Structure of 4-(2-chloro-4,5-dimethoxybenzylidene)-2-methyl-5-oxazolone. X-ray and NMR study

The azlactone of 6-chloroveratraldehyde 3 (4-(2-chloro-4,5-dimethoxybenzyli dene)-2-methyl-5-oxazolone) was synthesized from 6-chloroveratraldehyde 2 a nd its structure investigated using X-ray crystallographic and nuclear magn etic resonance methods. Compound 3 crystallized in the P2(1)/c (#14) space group (Z = 4) with cell dimensions a = 9.148(2), b = 22.938(2), c = 6.707(1 ) Angstrom, and beta = 111.50(2)degrees. The X-ray study shows that azlacto ne 3 exists as the Z-isomer and crystallizes as a planar structure, i.e., b oth the phenyl and azlactone ring systems, as well as the functional groups attached to them, lie in the same plane. The H-1 and C-13 NMR spectral val ues also support the formation of the Z-isomer only, during the synthesis o f 4-(2-chloro-4,5-dimethoxybenzylidene)-2-methyl-5-oxazolone.