4 METHYL AZOLYL-3-PROPENOATES

The structures of four azolyl-3-propenoic esters, methyl (E)-3-(imidaz ol-4-yl)propenoate, (2), as its hemihydrate, C7H8N2O2.0.5H(2)O, methyl (E)-3-(pyrrol-2-yl)-propenoate, C8H9NO2, (3), methyl (E)-3-(imidazol- 2-yl)propenoate, C7H8N2O2, (4), and methyl (Z)-3-(imidazol-2-yl)propen oate, C7H8N2O2, (5), are reported. In the pyrrole and imidazole deriva tives, (3) and (4), the N-H function has an s-Z configuration with res pect to the propenoate chain, whereas in the urocanate, (2), protonati on has occurred at the N atom further from the side chain. In (5), an intramolecular N-H . . . O hydrogen bond causes a relative widening of the angles in the side chain. In all four compounds, both the azole r ings and the side chains are almost planar. In the hemihydrate of (2), there is extensive hydrogen bonding, primarily of the type N-H . . . O but supplemented by much longer C-H . . . O interactions. In (3) and (4), the hydrogen bonding is much simpler, with molecules linked into ribbons via N-H . . . O contacts.