Synthesis and Structural Elucidation of Novel Bisarylmethylidenes of Cyclic Enones

One-pot synthesis of benzofurans via heteroannulation of benzoquinones

Three different reactions were explored leading to the synthesis of various benzofurans. All reactions took place under AcOH catalysis in a one-pot manner. As a result, benzoquinone derivatives underwent heteroannulation with either itself or cyclohexanones to produce furanylidene-benzofuran or benzofuran structures, respectively.

Ultrasound mediated synthesis of dihydropyrano[3,2-d][1,3]dioxin-7-carbonitrile derivatives in H2O/EtOH medium

A one-pot cyclocondensation of 1,3-dioxane-5-one (1) with malononitrile and aromatic aldehydes in aqueous sodium hydroxide under ultrasonic irradiation furnishes a series of pyrano[3,2-d][1,3]dioxin derivatives 3. Reactions are completed after a few minutes and the precipitated products are purified by simple crystallization from ethanol. The reaction with ethyl cyanoacetate instead of malononitrile gives the respective analogous products in high yields.

(2E,6E)-2,6-Bis(4-methyl-benzyl-idene)cyclo-hex-3-en-1-one

The title compound, C(22)H(20)O, shows an approximately planar cyclo-hexenone ring [maximum deviation = 0.069 (4) Å], with a disordered position of the C=C bond [ratio = 0.71 (2)/0.29 (2)]. The benzene rings of the 4-methyl-benzyl-idene units, attached in the 2- and 6-positions to the cyclo-hexenone ring, are rotated in the same direction by 28.6 (4) and 22.4 (4)°, with respect to the mean plane of the cyclo-hexenone ring [fraction 0.71 (2); maximum deviation = 0.06 (3) Å]. In the crystal, mol-ecules are packed in the manner of a distorted hexa-gonal rod packing with their long axes all aligned along [201]. A number of C-H⋯π inter-actions stablize the crystal structure.

Synthesis and X-ray Crystallographic Analysis of a bis(arylmethylidene) Pyranone Structure

The exocyclic olefinic bonds and their E-E configuration in a bis(arylmethylidene)pyranone system are confirmed for the first time by X-ray crystallography of the 3,5-dibenzylidene-tetrahydropyran-4-one derivative.