2-{3-Cyano-4-[2-(4-diethylamino-2-hy-droxyphenyl)ethenyl]-5,5-dimethyl-2,5-dihydrofuran-2-ylidene}malononitrile acetone 0.25-solvate.

In the title compound, C(22)H(22)N(4)O(2)·0.25C(3)H(6)O, the disordered acetone mol-ecule lies with partial occupancy about the 2 axis. The mol-ecule of the malononitrile derivative is essentially planar excluding the methyl groups, with the largest deviation from the mean plane through the non-H atoms being 0.1955 (13) Å. Two rotamers with different orientations of the benzene ring are observed in the ratio of 0.919 (2):0.081 (2), and as a result the OH group is disordered over two sets of sites. In the crystal, the mol-ecules form ribbons along (101) utilizing a strong O-H⋯N(cyano) hydrogen bond. Inter-leaving of the nearly planar ribbons is provided by the twofold disordered acetone molecule through C-H⋯O inter-actions.