported. The benzene rings in (I), ho xyphenyl)-4-[2-(2-methoxyphenyl)ethenyl]-2-oxo-5 ,6-dihydro-2H-pyran-3 -carboxylic ac id, C-22 H-20 O-6, and in (II), l)ethenyl]-2-oxo-5,6-di hydro-2H-pyran-3-carboxylic acid, C22H20O6, are substituted at the ort ho and at the para positions, respectively. These compounds are typica l of a series of analogues obtained as by-products in some Knoevenagel condensations of alpha,beta ethylenic aldehydes with the dimethyl est er of isopropylidenemalonic acid.